Midterm Study Deck Flashcards
3 Domains
Bacteria, Archaea, Eukaryotic
What are humans classified as?
Eukarya, Animelia, HomoSapiens
What are the 4 kingdoms of Eukarya?
Protista, Animalia, Fungi, Plantae
Human Characteristics
Bipedalism: walk on two legs, frees hands for carrying
Large brain: relative to body size
Capacity for complex language: written, oral, symbols, etc.
Opposable thumbs: thumbs can move into position to oppose the tips of the fingers
How to answer questions in science?
- Observe and generalize
- Formulate a hypothesis
- Make a testable prediction
- Experiment or observe
* Independent variable: intentionally manipulated or changed
* Dependent variable: changes in response to changes - Modify the hypothesis as necessary and repeat
Chemistry of Living Things: Broken Down
Atoms are the smallest functional units of elements, elements make up matter, matter occupies mass and space, chemical bonds link atoms to form molecules
Name the 5 types of chemical bonds
o Polar covalent bonds
o Non-polar covalent bonds
o Ionic bonds
o Hydrogen bonds
o Van der Waals Force
6 main elements in the body
Oxygen
Carbon
Hydrogen (one of the most important ions in the body)
Nitrogen
Calcium
Phosphorus
Acid
high H+ concentration in solution, pH < 7
Base
Loq H+ concentration in solution, pH > 7
Buffer
any substance that tends to minimize the changes in pH that might otherwise occur when an acid or base is added to a solution
4 types of organic molecules
Carbohydrates
Lipids
Proteins
Nucleic acids
Carbon
Comprises 18% of the body by weight
Can form single, double or triple bonds
Often bonds with hydrogen, nitrogen, oxygen, or other carbons
Can form linear, branched, or ring-shaped molecules
4 valence electrons so wants 4 more
Carbohydrates
Used for energy and structural support
General formula CH2O
Backbone of carbons with hydrogen and oxygen attached in the same proportion as they appear in water
Functions:
* Energy source for most organisms
* Structural support, such as cellulose in plant cell walls
Monosaccharides
Simple sugars
Eg. Glucose, fructose, galactose, RNA, DNA
Glucose monomers can be joined to form more complex carbs
Monosaccharides can be linked together vis dehydration synthesis
* Also called condensation reaction
* Bonding of molecules with removal of water molecule
Disaccharides
two monosaccharides linked together
Sucrose: glucose + fructose
Maltose: glucose + glucose
Lactose: glucose + galactose
Polysaccharides
Store energy
Thousands of monosaccharides joined in linear and/or branched chains
Functions:
* Energy storage
o Starch: made in plants
o Glycogen: made in animals
* Structural support
o Cellulose: indigestible polysaccharide made in plants for structural support
Hydrolysis
Break down organic molecules by addition of water molecule
Lipids
o Insoluble in water (hydrophobic)
o 3 classes
o Lipids are the only class of macromolecules that are not assembled by joining monomers to form polymers
Triglycerides
- Energy storage molecules
- AKA fats and oil
- Composed of glycerol bonded to three fatty acids
o Fatty acudes
Saturated (in fats) - all single bonds between carbons - Can be closely packed
- Generally solid at room temperature
Unsaturated (in oils)—include some double bonds between carbons - Better for you because don’t come together as much
o Stored in adipose tissue
Phospholipids
- Cell membrane structure
o Glycerol plus two fatty acids and phosphate group
o One end of molecule (phosphate and glycerol) is water soluble (hydrophilic head)
o Other end of molecule (two fatty acid tails) is water insoluble (hydrophobic tails)
o Primary component of cell membranes
Steroids
- Carbon-based ring structures – four carbon rings
- E.g. cholesterol
- Hormones
o Estrogen,
o testosterone
Proteins
o Complex structures constructed of amino acides
Long chains (polymers) of subunits (monomers) called amino acids
* A polypeptide longer than 100 amino acids that has a complex structure and function
o Protein Function Depends on Structure, Charges can change the shape of proteins, but function of protein depended on shape.
