Biology Flashcards
Cell theory
- All living things are made of cells
- The cell is basic functional unit of life
- All cells arise from other cells
- Genetic information is carried in the form of deoxyribonucleic acid (DNA) and is passed from parent to daughter cell
Nucleus
Stores genetic information and is the site of transcription
Mitochondrion
Involved in ATP production and apoptosis
Lysosome
Contain hydrolytic enzymes that break down molecules ingested through endocytosis and cellular waste products
Can also be involved in apoptosis when its enzymes are released
Rough endoplasmic reticulum
Synthesizes proteins destined for secretion
Smooth endoplasmic reticulum
Involved in lipid synthesis and detoxification
Golgi apparatus
Packages, modifies and distributes cellular products
Peroxisome
Break down very long chain fatty acids, synthesize lipids and contribute to the pentose phosphate pathway
Dependent on hydrogen peroxide for function
Participate in phospholipid synthesis
Cytoskeletal elements
Microfilaments, microtubules, intermediate filaments, centrioles and flagella
Which proteins make up microfilaments?
Actin
Which proteins make up microtubules?
Tubulin
Which proteins make up intermediate filaments?
Keratin, design, vimentin and lamins (depending on cell type)
Centrioles
Consist of nine triplets of microtubules around a hollow center
Found in centrosomes
Involved in microtubule organization in the mitotic spindle
Components of flagella
Consist of nine doublets of microtubules on the outside and two microtubules on the inside
What do fibroblasts produce?
Collagen
Are fibroblasts epithelial cells or connective tissue?
Connective tissue
Endothelial cells
Line blood vessels
Are endothelial cells epithelial cells or connective tissue?
Epithelial cells
Alpha-cells
Produce glucagon in the pancreas
Are alpha-cells epithelial cells or connective tissue?
Epithelial cells
Osteoblasts
Produce osteoid
Osteoid
The material that hardens into bone
Are osteoblasts epithelial cells or connective tissue?
Connective tissue
Chondroblasts
Produce cartilage
Are condroblasts epithelial cells or connective tissue?
Connective tissue
Where do archaea live?
Live in harsh environments
Use alternative sources of energy
Shapes of bacteria
Cocci, bacilli and spirilli
Cocci
Bacteria that is spherical
Bacilli
Bacteria that is rod-shaped
Spirilli
Bacteria that is spiral-shaped
Obligate aerobe
Can survive when oxygen is present
Can carry out aerobic metabolism when oxygen is present
Cannot survive when oxygen is absent
Cannot carry out anaerobic metabolism when oxygen is absent
Facultative anaerobe
Can survive when oxygen is present
Can carry out aerobic metabolism when oxygen is present
Can survive when oxygen is absent
Can carry out anaerobic metabolism when oxygen is absent
Obligate anaerobe
Cannot survive when oxygen is present
Cannot carry out aerobic metabolism when oxygen is present
Can survive when oxygen is absent
Can carry out anaerobic metabolism when oxygen is absent
Aerotolerant anaerobe
Can survive when oxygen is present
Cannot carry out aerobic metabolism when oxygen is present
Can survive when oxygen is absent
Can carry out anaerobic metabolism when oxygen is absent
Can obligate aerobe survive with oxygen?
Yes
Can obligate aerobe carry out aerobic metabolism when oxygen is present?
Yes
Can obligate aerobe survive without oxygen?
No
Can obligate aerobes carry out anaerobic metabolism when oxygen is absent?
No
Can facultative anaerobe survive with oxygen?
Yes
Can facultative anaerobe carry out aerobic metabolism when oxygen is present?
Yes
Can facultative anaerobe survive without oxygen?
Yes
Can facultative anaerobe carry out anaerobic metabolism when oxygen is absent?
Yes
Can obligate anaerobe survive with oxygen?
No
Can obligate anaerobe carry out aerobic metabolism when oxygen is present?
No
Can obligate anaerobe survive without oxygen?
Yes
Can obligate anaerobe carry out anaerobic metabolism when oxygen is absent?
Yes
Can aerotolerant anaerobe survive with oxygen?
Yes
Can aerotolerant anaerobe carry out aerobic metabolism when oxygen is present?
No
Can aerotolerant anaerobe survive without oxygen?
Yes
Can aerotolerant anaerobe carry out anaerobic metabolism when oxygen is absent?
Yes
Gram-positive bacteria
Have a thick layer of peptidoglycan and lipoteichoic acid
Contain no outer membrane
Gram-negative bacteria
Have a thin layer of peptidoglycan
Have an outer membrane containing lipopolysaccharides and phospholipids
Eukaryotic flagella
Contain microtubules composed of tubulin, organized in a 9+2 arrangement
Bacterial flagella
Made of flagellin and consist of a filament, a basal body and a hook
Mechanisms of bacterial genetic recombination
Transformation, conjugation and transduction
Transformation
The acquisition of genetic material from the environment that can be integrated into the bacterial genome
Conjugation
The transfer of genetic information from one bacterium to another across a conjugation bridge
Transduction
The transfer of genetic material from one bacterium to another using a bacteriophage as a vector
What can be transferred across a conjugation bridge?
A plasmid can be transferred from F+ cells to F- cells
Or
A portion of the genome can be transferred from Hfr cell to a recipient
Four phases of bacterial growth curve
Lag phase, exponential phase, stationary phase and death phase
Lag phase
Bacteria gets used to environment; little growth during this time
Exponential (log) phase
Bacteria use available resources to multiply at an exponential rate
Stationary phase
Bacterial multiplication ceases as resources are used up
Death phase
Bacteria die as resources become insufficient to support the colony
Why are viruses considered obligate intracellular parasites?
Because they do not contain organelles such as ribosomes; therefore, in order to reproduce and synthesize proteins, they must infect cells and hijack their cellular machinery
The pathway of retroviral nucleic acids from infection of a host cell to release of viral progeny
Nucleic acid enters as single-stranded RNA –> RNA undergoes reverse transcription (using reverse transcriptase) to form double-stranded DNA –> DNA can enter the host genome and replicate with the host cell –> DNA is transcribed to mRNA –> mRNA can be used to make structural proteins –> mRNA doubles as the viral genome for new virions –> virions are assembled from the structural proteins and mRNA genome –> virions can be released to infect other cells
Lytic cycle
Bacteriophages replicate in the host cell in extremely high numbers until the host cell lyses and releases the virions
Lysogenic cycle
Bacteriophage genome enters the host genome and replicates with the host cell as a provirus. At some point (after exposure to a particular stimulus), the provirus leaves the host genome and can be used to synthesize new virions
How do prions cause disease
They cause disease by triggering a change in the conformation of a protein from an alpha-helix to a beta-pleated sheet. This change reduces solubility of the protein and makes it highly resistant to degradation
Why are viruses not considered living things?
They are acellular, cannot reproduce without the assistance of a host cell, and many contain RNA as their genetic material
Nucleolus
A subsection of the nucleus in which ribosomal RNA (rRNA) is synthesized
Microfilaments
Composed of actin
Provide structural protection for the cell
Can cause muscle contraction through interactions with myosin
Help form the cleavage furrow during cytokinesis in mitosis
Microtubules
Composed of tubulin
Create pathways for motor proteins like kinesis and dynein to carry vesicles
Contribute to the structure of cilia and flagella, where they are organized into nine pairs of microtubules in a ring with two microtubules at the center (9+2 structure)
Intermediate filaments
Involved in cell-cell adhesion or maintenance of the integrity of the cytoskeleton
Help anchor organelles
Epithelial tissues
Cover the body and line its cavities, protecting against pathogen invasion and desiccation
Form parenchyma
Polarized (one side facing the lumen and the other facing the outside)
Parenchyma
The functional parts of the organ
Classifications of epithelia
Simple epithelia, stratified epithelia and pseudostratified epithelia
Simple epithelia
Have one layer
Stratified epithelia
Have many layers
Pseudostratified epithelia
Appear to have multiple layers because of differences in cell heights, but actually have one layer
Epithelia shapes
Cuboidal cells, columnar cells, squamous cells
Connective tissue function
Support and provide a framework for epithelial cells
Form the stroma by secreting materials to form an extracellular matrix
Stroma
Support structure
Examples of connective tissues
Bone, cartilage, tendons, ligaments, adipose tissue and blood
How to classify bacteria?
Gram staining bacteria with crystal violet stain, followed by a counterstain with safranin. Gram-positive bacteria turn purple. Gram-negative bacteria turn pink-red.
Chemotaxis
Moving in response to chemical stimuli
How do prokaryotes carry out the electron transport chain?
Using the cell membrane
Prokaryotic ribosomes
30S and 50 S
Eukaryotic ribosomes
40S and 60S
Binary fission
The prokaryote’s chromosome replicated while the cell grows in size, until the cell wall begins to grow inward along the midline of the cell and divides it into two identical daughter cells
Plasmids
Carry extrachromosomal material
Contain antibiotic resistance genes
Virulence factors
Antibiotic resistance genes
Episomes
Plasmids that can integrate into the genome
Transpons
Genetic elements that can insert into or remove themselves from the genome
Capsid
A protein coat in a virus
Bacteriophages
Viruses that target bacteria
Contain a tail sheath, which injects the genetic material into a bacterium
Contain a tail fiber, which allows the bacteriophage to attach to the host cell
Positive sense viruses
Single-stranded RNA can be translated by the host cell
Negative sense viruses
A complementary strand to the single-stranded RNA must be synthesized using RNA replicase, which can then be translated
Retroviruses
Contain a single-stranded RNA genome, to which a complementary DNA is made using reverse transcriptase
The DNA strand can then be integrated into the genome
Viroids
Plant pathogens that are small circles of complementary RNA that can turn off genes, resulting in metabolic and structural derangements of the cell and, potentially, cell death
Can a virus have single-stranded DNA?
Yes
Can a virus have double-stranded DNA?
Yes
Must use the cell’s RNA polymerase machinery in the nucleus to make its own mRNA
Can a virus have single-stranded RNA?
Yes
Can a virus have double-stranded RNA?
Yes
How are archaea similar to bacteria?
They are single-celled organisms that lack a nucleus or membrane-bound organelles, contain a single circular chromosome, divide by binary fission or budding
How are archaea similar to eukaryotic cells?
They start translation with methionine, contain similar RNA polymerases and associate their DNA with histones
What kind of genetic information can viruses have?
Either single-stranded or double-stranded DNA or RNA
Cell cycle stages
G0, G1, S, G2, M
G0 stage
The cell performs its normal functions and it is not planning to divide
G1 stage (presynthetic gap)
Cell grows and performs its normal functions. DNA is examined and repaired
Cells create organelles for energy and protein production, while also increasing their size
Has the restriction point
S stage (synthesis)
Replication of DNA and sister chromatids are held together at the centromeres
G2 stage (post synthetic gap)
Cell continues to grow and replicates organelles in preparation for mitosis. Cell continues to perform its normal function
M stage
Mitosis
Mitotic phases
Prophase, metaphase, anaphase, telophase and cytokinesis
Prophase
Nuclear membrane disappears, chromosomes become tightly coiled, centrioles move to opposite poles of the cell and begin to form the spindle apparatus and spindle fibers attach at the kinetochore of each chromosome
Metaphase
Centrioles align chromosomes along the midline of the cell (metaphase plate) using spindle fibers
Anaphase
Spindle fibers pull sister chromatids apart so there’s a set of chromosomes on either pole of the cell
Telophase and cytokinesis
Organelles separate moving to either pole of the cell, cell membrane splits the cell in half with each half having its own genetic material and organelles, nuclear membrane re-forms in each identical daughter cell, chromosomes loosen up and the spindle apparatus breaks down
What is the ploidy of the daughter cells produced from meiosis I?
Two haploid daughter cells
What is the ploidy of the daughter cells produced from meiosis II?
Four haploid daughter cells
Homologous chromosomes
XX
Four copies of the same chromosome
Related chromosomes of opposite parental origin
Sister chromatids
Identical copies of the came DNA that are held together at the centromere
| or X
Two copies of the same chromosome
Meiosis I phases
Prophase I, metaphase I, anaphase I and telophase I
Prophase I
Nuclear membrane disappears, chromosomes become tightly coiled, centrioles move to opposite poles of the cell and begin to form the spindle apparatus and spindle fibers attach at the kinetochore of each chromosome
Homologous chromosomes come together as tetrads during synapsis; crossing over
Metaphase I
Centrioles align homologous chromosomes along opposite sides the midline of the cell (metaphase plate) using spindle fibers
Anaphase I
Spindle fibers pull homologous chromosomes apart so there’s a set of chromosomes on either pole of the cell
Contromeres do not break
Telophase I
Organelles separate moving to either pole of the cell, cell membrane splits the cell in half with each half having its own genetic material and organelles, nuclear membrane re-forms in each haploid daughter cell, chromosomes may or may not loosen up and the spindle apparatus dissolves
Interstitial cells of Leydig
Secrete testosterone and other male sex hormones (androgens)
Sertoli cells
Nourish sperm during their development
During which phase of meiosis is a primary oocyte arrested?
Prophase I
During which phase of meiosis is a secondary oocyte arrested?
Metaphase II
Acrosome
Contains enzymes that are capable of penetrating the corona radiata and zone pellucid of the ovum, permitting fertilization to occur
Which organelle forms the acrosome?
