Biology Flashcards
What are the four basic tenets of the cell theory?
- All living things are composed of cells
- The cell is the basic fundamental unit of life
- Cells arise only from preexisting cells
- Cells carry genetic information in the form of DNA. This genetic material is passed on from parent to daughter cell
Why are viruses not considered to be living things?
Because they are acellular, cannot reproduce without the assistance of a host cell, and may contain RNA as their genetic material
What is membrane-bound in eukaryotes?
Organelles and the nucleus
Are eukaryotes unicellular or multicellular?
Can be either
What are the cell membranes and membranes of organelles made of?
Phospholipids
How do phospholipids organize themselves?
Form a hydrophilic interior and exterior surfaces with a hydrophobic core
What does the cytosol do?
Suspends the organelles and allows diffusion of molecules throughout the cell
What does the nucleus do?
Contain DNA that is organized into chromosomes
What is the nucleus surrounded by? What does it allow?
The nuclear membrane or envelope (double membrane)
Contains pores for two-way exchange of materials between and the nucleus and the cytosol
How is DNA organized?
Into regions called genes
What is the nucleolus?
A subsection of the nucleus in which ribosomal RNA (rRNA) is synthesized
Explain the layout of the mitochondria and what occurs within the mitochondria.
Mitochondria contain an outer and inner membrane. The outer membrane forms a barrier with the cytosol; the inner membrane is folded into cristae and contains enzymes for the electron transport chain. Between the membranes is the inermembrane space; inside the inner mitochondrial membrane is the mitochondrial matrix
How does the mitochondria divide?
Can divide independently of the nucleus via binary fission; they can trigger apoptosis by releasing mitochondrial enzymes into the cytoplasm
What plain what occurs in the lysosome? What is the lysosome?
Lysosomes contain hydrolytic enzymes that can break down substances ingested by endocytosis and cellular waste products. When these enzymes are released, autolysis of the cell can occur
What is the endoplasmic reticulum?
ER - a series of interconnected membranes and is continuous with the nuclear envelope
What is the rough ER?
RER - studied with ribosomes
Permits the translation of proteins destined for secretion
What is smooth ER?
SER - used for lipid synthesis and detoxification
What is the Gogli apparatus?
Consists of stacked membrane-bound sacs in which cellular products can be modified, packaged, and directed to specific cellular locations
What are peroxisomes?
Contain hydrogen peroxide and can break down very long chain fatty acids via β-oxidation. They also participate in phospholipid synthesis and the pentose phosphate pathway
What does the cytoskeleton do?
Provide stability and rigidity to the overall structure of the cell, while also providing transport pathways for molecules within the cell
What are microfilaments composed of? What do they do?
Composed of actin. They provide structural protection from the cell and can cause muscle contraction through interactions with myosin. They also help form the cleavage furrow during cytokinesis in mitosis
What are microtubules composed of? What do they do?
Composed of tubulin. They create pathways for motor proteins like kinesis and dyne to carry vesicles. They also 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).
Where are centrioles fount in and what are they involved in?
Centrioles are found in centrosomes and are involved in microtubule organization in the mitotic spindle
What are intermediate filaments involved in? Examples?
Intermediate filaments are involved in cell-cell adhesion or maintenance of the integrity of the cytoskeleton; they help anchor organelles. Common examples include keratin and desmin
What do epithelial tissues cover and what do they do?
Epithelial tissues covers the body and lines its cavities, protecting against pathogen invasion and desiccation. Some epithelial cells absorb or secrete substances, or participate in sensation
In most organs, epithelial cells form what part of the organ?
The parenchyma, the functional part of the organ
How are epithelial cells polarized?
One side faces the lumen or the outside world, and the other side faces blood vessels and structural cells
How are epithelial cells classified?
By the number of layers they contain and by the shape of the cells they contain
How many layers does simple epithelial tissue contain?
One layer
How many layers does stratified epithelial tissue contain?
Many layers
How many layers does pseudo-stratified epithelia have?
Appear to have multiple layers because of differences in cell heights, but only actually have one layer
What are cuboidal cells shaped like in epithelial tissue?
Cube-shaped
What are columnar cells shaped like in epithelial tissue?
Long and narrow
What are squamous cells shaped like in epithelial tissue?
Flat and scalelike
What does connect tissue provide?
Support for the body and provides a framework for epithelial cells
In most organs, what does the connective tissue form?