Amino Acids
- 20 different types
- Amino end, carboxyl end, R group
Amino acids are joined by peptide bonds, which are produced by dehydration synthesis reactions
Peptide Bond
- Forms between carboxyl end of one amino acid and amino end of the next amino acid
Polypeptide
- A polymer of 3–100 amino acids
Primary Structure
- Amino acide sequence
- Stabilized by peptide bonds
Secondary Structure
- How the chain is oriented in space
- Alpha helix
- Beta pleated sheets
- Stabilized by hydrogen bonds
Tertiary Structure
- Three-dimensional shape how proteins twist and fold
- Stabilized by a combination of covalent bonds, ionic bonds, hydrophobic interactions, and hydrogen bonds
- Creates polar and nonpolar areas within the protein molecule
Quaternary Structure
- Two or more polypeptide chains are joined.
Denaturation
permanent disruption of protein structure leading to loss of biological function
Nucleic Acid
o Store genetic information
o Nucleic acids are long chains (polymers) containing monomer subunits known as nucleotides
o Two types of nucleic acids
DNA: deoxyribonucleic acid
RNA: ribonucleic acid
DNA
o DNA contains the instructions for producing RNA
RNA
o RNA contains the instructions for producing proteins
o RNA is shorter, representing only the segment of DNA that codes for one or more proteins
Nucleotides
Building blocks (monomers) of nucleic acids
o Each nucleotide contains
Five-carbon sugar
* Deoxyribose (in DNA nucleotides)
* Ribose (in RNA nucleotides)
Nitrogenous base
* A,G,C,T,U
Phosphate group
Pairing of bases DNA
Adenine-Thyamine (double bonded)
Cytosine-Guanine (triple bonded)
Pairing of bases RNA
- A-Uracil (double bonded)
- G-C (triple bonded)
Prokaryotic Cells
o More “primitive”
o Internal environment of cell is not divided into membrane-bound compartments
o Prokaryotes Lack a Nucleus and Organelles
Prokaryotes include all organisms in the domains Bacteria and Archaea
Prokaryotic cell structure consists of:
* Plasma membrane
* Cytoplasm
* Genetic material is not enclosed by a membrane
* No membrane-bound organelles
Prokaryotic cells are generally smaller than eukaryotic cells
Eukaryotic Cells
o Internal environment is divided into membrane-bound compartments called organelles
o Eukaryotes Have a Nucleus, Cytoplasm, and Organelles
Eukaryotes include human and all other animals, plants, fungi, and protists
Eukaryotic cell structure includes:
* Plasma membrane
* Nucleus
o Membrane-bound genetic material
* Cytoplasm
o Internal cell contents, excluding the nucleus
o Includes soft gel-like fluid called cytosol
* Organelles
o Variety of membrane-bound structures within the cytoplasm with specialized functions
Light Microscope
o Magnifies up to 1000x
o Can be used to view living samples
Transmission Electron Microscope
o Magnifies up to 100 000x
Can reveal internal details of cell structure
Scanning Electron Microscope
Magnifies up to 100 000x
Provides three-dimensional view of cell surface
Nucleus
Controls the cell, information centre Contains DNA.
Large, spherical organelle in the cell. Appears with multiple pores on the surface. Contains a smaller sphere within it
o Double-layered nuclear membrane
o Nuclear pores: permit passage of RNA and proteins
o Chromosomes: D N A (genetic information)
o Nucleolus: site of synthesis of ribosome components
Ribosomes
Synthesize proteins
- Composed of RNA and protein
- Role of ribosomes: site of protein synthesis
- Location
o Free: floating in cytoplasm
These ribosomes synthesize proteins for immediate use in the cell
o Bound: attached to outer surface of endoplasmic reticulum
These ribosomes synthesize proteins that will be transported to other organelles or exported from the cell
Rough Endoplasmic reticulum
manufacturing center (calcium storage, protein synthesis, lipid metabolism)
Layered and ruffled membranous structure continuous with the nuclear membrane. Dotted with ribosomes.
- Highly folded membranous network
- Two types of endoplasmic reticulum (E R)
o Rough E R (has ribosomes on surface)
Attached ribosomes manufacture proteins which may be modified in the E R, particularly those that will be secreted from the cell
o Smooth E R (no ribosomes on surface)
Lipid synthesis, including the synthesis of some hormones
Packaging of proteins and lipids for delivery to Golgi apparatus
Golgi Apparatus
Refines, packages, and ships
Large organelle consisting of stacks of flattened membranous sacs and tubules
- Refines synthesized products
- Serves as packaging and shipping center
- Products are packaged into vesicles and shipped to other locations within the cell or to the cell membrane for export
Vesicles
Membrane bound storage and stripping centers
Small Spherical vesicle that has fused with the inside of the plasma membrane.