Golgi apparatus
Phases of the menstrual cycle
Follicular phase, ovulation, luteal phase and menses
Features of the follicular phase
Egg develops, endometrial lining becomes vascularized and glandularized
GnRH secretion stimulates FSH and LH secretion, which promotes follicle development –> Estrogen is released, stimulating vascularization and glandularization of the decidua
Features of ovulation
Egg is released from follicle into peritoneal cavity
Stimulated by sudden surge in LH
Features of the luteal phase
Corpus luteum produces progesterone to maintain the endometrium
LH promotes the ruptured follicle to become the corpus luteum, which secretes progesterone, which maintains the uterine lining –> High estrogen and progesterone levels cause negative feedback on GnRH, FSH and LH
Features of menses
Shedding of endometrial lining
Estrogen and progesterone levels drop –> endometrial lining is sloughed off –> the block on GnRH production is removed
FSH levels in the follicular phase
High
FSH levels in ovulation
High
FSH levels in the luteal phase
Low
FSH levels in menses
Low
LH levels in the follicular phase
No changes
LH levels in ovulation
Super high (LH spike)
LH levels in the luteal phase
No changes
LH levels in menses
Low
Estrogen levels in the follicular phase
Low, then high
Estrogen levels in ovulation
High
Estrogen levels in the luteal phase
High
Estrogen levels in menses
Low
Progesterone levels in the follicular phase
Low
Progesterone levels in ovulation
Low
Progesterone levels in the luteal phase
High
Progesterone levels in menses
Low
Androgens
Male sex hormones
Diploid (2n) cells
Have two copies of each chromosome
Haploid (n) cells
Have one copy of each chromosome
Interphase
G1, S and G2 phases
DNA is uncoils in the form of chromatin
Restriction point
Present in G1
DNA is checked for quality
Must be passed for the cell to move into the S stage
p53
Plays a role in the two major checkpoints of the cell cycle G1 to S and G2 to M
Cyclins
Bind to cyclin-dependent kinases (CDK), phosphorylating and activating transcription factors for the next stage of the cell cycle
Cancer
Occurs when cell cycle control becomes deranged, allowing damaged cells to undergo mitosis without regard to quality or quantity of the new cells produced
Cancerous cells may begin to produce factors that allow them to escape their site and invade or metastasize elsewhere
Tetrad
Four chromatids of homologous chromosomes
Which stage of meiosis represents Mendel’s second law (the law of independent assortment)?
Prophase I
Which stage of meiosis represents Mendel’s first law (the law of segregation)?
Anaphase I
Is meiosis II more similar to meiosis I or mitosis?
Mitosis, except the daughter cells are haploid
X chromosome
Carries a sizable amount of genetic information
Mutations of X-linked genes
Cause sex-linked disorders
Hemizygous
Males because they have unpaired X chromosomes
Who most often expresses sex-linked disorders?
Males because they are hemizygous for the X chromosome
Who is most often a carrier to sex-linked disorders?
Women because they have two copies of the X chromosome
Y chromosome
Carries little genetic information
Contains the SRY (sex-determining region Y) gene
SRY (sex-determining region Y) gene
Present on Y chromosome
Causes gonads to differentiate into testes
Where does sperm develop?
Seminiferous tubules in the testes
How are sperm nourished?
By sertoli cells
What secrets testosterone and androgens in the testes?
Interstitial cells of Leydig
Epididymis
Stores sperm and gives it mobility
Ejaculation pathway
Vas deferens –> ejaculatory duct –> urethra –> penis
Seminal vesicles
Contribute fructose to nourish sperm and produce alkaline fluid
Prostate gland
Produces alkaline fluid
Bulbourethral glands
Produce clear viscous fluid that cleans out any remnants of urine and lubricates the urethra during sexual arousal
Semen
Sperm + seminal fluid
Spermatogenesis
Four haploid sperm are produced from a spermatogonium
Primary spermatocytes
Germ cells after S phase
Secondary spermatocytes
Germ cells after meiosis I
Spermatids
Germ cells after meiosis II
Spermatozoa
Germ cells after maturation
Sperm parts
Head, midpiece and flagellum
Sperm head
Contains genetic material and is covered with an acrosome
Sperm midpiece
Generates ATP from fructose and contains many mitochondria
Sperm flagellum
Promotes sperm mobility
Where are ova (eggs) produced?
Follicles in the ovaries
Where does an egg get ovulated each month?
Peritoneal sac and then it gets drawn into the Fallopian tube (oviduct)
Where is sperm deposited during intercourse?
Vaginal canal
Vulva
External female anatomy
Oogenesis
One haploid ovum and a variable number of polar bodies are formed from an oogonium
Primary oocyte
Present at birth and arrested in prophase I
Secondary oocyte
Only one is present after every ovulation and arrested in metaphase II until either menses or fertilization
When does an oocyte complete meiosis II?
When it is fertilized
Zona pellucida
Surround the oocyte
Acellular mixture of glycoproteins that protect the oocyte and contain the compounds necessary for sperm binding
Corona radiata
Surround the oocyte
A layer of cells that adhered to the oocyte during ovulation
What releases gonadotropin-releasing hormone (GnRH)?
Hypothalamus
Gonadotropin-releasing hormone (GnRH)
Causes the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Follicle-stimulating hormone (FSH) in males
Stimulates Sertoli cells
Trigger spermatogenesis
Luteinizing hormone (LH) in males
Cause the interstitial cells to produce testosterone
Testosterone
Responsible for the maintenance and development of the male reproductive system and male secondary sex characteristics (facial and axillary hair, deepening of the voice and changes in growth patterns)
Follicle-stimulating hormone (FSH) in females
Stimulates ovarian follicles
Stimulate the production of estrogen and progesterone
Luteinizing hormone (LH) in females
Causes ovulation
Stimulate the production of estrogen and progesterone
Why does the sudden surge in LH occur?
Estrogen stops having negative feedback effects at a certain threshold and begins to have positive feedback effects
What causes negative feedback on GnRH, LH and FSH levels?
High levels of estrogen and progesterone
What happens if fertilization occurs?
The blastula produces human chorionic gonadotropin (hCG) which, as an LH analog, can maintain the corpus luteum
What happens near the end of the first trimester?
hCG levels drop as the placenta takes over progesterone production
Menopause
Occurs when the ovaries stop producing estrogen and progesterone (ages 45 and 55)
Menstruation stops
FSH and LH levels rise
Sperm development
Spermatogonium –> primary spermatocyte –> secondary spermatocyte –> spermatid –> spermatozoan
Vas deferens
Tube connecting the epididymis to the ejaculatory duct
Cowper’s glands
Produce a fluid to clear traces of urine in the urethra
What is the last point in the meiotic cycle in which the cell has a diploid number of chromosomes?
Telophase I
Determinate cleavage
Cell division that results in cells having definitive lineages; that is, at least one daughter cell is already programmed to differentiate into a particular cell type
Indeterminate cleavage
Cell division that results in cells that can differentiate into any cell type (or a whole organism)
Stages of development from zygote to gastrula
Zygote –> 2-cell embryo –> 4-cell embryo –> 8-cell embryo –> 16-cell embryo –> morula –> blastula (blastocyst) –> gastrula
During which stage of development does implantation occur?
Blastula (blastocyst)
Primary Germ Layers
Ectoderm, mesoderm, endoderm
Ectoderm
Nervous system, integumentary system, eyes and ears
Mesoderm
Musculoskeletal system, circulatory system, excretory system, endocrine system, reproductive system, digestive system, respiratory system
Endoderm
Epithelial linings of organs, liver, pancreas, thyroid, bladder, distal tracts of the excretory and reproductive systems
Induction
The process by which nearby cells influence the differentiation of adjacent cells
What tissues do neural crest cells develop into?
PNS and skin
Why is induction important?
It insures the proper spatial location and orientation of cells that share function or have complementary functions
Determination
The commitment of a cell to a particular lineage
Differentiation
The actual changes that occur in order for the cell to assume the structure and function of the determined cell type
Types of potency
Totipotency, pluripotency and multipotency
Types of cell-cell communication
Autocrine, paracrine, juxtacrine and endocrine
Apoptosis
Programmed cell death
Necrosis
Cell death due to injury
Totipotent cell lineages
Any cell type in the developing embryo (primary germ layers) or in extra-embryonic tissues (amnion, chorion, placenta)
Pluripotent cell lineages
Any cell type in the developing embryo (primary germ layers)
Multipotent cell lineages
Any cell type within a particular lineage (hematopoietic stem cells)
Autocrine
The signal acts on the same cell that secreted it
Paracrine
The signal acts on local cells
Juxtacrine
The signal acts on an adjacent cell through direct receptor stimulation
Endocrine
The signal travels via the bloodstream to act at distant sites
What does apoptosis result in?
Contained blebs of the dead cell that can be picked up and digested by other cells
What does necrosis result in?
Spilling of cytoplasmic contents
What is the oxygenation status of the blood in the umbilical arteries?
Deoxygenated
What is the oxygenation status of blood in the umbilical vein
Oxygenated
Three fetal shunts
Foramen ovale, ductus arteriosus, ductus venosus
What vessels or heart chambers does the foramen ovale connect?
Right atrium to left atrium
What vessels or heart chambers does the ductus arteriosus connect?
Pulmonary artery to aorta
What vessels or heart chambers does the ductus venosus connect?
Umbilical vein to inferior vena cava
Which organ does the foramen ovale bypass?
Lungs
Which organ does the ductus arteriosus bypass?
Lungs
Which organ does the ductus venosus bypass?
Liver
Key developmental features of the first trimester
Organogenesis
Key developmental features of the second trimester
Growth, movement, face develops, digits elongate
Key developmental features of the third trimester
Growth, brain development, transfer of antibodies to the fetus
Organogenesis in the first trimester
Heart, eyes, gonads, limbs, liver and brain
First phase of birth
Cervix thins and the amniotic sac ruptures
Second phase of birth
Urine contractions and birth of the fetus
What coordinates uterine contractions?
Prostaglandins and oxytocin
Third stage of birth
Placenta and umbilical cord expulsion
Fertilization
The joining of a sperm and an ovum
Where does fertilization occur?
In the ampulla of the fallopian tube
How does the sperm fertilize the egg (i.e. the cortical reaction)?
It uses ayrosomal enzymes to penetrate to corona radiata and zona pellucida –> Once it contacts the oocyte’s plasma membrane, the sperm establishes the acrosomal apparatus and injects its pronucleus –> When the first sperm penetrates, it causes the release of calcium ions, which prevents additional sperm from fertilizing the egg and increases the metabolic rate of the resulting diploid zygote
Fraternal (dizygotic) twins
Result from the fertilization of two eggs by two different sperm
Identical (monozygotic) twins
Result from the splitting of a zygote in two
Cleavage
The early divisions of cells in the embryo
These mitotic divisions result in a larger number of smaller cells, as the overall volume does not change
Why does a zygote become an embryo after the first cleavage?
Because it is no longer unicellular
Morula
A solid mass of cells seen in early development
Blastula (blastocyst)
Has a fluid-filled center called a blastocoel and has two different cell types, including trophoblasts and the inner cell mass
Blastocoel
Fluid inside the center of a blastula
Types of cells in a blastula
Trophoblasts and inner cell mass
Trophoblasts
Become placental structures
Inner cell mass
Become the developing organism
Where does a blastula implant?
In the endometrial lining
What happens after the blastula implants?
It forms the placenta
Chorion
Penetrate the endometrium and create the interface between maternal and fetal blood using chorionic villi
How is the embryo supported before the placenta forms?
Yolk sac
Allantois
Involved in early fluid exchange between the embryo and the yolk sac
Amnion
Lies inside the the chorion and produces amniotic fluid
How is the developing organism connected to the placenta?
Via the umbilical cord
Gastrulation
The archenteron is formed with a blastopore at the end. As the archenteron grows through the blastocoel, it contacts the opposite side, establishing three primary germ layers (ectoderm, endoderm and mesoderm)
Neurulation
The development of the nervous system
When does neurulation occur?
After the formation of the three germ layers
How does neurulation occur?
The notochord induces a group of overlying ectodermal cells to form neural folds surrounding a neural groove –> the neural folds fuse to form the neural tube, which becomes the CNS –> the tip of each neural fold contains neural crest cells
What does the neural tube become?
CNS
Teratogens
Substances that interfere with development, causing defects or even death of the developing embryo
How does diabetes in pregnant women affect the fetus?
Increase fetal size and cause hypoglycemia after birth
How does folic acid deficiency in pregnant women affect the fetus?
Neural tube defects
How is determination accomplished?
Uneven segregation of cellular material during mitosis
Using morphogens
Morphogens
Promote development down a specific cell line
How can a cell respond to a morphogen?
It must have competency
How is differentiation accomplished?
Via selective transcription to take on characteristics appropriate to its cell line
Stem cells
Cells that are capable of developing into various cell types
Totipotent cells
Able to differentiate into all cell types, including the three germ layers and placental structures
Pluripotent cells
Able to differentiate into all three germ layers and their derivatives
Multipotent cells
Able to differentiate only to a specific subset of cell types
Inducer
Releases factors to promote the differentiation of a competent responder
Growth factors
Peptides that promote differentiation and mitosis in certain tissues
Reciprocal induction
When two tissues both induce further differentiation in each other
How does signaling occur?
Via gradients
Do cells migrate to arrive at their anatomically correct location?
Yes
When is apoptosis useful?
Sculpting anatomical structures (e.g. removing webbing between digits)
Regenerative capacity
The ability of an organism to regrow certain parts of the body
Does the liver have high or low regenerative capacity?
High
Does the heart have high or low regenerative capacity?
Low
Does the kidneys have high or low regenerative capacity?
High
Senescence
The result of multiple molecular and metabolic processes; most notably, the shortening of telomeres during cell division
Where does nutrient, gas and waste exchange occur in the fetus?
At the placenta
How are oxygen and carbon dioxide exchanged between the mother and fetus?
Passively through changes in concentration gradient
Fetal hemoglobin (HbF)
Has a higher affinity for oxygen than adult hemoglobin (primarily HbA), which also assists in the transfer (and retention) of oxygen into the fetal circulatory system
Placental barrier
Serves as the immune protect against many pathogens
Transfers antibodies from mother to fetus
Secretes estrogen, progesterone and human chorionic gonadotropin (hCG)
Notochord
Forms from the mesoderm and causes neurulation
Can a fetus produce immunoglobulins?