The stroma or support structure by secreting materials to form an extracellular matrix
What are types of connective tissue?
Bone, cartilage, tendons, ligaments, adipose tissue, and blood
Do prokaryotes contain membrane-bound organelles?
No
How do prokaryotes organize their genetic material?
In a single circular molecule of DNA consternated in the nucleoid region
What are the three domains of life?
Archaea, bacteria, and eukarya
Archaea and bacteria are prokaryotes
What are archaea? How do they get energy?
Often extremophiles, living in harsh environments (high temperature, high salinity, no light)
Often use alternative sources of energy, like chemosynthesis
How are archaea similar to eukaryotes?
Start translation with methionine, similar RNA polymerases, histones
How are archaea similar to bacteria?
Single circular chromosome, divide by binary fission or budding
How are bacteria similar to eukaryotes?
Many similar structures
What is the relationship bacteria has with humans?
Complex relationship
Includes symbiosis and pathogenies
What are the three classifications of bacteria by shape?
Cocci - spherical bacteria
Bacilli - rod-shaped bacteria
Spirilli - spiral-shpaed bacteria
What are the classifications for bacteria based on metabolic processes??
Obligate aerobes: require oxygen for metabolism
Obligate anaerobes: cannot survive in oxygen-containing environments and can only carry out anaerobic metabolism
Facultative anaerobes: can survive in environments with or without oxygen and will toggle metabolism processes based on the environment
Aerotolerant anaerobes: cannot use oxygen for metabolism, but can survive in an oxygen-containing environment
What forms the envelope? What does this control?
The cell wall and cell membrane form the envelope.
Controls the movement of solutes into and out of the cell
How can bacteria be classified by Gram staining?
The color of their cell walls turn different colors with Gram staining with a crystal violet stain, followed by a counterstain with safranin.
Gram-positive bacteria turn purple
Gram-negative bacteria will turn pink-red
What is the wall of a Gram-positive bacteria made of?
A thick cell wall composed of peptidoglycan and lipoteichoic acid
What is the wall of a Gram-negative bacteria made of?
A thin cell wall composed of peptidoglycan and an outer membrane containing phospholipids and lipopolysaccharides
How many flagella may bacteria have? What does it do?
May have one, two or many flagella
Generates propulsion to move the bacterium toward food or away from immune cells
What is chemotaxis?
Moving in response to a chemical stimuli
What do bacterial flagella contain?
A filament composed of flagellin, a basal body that anchors and rotates the flagellum, and a hook that contains the two
How do prokaryotes carry out the electron transport chain?
Using the cell membrane
How do prokaryotic ribosomes compare to eukaryotic?
They are smaller
30S and 50S rather than 40S and 60S
How do prokaryotes multiply?
Through binary fission
What is binary fission?
When the chromosome replicates while the cell grows in size until the cell wall begins to grow inward alone the midline of the cell and divides it into two identical daughter cells
What are plasmids?
Extrachromosomal material
May contain antibiotic resistance genes or virulence factors.
What are episomes?
Plasmids that can integrate into he genome
What is transformation?
The acquisition of genetic material from the environment, which can be integrated into the bacterial genome
What is conjugation?
The transfer of genetic material from one bacterium to another 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 an Hfr cell to a recipient
What is transduction?
The transfer of genetic material from one bacterium to another using a bacteriophage as a vector
What are transposons?
Genetic elements that can insert into or remove themselves from the genome
What is the predictable pattern of bacterial growth?
The bacteria adapt to new local conditions during the lag phase
Growth increases exponentially during the exponential (log) phase
As resources are reduced, growth levels off during the stationary phase
As resources become insufficient, bacteria undergo a death phase
What do viruses contain?
Genetic material, a protein coat (capsid), and sometimes a lipid-containing envelope
Viruses are obligate intracellular parasites. What does this mean?
Viruses cannot survive and replicate outside of a host cell
What are bacteriophages? What do they contain?
Bacteriophages are viruses that target bacteria. In addition to the other structures, they contain a full sheath, which injects the genetic material into a bacterium, and tail fibers, which allow the bacteriophage to attach to the host cell
What are viral genomes made up of?
DNA or RNA. May be single or double-stranded.
SsRNA viruses can be positive sense (translated directly by the host cell) or negative sense (a complementary strand must be synthesized using RNA replicase).