Mitochondria
Provide energy (powerhouse of the cell)
Oval or kidney shaped organelle that is filled with a matrix of ruffles.
- Surrounded by a double membrane
- Inner membrane is highly folded, more surface area
- Divides mitochondria into:
Inner compartment
Outer compartment
- Site of cellular respiration
- Utilizes O2 and produces CO2
- Generates (36-38) ATP—a quick source of energy
Nucleolus
Synthesis of ribosomal subunits
A small, dense spherical structure in the nucleus
Plasma Membrane
Controls movement of materials into and out of the cell. Description, Outer edge and barrier of the cell
Cytosol
Semifluid gel material inside the cell
The region between the plasma membrane and the nucleus.
Peroxisome
Destroys cellular toxic waste.
Small, spherical vesicle.
Centrioles.
Microtubular structures involved in cell division
Two bundles of long rods.
Cytoskeleton
Structural framework of the cell.
Long, thin filaments found throughout the cell.
Lysosome
Digests damaged organelles and cellular debris.
Small Spherical vesicle.
Fat
Long term energy source
o Triglycerides
o Long-term energy storage in animals
o Stored in cytoplasm of fat cells
Glycogen
Short term energy source
o Carbohydrate storage
o Short-term energy storage in animals
o Stored in cytoplasm of muscle cells and liver cells
Cytoskeleton
Internal scaffolding - helps maintain cell shape
- Cytoskeleton is composed of:
o Microtubules: tiny hollow tubes of protein
o Microfilaments: thin solid fibers of protein
o Microtubules and microfilaments form framework that supports the cell
Much like tent poles support a tent
o Cytoskeleton also supports and anchors other cellular structures
Cilia
specialized for movement
o Short, many
o Found on cells lining airways and certain ducts
Flagella
specialized for movement
o Long, single
o Enable spermatozoa to swim
Plasma Membrane
Surrounds the cell
- Separates a cell from its environment
- Is selectively permeable
o Permits movement of some substances into and out of the cell, but blocks others
- Enables transfer of information between environment and cell
The Plasma Membrane Is a Lipid Bilayer
- Plasma membrane is composed of:
o Phospholipids: two layers (bilayer)
Polar heads face outside and face the cytoplasm
Nonpolar tails meet in center
o Cholesterol: increases mechanical strength
o Proteins: provide means of transport through membrane for molecules and for information
- Nonrigid
Passive Transport
cell does not need to expend energy for this
o Diffusion
o Osmosis
o Facilitated diffusion
o a type of cellular transport in which substances such as ions and molecules move down their respective concentration gradients.
Active transport
cell must expend energy
Bulk transport
o Involves membranous vesicles to move larger substances
Endocytosis
Exocytosis
- the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.
- Requires a membrane protein (transporter)
- These proteins are sometimes called “pumps”
- Requires A T P or other energy source
Diffusion
movement of molecules from a region of high concentration to a region of low concentration
- Requires that there be a concentration gradient
- A difference in concentration between two points
- High concentration → low concentration
- When the concentration of a substance is the same throughout a solution—it has reached equilibrium
- Diffusion is only effective in the body over short distances (across membranes, within cells)
Osmosis
Diffusion of water across a selectively permeable membrane
* Water moves from an area of low solute concentration to an area of high solute concentration
* Water moves down its own concentration gradient
* Osmotic pressure: fluid pressure required to stop or oppose osmosis
Diffusion Directly Through the Lipid Bilayer
- Small lipid soluble substances can move directly through the phospholipid bilayer without the assistance of a channel or transporter protein
- Transport of small, uncharged, nonpolar molecules
Diffusion Through Protein Channels
- Protein channels span the membrane and enable the transport of some molecules
- Size, shape, and electrical charges of amino acids lining the channel determine what molecules can pass through
o Some always open
o Others are “gated”—the channel can open or close under certain conditions
o Examples of substances transported:
- (osmosis) - Ions
Facilitated Transport
- Also referred to as facilitated diffusion
- Binding of a specific molecule to a membrane transport protein triggers a change in the shape of the protein which then carries the molecule through the membrane bilayer
- Transporter proteins are highly selective for specific substances
- Examples of substances transported:
o Glucose
o Amino acids
sodium-potassium pump
Active Transport
* Transports sodium out of the cell
* Transports potassium into the cell
* Both ions are transported against their concentration gradient
Endocytosis
brings substances into the cell
o A substance in the extracellular environment is surrounded by the cell’s plasma membrane and internalized, forming a membrane-bound vesicle
o Some vesicles are selective and have receptors for specific substances
Example: transport of insulin into cells
Exocytosis
expels substances from the cell
o Substance is contained within a membranous vesicle, which then fuses with the plasma membrane, releasing the substance to the external environment
o Release of wastes, indigestible material, secretion of special products
Tonicity
relative concentration of solutes in two fluids
Isotonic
o Extracellular and intracellular solute concentrations are equal.