No, because they are immunologically naive
Can fetal hemoglobin cross the placenta?
No, because it’s too large
Is fetal hemoglobin the same size as adult hemoglobin?
No, it’s larger
When do somatic cells stop dividing?
When the telomeres become too short to effectively protect genomic material
Telomerase
An enzyme that allows for synthesis of telomeres to counteract telomere shortening during mitosis
Why are embryonic stem cells controversial?
Because they require destruction of an embryo to harvest
How can one increase the level of potency of adult stem cells?
Treatment with various transcription factors
Would using one’s own stem cells remove the risk or rejection when the cells are introduced into an individual?
Yes
Can adult stem cells be pluripotent?
Rarely so, unless pluripotency has been induced by strategic use of transcription factors
Incomplete regeneration
Newly formed tissues are not identical in structure or function to the tissues that have been injured or lost (e.g. scars)
What is the last structure to become fully functional in a fetus?
The lungs
Axon
Transmits electrical signals (action potentials) from the soma to the synaptic knob
Axon hillock
Integrates excitatory and inhibitory signals from the dendrites and fires an action potential if the excitatory signals are strong enough to reach threshold
Dendrite
Receive incoming information signals and carry them to the soma
Myelin sheath
Acts as insulation around the axon and speeds conduction
Prevents signal loss
Prevents the dissipation of the neural impulse and crossing of neural impulses from adjacent neurons
Soma
The cell body of a neuron, contains the nucleus, ER and ribosomes
Synaptic bouton (nerve terminal)
Lies at the end of the axon and releases neurotransmitters
The collection of cell bodies in the CNS
Nucleus
The collection of cell bodies in the PNS
Ganglion
Astrocyte
Nourish neurons and form the blood-brain barrier
Ependymal cell
Produce cerebrospinal fluid
Microglia
Phagocytic cells that ingest and breakdown waste products and pathogens in CNS
Oligodendrocyte
Produce myelin and the CNS
Schwann cell
Produce myelin the PNS
When does an axon hillock fire an action potential?
When the excitatory signals are strong enough to reach threshold
Which part of the neuron fires an action potential?
The axon hillock
Which part of the neuron releases neurotransmitters?
The synaptic bouton
What produces myelin in the CNS?
Oligodendrocytes
What produces myelin in the PNS?
Schwann cells
How is the resting membrane potential maintained?
Sodium/potassium ATPase and selective permeability of ions
What is the approximate voltage of the resting membrane potential?
-70 mV
Temporal summation
The integration of multiple signals close to each other in time
Spatial summation
The integration of multiple signals close to each other in space
During the action potential, which ion channel opens first?
Sodium ion channels
How are sodium ion channels regulated?
Inactivation, the opening of potassium ion channels, at +35 mV
What effect does the opening of the sodium ion channel have on the polarization of the cell?
It depolarizes the cell
During the action potential, which ion channel opens second?
Potassium ion channels
How are potassium ion channels regulated?
Closing at low potentials (slightly below -70 mV)
What effect does the opening of the potassium ion channel have on the polarization of the cell?
Repolarization of the cell and eventually hyper-polarization
Absolute refractory period
It does not matter how much or how strong the stimuli are, no further action potential will be initiated
Relative refractory period
Occurs during the hyper polarization phase
If strong enough stimulus is present, another action potential will be fired
What ion is primarily responsible for the fusion of neurotransmitter-containing vesicles with nerve terminal membrane?
Calcium
What are the three main methods by which a neurotransmitter’s action can be stopped?
Enzymatic degradation, reuptake and diffusion
When do sodium ion channels open?
At -50 mV
How can the inactivation of sodium ion channels be reversed?
By repolarizing the cell
When do potassium ion channels open?
At +35 mV
Central Nervous System (CNS)
Brain and spinal cord
Peripheral Nervous System (PNS)
Afferent and efferent neurons
Afferent neurons
Carry sensory information from the periphery to the CNS
Efferent neurons
Carry information from the CNS to the periphery to initiate an action
Somatic nervous system
Voluntary
Autonomic nervous system
Involuntary
Sympathetic nervous system
Fight or flight response
Increased heart rate, bronchial dilation, redistribution of blood to locomotor muscles, dilation of pupils, slowing of digestive and urinary function
Parasympathetic nervous system
Rest and digest response
Slowed heart rate, bronchial constriction, redistribution of blood to the gut, promotion of exocrine secretions, constriction of pupils, promotion of peristalsis and urinary function
Monosynaptic reflex
A sensory (afferent, presynaptic) neuron fires directly onto a motor (efferent, postsynaptic) neuron
Polysynaptic reflex
A sensory (afferent, presynaptic) neuron may fire directly onto a motor neuron (efferent, postsynaptic) neuron, but interneurons are used as well. The interneurons fire onto other motor neurons.
Neurons
Highly specialized cells responsible for the conduction of impulses
Do neurons communicate through electrical or chemical forms?
Both
How does electrical communication among neurons work?
Via ion exchange and the generation of membrane potentials down the length of the axon
How does chemical communication among neurons work?
Via neurotransmitter release from the presynaptic cell and the binding of these neurotransmitters to the postsynaptic cell
Nodes of Ranvier
Exposed areas of myelinated axons that permit saltatory conduction
Synapse
Consist to the nerve terminal of the presynaptic neuron, the membrane of the postsynaptic cell, and the space between the two
Synaptic cleft
The space between two neurons
What are individual axons bundled into?
Nerves or tracts
Can a single nerve carry multiple types of information?
Yes, including sensory, motor or both
Can a single tract carry multiple types of information?
No
Ganglia
Cell bodies of neurons of the same type within a nerve cluster in the PNS
Nuclei
Cell bodies of the individual neurons within a tract cluster in the CNS
Neuroglia (Glial cells)
Other cells within the nervous system in addition to neurons
Blood-brain barrier
Controls the transmission of solutes from the bloodstream into nervous tissue
Where are ependymal cells?
They line the ventricles of the brain
Cerebrospinal fluid
Physically supports the brain and serves as a shock absorber
Sodium/Potassium ATPase
Pumps three sodium ions out of the cell for every two potassium ions pumped in
Excitatory signals
Cause a neuron to depolarize
Inhibitory signals
Cause a neuron to hyperpolarize
How are signals propagated down the axon?
Through an action potential
Why does an impulse propagate down the length of the axon?
Because the influx of sodium in one segment of the axon brings the subsequent segment of the axon to threshold. The fact that the preceding segment of the axon is in its refractory period means that the action potential can only travel in one direction
Where are neurotransmitters released from a neuron?
At the nerve terminal into the synapse
What happens when the action potential arrives at the nerve terminal?
Voltage-gated calcium channels open
Do calcium ions flow into or out of the neuron when the voltage-gated calcium channels open?
Into the neuron
What happens when the voltage-gated calcium channels open?
Vesicles filled with neurotransmitter fuse with the presynaptic membrane, resulting in the exocytosis of neurotransmitter into the synaptic cleft, which then bind to their receptors on the postsynaptic cell
How to stop the propagation of a signal?
Neurotransmitters must be cleared from the postsynaptic cleft through: enzymatic breakdown of the neurotransmitters, reabsorption of the neurotransmitter by the presynaptic cell through reuptake channels, the neurotransmitter can diffuse out the of the synaptic cleft
What is the white matter in the CNS made of?
Myelinated axons
What is the grey matter in the CNS made of?
Unmyelinated cell bodies and dendrites
In the brain, is the white matter deeper than the grey matter?
Yes
In the spinal cord, is the white matter deeper than the grey matter?
No
Reflex arcs
Use the ability of interneurons in the spinal cord to relay information to the source of a stimulus while simultaneously routing it to the brain
Action potential
All or nothing response
Where do sensory neurons enter the spinal cord?
On the dorsal side
Where do motor neurons exit the spinal cord?
On the ventral side
Neurotransmitter released by pre-ganglionic neurons
Acetylcholine
Is acetylcholine released by the parasympathetic or the sympathetic pre-ganglionic neurons?
Both
What does a sympathetic post-ganglionic neuron release?
Epinephrine or norepinephrine
What does a parasympathetic post-ganglionic neuron release?
Acetylcholine
What color does gram-positive bacteria turn into after staining?
Purple
What color does gram-negative bacteria turn into after staining?
Pink-red
What does the tail sheath on a bacteriophage do?
Injects the genetic material into a bacterium
What does the tail fiber on a bacteriophage do?
Allows the bacteriophage to attach to the host cell
What is the chemical precursor for a peptide hormone?
Amino acids (polypeptides)
What is the chemical precursor for a steroid hormone?
Cholesterol
Where is the receptor fir a peptide hormone?
On the cell membrane
Where is the receptor fir a steroid hormone?
Inside the cell
What is the mechanism of action for a peptide hormone?
Stimulates a receptor (usually a G protein-coupled receptor), affecting levels of second messengers (commonly cAMP)
Initiates a signal cascade
What is the mechanism of action for a steroid hormone?
Binds to a receptor, induces conformational change and regulates transcription at the level of the DNA
What is the method of travel in the bloodstream for a peptide hormone?
Dissolves and travels freely
What is the method of travel in the bloodstream for a steroid hormone?
Binds to a carrier protein
How fast do the effects of a peptide hormone onset?
Very quickly
How fast do the effects of a steroid hormone onset?
Very slowly
What is the duration of action for a peptide hormone?
Short-lived
What is the duration of action for a steroid hormone?
Long-lived
How are amino acid-derivative hormones synthesized?
Amino acid-derivative hormones are made by modifying amino acids, such as the addition of iodine to tyrosine (in thyroid hormone production)
Direct hormone
Secreted into the bloodstream and travel to a target tissue where they have direct effects
Tropic hormone
Cause secretion of another hormone that then travels to the target tissue to cause an effect
Hypothalamus hormones
Gonadotropin-releasing hormone (GnRH), corticotropin-releasing factor (CRF), thyroid-releasing hormone (TRH), dopamine and growth hormone-releasing hormone (GHRH)
Gonadotropin-releasing hormone (GnRH)
Releases follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary
Corticotropin-releasing factor (CRF)
Releases adrenocorticotropic hormone (ACTH) from the anterior pituitary
Thyroid-releasing hormone (TRH)
Releases thyroid stimulating hormone (TSH) from the anterior pituitary
Dopamine (Prolactin-inhibiting factor, PIF)
A decrease in dopamine promotes prolactin secretion by the anterior pituitary
Growth hormone-releasing hormone (GHRH)
Releases growth hormone (GH) from the anterior pituitary
What is the target organ of gonadotropin-releasing hormone (GnRH)?
Ovaries or testes
What is the target organ of corticotropin-releasing factor (CRF)?
Adrenal cortex
What is the target organ of thyroid-releasing hormone (TRH)?
Thyroid gland
What is the target organ of dopamine?
Breast tissue
What is the target organ of growth hormone-releasing hormone (GHRH)?
Muscles and bones
What are the hormones released by the target organ of gonadotropin-releasing hormone (GnRH)?
Estrogen and progesterone or testosterone
What are the hormones released by the target organ of corticotropin-releasing factor (CRF)?
Glucocorticoids (cortisol and cortisone)
What are the hormones released by the target organ of thyroid-releasing hormone (TRH)?
Triiodothyronine (T3) and thyroxine (T4)
Which two hormones are primarily involved in calcium homeostasis?
Calcitonin and parathyroid hormone
Which endocrine tissue synthesizes catecholamines?
The adrenal medulla
What are the two main catecholamines it produces?
Epinephrine and norepinephrine
Which two pancreatic hormones are the major drivers of glucose homeostasis?
Insulin and glucagon
Where does insulin come from?
Beta cells in the pancreas
Where does glucagon come from?
Alpha cells in the pancreas
What effect does insulin have on blood glucose?
Lowers it by stimulating glucose uptake by cells and anabolic processes like glycogen, fat and protein synthesis
What effect does glucagon have on blood glucose?
Increases it by stimulating protein and fat degradation, glycogenolysis and gluconeogenesis
Which three hormones are primarily involved in water homeostasis?
Antidiuretic hormone (ADH or vasopressin), aldosterone and atrial natriuretic peptide (ANP)
What releases calcitonin?
Parafollicular (C-) cells of the thyroid
Calcitonin
Decreases blood calcium concentration by promoting calcium excretion in the kidneys, decreasing calcium absorption in the gut and promoting calcium storage in bones
What releases parathyroid hormone?
Parathyroid glands
Parathyroid hormone (PTH)
Increases blood calcium concentration by decreasing calcium excretion by the kidneys and increasing bone resorption
Activates vitamin D
Promotes resorption of phosphate from bone
Reduces phosphate reabsorption in the kidney
What releases antidiuretic hormone (ADH or vasopressin)?
The hypothalamus via posterior pituitary
Antidiuretic hormone (ADH or vasopressin)
Increases blood volume and decreases blood osmolarity
By increasing reabsorption of water in the collecting duct of the nephron
What releases aldosterone?
Adrenal cortex
Aldosterone
Increases blood volume with no effect on blood osmolarity by promoting sodium reabsorption in the distal convoluted tubule and collecting duct, thus increasing water reabsorption
Increases potassium and hydrogen ion excretion
Regulated by renin-angiotensin-aldosterone system
What releases atrial natriuretic peptide (ANP)?
The heart
Atrial natriuretic peptide (ANP)
Decreases blood volume with no effect on blood osmolarity by promoting excretion of salt and water in the kidneys in response to stretching to the atria (high blood volume)
Are peptide hormones polar or non-polar?
Polar
Can peptide hormone pass through the cell membrane?
No, because they are polar
Are steroid hormones polar or non-polar?
Non-polar
Can steroid hormones pass through the cell membrane?
Yes, because they are non-polar
How do steroid hormones function?