Retroviruses contain a ssRNA. A complementary DNA strand is made using reverse transcriptase. The DNA strand can then be integrated into the genome.
How do viruses infect cells?
They attach to specific receptors. They then either fuse with the plasma membrane and brought in through endocytosis or they inject their genetic material into the cell
How does a virus reproduce?
They replicate and translate genetic material using the host cell’s ribosomes, tRNA, amino acids, and enzymes
How are viral progeny released?
Through cell death, lysis, or extrusion
What are the two specific life cycles of bacteriophages? What occurs in each?
The lytic cycle: bacteriophage produces massive numbers of new virions until the cell losses. Bacteria in this cycle are termed virulent
The lysogenic cycle: The virus integrates into the host genome as a provirus or prophage, which can then reproduce along with the cell. The provirus then leaves the genome in response to a stimulus at some later tie and enters the lytic cycle.
What are prions? What do they do?
Infectious proteins. They trigger misfiling of other proteins, usually converting an alpha-helical structure into a beta-pleated sheet. This decreases the solubility and degradability of the mid folded protein
What are 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
What are diploid cells?
2n
Have 2 copies of each chromosome
What are haploid cells
n
Have one copy of each chromosome
How many stages are in the cell cycle? What are their names?
5 stages
G1, S, G2, M, G0
What stages make up interphase? What is interphase?
G1, S, G2
The DNA is uncoiled in the form of a chromatin
What occurs during the G2 stage?
Presynaptic gap.
Cells create organelles for energy and protein production, while also increasing their size. The restriction point, during which the DNA is checked for quality, must be passed for the cell to move into the S stage
What occurs during the S stage?
Synthesis
DNA is replicated. The strands of DNA, called the chromatids, are held together at the centromere
What occurs in the G2 stage?
Postsynaptic gap
There is further cell growth and replication of organelles in preparation for mitosis. Another quality checkpoint must be passed for the cell to enter mitosis
What occurs in the M stage?
Mitosis and cytokinesis
What occurs in the G0 stage?
The cell performs its function without any preparations for division
What role does p53 play?
A role in two major checkpoints of the cell cycle. From G1 to S and from G2 to M
What is the levels of cyclins and cyclin-dependent kinases (CDK) throughout the cell cycle
They rise and fall throughout
What do cyclins do?
Bind to CDKs
Phosphorylate and activate transcription factors for the next stage of the cell cycle
Why does cancer occur?
when the 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
What does mitosis produce? What type of cells does mitosis occur in?
Two genetically diploid daughter cells from a single cell and occurs in somatic cells
How many phases are in mitosis? What are they?
4 Prophase Metaphase Anaphase Telophase
What occurs in prophase?
The chromosomes condense, nuclear membrane dissolves, nucleoli disappear, centrioles migrate to opposite sides of the cell, and the spindle apparatus begins to form. The kinetochore of each chromosomes is contacted by a spindle fiber
What occurs in metaphase?
Chromosomes line up along the metaphase plate (equatorial plate)
What occurs in anaphase?
Sister chromatids are separated and pulled to opposite poles
What occurs in telophase?
The nuclear membrane reforms, spindle apparatus disappears, and cytosol and organelles are split between the two daughter cells through cytokinesis
What type of cells does meiosis occur in? What does meiosis produce?
Gametocytes (germ cells)
Produces up to four nonidentical haploid sex cells (gametes)
How many rounds of replication and division does meiosis have?
One round of replication followed by two rounds of division (the reductional and equational divisions)
What occurs in meiosis I?
Homologous pairs of chromosomes (homologues) are separated from each other
What are homologues?
Chromosomes that are given the same number, but are opposite parental origin
What occurs in prophase I?
The same events occur as in prophase of mitosis, except that homologues come together and intertwine in a process called synapsis. The four chromatids are referred to as a tetrad, and crossing over exchanges genetic material from one chromatid with material from a chromatid in the homologous chromosome
What occurs in metaphase I?
Homologous chromosomes lines up on opposite sides of the metaphase plate
What occurs in anaphase I?
Homologous chromosomes are segregated to opposite poles of the cell. This accounts for Mendel’s first law (of segregation). The recombination of genes during crossing over also accounts for Mendel’s second law (of independent assortment)
What occurs in telophase I?
The chromosomes may or may not fully decondense, and the cell may enter interkinesis after cytokinesis
What occurs in meiosis II?