o Cells maintain a normal volume in isotonic extracellular fluids.
o Regulatory mechanisms maintain extracellular fluid that is isotonic with intracellular fluid
Hypertonic
o Extracellular solute concentration higher than intracellular solute concentration (OUTSIDE HIGHER THAN INSIDE)
o Water will diffuse out of cell (osmosis)—moving toward the higher solute concentration
o Cell may shrink and die
Hypotonic
o Extracellular solute concentration lower than intracellular solute concentration (OUTSIDE LOWER THAN INSIDE)
o Water will diffuse into cell (osmosis)—moving toward higher solute concentration
o Cell may swell and burst
Glucose
- Energy in glucose is used to generate A T P.
- One glucose molecule may yield 36 A T P.
- A T P can then be used to do cellular work., more readily used
Cellular Respiration
the breakdown of glucose in the presence of oxygen to yield A T P
- Four stages of cellular respiration
- Glycolysis
- Preparatory step
- Citric acid cycle
- Electron transport system and oxidative phosphorylation
Glycogen
1% of total energy reserves
- Can be rapidly catabolized to glucose, which then participates in cellular respiration
Fats
78% of total energy reserves
- Triglycerides have twice the energy of an equal amount of carbohydrates
Proteins
21% of total energy reserves
- Have the same amount of energy as an equal amount of carbohydrates
Lactic Acid
Made when cellular respiration doesn’t have oxygen, pyruvate will build up which converts to lactic acid. Build up in muscle causes burning sensation.
- In the absence of oxygen, glycolysis is the only ATP-producing step available. Glycolysis without oxygen results in lactic acid buildup.
Unicellular Organisms
- Earliest organisms were unicellular
- Unicellular organisms consist of just one cell
- Unicellular organisms depend on their immediate external environment which may vary extensively
Multicellular Organisms
- Consist of many cells
- Larger size
- Able to seek out or maintain a favorable external environment
- Cells specialize and contribute to the well-being of other cells
Tissues
- groups of specialized cells that are similar in structure and perform a common function
- Several types of tissue may be grouped to form an organ
- Four primary tissues
- Connective tissue
- Epithelial tissue
- Muscle tissue
- Nervous tissue
Epithelial Tissues
- Organized as sheets of cells that line or cover various surfaces and body cavities, one or more layers
- Ex. Skin, mouth lining, inner surfaces of digestive tract, lungs, bladder, blood vessel and kidney tubules
- Two basic purposes
- Protection, secretion, and absorption
Glandular epithelia
Epithelial cells adapted to form glands
Glands: epithelial tissues specialized to synthesize and secrete a product
Exocrine glands
(exo- means “outside” or “outward”)
* Secrete their products into a hollow organ or duct.
Examples of exocrine glands are the glands in your mouth that secrete saliva, glands in your skin that excrete sweat, and glands in your stomach that produce digestive acid.
Endocrine gland
- Secrete substances called hormones into the bloodstream.
One endocrine gland is the thyroid gland, which secretes several hormones that help regulate your body’s growth and metabolism.