They bind to and promote a conformational change of intracellular or intranuclear receptors; the hormone-receptor complex binds to DNA, affecting the transcription of a particular gene
Amino acid-derivative hormones
Modified amino acids
Share some features with peptide hormones and some features with steroid hormones
Examples of amino acid-derivative hormones
Epinephrine, norepinephrine, triiodothyronine and thyroxine
Do direct hormones affect endocrine or non-endocrine tissues?
Non-endocrine
Do tropic hormones affect endocrine or non-endocrine tissues?
Endocrine
What is the bridge between the nervous and endocrine systems?
The hypothalamus
Negative feedback
The final hormone (or product) of a pathway inhibits hormones (or enzymes) earlier in the pathway, maintaining homeostasis
How does the hypothalamus stimulate the anterior pituitary gland?
Through paracrine release of hormones into the hypophyseal portal system, which directly connects the two organs
Anterior pituitary hormones
Follicle-stimulating hormone (FSH), luteinizing hormone (LH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), prolactin, endorphins and growth hormones
Tropic hormones released by the anterior pituitary
FSH, LH, ACTH and TSH
Direct hormones released by the anterior pituitary
Prolactin, endorphins and growth hormones
Posterior pituitary
Releases two hormones produced in the hypothalamus: Antidiuretic hormone (ADH or vasopressin) and oxytocin
What triggers ADH release?
Low blood volume or increased blood osmolarity
Oxytocin
Secreted during childbirth and promotes uterine contractions
Promotes milk ejection
Involved in bonding behavior
Has a positive feedback loop
Hormones produced by the thyroid
Triiodothyronine (T3), thyroxine (T4) and calcitonin
Hormones released by follicular cells
T3 and T4
Triiodothyronine (3) and thyroxine (T4)
Contain iodine
Increase metabolic rate
Alter utilization of glucose and fatty acids
Vitamin D
Necessary for calcium and phosphate absorption from the gut
Adrenal cortex hormones
Cortisol, cortisone, aldosterone, androgens (like testosterone) and estrogen
Glucocorticoids released by the adrenal cortex
Cortisol and cortisone
Mineralocorticoids released by the adrenal cortex
Aldosterone
Cortical sex hormones released by the adrenal cortex
Androgens (like testosterone) and estrogen
Cortisol and cortisone
Increase blood glucose concentration Reduce protein synthesis Inhibit the immune system Participate in the stress response Stimulated by ACTH
How is aldosterone regulated?
By the renin-angiotensin-aldosterone system
Adrenal medulla hormones
Epinephrine and norepinephrine
Epinephrine and norepinephrine
Involved in fight-or-flight response, promote glycogenolysis, increase the basal metabolic rate, increase heart rate, dilate the bronchi and alter blood flow
Hormones produced by the pancreas
Glucagon, insulin and somatostatin
What produces somatostatin?
Delta-cells of the pancreas
Somatostatin
Inhibits insulin and glucagon secretion
Pineal gland
Releases melatonin
Melatonin
Helps regulate circadian rhythms
Hormones produced by the stomach
Secretin, gastrin and cholecystokinin
Hormones produced by the kidneys
Erythropoietin
Erythropoietin
Stimulate bone marrow to produce erythrocytes in response to low oxygen levels in the blood
Hormones secretes by the thymus
Thymosin
Thymosin
Important for proper T-cell development and differentiation
What releases corticoids?
The adrenal cortex
What happens if there is overproduction of growth hormone in children?
Gigantism
What happens if there is overproduction of growth hormone in adults?
Acromegaly
Acromegaly
Enlargement of the small bones in the extremities and of certain facial bones, such as the jaw
What happens if there is a deficiency of growth hormone in children?
Dwarfism
Causes of hypothyroidism
Inflammation of the thyroid
Iodine deficiency
What happens if a newborn has hypothyroidism?
Cretinism
Cretinism
Poor neurological and physical development, including mental retardation, short stature and coarse facial features
Goiter
Swelling of the thyroid
Causes of hyperthyroidism
Goiter
Is oxytocin a peptide or steroid hormone?
Peptide
What stimulates somatostatin secretion?
High blood glucose or high blood amino acid levels
Is somatostatin inhibitory or excitatory?
Inhibitory
What stimulates renin production?
Low blood pressure causes the juxtaglomerular cells of the kidney to produce renin
Renin
An enzyme that converts the plasma protein angiotensinogen to angiotensin I
Where does angiotensin I convert into angiotensin II?
In the lungs via angiotensin-converting enzymes
Angiotensin II
Stimulates the adrenal cortex to secrete aldosterone
Is vasopressin a peptide or steroid hormone?
Peptide
Respiratory pathway
Nares –> nasal cavity –> pharynx –> larynx –> trachea –> bronchi –> bronchioles –> alveoli
Which muscles are involved in inhalation?
Diaphragm and external intercostal muscles
Muscles involved in exhalation?
Passive: recoil of diaphragm and external intercostal muscles
Active: internal intercostal muscles and abdomen
What is the purpose of surfactant?
Reduces surface tension at the air-liquid interface in the alveoli to prevent their collapse
What is the mathematical relationship between vital capacity (VC), inspiratory reserve volume (IRV), expiratory reserve volume (ERV) and tidal volume (TV)?
VC = IRV + ERV + TV
If blood levels of CO2 become too low, how does the brain alter the respiratory rate to maintain homeostasis?
Decrease breathing rate
What are some of the mechanisms used in the respiratory system to prevent infection?
Immune mechanisms in the respiratory system include vibrissae in the nares, lysosome in the mucous membranes, the mucociliary escalator, macrophages in the lungs, mucosal IgA antibodies and mast cells
What is the chemical equation for the bicarbonate buffer system?
CO2 (g) + H2O (l) H2CO3 (aq) H+ (aq) +HCO- (aq)
Respiratory failure refers to inadequate ventilation to provide oxygen to the tissues. How would the pH change in respiratory failure?
In respiratory failure, ventilation slows, and less carbon dioxide is blown off. As this occurs, the buffer equation shifts to the right, and more hydrogen ions are generated. This results in a lower pH of the blood.
Where does the air inhaled get warmed and humidified?
Nares
Vibrissae
Nasal hairs
Where does the air inhaled get filtered?
Nasal hairs (vibrissae), mucous membranes and mucocilliary escalator
Alveoli
Small sacs that interface with the pulmonary capillaries, allowing gases to diffuse across a one-cell-thick membrane
Where is surfactant?
In the alveoli
Pleurae
Cover the lungs and line the chest wall
Visceral pleura
Lies adjacent to the lung itself
Parietal pleura
Lines the chest wall
Intrapleural space
Lies between the visceral and partial pleurae and contains a thin later of fluid, which lubricates the two pleural surfaces
Diaphragm
A think skeletal muscle that helps to create the pressure differential required for breathing
Is inhalation an active or passive process?
Active
Inhalation (negative-pressure breathing)
The diaphragm and external intercostal muscles expand the thoracic cavity –> volume of the intrapleural space increases –> pressure of the intrapleural space decreases –> lungs expand –> lung pressure is dropped –> air from the environment enters
Is exhalation an active or passive process?
It can be either
Passive exhalation
Relaxation of the muscles of inspiration (diaphragm and external intercostal muscles) –> elastic recoil of the lungs –> chest cavity decreases in volume –> pressure differentials seen during inhalation are reversed
Active exhalation
Internal intercostal muscles and abdominal muscles are used to forcibly decrease the volume of the thoracic cavity –> air is pushed out
Spirometer
Measures lung capacities and volumes
Total lung capacity (TLC)
The maximum volume of air in the lungs when one inhales completely
Residual volume (RV)
The minimum volume of air in the lungs when one exhales completely
Vital capacity (VC)
The difference between the minimum and maximum volume of air in the lungs
Tidal volume (TV)
The volume of air inhaled or exhaled in a normal breath
Expiratory reserve volume (ERV)
The volume of additional air that can be forcibly exhaled after a normal exhalation
Inspiratory reserve volume (IRV)
The volume of additional air that can be forcibly inhaled after a normal inhalation
Ventilation center
Regulated ventilation
A collection of neurons in the medulla oblongata
Chemoreceptors
Respond to carbon dioxide concentrations, increasing the respiratory rate when there are high concentrations of carbon dioxide in the blood
Hypercarbia
High carbon dioxide concentrations in the blood
Hypercapnia
High carbon dioxide concentrations in the blood
How does the ventilation center respond to low oxygen concentrations in the blood?
Increasing breathing rate
Hypoxemia
Low oxygen concentrations in the blood
How can ventilation be consciously controlled?
With the cerebrum (although the medulla oblongata will override the cerebrum during extended periods of hypo- or hyperventilation)
How do lungs perform gas exchange with the blood?
Simple diffusion across concentration gradients
Pulmonary arteries
Carry deoxygenated blood with high carbon dioxide concentration to the lungs
Pulmonary veins
Carry oxygenated blood with low carbon dioxide concentration away from the lungs
How do lungs participated in thermoregulation?
The large surface area of interaction between the alveoli and capillaries allows the respiratory system to assist in thermoregulation through vasodilation and vasoconstriction of capillary beds
How do lysozyme in the nasal cavity and saliva protect the respiratory system?
Attack peptidoglycan cell walls of gram-positive bacteria
How do macrophages protect the respiratory system?
They engulf and digest pathogens and signal to the rest of the immune system that there is an invader
What are mucosal surfaces covered with?
IgA antibodies
How do mast cells protect the respiratory system?
They have antibodies on their surface that, when triggered, can promote the release of inflammatory chemicals
Involved in allergic reactions
How is the respiratory system involved in pH control?
Through the bicarbonate buffer system
How does the respiratory system control pH when blood pH decreases?
Respiration rate increases to compensate by blowing off carbon dioxide. This causes a left shift in the buffer equation, reducing hydrogen ion concentration.
How does the respiratory system control pH when blood pH increases?
Respiration rate decreases to compensate by trapping carbon dioxide. This causes a right shift in the buffer equation, increasing hydrogen ion concentration.
Total lung capacity (TLC)
= VC (vital capacity) + RV (residual volume)
What can introducing fluid or air to the intrapleural space do?
Collapse the lung
Epiglottis
Covers the glottis during swelling to ensure that no food enters the trachea
Are the trachea and bronchi lined by ciliated epithelial cells?
Yes
Where are the vocal cords?
Larynx
What happens if the lungs become stiff?
Inspiratory reserve volume decreases
Hyperventilation
Decreases blood carbon dioxide concentration
Positive end-expiratory pressure
Providing a higher pressure than normal at the end of expiration, forcing extra air into the alveoli to prevent alveolar collapse
Heart chambers
Right atrium, right ventricle, left atrium, left ventricle
Which valve prevents back flow to the right atrium?
Tricuspid valve (between right atrium and right ventricle)
Which valve prevents back flow to the right ventricle?
Pulmonary valve (between right ventricle and pulmonary artery)
Which valve prevents back flow to the left atrium?
Mitral (bicuspid valve) (between left atrium and left ventricle)
Which valve prevents back flow to the left ventricle?
Aortic valve (between left ventricle and aortic artery)
Structures in the conduction system of the heart
Sinoatrial node (SA node) –> atrioventricular node (AV node) –> bundle of His (AV bundle) and its branches –> Purkinje fibers
In which direction do arteries carry blood?
Away from the heart
In which direction do capillaries carry blood?
From arterioles to venules
In which direction do veins carry blood?
Towards the heart
Are arteries thick or thin?
Thick
Are capillaries thick or thin?
Very thin (one cell layer)
Are veins thick or thin?
Thin
Do arteries have smooth muscles?
Yes (a lot)
Do capillaries have smooth muscles?
No
Do veins have smooth muscles?
Yes (a little)
Do arteries have valves?
No
Do capillaries have valves?
No
Do veins have valves?
Yes
Why does the right side of the heart contain less cardiac muscle than the left side?
The right side of the heart pumps blood into a lower-resistance circuit and must do so at lower pressure; therefore, it requires less muscle. The left side of the heart pumps blood into a higher-resistance circuit at higher pressures; therefore, it requires more muscle.
The left side of the heart contains more muscle than the right side because the systemic circulation has a much higher resistance and pressure.
If all autonomic input to the heart were cut, what would happen?
The heart would continue beating at the intrinsic rate of the pacemaker (SA node). The individual would be unable to change his or her heart rate via the sympathetic or parasympathetic nervous system, but the heart would not stop beating.
Components of plasma
Nutrients, salts, respiratory gases, hormones and blood proteins (clotting proteins, immunoglobulin, etc.)
Hematocrit
The percentage of a blood sample occupied by red blood cells
Hematocrit units
Percentage points
Which types of leukocytes are involved in the specific immune response?
Lymphocytes
Where do platelets come from?
Megakaryocytes in the bone marrow
Which cell types in blood contain a nucleus?
Leukocytes (including neutrophils, eosinophils, basophils, monocytes/macrophages and lymphocytes)
Which cell types in blood do not contain a nucleus?
Erythrocytes and platelets
Platelets
Cellular fragments or shards
In bacterial sepsis (overwhelming bloodstream infection), a number of capillary beds throughout the body open simultaneously. What effect would this have on the blood pressure? Besides the risk of infection, why might sepsis be dangerous for the heart?
Opening up more capillary beds (which are in parallel) will decrease the overall resistance of the circuit. The cardiac output will therefore increase in an attempt to maintain constant blood pressure. This is a risk to the heart because the increased demand on the heart can eventually tire it, leading to a heart attack or a precipitous drop in blood pressure.
What is the chemical equation for the bicarbonate buffer system?
CO2 (g) + H2O (l) H2CO3 (aq) H+ (aq) + HCO3- (aq)
What enzyme catalyzes the bicarbonate buffer system?
The combining of carb on dioxide and water is catalyzed by carbonic anhydrase
Where should you look on the oxyhemoglobin dissociation curve to determine the amount of oxygen that has been delivered to tissues?
The amount of oxygen deliver can be seen as a drop in the y-value (percent hemoglobin saturation) on an oxyhemoglobin dissociation curve.