Sister chromatids are separated from each other in a process that is functionally identical to mitosis. Sister chromatids are copies of the same DNA held together at the centromere
What is biological sex determined by?
The 23rd pair of chromosomes in humans, with XX being female and XY being male
What do mutations of X-linked genes cause?
Sex-linked disorders.
The X chromosome carries a sizable amount of genetic information
Who is more likely to get sex-linked disorders? Why?
Males are homozygous with respect to the unpaired genes on the X chromosome, so they will express sex-linked disorders, even if they only have one recessive disease-carrying allele. Women with one copy of the affected allele are called carriers
What information is carried on the Y chromosome?
The Y chromosome carries little genetic information, but contains the SRY (sex-determining region Y) gene, which causes the gonads to differentiate into testes
What type of structures does the male reproductive system contain?
Both internal and external structures
Where do sperm develop? What nourishes them?
Sperm develop in the seminiferous tubules in the testes. They are nourished by Sertoli cells
What do interstitial cells (of Leydig) do?
Interstitial cells (of Leydig) secrete testosterone and other male sex hormones (androgens)
Where are the testes located? Why are they located there?
The testes are located in the scrotum, which hangs outside of the abdominal cavity and has a temperature 2° to 4° lower than the body
Where are sperm stored until ejaculation?
Once formed, sperm gain motility in the epididymis and are stored there until ejaculation
What do sperm travel through during ejactulation?
During ejaculation, sperm travel through the vas deferens to the ejactulatory duct to the urethra and out through the penis
What do the seminal vesicles contribute to sperm?
The seminal vesicles contribute fructose to nourish sperm and produce alkaline fluid
What does the prostate gland produce?
Alkaline fluid
What does the bulbourethral gland produce?
The bulbourethral glands produce a clear viscous fluid that cleans out any remnants of urine and lubricates the urethra during sexual arousal
What is semen composed of?
Semen is composed of sperm and seminal fluid from various glands
What is produced in spermatogenesis?
Four haploid sperm are produced from a spermatogonium
After the S stage of spermatogenesis, what are the germ cells called?
Spermocytes
After meiosis I stage of spermatogenesis, what are the germ cells called?
Spermatids
After meiosis II stage of spermatogenesis, what are the germ cells called?
Spermatids
After maturation in spermatogenesis, what are the germ cells called?
Spermatozoa
What are the three parts of a sperm?
A head, midpiece, and flagellum
What does the head of a sperm contain?
The head contains the genetic material and is covered with an acrosome - a modified Golgi apparatus that contains enzymes that help the sperm fuse to and penetrate the ovum
What does the midpiece of a sperm do?
The midpiece generates ATP from fructose and contains many mitochondria
What does the flagellum of a sperm do?
The flagellum promotes motility
What type of structures does the female reproductive system contain?
Only internal structures
Where are the ova (eggs) produced
In follicles in the ovaries
How often is an egg ovulated? Where does it go?
One each month, an egg is ovulated into the peritoneal sac and is drawn into the fallopian tube or oviduct
Where are the fallopian tubes attached to?
The fallopian tubes are connected to the uterus, the lower end of which is called the cervix
Where is the vaginal canal located? What occurs in it?
The vaginal canal lies below the cervix and is the site where sperm are deposited during intercourse. Birth also occurs through the vaginal canal
What is the external female anatomy called?
The vulva
What is produced during oogenesis?
In oogenesis, one haploid ovum and a variable number of polar bodies are formed from an oogonium
At birth, what stage is oogenesis arrested in?
At birth, all oogonia have already gone replication and are considered primary oocytes. They are arrested in prophase I
What stage is an ovulated egg arrested in?
The ovulated egg each month is a secondary oocyte, which is arrested in metaphase II
How is cytokinesis in oogenesis?
Cytokinesis is uneven in oogenesis. The cell receiving very little cytoplasm and organelles is called a polar body
What is the zona pellucida and the corona radiata? What do they do?
Oocytes are surrounded by the zona pellucida, an acellular mixture of glycoproteins that protect the oocyte and contain the compounds necessary for sperm binding, and the corona radiata, which is a layer of cells that adhere to the oocyte during ovulation
What does gonadotropin-releasing hormone do?
Gonadotropin-releasing hormone (GnRH) from the hypothalamus causes the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the functions of which depend on the sex of the individual
What does FSH and LH do in males?