Squamous Tissue
Flattened cells
Forms outer surface of the skin
Line blood vessels, lungs, mouth, throat
Cuboidal Tissue
Cube-shaped cells
Form lining of kidney tubules, glandular tissue
Columnar
Column-shaped (tall, rectangular) cells
Line digestive tract, certain reproductive organs, larynx
May include goblet cells that secrete mucus
Single Layered Epithelial Tissue
Adapted for diffusion across cell barriers
Line glands, and respiratory, digestive, reproductive systems
Stratified: Multi Layer Epithelial Tissue
Provide protection, as in the skin surface
Basement Membrane
- Noncellular layer directly beneath epithelial tissue
- Composed of proteins secreted by epithelial cells and connective tissue
- Provides structural support to overlying cells
- Attaches epithelial layer to underlying connective tissue
Connective Tissue
- Supports the softer organs of the body against gravity
- Connects the parts of the body together
- Stores fat
- Produces the cells of blood
- Matrix provides the strength
- Two general types
- Fibrous
- Specialized
Fibrous Connective Tissue
- Function: provides strength, support, and elasticity
- Contains fibers and cells embedded in matrix
- Cells: fibroblasts, macrophages, lymphocytes, and neutrophils
- Fibers: collagen, elastic, and reticular
Fibers in Fibrous Connective Tissue
- Collagen fibers: strong, slightly flexible
- Elastic fibers: thinner, can stretch
- Reticular fibers: thin interconnective fibers of collagen
- Provide internal structural framework for soft organs (liver, spleen, lymph nodes)
Fibroblasts
produce and secrete proteins that form the fibers (collagen, elastin)
Cartilage
- Functions:
- Transitional tissue from which bone develops
- Maintains shape of nose and ears
- Protects and cushions joints and vertebrae
- Structure:
- Dense connective tissue of collagen fibers
- Slow to heal when injured
- There are no blood vessels in cartilage, so the mature cells (called chondrocytes) obtain their nutrients only by diffusion through the ground substance from blood vessels located outside the cartilage. Consequently, cartilage is slow to heal when injured.
Bone
- Contains relatively few living cells
- Matrix (ground substance) composed of calcium phosphate
- Does it contain blood vessels?
o Unlike cartilage, bone contains numerous blood vessels, and for this reason it can heal within four to six weeks after being injured.
Blood
- Plasma: cells suspended in a fluid matrix
- Cells: derived from stem cells in bone marrow
- Cell types include:
- Red blood cells: transport oxygen and nutrients to body cells and carry away the waste products of the cells metabolism.
- White blood cells: Found in the immune system to defend the body.
Platelets: Participate in the mechanisms that cause blood to clot following an injury
Adipose Tissue
- Function: fat storage
- Adipocytes: fat cells store fat in vacuoles
- Location of adipose tissue:
- Under the skin
- Around internal organs
- Beneficial roles:
- Insulation
- Cushioning
- Weight loss reduces size of individual adipocytes but does not necessarily reduce their number
Muscle Tissue
- Muscle cells shorten or contract, producing movement
- Muscle cells are called muscle fibers
- Long, thin
- Arranged parallel to each other
Skeletal Muscles
- Connect to tendons which attach to bone
- Contract (shorten) to move body parts
- Composed of thousands of individual muscle fibers (cells) arranged in parallel
- Fibers have multiple nuclei
- Voluntary—under conscious control
- Activated only by nerves
- 600 skeletal muscles
Cardiac Muscle
- Located only in the heart
- Shorter cells, blunt-ended, one nucleus per cell
- Gap junctions: allow direct electrical connections between adjoining cells
- Enable coordinated contraction of entire heart
- Involuntary: heart contracts rhythmically entirely on its own
Smooth Muscle
- Surrounds hollow organs and tubes
- blood vessels
- digestive tract
- uterus
- bladder
- Slim cells tapered at ends
- One nucleus per cell
- Gap junctions enable coordinated contraction
- Involuntary
Nervous Tissue
Consists primarily of cells that are specialized for generating and transmitting electrical impulses throughout the body. It forms a rapid communication network for the body. Nervous tissue is located in the brain, the spinal cord, and the nerves that transmit information to and from various organs.
Neuron
specialized nervous system cell
- Function: generate and transmit electrical impulses
- Structural components
cell body: nucleus and most of the cytoplasm
dendrites: cytoplasmic extensions from cell body, receive signals from other neurons
axon: transmits electrical impulses long distances
Glial Cells
- Function:
Surround and protect neurons
Provide nutrients to neurons
Organs
- Structures composed of two or more tissue types joined together; perform specific functions
Organ Systems
- Groups of organs that together serve a broad function that is important to survival either of the individual organism or a species.