E.g. if the blood is 100% saturated while in the lungs (at 100 mmHg O2) and only 80% saturated while in the tissues (40 mmHg O2), then 20% of the oxygen has been released to tissues.
What can cause a right shift of the oxyhemoglobin dissociation curve?
Increased CO2
Increased [H+] (i.e. decreased pH)
Increased temperature
Increased 2,3-BPG
What can cause a left shift of the oxyhemoglobin dissociation curve?
Decreased CO2
Decreased [H+] (i.e. increased pH)
Decreased temperature
Decreased 2,3-BPG
Exposure of which subendothelial compounds start the coagulation cascade?
Collagen and tissue factor
Which protein helps stabilize the clot formed by the coagulation cascade?
Fibrin
Cardiac output (CO)
= HR x SV = heart rate x stroke volume
Ohm’s law applied to circulation
delta P = CO x TPR
Cardiovascular system
Consists of a muscular four-chambered heart, blood vessels and blood
What kind of muscle composes the heart?
Cardiac muscle
What kind of circulation is supported by the heart?
Pulmonary circulation and systemic circulation
Atrioventricular valves
Separate the atria from the ventricles
Tricuspid (right heart)
Mitral (bicuspid) (left heart)
Where is the tricuspid valve?
Between the right atrium and the right ventricle
Where is the mitral (bicuspid) valve?
Between the left atrium and the left ventricle
How are the ventricles separated from the vasculature?
Semilunar valves
Pulmonary (right heart)
Aortic (left heart)
Where is the pulmonary valve?
Between the right ventricle and the pulmonary artery
Where is the aortic valve?
Between the left ventricle and the aortic artery
Pathway of blood
Right atrium –(tricuspid valve)–> right ventricle –(pulmonary valve)–> pulmonary artery –> lungs –> pulmonary veins –> left atrium –(mitral valve)–> left ventricle –(aortic valve)–> aorta –> arteries –> arterioles –> capillaries –> venules –> veins –> venae cavae –> right atrium
Systole
The period during ventricular contraction when the AV valves are closed
Diastole
The heart is relaxed and the semilunar valves are closed
Arteries
Thick, highly muscular structures with an elastic quality
Why is it important for arteries to have an elastic quality?
For recoil and propelling blood forward within the system
Arterioles
Small muscular arteries that control flow into the capillary beds
Have the ability to contract and dilate in order to affect blood pressure
Capillaries
Have walls that are one cell thick
They are the sites of gas and solute exchange
Why is it important for capillaries to have one-cell thick walls?
It makes them narrow enough that red blood cells can travel through them in single-file lines
Veins
Inelastic, thin-walled structures that transport blood to the heart
They are able to stretch, but they cannot recoil
Have valves
Why is it important for veins to be able to stretch?
To accommodate large volumes of blood
Since veins are able to stretch but cannot recoil, how are veins compressed?
By the surrounding skeletal muscles
Why is it important for veins to have valves?
To maintain one-way flow in the system
Venules
Small veins
Portal system
Blood passes through two capillary beds in series
Hepatic portal system
Blood travels from the gut capillary beds to the liver capillary bed via the hepatic portal vein
Hypophyseal portal system
Blood travels form the hypothalamus to the anterior pituitary
Renal portal system
Blood travels form the glomerulus to the vasa recta through an efferent arteriole
Erythrocytes (red blood cells)
Lack mitochondria, a nucleus and organelles
Why is it that erythrocytes lack mitochondria, a nucleus and organelles?
To make room for hemoglobin
Hemoglobin
A protein that carries oxygen
Leukocytes (white blood cells)
Partake in the immune system
Where are leukocytes (WBCs) formed?
In the bone marrow
Types of leukocytes
Granular leukocytes and agranulocytes
Granular leukocytes
Act in nonspecific immunity
Neutrophils, eosinophils, basophils
Agranulocytes
Act in specific immunity
Lymphocytes and monocytes
Thrombocytes (platelets)
Cell gradients from megakaryocytic that are required for coagulation
Blood antigens
A, B, O, Rh factor (D)
What is the relationship between I^A (A), I^B (B) and i (O)?
I^A (A) and I^B (B) are codominant
I (O) is recessive
Does an individual have ABO antibodies for ABO allele he or she has or does not have?
Does not have
Is positive Rh factor a dominant or recessive trait?
Dominant
What kind of antibodies would an Rh-negative individual create?
Anti-Rh antibodies, but only after exposure to Rh-positive blood
Blood pressure
The force per unit area that is exerted on the walls of blood vessels by blood
Divided into systolic and diastolic components
It must be high enough to overcome the resistance created by arterioles and capillaries, but low enough to avoid damaging the vasculature and surrounding structures
How is blood pressure measured?
With a sphygmomanometer
How is blood pressure maintained?
By baroreceptor and chemoreceptor reflexes
Hormones released when blood pressure is low
Aldosterone and antidiuretic hormone (ADH or vasopressin)
Hormones released when blood osmolarity is high
ADH (antidiuretic hormone or vasopressin)
Hormones released when blood pressure is high
Atrial natriuretic peptide (ANP)
Where does gas and solute exchange occur?
At the capillaries
What does gas and solute exchange rely on?
Concentration gradients to facilitate diffusion across the capillary walls
Are capillaries leaky?
Yes, which aids in transport of gases and solutes
Starling forces
Consist of hydrostatic pressure and osmotic (oncotic) pressure
Hydrostatic pressure
The pressure of the fluid within the blood vessel
Forces fluid out at the arteriolar end of a capillary bed
Osmotic pressure
The sucking pressure drawing water towards solutes
Oncotic pressure
Osmotic pressure due to proteins
Draws fluid back into the capsular bed at the venue end
Does hemoglobin exhibit cooperative binding?
Yes
Is there a high or low partial pressure of oxygen in the lungs?
High
Why is it important for the lungs to have high partial pressure of oxygen?
To promote the loading of oxygen onto hemoglobin
Is there a high or low partial pressure of oxygen in the tissues?
Low
Why is it important for the tissues to have low partial pressure of oxygen?
To promote the unloading of oxygen
Why is it important for hemoglobin to exhibit cooperative binging?
With each successive oxygen bound to hemoglobin, the affinity of the other subunits to oxygen increases. With each successive oxygen release from hemoglobin, the affinity of the other subunits to oxygen decreases.
How is carbon dioxide carried in the blood?
In the form of carbonic acid or bicarbonate and hydrogen ions
Why does carbon dioxide travel in the blood in the form of carbonic acid or bicarbonate and hydrogen ions?
Carbon dioxide is non polar and not particularly soluble, while bicarbonate, hydrogen ions and carbonic acid are polar and highly soluble
What does a right shift in the oxyhemoglobin dissociation curve mean?
Decreased affinity for oxygen
What does a left shift in the oxyhemoglobin dissociation curve mean?
Increased affinity for oxygen
Where can a left shift in the oxyhemoglobin dissociated curve be seen?
The lungs and in fetal hemoglobin
Coagulation
Results from an activation cascade
Endothelial lining of a blood vessel is damaged –> collagen and tissue factor underlying the endothelial cells are exposed –> Coagulation cascade is activated –> Blood clot forms over the damaged area
What is fibrin activated by?
Thrombin
How can clots be broken down?
By plasmin
Are erythrocytes aerobic or anaerobic?
Anaerobic
Where are erythrocytes phagocytized?
In the spleen and liver
Where are erythrocytes produced?
In the red bone marrow
How long do erythrocytes circulated in the blood?
For 120 days
What is the correct sequence of a cardiac impulse?
SA node –> atria –> AV node –> bundle of His –> Purkinje fibers –> ventricles
How does the osmotic pressure relate to the hydrostatic pressure at the venous end of a capillary bed?
It is greater than the hydrostatic pressure
How does the osmotic (oncotic) pressure change in a capillary end from the arterial end to the venous end?
It doesn’t
How does the hydrostatic pressure change in a capillary end from the arterial end to the venous end?
It decreases from the arterial end to the venous end
Do proteins normally cross the capillary wall?
No
How is pressure in the aorta related to pressure in the superior vena cava?
It is always higher than the pressure in the superior vena cava
Due to kidney disease, a person is losing albumin into the urine. What effect is this likely to have within the capillaries?
Decreased oncotic pressure
What generates osmotic (oncotic) pressure?
Plasma proteins
The world record for the longest-held breath is 22 minutes and 0 seconds. If a sample were taken from this individual during the last minute of breath-holding, which of the following might be observed?
Decreased pH
Holding one’s breath for a prolonged period would result in a drop of oxygenation and an increase in pCO2. The increased carbon dioxide would associate with water to form carbonic acid, which would dissociate into a proton and bicarbonate anion. Further, the low oxygen saturation would eventually lead to anaerobic metabolism in some tissues, causing an increase in lactic acid. These would all lead to a decreased pH
A person has a heart attack that primarily affects the wall between the two ventricles. Which portion of the electrical conduction system is most likely affected?
Bundle of His
Which vascular structure creates the most resistance to blood flow?
Arterioles
Which vascular structure creates the greatest drop in blood pressure?
Arterioles
Innate (nonspecific) immunity
Consists of defenses that are always active against pathogens, but that are not capable of targeting specific invaders and cannot maintain immunologic memory
Adaptive (specific) immunity
Response targets a specific pathogen and maintains immunologic memory of the infection to mount a faster response during subsequent infections
Site of B-cell development
Bone marrow
Site of T-cell development
Bone marrow
Site of B-cell maturation
Bone marrow (but are activated in the spleen or lymph nodes)
Site of T-cell maturation
Thymus
Major functions of B-cells
Produce antibodies
Major functions of T-cells
Coordinate immune system and directly kill infected cells
Are B-cells specific or nonspecific?
Specific
Are T-cells specific or nonspecific?
Specific
Are B-cells humoral or cell-mediated?
Humoral
Are T-cells humoral or cell-mediated?
Cell-mediated
Which cells are considered granulocytes?
Neutrophils, eosinophils, basophils and mast cells
Which cells are considered agranulocytes?
Lymphocytes (B-cells and T-cells) and macrophages (monocytes)
Is innate immune faster or slowed than adaptive immunity?
Faster
Site of B-cell activation
Spleen or lymph nodes
What is the immunologic function of skin?
Physical barrier
Secretion of antimicrobial enzymes
What is the immunologic function of defensins?
Antibacterial enzymes on the skin
What is the immunologic function of lysozyme?
Antimicrobial
Present in tears and saliva
What is the immunologic function of mucus?
Present on mucous membranes
Traps incoming pathogens (in the respiratory system, cilia propel the mucus upward so it can be swallowed or expelled)
What is the immunologic function of stomach acid?
Antimicrobial
What is the immunologic function of normal gastrointestinal flora?
Provides competition, making it hard for pathogenic bacteria to grow in the gut
What is the immunologic function of complement?
A set of proteins in the blood that can create holes in bacteria
Which cells are professional antigen-presenting cells?
Macrophages, dendritic cells in the skin, some B-cells and certain activated epithelial cells
MHC-I
Found in all nucleated cells and presents proteins created within the cell (endogenous antigens); this can allow for detection of cells infected with intracellular pathogens (especially viruses)
MHC-II
Only found in antigen-presenting cells and presents proteins that result from the digestion of extracellular pathogens that have been brought in by endocytosis (exogenous antigens)
What activates natural killer cells?
Cells that do not present MHC (such as virally infected cells and cancer cells)
What activates neutrophils?
Bacteria, especially those that have been opsonized (tagged with an antibody on their surface)
What activates eosinophils?
Invasive parasites and allergens
What activates basophils?
Allergens
What activates mast cells?
Allergens
Where are defensins?
On the skin
Where are lysozymes?
In tears and saliva
Where are mucosa?
On mucous membranes
Where are complements?
In the blood
Where is MHC-I?
On all nucleated cells
Where is MHC-II?
On antigen-presenting cells
Opsonization
Mark a pathogen for destruction by phagocytic cells
Plasma cell
Form from B-cells exposed to antigen and produce antibodies
Memory B-cell
Form from B-cells exposed to antigen and lie in wait for a second exposure to a I=given antigen to be able to mount a rapid, robust response
Helper T-cell (CD4+ cells)
Coordinate the immune system through lumphokines and respond to antigen bound to MHC-II
Cytotoxic T-cell (CD8+ cells)
Directly kill virally infected cells and response to antigen bound to MHC-I
Suppressor (regulatory) T-cell
Quell the immune response after a pathogen has been cleared and promote self-tolerance
Memory T-cell
Lie in wait until a second exposure to a pathogen to be able to mount a rapid, robust response
What are the three main effects circulating antibodies can have on a pathogen?
Opsonization, causing angulation of the pathogen in insoluble complexes that can be taken up by phagocytic cells, or neutralize the pathogen by preventing its ability to invade tissues
How do antibodies become specific for a given antigen?
B-cells originally mature in the bone marrow and have some specificity at that point; however, antibodies that can respond to a given antigen undergo hypermutation, or rapid mutation of their antigen-binding sites. Only those B-cells that have the highest affinity for the antigen survive and proliferate, increasing the specificity for the antigen over time.
Positive selection
Occurs when T-cells in the thymus that are able to respond to antigen presented on MHC are allowed to survive (those that do not respond undergo apoptosis)
Negative selection
Occurs when T-cells that respond to self-antigens undergo apoptosis before leaving the thymus
Which cells account for the fact that the secondary response to a pathogen is much more rapid and robust than the primary response?
Memory cells
Active immunity
The stimulation of the immune system (activation of B-cells) to produce antibodies against a pathogen
Passive immunity
The transfer of antibodies to prevent infection, without stimulation of the plasma cells that produce these antibodies
Filariasis is the name for an infection with a certain group of parasites, most notable Wuchereria bancrofti. This parasite resides in lymph nodes and causes blockage of flow. If an individual had W. bancrofti infection in the lymph nodes of his or her thigh, what would likely happen?