In males, FSH stimulates the Sertoli cells and triggers spermatogenesis, while LH causes the interstitial cells to produce testosterone.
What is testosterone responsible for?
Testosterone is 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)
In females, what does FSH and LH do?
In females, FSH stimulates development of the ovarian follicles, while LH causes ovulation. These hormones also stimulate production of estrogens and progesterone
What is the menstrual cycle?
The menstrual cycle is a periodic growth and shedding of the endometrial lining
What occurs in the follicular phase of the menstrual cycle?
In the follicular phase, GnRH secretion stimulates FSH and LH secretion, which promotes follicle development. Estrogen is released, stimulating vascularization and glandularization of decidua
What is ovulation stimulated by?
Ovulation is stimulated by a sudden surge in LH. This surge occurs because estrogen stops having negative feedback effects at a certain threshold and begins to have positive feedbacks
What occurs in the luteal phase of the menstrual cycle?
In the luteal phase, LH promotes the ruptured follicle to become the corpus luteum, which secretes progesterone that maintains the uterine lining. High estrogen and progesterone levels cause negative feedback on GnRH, LH, and FSH
When does menstruation occur?
Menstruation occurs if there is no fertilization. As the estrogen and progesterone levels drop, the endometrial lining is sloughed off, and the block on GnRh production is removed
What occurs if fertilization occurs?
If fertilization does occur, the blastula produces human chorionic gonadotropin (hCG) which, as an LH analogue, can maintain the corpus luteum. Near the end of the first trimester, hCG levels drop as the placenta takes over progesterone production
Why does menopause occur?
Menopause occurs when the ovaries stop producing estrogen and progesterone, usually between the ages of 45 and 55. Menstruation stops and FSH and LH levels rise. Physical and physiological changes accompanying menopause include flushing, hot flashes, bloating, headaches, and irritability
What is fertilization?
The joining of a sperm and ovum
Where does fertilization usually occur?
It usually occur in the ampulla of the fallopian tube
How does the sperm penetrate the ovum?
The sperm uses acrosomal enzymes to penetrate the corona radiata and zone pellucida
What occurs once the sperm contacts the plasma membrane of the oocyte?
Once is contacts the oocyte’s plasma membrane, the sperm establishes the acrosomal apparatus and injects its nucleus
What happens after the first sperm penetrates the ovum?
When the first sperm penetrates, it causes a release of calcium ions, which prevents additional sperm from fertilizing the egg and increases the metabolic rate of the resulting diploid zygote. This is called the cortical reaction
How do dizygotic (fraternal) twins result?
Fraternal (dizygotic) twins result from the fertilization of two eggs by two different sperm.
How do monozygotic (identical) twins result?
Identical (monozygotic) twins result from the splitting of a zygote in two.
How can monozygotic twins be classified?
Monozygote twins can be classified by the placenta structures they share (mono- vs. diamniotic, mono- vs. dichorionic)
What is cleavage? What results from it?
Cleavage is defined as the early divisions of cells in the embryo. These mitotic divisions result in a large number of smaller cells, as the overall volume does not change
When does a zygote become an embryo?
The zygote becomes an embryo after the first cleavage because it is no longer unicellular
What is the difference between indeterminate and determinant cleavage?
Indeterminate cleavage results in cells that are capable of becoming any cell in the organism, while determinate cleavage results in cells that are committed to differentiating into a specific cell type
What is a morula?
The morula is a solid mass of cells in early development
What is the structure of a blastula?
The blastula (blastocyst) has a fluid-filled center called a blastocoel and has two different cell types, including trophoblasts (which become placental structures) and the inner cell mass (which becomes the developing organism)
Where does the blastula implant? What does it form?
The blastula implants in the endometrial lining and forms the placenta
What does the chorion contain? What does it do?
The chorion contains chorionic villi, which penetrate the endometrium and create the interface between maternal and fetal blood
What supports the embryo before the placenta is established?
Before the placenta is established, the embryo is supported by the yolk sac
What is the allantois involved in?
The allantois is involved in early fluid exchange between the embryo and the yolk sac
Where is the amnion located and what does it do?
The amnion lies just inside the chorion and produces amniotic fluid
How is the fetus connected to the placenta?
The developing organism is connected to the placenta via the umbilical cord
What is formed during gastrulation?