Anterior Cavity
- Whole Front of body
- Divided by diaphragm into:
Thoracic cavity
Two pleural cavities (each contains a lung)
Pericardial cavity (encloses the heart)
Abdominal Cavity
Pelvic cavity: lower part of abdominal cavity
Posterior cavity
Back of head: Cranial + Vertebral
Cranial Cavity
Head
Spinal Cavity
Spine
Three body planes
- Midsagittal
Divides body into left and right sides - Frontal
Divides body into front and back - Transverse
Divides body into top and bottom
Anterior
at or near front
Posterior
at or near back
Procimal
nearer to any point of reference, usually the body trunk
DIstal
farther away from a point of reference
Superior
situated above or directly upward
Inferior
situated below or directed downward
Integumentary system
includes skin, hair, nails, glands
* Protection from dehydration (helps prevent our bodies
from drying out)
* Protection from injury (such as abrasion)
* Defense against invasion by bacteria and viruses
* Regulation of body temperature
* Synthesis of an inactive form of vitamin D
* Sensation: provides information about the external
world via receptors for touch, vibration, pain, and
temperature
Epidermis
- Outer layer of skin
- Multiple layers of stratified squamous epithelial cells
- Continually replaced by dividing cells at base of epidermis
- No blood vessels
Keratinocytes
Provide structural integrity to the epidermis. It produces a tough waterproof protein called keratin.
Melanocytes
Located near the base of the epidermis, produce a dark brown pigment called melanin, which is then picked up and stored by the nearby keratinocytes.
Protects us against the suns ultraviolet radiation, exposure to sunlight increases melanocytes activity
Dermis
- Primarily dense connective tissue
Collagen, elastic, reticular fibers - Lies underneath the epidermis
- Supports tissues
Hair
- Shaft above the skin surface
- Root below surface in the hair follicle
- Follicle: sheath of several cell layers that supports the root
Smooth Muscle
- Attached to hair follicle, Why?
o Contracts when you are frightened or cold, causing your hair to become more erect
Sebaceous Glands
- Secrete sebum, which moistens and softens skin
Sweat Glands
- Secrete sweat to help in temperature regulation
- Contains antimicrobial peptide that protects against bacteria
Blood Vessels
- Supply nutrients, remove waste, assist in temperature regulation
Sensory Nerve Endings
- Detect heat, cold, touch, deep pressure, vibration
Homeostasis
Constancy of the conditions within the internal environment
* Multicellular organisms devote a significant portion of their metabolic activities to maintaining homeostasis
Homeostasis Is Maintained by Negative Feedback
Negative Feedback
Deviations from normal are detected and counteracted
* Components of a negative feedback control system
* Controlled variable: any physical or chemical property that might vary and must be controlled to maintain homeostasis
* Sensor (receptor): monitors current value for controlled variable and sends information to control center
* Control center: receives input from sensor, compares value to set point, signals the effector if necessary
* Effector: takes action to correct the imbalance, based on information from the control center
Positive Feedback
- Relatively uncommon in living organisms
- A change in a controlled variable causes a series of events that amplifies the original change
- Example: Childbirth, once labor has started the child must be born to end the positive feedback loop
- Positive feedback is NOT a mechanism for maintaining homeostasis
Muscle Composition
- Muscle tissue is found in every organ
- Muscles participate in every activity that requires movement
- All muscle cells have one mechanism of action
– They contract, then relax - Large proportion of body weight is muscle
– 40% of body weight in males
– 32% of body weight in females
Voluntary Movement
conscious control over movement (picking up a pen)
Involuntary Movement
unconscious control over movement (beating of heart)
Synergistic muscles
act around a moveable joint to produce motion similar to or in concert with agonist muscles. They often act to reduce excessive force generated by the agonist muscle and are referred to as neutralizers
Antagonistic muscles
The muscle that works in the opposite direction as that of the primary muscle or agonist muscle, which is engaged in some activity.
Tendons
Muscle to bone attachment
Composed of tough connective tissue containing collagen
Tears and other injuries are very slow to heal
Fascicles
Bundles of muscle fibers (cells)
wrapped with connective tissue
(fascia)
Sarcomere
contractile unit of myofibrils
A sarcomere is a segment of myofibril extending
from one Z-line to the
One myofibril within one muscle cell may have
100,000 sarcomeres arranged end to end
Myosin
Forms thick filaments
Myosin filaments are in middle of
sarcomere, between actin filaments
Actin
Forms thin filaments
Actin filaments are linked to Z-line
Z-lines
Attachment points for sarcomeres
Muscle Contraction
- Muscle contraction: each sarcomere shortens a little
- Basic process of contraction
- Skeletal muscle must be activated by a nerve impulse
- Nerve activation increases the concentration of calcium ions in the vicinity of the contractile proteins
- Presence of calcium ions enables contractions
- When nerve stimulation stops, contraction stops
- Acetylcholine
- Acetylcholine (neurotransmitter) is released from motor neuron at neuromuscular junction.