Fluid would be unable to return from the lower leg, and edema would result. This infection leads to elephantiasis, severe swelling of the limb with thickening of the skin.
What structure is primarily responsible for returning material from lymphatic circulation to the cardiovascular system?
The thoracic duct carries lymphatic fluid into the left subclavian vein
The immune system divisions
Innate immunity
Adaptive immunity
Where do immune cells come from?
Bone marrow
Where are immune responses mounted?
Spleen and lymph nodes
Gut-associated lymphoid tissue (GALT)
Tonsils and adenoids
Nonspecific (innate) noncellular defenses
Skin, defensins, mucous, lysozyme, stomach acid, colonization of the gut (i.e. flora), complement, interferons
Interferons
Given off by virally infected cells and help prevent viral replication and dispersion to nearby cells
Nonspecific (innate) cellular defenses
Macrophages, MHC-I, MHC-II, dendritic cells, natural killer cells, granulocytes (neutrophils, eosinophils, basophils, and mast cells)
Macrophages
Ingest bathoses and present them on major histocompatibility complex (MHC)
Secrete cytokines
Dendritic cells
Antigen presenting cells in the skin
Where are dendritic cells?
In the skin
Natural killer cells
Attack cells not presenting MHC molecules, including virally infection cells and cancer cells
Neutrophils
Ingest bacteria, particularly opsonized bacteria
Can follow bacteria using chemotaxis
How do neutrophils follow bacteria?
Chemotaxis
Eosinophils
Usual in allergic reactions and invasive parasitic infections
Releases histamine, causing an inflammatory response
Basophils
Used in allergic reactions
Mast cells
Used in allergic reactions
Found in the skin
Where are mast cells?
In the skin
Humoral identity
Centered on antibody production by plasma cells, which are activated by B-cells
How are plasma cells activated?
By B-cells
Antibodies
Target a particular antigen
Contain two heavy chains and two light chains
Have a constant region and variable region
The tip of the variable region is the antigen-binding region
What happens when an antibody is activated?
The antigen-binding region undergoes hypermutation to improve the specificity of the antibody produced
Cells may be given signals to switch isotopes of antibody (IgM, IgD, IgG, IgE, IgA)
What do cell-surface antibodies do?
Activate immune cells or mediate allergic reactions
Humoral immunity activation
Antibodies bind to antigens –> hypermutation in the antigen-binding region occurs –> antibody-antigen complex response (opsonization, aggulation or neutralization) –> immune response activated or allergic reaction activated –> Memory B-cells wait for second exposure in order to become more rapid
Cell-mediated (cytotoxic) immunity
Centered on the functions of T-cells
T-cells undergo maturation in thymus through positive selection and negative selection –> the peptide hormone thyroxine promotes T-cell development –> helper T-cells respond to antigen on MHC-II and coordinate the rest of the immune response, secreting lymphokines to activate various arms of immune defense –> Th1 cells secrete interferon gamma, which acerbates macrophages –> Th2 cells activate B-cells, primarily in parasitic infections –> cytotoxic T-cells (Tc, CTL, CD8+) respond to antigen on MHC-I and kill virally infected cells –> suppressor (regulatory) T-cells (Treg) tone down the immune response after an infection and promote self-tolerance
Autoimmune conditions
A self-antigen is recognized as foreign, and the immune system attacks normal cells
Allergic reactions
Nonthreatening exposures incite an inflammatory response
What form of immunity is immunization?
Active immunity
Lymphatic system
A circulatory system that consists of one-way vessels with intermittent lymph nodes
Equalizes fluid distribution, transports fats and fat-soluble compounds in chylomicrons and provides sites for mounting immune responses
How does the lymphatic system connect to the cardiovascular system?
Thoracic duct in the posterior chest
In DiGeorge syndrome, the thymus can be completely absent. The absence of the thymus would leave an individual unable to mount specific defenses against which of the following types of pathogens?
Viruses
T-lymphocytes, which mature in the thymus, are the only specific defense against intracellular pathogens.
Where are most self-reactive T-cells eliminated?
Thymus
What is the response of the immune system to down regulation of MHC molecules on somatic cells?
Natural killer cells induce apoptosis of affected cells
Healthy cells exhibit MHC-I molecules. Natural killer cells monitor the expression of MHC molecules on the forces of cells. Viral infection and cancer often cause a reduction in the expression of MHC-I molecules on the cell surface. Natural killer cells detect this lack of MHC and induce apoptosis in the affected cells
What happens when CD8+ T-cells are activated?
Cytotoxic chemicals are secreted
Lymphoma is cancer of the cells of the lymphoid lineage. These cells often reside within lymph nodes. What type of cell is not likely to cause a lymphoma?
Any cell that is not in the B-cell or T-cell lineages
Clonal selection
When the adaptive immune system encounters an antigen, only the cells with receptors (antibodies or T-cell receptors) specific to that antigen are activated
Which cell type is a phagocyte that attacks bacterial pathogens in the bloodstream?
Neutrophils
Dendritic cells also have a similar function, but they exist in the skin, not the bloodstream
What type of immunity is likely to be affected by removal of the spleen?
Humoral immunity because it’s where B-cells mature and proliferate
Mechanical digestion
Physically breaks food into smaller pieces
e.g. chewing
Chemical digestion
Involves hydrolysis of bonds and breakdown of food into smaller biomolecules
Path of food through the body
Oral cavity (mouth) –> pharynx –> esophagus –> stomach –> small intestine –> large intestine –> rectum –> anus
What effect does the parasympathetic nervous system have on the digestive system?
Increases secretion from all of the glands of the digestive system and promotes peristalsis
What effect does the sympathetic nervous system have on the digestive system?
Decreases secretion from all of the glands of the digestive system and slows peristalsis
What two main enzymes are found in the saliva?
Salivary amylase (ptyalin) and lipase
What does the mucous cell secrete?
Mucus (rich in bicarbonate)
What does the chief cell secrete?
Pepsinogen
What does the parietal cell secrete?
HCl and intrinsic factor
What does the G-cell secrete?
Gastrin
What does the mucous cell do?
Protects lining of stomach Increases pH (bicarbonate)
What does the chief cell do?
Digests proteins once activated by H+
What does the parietal cell do?
HCl: decreases pH, kills microbes, denatures proteins, some chemical digestion
Intrinsic factor: absorption of vitamin B12
What does the G-cell do?
Increases HCl production
Increases gastric motility
Is sucrase an enzyme or a hormone?
Enzyme
Is secretin an enzyme or a hormone?
Hormone
Is Dipeptidase an enzyme or a hormone?
Enzyme
Is cholecystokinin an enzyme or a hormone?
Hormone
Is enteropeptidase an enzyme or a hormone?
Enzyme
What does sucrase do?
Brush-border enzyme
Breaks down sucrose (a disaccharide) into monosaccharides (glucose and fructose)
What does secretin do?
Increases pancreatic secretions into the digestive tract, especially bicarbonate
Reduces HCl secretion
Decreases motility
What does dipeptidase do?
Brush-border enzyme
Breaks down dipeptides into free amino acids
What does cholecystokinin do?
Recruits secretions from gallbladder and pancreas
Promotes satiety
What does enteropeptidase do?
Activates trypsinogen and procarboxypeptidases, which initiates an activation cascade
How do bile and pancreatic lipase work together to digest fats?
Bile accomplishes mechanical digestion of fats, emulsifying them and increasing their surface area. Pancreatic lipase accomplishes chemical digestion of fats, breaking their ester bonds.
Salivary amylase (ptyalin)
Digests starch into smaller sugars (maltose and dextrin)
Lipase
Digests fats
Which pancreatic enzyme(s) can digest carbohydrates?
Pancreatic amylase
Which pancreatic enzyme(s) can digest proteins?
Trypsin, chymotrypsin, carboxypeptidases A and B
Which pancreatic enzyme(s) can digest fats?
Pancreatic lipase
What are the main components of bile?
Bile salts (amphipathic molecules derived from cholesterol that emulsify fats), piglets (especially bilirubin from the breakdown of hemoglobin) and cholesterol
Where is bile synthesized?
Liver
Where is bile stored?
gallbladder
Where does bile carry out its digestive function?
Duodenum
Functions of the liver
Process nutrients (through glycogenesis and glycogenolysis, storage and mobilization of fats and gluconeogenesis) Produces urea Detoxifies chemicals Activates or inactivates medications Produces bile Synthesizes albumin and clotting factor
The accessory organs of digestion originate from which primary germ layer?
Endoderm
Bile salts
Amphipathic molecules derived from cholesterol that emulsify fats
How does the liver process nutrients?
Glycogenesis
Glycohenolysis
Storage and mobilization of fats
Gluconeogenesis
What are the two circulatory vessels in a villus?
Capillaries and lacteals
What are the four fat-soluble vitamins?
Vitamins A, D, E, K
What are the three sections of the small intestine?
Duodenum, jejunum and ileum
What are the three sections of the large intestine?
Cecum, colon and rectum
Vibrio cholera causes a severe infection in the intestines, leading to massive volumes of watery diarrhea - up to 20 liters per day. Given these symptoms, Dows cholera likely impose the small intestine or the large intestine?
While the large intestine’s main function is to absorb water, the small intestine actually absorbed a much larger volume of water. This, massive volumes of watery diarrhea are more likely to arise from infections in the small intestine than the large intestine.
What do the capillaries in a villus absorb?
Water-soluble nutrients
e.g. monosaccharides, amino acids, small fatty acids, water-soluble vitamins and water
What do the lacteals in a villus absorb?
Fat-soluble nutrients
e.g. fats, cholesterol and dat-soluble vitamins
Intracellular digestion
Involves the oxidation of glucose and fatty acids to make energy
Extracellular digestion
Occurs in the lumen of the alimentary canal
Accessory organs of digestion
Salivary glands, pancreas, liver and gallbladder
Enteric nervous system
In the wall of the alimentary canal and controls peristalsis
Its activity is unregulated by the parasympathetic nervous system and down regulated by the sympathetic nervous system
Hormones that regulate feeding behavior
Antidiuretic hormone (ADH or vasopressin), aldosterone, glucagon, ghrelin, leptin and cholecystokinin
How does antidiuretic hormone (ADH or vasopressin) regulate feeding behavior?
Promotes thirst
How does aldosterone regulate feeding behavior?
Promotes thirst
How does glucagon regulate feeding behavior?
Promotes hunger
How does ghrelin regulate feeding behavior?
Promotes hunger
How does leptin regulate feeding behavior?
Promotes satiety
How does cholecystokinin regulate feeding behavior?
Promotes satiety
Digestion in the oral cavity
Mastication starts the mechanical digestion of food
Salivary amylase and lipase start the chemical digestion food
Food is formed into a bolus and swallowed
Pharynx
Connects the moth and posterior nasal cavity to the esophagus
Esophagus
Propels food to the stomach using peristalsis
How does food enter the stomach?
Through the lower esophageal (cardiac) sphincter)
Parts of the stomach
Fundus, body, antrum and pulorus
Stomach
Has a lesser and greater curvature and is thrown into folds called rugae
Secretory cells lining the stomach
Mucous cells, chief cells, partial cells and G-cells
Pepsinogen
Secreted by chief cells in the stomach
A protease activated by the acidic environment of the stomach
Gastrin
Secreted by G-cells in the stomach
A peptide hormone that increases HCl secretion and gastric motility
Chyme
Food particles that have undergone mechanical and chemical digestion in the stomach
How does food pass into the duodenum?
Through the pyloric sphincter
Duodenum
The first part of the small instance
Primarily involved in chemical digestion
Disaccharidases
Brush-border enzymes that break down maltose, iso-maltose, lactose, and sucrase into monosaccharides
Peptidases
Brush-border enzymes
Types of peptidases
Aminopeptidase and dipeptidase
Acinar cells
In the pancreas
Produce pancreatic juices that contain bicarbonate, pancreatic amylase, pancreatic peptidases and pancreatic lipase
Pancreatic peptidases
Trypsinogen, chymotrypsinogen, carboxypeptidases A and B
Bile
Emulsifies fats, making them soluble and creasing their surface area
Gallbladder
Stores and concentrates bile
Jejunum
In the small intestine
Primarily involved in absorption
Ileum
In the small intestine
Primarily involved in absorption
What is the small intestine lined with?
Villi
What are the villi of the small intestine covered with?
Microvilli
Microvilli
Cover the villi of the small intestine to increase their surface are available for absorption
Lacteal
A vessel of the lymphatic system
Large intestine
Absorbs water and salts, forming semisolid feces
Cecum
An out pocketing that accepts fluid from the small intestine through the iléocaecal valve
The site of attachment of the appendix
Colon divisions
Ascending, transverse, descending and sigmoid portions
Rectum
Stores feces
Anus
Excretes feces
What do gut bacteria produce?
Vitamin K and biotin (vitamin B7)
Biotin
Vitamin B7
Do G-cells produce HCl?
No, they produce gastrin
What produces HCl in the stomach?
Parietal cells
Do chief cells produce pepsinogen?
Yes
Do parietal cells produce alkaline mucus?
No, they they produce HCl and intrinsic factors
What produces alkaline mucus in the stomach?
Mucous cells
Do mucous cells produce intrinsic factor?
No, they produce alkaline mucus
What produces intrinsic factor in the stomach?
Parietal cells
In an experiment, enteropeptidase secretion was blocked. As a direct realist, levels of all of the following active enzymes would likely be affected except:
a. Trypsin
b. Aminopeptidase
c. Chymotrypsin
d. Carboxypeptidase A
Aminopeptidase
Aminopeptidase is a brush-border peptidase secreted by the cells lining the duodenum; it does not require enteropeptidase for activation. Both trypsinogen and procarboxypeptidases A and B are activated by enteropeptidase. Once activated, trypsin can activate chymotrupsinogen; if trypsinogen cannot be activated, then chymotrypsinogen will not be activated either.