During 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
What does the ectoderm become?
The ectoderm becomes epidermis, hair, nails, and the epithelia of the nose, mouth, and anal canal, as well as the nervous system (including adrenal medulla) and lens of the eye
What does the mesoderm become?
The mesoderm becomes much of the musculoskeletal, circulatory and excretory systems. Mesoderm also gives rise to the gonads and the muscular and connective tissue layers of the digestive and respiratory systems, as well as the adrenal cortex
What does the endoderm become?
The endoderm becomes much of the epithelial linings of the respiratory and digestive tracts, and parts of the pancreas, thyroid, bladder, and distal urinary tracts
What is neurulation? When does it begin?
Neurulation, or development of the nervous system, begins after the formation of the three germ layers
What does the notochords include?
The notochord includes a group of overlying ectodermal cells to form neural folds surrounding a neural groove
What becomes the central nervous system in the developing organism?
The neural folds fuse to form the neural tube, which becomes the central nervous system
What does the tip of each fold of the neural tube become?
The tip of each fold contains neural crest cells, which become the peripheral nervous system (sensory ganglia, autonomic ganglia, adrenal medulla, and Schwann cells) as well as specific types in other tissues (calcitonin-producing cells of the thyroid, melanocytes in the skin, and others)
What are teratogens? What do they do?
Teratogens are substances that interfere with development, causing defects or even death of the developing embryo. Teratogens include alcohol, certain prescription drugs, viruses, bacteria, and environmental chemicals
How can maternal health effect the development of the fetus?
Maternal health can affect development, including diabetes (increased fetal size and hypoglycemia after birth) and folic acid deficiency (neural tube defects)
What does cell specialization occur as a result of?
Cell specialization occurs as a result of determination and differentiation
What is determination?
Determination is the commitment to a specific cell lineage, which may be accomplished by uneven segregation of cellular material during mitosis or morphogens, which promote development down a specific cell line. To respond to a specific morphogen, a cell must have competency
What is differentiation?
Differentiation refers to the changes a cell undergoes due to selective transcription to take on characteristics appropriate to its cell line
How are stem cells classified? What are they capable of?
Stem cells are cells that are capable of developing into various cell types. They can be classified by potency
What are totipotent cells?
Totipotent cells are able to differentiate into all cell types, including the three germ layers and placental structures
What are pluripotent cells?
Pluripotent cells are able to differentiate into all three of the germ layers and there derivatives
What are multipotent cells?
Multipotent cells are able to differentiate only into a specific subset of cell types
How do cells communicate?
Cells communicate through a number of different signaling methods. An inducer releases factors to promote the differentiation of a competent responder
What do autocrine signals act on?
Autocrine signals act on the same cell that released the signal
What do paracrine signals act on?
Paracrine signals act on cells in the local area
What do juxtacrine signals act on?
Juxtacrine signals act through direct stimulation of the adjacent cells
What do endocrine signals act on?
Endocrine signals act on distant tissues after traveling through the bloodstream
What substance is inducers for communication typically? What do they do?
Theses are often growth factors, which are peptides that promote differentiation and mitosis in certain tissues
What is reciprocal induction?
If two tissues both include further differentiation in each other, this is termed reciprocal induction
How does signaling often occur?
Via gradients
How do cells get to the right location?
Cells may need to migrate to arrive at their anatomically correct location
What is apoptosis?
Apoptosis is programmed cell death via the formation of apoptotic blebs that can subsequently be absorbed and digested by other cells. Apoptosis can be used for sculpting certain anatomical structures, such as removing the webbing between digits
What is regenerative capacity?
Regenerative capacity is the ability of an organism to regrow certain parts of the body. The liver has high regenerative capacity, while the heart has low regenerative capacity
What is senescence the result of?
Senescence is 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 developing organism?
At the placenta
How are oxygen and carbon dioxide exchanged in the placenta?
Passively due to concentration gradients
How does HbF and HbA differ? (Fetal and adult hemoglobin)
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
What are some functions of the placenta?
The placental barrier also serves as immune protection against many pathogens, and antibodies are transferred from mother to child.
The placenta serves endocrine functions, secreting estrogen, progesterone, and human chorionic gonadotropin (hCG).
What kind of blood goes in the umbilical artery and vein?