Does trypsin hydrolyze specific peptide bonds?
Yes
Does lactase hydrolyze lactose to glucose and galactose?
Yes
Does pancreatic amylase hydrolyze starch to maltose?
Yes
Does lipase emulsify fats?
No, it is involved in the digestion of fats chemically in the duodenum, allowing them to be brought into duodenal cells and packaged into chylomicrons
What emulsifies fats in the intestines?
Bile
Where are proteins digested?
In the stomach and small intestines
Stomach digestion of proteins
Pepsin (secreted as pepsinogen) hydrolyzes specific peptide bonds
Small intestines digestion of proteins
Trypsin (secreted as trypsinogen), chymotrypsin (secreted as chymotrypsinogen), carboxypepdases A and B (secreted as procarboxypeptidases A and B), amino peptidase and dipeptidases hydrolyze specific parts of the peptide
Is sucrase secreted by the salivary glands?
No, it is a brush-border enzyme found on duodenal cells
Is carboxypeptidase secreted by the pancreas?
Yes
Is trypsin secreted by the pancreas?
Yes
Is lactase secreted by the duodenum?
Yes
A two-week-old male infant is bright to the ER. His mother reports that he has been unable to keep any milk down; shortly after he nurses, he has sudden projectile vomiting. During exam, an olive-shaped mass can be felt in his upper abdomen. It is determined that there is a constriction in the digestive system that prevents food from reaching the small instant from the stomach. Which structure is most likely the site of the problem?
Pyloric sphincter
Many medications have anticholinergic side effects, which block the activity of parasympathetic neurons throughout the body. Older individuals may be on many such medications simultaneously, exacerbating the side effects. Which of the following would not be expected in an individual taking medications with anticholinergic activity?
a. Dry mouth
b. Diarrhea
c. Slow gastric emptying
d. Decreased gastric acid production
Diarrhea
Enzymes in the stomach function in which pH range?
Acidic pH
Enzymes in the duodenum function in which pH range?
Neutral-slightly alkaline pH
Cholangiocarcinoma: a cancer of the bile ducts that can ultimately lead to full occlusion of the duct lumen
Can it lead to elevated levels of bilirubin in the blood?
Yes
Autoimmune hemolytic anemia: a disease in which the RBCs are attacked by antibodies and are lysed
Can it lead to elevated levels of bilirubin in the blood?
Yes
Ménétrier’s disease: rugae thicken and overlying glands lose secretory ability
Can it lead to elevated levels of bilirubin in the blood?
No
Acetaminophen (Tylenol) overdose: the accumulation go toxic metabolites can cause rapid liver failure
Can it lead to elevated levels of bilirubin in the blood?
Yes
Elevated bilirubin
Implies a blockage to bile flow, increased production of bilirubin (from massive hemoglobin release), or an inability of the liver to produce bile
Rugae
Folds in the stomach wall
What is the primary site of chylomicrons absorption?
Lacteals in small intestines
What is the primary site of amino acid absorption?
Capillary beds in small intestines
What is the primary site of vitamins A and E absorption?
Lacteals in small intestines
What is the primary site of cholesterol absorption?
Lacteals in small intestines
Starch is hydrolyzed into maltose by enzymes from:
Salivary glands and pancreas
Does vitamin D (cholecalciferol) drain to the liver before arriving at the right side of the heart?
No
Does threonine (an amino acid) drain to the liver before arriving at the right side of the heart?
Yes
Does fructose (a monosaccharide) drain to the liver before arriving at the right side of the heart?
Yes
Does vitamin B5 (pantothenic acid) drain to the liver before arriving at the right side of the heart?
Yes
Where do capillary beds in the small intestines lead to?
They come together, forming the portal vein, which drains to the liver
Where do lacteals in the small intestines lead to?
They come together, forming the thoracic duct, which drains directly into the left subclavian vein
Structures in the excretory pathway
Bowman’s space –> proximal convoluted tubule –> descending limb of the loop of Henle –> ascending limb of the loop of Henle –> distal convoluted tubule –> collecting duct –> renal pelvis –> ureter –> bladder –> urethra
Vessels in the renal vascular pathway
Renal artery –> afferent arteriole –> glomerulus –> efferent arteriole –> vasa recta –> renal vein
What arm of the nervous system is responsible for contraction of the detrusor muscle?
The parasympathetic system
What are the three processes by which solutes are exchanged between the filtrate and the blood?
Filtration, secretion and reabsorption
Bowman’s capsule
The site of filtration, through which water, ions, amino acids, vitamins, and glucose pass (essentially everything besides cells and proteins)
Proximal convoluted tubule (PCT)
Controls solute identity, reabsorbing vitamins, salt, water, amino acids and glucose, while secreting potassium and hydrogen ions, ammonia and urea
Descending limb of the loop of Henle
Water reabsorption using the medullary concentration gradient
Permeable to water, but not salt
Ascending limb of the loop of Henle
Salt reabsorption and allowing dilution go the urine in the diluting segment (passive and active reabsorption)
Permeable to salt, but not water
Distal convoluted tubule (DCT)
Reabsorbing salts while secreting potassium and hydrogen ions, ammonia and urea
Responsive to aldosterone only
Collecting duct
Urine concentration
Its variable permeability allows water to be reabsorbed based on the needs of the body
Responsive to aldosterone and antidiuretic hormone
Filtration
The movement of solutes from blood into filtrate at Bowman’s capsule
The direction and rate of filtration is determined by Starling forces, which account for the hydrostatic and oncotic pressure differentials between the glomerulus and Bowman’s space
Secretion
The movement of solutes from blood into filtrate anywhere besides Bowman’s capsule
Reabsorption
The movement of solutes from filtrate into blood
What is the predominant cell type in the epidermis?
Keratinocytes
What are the layers of the epidermis, from superficial to deep?
Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale
What are the layers of the dermis, from superficial to deep?
Papillary layer
Reticular layer
What are some mechanisms the body uses to cool itself?
Sweating
Vasodilation
What are some mechanisms the body uses to retain heat?
Shivering
Vasoconstriction
Piloerection
Insulation provided by fat
Excretory system
Regulation of blood pressure
Blood osmolarity
Acid-base balance
Removal of nitrogenous wastes
Kidney
Produces urine
Pathway of urine
Leaves the kidney –> renal pelvis –> ureter –> bladder –> urethra
Parts go the kidney
Cortex, medulla, hilum
Kidney hilum
Contains a renal artery, renal vein and ureter
Does the kidney contain a portal system (two capillary beds in series)?
Yes
Blood flow in the renal portal system
Renal artery –> afferent arterioles –> glomeruli in Bowman’s capsule (the first capillary bed) –< efferent arteriole –> vasa recta –> nephron (second capillary bed) –> renal vein
Detrusor muscle
The bladder muscular lining
Is under parasympathetic control
Bladder sphincters
Internal urethral sphincter and external urethral sphincter
Internal urethral sphincter
Consists of smooth muscle and is under involuntary (parasympathetic) control
External urethral sphincter
Consists of skeletal muscle and is under voluntary control
Countercurrent multiplier system
Created by the flows in the vasa recta and nephron being in opposite directions
Allows for maximal reabsorption of water
Where is the diluting segment in the ascending limb of the loop of Henle?
In the outer medulla, because salt is actively reabsorbed in this site. The solution is, therefore, hypotonic compared to the blood.
How does the kidney function when blood pressure (and volume) are low?
Aldosterone (steroid hormone regulated by the renin-angiotensin-aldosterone system) increases sodium reabsorption in the distal convoluted tubule and collecting duct, there by increasing water reabsorption. This results in an increased blood volume (and pressure), but no change in blood osmolarity.
Antidiuretic hormone (ADH or vasopressin :: a peptide hormone synthesized by the hypothalamus and released by the posterior pituitary :: stimulated by low blood volume and high blood osmolarity) increases the permeability of the collecting duct to water, increasing water reabsorption. This results in an increased blood volume (and pressure) and a decreased blood osmolarity.
How can the kidney regulate pH?
By selective reabsorption or secretion of bicarbonate or hydrogen ions
Skin
Acts as a barrier, protecting from the elements and invasion by pathogens
Thermoregulation (maintenance of a constant internal temperature)
Prevention of dehydration and salt loss from the body
Skin layers
Hypodermis (subcutaneous layer), dermis and epidermis
Stratum basale
Contains temp cells that proliferate to form keratinocytes
Keratinocytes
Their nuclei are lost in the status granulosum and many thin layers form in the stratum corneum
Melanocytes
Produce melanin
Melanin
Protects the skin from DNA damage caused by ultraviolet radiation
Passed to the keratinocytes
Langerhans cells
Special macrophages that serve as antigen-presenting cells in the skin
Where are the sensory cells in the skin located?
In the dermis
Sensory cells in the dermis
Merkel cells (deep pressure and texture), free nerve endings (pain), Meissner’s corpuscles (light touch), Ruffini endings (stretch) and Pacinian corpuscles (deep pressure and vibration)
Merkel cells detect:
Deep pressure and texture
Meissner’s corpuscles detect:
Light tough
Free nerve endings in the dermis detect:
Pain
Ruffini endings detect:
Stretch
Pacinian corpuscles detect:
Deep pressure and vibration
What are sweat glands intreated by?
Postganglionic cholinergic sympathetic neurons
Piloerection
Arrector pili muscles contract, causing hairs to stand on end, trapping a layer of warmed air around the skin
Where in the nephron is sodium actively transported?
Proximal convoluted tubule, distal convoluted tubule and the thick ascending loop of Henle
Which region of the kidney has the lowest solute concentration under normal physiological circumstances?
The cortex
In the nephron, amino acids enter the casa recta via the process of:
Reabsorption
On a very cold day, a man waits for over an hour at the bus stop. Which structure helps his body set and maintain a normal temperature?
The hypothalamus
Glucose reabsorption in the nephron occurs in the:
Proximal convoluted tubule
Under normal physiological circumstances, the primary function of the nephron is to create urine that is hypertonic, hypotonic or isotonic to the blood?
Hypertonic
Diabetic nephropathy is commonly detected by finding protein in the urine of a patient. In such a disease, where is the likely defect in the nephron?
The glomerulus
A laceration cuts down into a layer of loose connective tissue in the skin. Which layer of the skin is this?
Papillary layer
Papillary layer
In the dermis
Predominantly loose connective tissue
Stratum corneum
In the epidermis
Contains dead keratinocytes
Stratum lucidum
In the epidermis
Contains dead keratinocytes
Reticular layer
In the dermis
Predominantly dense connective tissue
When the pH of the blood is high, which substance is likely to be excreted in larger quantities in the urine?
Bicarbonate ions
In which layer of the skin can the stem cells of keratinocytes be found?
Stratum basale
Sarin is a potent organophosphate that can be used in chemical warfare. As an inhibitor of acetylcholinesterase, sarin causes excessive buildup of acetylcholine in all synapses where it is the neurotransmitter.
Is urination likely to increase or decrease?
Is sweating likely to increase or decrease?
Urination is likely to increase and sweating is likely to increase
An excess of acetylcholine will lead to activation of all parasympathetic neurons, pre-ganglionic sympathetic neurons, and the post-ganglionic sympathetic neurons that interval sweat gland. Because the parasympathetic nervous system causes contractions of the bladder, one would expect increased urination. The increased activation of swat glands would lead to increased sweating as well.
Which type(s) of muscles is(are) striated?
Skeletal and cardiac
Which type(s) of muscles is(are) always uninucleated?
Smooth
Which type(s) of muscles is(are) always polynucleated?
Skeletal
Which type(s) of muscles is(are) voluntary?
Skeletal
Which type(s) of muscles is(are) innervated by the autonomic nervous system?
Smooth and cardiac
Which type(s) of muscles is(are) exhibiting myogenic activity?
Smooth and cardiac
Which zone or band in the sarcomere does not change its length during muscle contraction?
A-band :: it is the enter length of the myosin filament. Filaments do not change length, but rather slide over each other.
What are the events that initiate muscle contraction?
Release of acetylcholine from motor neuron –> activation of acetylcholine receptors in sarcolemma –> depolarization of sarcolemma –> spreading of signal using T-tubules –> release of calcium from sarcoplasmic reticulum (SR) –> binding of calcium to troponin –> conformational shift of tropomyosin –> exposure of myosin-binding sites –> myosin binds to actin
What role does the binding of ATP to the myosin head play in the cross bridge cycle?
It allows the myosin filament to disconnect from actin
What role does the dissociated of ADP and inorganic phosphate from the myosin head play in the cross bridge cycle?
It causes the powerstroke
Tetanus (the physiological phenomenon, not the disease)
The summation of multiple simple twitches that occur too quickly for the muscle to relax, leading to a stronger and more prolonged contraction of the muscle
Compact bone
Dense
Used for strength
Forms most of the outer layers of a bone
Spongy (cancellous) bone
Has many spaces between bony spicules called trabeculae
The sire of marrow production
Found in the interior core of the bone
Helps distribute forces or pressures on the bone
Structural parts of a bone
Diaphysis –> metaphyses –> epiphyses (which have epiphyseal [growth] plates)
Which part of the bone contributes most to linear growth?
Epiphyses :: it has the growth plates that contribute to linear growth
What chemical forms most of the inorganic component of bone?
Hydroxyapatite crystals
Osteoblast
Build bone
Osteoclast
Chew bone (break it down)
Chondrocyte
Form cartilage
What liquid provides the lubrication for movable joints?