The umbilical arteries carry deoxygenated blood from the fetus to the placenta; the umbilical vein carried oxygenated blood from the placenta back to the fetus
How does the fetal circulatory system differ from the adult version?
It has three shunts:
- The foramen oval connects the right atrium to the left atrium; bypassing the lungs
- The ductus arterioles connects the pulmonary artery to the aorta, bypassing the lungs
- The ductus venous connects the umbilical vein to the inferior vena cava, bypassing the liver
What occurs in the first trimester?
In the first trimester, organogenesis occurs (development of heart, eyes, gonads, limbs, liver, brain)
What occurs in the second trimester?
In the second trimester, tremendous growth occurs, movement begins, the face becomes distinctly human, and the digits elongate
What occurs in the third trimester?
In the third trimester, rapid growth and grain development continue, and there is a transfer of antibodies to the fetus
What occurs during birth (in the mother)?
During birth, the cervix thins out and the amniotic sac ruptures. Then uterine contractions, coordinated by prostaglandins and oxytocin, result in birth of the fetus. Finally, the placenta and umbilical cord are expelled
What are neurons?
Neurons are highly specialized cells responsible for the conduction of impulses
How do neurons communicate?
Neurons communicate using both electrical and chemical forms of communication
How does electrical communication occur?
Electrical communication occurs via ion exchange and the generation of membrane potentials down the length of the axon
How does chemical communication occur?
Chemical communication occurs via neurotransmitter release from the presynaptic cell and the binding of these neurotransmitters to the postsynaptic cell
What are the different parts of a neuron?
Dendrites The cell body The axon hillock The axon The nerve terminal Nodes of Ranvier
What are dendrites?
Dendrites are appendages that receive signals from other cells
What are cell bodies?
The cell body or soma is the location of the nucleus as well as organelles such as the endoplasmic reticulum and ribosomes
What are axon hillocks?
The axon hillock is where the cell body transitions to the axon, and where action potentials are initiated
What is the axon?
The axon is a long appendage down which an action potential travels
What is the nerve terminal?
The nerve terminal or synaptic bouton is the end of the axon from which neurotransmitters are released
What are Nodes of Ranvier?
Nodes of Ranvier are exposed areas of myelinated axons that permit saltatory conduction
What does the synapse consist of?
The synapse consists of the nerve terminal of the presynaptic neuron, the membrane of the postsynaptic cell, and the space between the two, called the synaptic cleft
What is myelin?
Many axons are coated in myelin, an insulating substance that prevents signal loss
What creates myelin?
Myelin is created by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system
What does myelin do?
Myelin prevents dissipation of the neural impulse and cross of neural impulses from adjacent neurons
How are axons organized?
Individual axons are bundled into nerves or tracts
What is the difference between a nerve and a tract?
A single nerve may carry multiple types of information, including sensory, motor, or both. Tracts contain only one type of information
What is a ganglia?
Cell bodies of neurons of the same type within a nerve cluster in ganglia in the peripheral nervous system
What is a nuclei?
Cell bodies of the individual neurons with a tract cluster in nuclei in the central nervous system
What are neuroglia or glial cells?
Neuroglia or glial cells are other cells within the nervous system in addition to neurons
What are astrocytes
Astrocytes nourish neurons and from the blood-brain barrier, which controls the transmutation of solutes from the bloodstream into nervous tissue
What are ependymal cells
Ependymal cells line the ventricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shock absorber
What are microglial cells
Microglia are phagocytic cells that ingest and breakdown waste products and pathogens in the central nervous system
What are oligodendrocytes and schwann cells?
Oligodendrocytes (CNS) and Schwann cells (PNS) produce myelin around axons
What is resting membrane potential?
All neurons exhibit resting membrane potential of approximately -70mV
How is resting potential maintained?
Resting potential is maintained using selective permeability of ions as well as the Na+/K+ ATPase
What does the Na+/K+ ATPase pumps do?
The Na+/K+ ATPase pumps three sodium ions out of the cell for every two potassium ions pumped in
What can incoming signals be?
Incoming signals can be either excitatory or inhibitory
What are excitatory signals?
Excitatory signals cause depolarization of the neuron
What are inhibitory signals?
Inhibitory signals cause hyperpolarization of the neuron
What is temporal summation?
Temporal summation refers to the addition of multiple signals near each other over time
What is spatial summation?
Spatial summation refers to the addition of multiple signals near each other in space