Synovial fluid
What tissue produces synovial fluid
Synovium
Synovial fluid
Lubricates movable joints
Types of muscles
Skeletal, smooth and cardiac
Skeletal muscles
Involved in support and movement
involved in propulsion of blood in the venous system
Involved in thermoregulation
Appear striated
Are under voluntary (somatic) control
Are polynucleated
Can be divided into red (slow-twitch) fibers and white (fast-twitch) fibers
Red (slow-twitch) fibers
Carry out oxidative phosphorylation
White (fast-twitch) fibers)
Rely on anaerobic metabolism
Smooth muscles
In the respiratory, reproductive, cardiovascular and digestive systems
Appear non-striated
Are under involuntary (autonomic) control
Are uninucleated
Can display myogenic activity
Myogenic activity
Contraction without neural input
Cardiac muscles
Comprise the contractile tissue of the heart
Appear striated
Are under involuntary (autonomic) control
Are uninucleated (sometimes binucleated)
Can display myogenic activity
Cells are connected with intercalated disks that contain gap junctions
Sarcomere
The basic contracile unit of striated muscle
What are sarcomeres made of?
Thick (myosin) and thin (actin) filaments
Where is troponin found on the sarcomere?
Thin (actin) filament
Where is tropomyosin found on the sarcomere?
Thin (actin) filamentThin (actin) filament
What does troponin do?
Regulates the actin-myosin interactions
What does tropomyosin do?
Regulates the actin-myosin interactions
Divisions of the sarcomere
Z-lines, M-line, I-band, H-zone, and A-band
Z-lines
The boundaries of the sarcomere
M-line
Located in the middle of the sarcomere
I-band
Contains only thin filaments
H-zone
Contains on thick filaments
A-band
Contains all the thick filaments
The only part of the sarcomere that maintains a constant size during contraction
Myofibrils
Sarcomeres attached end-to-end
Myocyte (muscle cell or muscle fiber)
Contains many myofibrils
Sarcoplasmic reticulum
Surrounds myofibrils
A calcium-containing modified ER
Sarcolemma
The cell membrane of a myocyte
T-tubules
Connected to the sarcolemma and oriented perpendicularly to myofibrils, allowing the incoming signal to reach all parts of the muscle
Where does muscle contraction begin?
At the neuromuscular junction
Neuromuscular junction
Where the motor neuron releases acetylcholine, which binds to receptors on the sarcolemma, causing depolarization
What happens when the sarcolemma is depolarized?
The depolarization spreads down the sarcolemma to the T-tubules, triggering the release of calcium ions
What happens when calcium ions are released?
Calcium bins to troponin, causing a shift in tropomyosin and exposure of the myosin-binding sites on the actin thin filament
When does the shortening of the sarcomere occur?
When myosin heads bind to the exposed sites on actin, forming cross bridges and pulling the actin filament alone the thick filament, resulting in contraction :: the sliding filament model
When does the muscle relax?
When acetylcholine is degraded by acetylcholinesterase, terminating the signal and allowing calcium to be Brough back into the SR. ATP binds to the myosin head, allowing it to release from actin
Simple twitch
Muscle cells exhibiting an all-or-nothing response
Frequency summation
Addition of multiple simple twitches before the muscle has an opportunity to fully relax
How do muscle cells reduce oxygen debt?
Muscle cells have additional energy reserves
Why is it important for muscles cells to reduce oxygen debt?
To forestall fatigue
Oxygen debt
The difference between the amount of oxygen needed and the amount of oxygen present
Creatine phosphate
Transfer a phosphate group to ADP, forming ATP
Myoglobin
Heme-containing protein that is a muscular oxygen reserve
Endoskeleton
Internal skeleton
Exoskeleton
External skeleton
Divisions of human skeletal system
Axial and appendicular skeletons
Axial skeleton
Consists of structures in the midline
e.g. skull, vertebral column, ribcage and hyoid bone
Appendicular skeleton
Consists of the bones of the limbs and the pectoral grille and the pelvis
Which embryonic layer gives rise to bones?
Mesoderm
Types of bones
Compact and spongy (cancellous)
Periosteum
A layer of connective tissue that surrounds bone
Serves as a site of attachment of bone to muscle
Cells of the periosteum may differentiate into osteoblasts
How are bones attached to muscles?
Tendons
How are bones attached to each other?
Ligaments
Bone matrix
Has organic components, like collagen, glycoproteins and other peptides
Has inorganic components, like hydroxyapatite
Bone organization
Bones are organized into concentric rings called lamellae around a central Harversian or Volkmann’s canal. This structural unit is called an osteon, or Haversian system
Between lamellar rings are lacunae, where osteocytes reside, which are connected with canaliculi to allow for n’eurent and waste transfer
What is the role of parathyroid hormone in bone building/breakdown?
It increases resorption of bone, increasing calcium and phosphate concentrations in the blood
What is the role of vitamin D in bone building/breakdown?
Increases resorption of bone, leading to increased turnover and, subsequently, the production of stronger bones
What is the role of calcitonin in bone building/breakdown?
Increases bone formation, decreasing calcium concentration in the blood
Cartilage
A firm, elastic material secreted by chondrocytes
Found in areas that require more flexibility or cushioning
Avascular
Not innervated
Chondrocytes
Secrete cartilage
Chondrin
Cartilage matrix
How do bones form in fetal life?
From cartilage through endochondral ossification
Where do the bones in the skull form from?
Undifferentiated tissue (mesenchyme) in intramembranous ossification
Joint classifications
Immovable or movable
Immovable joints
Fused together to form sutures or similar fibrous joints
Movable joints
Strengthened by ligaments and contain a synovial capsule
Articular cartilage
Coats each bone in the joint
Aids in movement and provides cushioning
Antagonistic pairs
Muscles that serve opposite functions :: when one muscle contracts, the other lengthens
An X-ray of the right femur in a child shows that it is shorter than the opposite femur, and below the average length for a child of this age. Which region of the bone is most likely to have caused this abnormality?
Epiphysis
When the knee moves back and forth during walking, what prevents the surfaces of the leg bones from rubbing against each other?
Articular cartilage
Yellow bone marrow
Contains predominantly adipose tissue
To facilitate the process of birth, an infant’s head is somewhat flexible. This flexibility is given in part by the two fontanelles, which are soft spots of connective tissue in the infant’s skull. With time, the fontanelles will close through a process known as:
Intramembranous ossification
A young woman presents to the ER with a broken hip. She denies any recent history of trauma to the joint. Blood tests reveal a calcium concentration of 11.5 mg/dL (normal: 8.4 – 10.2). Which tissue is likely responsible for these findings?
Parathyroid
What does it mean for an allele to be dominant?
Requires only one copy for expression
What does it mean for an allele to be recessive?
Requires two copies for expression
What does it mean for a genotype to be homozygous?
Both alleles are recessive or both alleles are dominant
What does it mean for a genotype to be heterozygous?
One allele is recessive and the other is dominant
What does it mean for a genotype to be hemizygous?
There is only one allele for a given gene
Complete dominance
Occurs when a gene has only one dominant and one recessive allele
Codominance
Occurs when a gene has more than one dominant allele and two different dominant allele can be expressed simultaneously
Incomplete dominance
Occurs when a gene has no dominant allele and heterozygotes have phenotypes that are intermediate between homozygotes
Penetrance
The portion of the population that expresses a phenotype, given a particular genotype
Expressivity
The differences in expression (severity, location, etc.) of a phenotype across affected members of a population
Which phase of meiosis most closely correlates to Mendel’s first law?
Anaphase I
Which phase of meiosis most closely correlates to Mendel’s second law?
Prophase I
Types of point mutations
Silent
Missense
Nonsense
Silent mutation
Change in the nucleotide at the wobble position
No change in the amino acid produced
Missense mutation
Change one nucleotide to another that results in change from one amino acid to another
Nonsense mutation
Change one nucleotide to another that results in change from one amino acid to a stop codon
Shortened protein
Types of frameshift mutation
Insertion
Deletion
Types of chromosomal mutations
Deletion Duplication Inversion Insertion Translocation
Duplication mutation
Occur when a segment of DNA is copied multiple times in the genome
Inversion mutation
Occur when a segment of DNA is reversed in the genome
Translocation mutation
Occur when a segment of DNA is from one chromosome is swapped with a segment of DNA from another chromosome
Why would genetic leakage in animals be rare prior to the last century?
It requires the formation of a hybrid organism that can then mate with members of one or the other parent species. While hybrids existed historically (especially mules), fertile hybrids were certainly rare before a more modern understanding of genetics (and a commercial, financial or academic impetus to create these organisms).
Why is genetic drift more common in small populations?
It occurs due to chance, so its effects will be more pronounced with a smaller sample size.
The founder effect
Occurs when a small group is reproductively isolated from the larger population, allowing certain alleles to take on a higher prevalence in the group than the rest of the population
All five criteria of the Hardy-Weinberg principle are required to imply what characteristic of the study population?
The study population is not undergoing evolution; thus, the allele frequencies will remain stable over time
Natural selection
Certain traits that arise from chance are more favorable for reproductive success in a given environment, and that that those traits will be passed on to future generations
Modern synthesis model (Neo-Darwinism)
Selection is for specific alleles, which are passed to future generations through formation of gametes, and that these favorable traits arise from mutations
Inclusive fitness
Reproductive success of an organism is not only due to the number of offspring it creates, but also the ability to care for young (that can then care for other); it explains changes not only at the individual level, but based on the survival of the species (and that individual’s alleles within the species, including in other related individuals).
Punctuated equilibrium
For some species, little evolution occurs for a long period, which is interrupted by rapid bursts of evolutionary change
Patterns of selection
Stabilizing
Directional
Disruptive
Change in population phenotype does the stabilizing pattern of selection bring?
Loss of extremes, maintenance of phenotype in a small window
Change in population phenotype does the directional pattern of selection bring?
Movement towards one extreme or the other
Change in population phenotype does the disruptive pattern of selection bring?
Movement towards both extremes with loss of the norm
Speciation may occur
Patterns of evolution
Divergent
Parallel
Convergent
What is the outcome of a divergent pattern of evolution?
Two species with a common ancestor become less similar because of different evolutionary pressures
What is the outcome of a parallel pattern of evolution?
Two species with a common ancestor remain similar because of similar evolutionary pressures
What is the outcome of a convergent pattern of evolution?
Two species with no recent common ancestor become more similar because of similar evolutionary pressures
Species
The largest group of organisms capable of breeding to form fertile offspring
Reproductively isolated from each other by pre- or post-zygotic mechanisms
Hardy-Weinberg equations
p + q = 1
p^2 + 2pq + q^2 = 1
Alleles
Alternative forms of a gene
Genotype
The combination of alleles one has at a given genetic locus
Phenotype
The observable manifestation of a genotype
Mendel’s first law of segregation
States that an organism has two alleles for each gene, which segregate during meiosis, resulting in gametes carrying only one allele for a trait
Mendel’s second law of independent assortment
The inheritance of one allele does not influence the probability of inheriting a given allele for a different trait
Griffith experiment
Demonstrated the transforming principle, converting non-virulent bacteria into virulent bacteria by exposure to heat-killed virulent bacteria
Avery-MacLeod-McCarty experiment
Demonstrated that DNA is the genetic material because degradation of DNA led to a cessation of bacterial transformation
Hershey-Chase experiment
Confirmed that DNA is the genetic material because only radio labeled DNA could be found in bacteriophage-infected bacteria
Gene pool
Composed of all the alleles in a given population
Mutations
Changes in DNA sequence
Deletion mutation
Occurs when a large segment of DNA is lost
Insertion mutation
Occurs when a segment of DNA is moved from one chromosome to another
Bottleneck effect
Suddenly isolates a small population
Outcomes of the bottleneck effect
Founder effect and inbreeding
Punnet squares
Visually represent the crossing of gametes from parents to show relative genotypic and phenotypic frequencies
Monohybrid cross
Accounts for one gene
Dihybrid cross
Accounts for two genes
Sex-linked cross
Sex chromosomes are usually used to indicate sec as well as genotype
Recombination frequency
The likelihood of two alleles being separated during crossing over in meiosis
Genetic maps
Can be made using recombination frequency as the scale in centimorgans
Hardy-Weinberg principle
States that if a population meets certain criteria (aimed at a lack of evolution), then the allele frequencies will remain constant (Hardy-Weinberg equilibrium)
Adaptive radiation
The rapid emergence of multiple species from a common ancestor, each of which occupies its own ecological niche
Molecular clock model
The degree of difference in the genome between two species is related to the amount of time since the two species broke off from a common ancestor
If a test cross on a species reveals the appearance of a recessive phenotype in the offspring, what must be true of the phenotypically dominant parent?
It must be genotypically heterozygous
In a species of plant, a homozygous red flower (RR) is crossed with a homozygous yellow flower (rr). If the G1 generation is self-crossed and the F2 generation has a phenotypic ratio of red:orange:yellow of 1:2:1, which characteristic accounts for these results?
Incomplete dominance
The five criteria of the Hardy-Weinberg principle
- The population is very large
- There are no mutations that affect the gene pool
- Mating between individuals in the population is random
- There is no migration of individuals into or out of the population
- The genes in the population are all equally successful at reproduction
As the climate became colder during the Ice Age, a particular species of mammal evolved a thicker layer of fur. What kind of selection occurred in this population?
Directional selection
At what point are two populations descended from the same ancestral stock considered to be separate species?
When they can no longer produce viable, fertile offspring
Darwin’s main argument in his theory of evolution
Natural selection is the driving force for evolution
There is a struggle for survival among organisms
Those individuals with fitter variations will survive and reproduce
Did Darwin consider the role of genetic mutation and recombination?
No because they were unknown at the time
A child is born with a number of unusual phenotypic features and genetic testing is performed. The child is determined to have partial trisomy 21, with three copies of some segments of DNA from chromosome 21, and partial monosomy 4, with only one copy of some segments of DNA from chromosome 4. Which mutation could have occurred in one of the parental gametes during development to explain both findings?
Translocation (It’s not an insertion mutation, because an insertion mutation only explains what happened in 21, but not what happened in 4. It’s not a deletion mutation, because a delegation mutation on explains what happened in 4, but not what happened in 21)