- Acetylcholine diffuses across neuromuscular junction to muscle cell receptors.
- Binding of Acetylcholine to muscle cell receptors generates electrical impulse within muscle cell.
- Electrical impulse is transmitted through the cytoplasm.
Calcium Initiates Sliding Filament
- Activation Releases Calcium
- Electrical impulse triggers calcium ion release.
- Calcium is released from sarcoplasmic reticulum (modified smooth endoplasmic reticulum). initiates chain of events that cause contraction when it contacts the myofibrils.
1. Calcium is released from sarcoplasmic reticulum.
2. Calcium binds to troponin.
3. Troponin–tropomyosin complex shifts position.
4. Myosin binding site on actin is exposed.
5. Myosin heads form cross-bridges with actin.
6. Myosin heads bend, pulling actin filaments toward center of
sarcomere.
7. Sarcomere shortens.
8. Muscle cells shorten.
9. Muscle shortens (contracts).
Sliding filament mechanism
Sliding filament mechanism
Resting muscle
Heads of myosin molecules (thick filaments) do not contact
actin (thin filaments)
Contraction Process
Myosin heads form cross-bridges between thin and thick
filaments
Myosin heads bend, pulling actin filaments toward center of
sarcomere
This process happens repeatedly, shortening the sarcomere
* Thousands of myosin cross-bridges form and myosin heads bend,
moving actin filaments relative to the myosin filaments.
* Hundreds of thousands of sarcomeres shorten, shortening muscle
cells and the entire muscle.
Absence of Ca++
the troponin–tropomyosin blocks the site on
actin where myosin heads can bind
Presence of Ca++
the troponin–tropomyosin complex shifts,
exposing myosin binding sites on actin filaments, enabling cross-
bridge formation
Principle source of energy: ATP
– ATP required for contraction
Provides energy to energize myosin head, form cross-bridge,
and undergo bending.
– ATP required for relaxation
Provides energy to detach myosin head from actin.
* As long as Ca is present, cycle of ATP breakdown, myosin binding,
bending, and detachment occurs repeatedly and sarcomere shortens.
* Nerve impulse ends, energy from ATP breakdown is used to actively
transport Ca back to sarcoplasmic reticulum, enabling relaxation.
Factors that influence muscle activity
Whether bones move
– Degree of nerve stimulation
– Type of muscle fiber
– Muscle mass
– Aerobic capacity
Strength training
– Resistance training
– Builds more myofibrils, particularly in fast-twitch fibers
– Increases muscle mass and strength
Aerobic training
– Activities that cause body to increase oxygen intake
– Builds endurance
– Increases blood supply to muscle cells
– Increase in mitochondria and myoglobin
Activation of Cardiac and Smooth
Muscles
- Involuntary—no conscious control
- Able to contract entirely on their own in absence of nerve
stimulation - Contraction is influenced by autonomic nervous system
- Cardiac muscle:
– Cardiac muscle cells are joined by intercalated discs
– Have gap junctions allowing cells to electrically
stimulate adjacent cells
– Pacemaker cells: cardiac muscle cells that set the
pace of contractions
Arrangement of Myosin and Actin
Filaments
Cardiac muscle
– Sarcomere arrangement of
thick and thin filaments
– Striated appearance
* Smooth muscle
– Filaments arranged in criss-
crossed bundles, not
sarcomeres
– No striations, no sarcomeres
Speed and Sustainability of Contraction
Skeletal muscle: fastest
* Cardiac muscle: moderate
* Smooth muscle
– Very slow
– Partially contracted all of the time
– Almost never fatigues
Muscular Dystrophy
refers to a group of genetic diseases that cause progressive weakness and degeneration of skeletal muscles
– Genetic disease: Duchenne muscular
dystrophy
– Modified dystrophin protein enables leakage of Ca++
into cells
– Extra Ca++ activates enzymes that destroy muscle proteins
– Muscle weakening and wasting
– Muscle mass is replaced with fibrous connective tissue
– Life expectancy: approximately 30 years
Tetanus
An infection caused by bacteria called Clostridium tetani
– Bacterial infection of a wound by Clostridium tetani
– Bacteria produce tetanus toxin
– Death due to respiratory failure
– Preventable by tetanus vaccine
Muscle Cramps
a sudden, unexpected tightening of one or more muscles
Pulled Muscle
when a muscle is stretched too much and part of it tears
Bone
Hard elements of the skeleton
Hard, rigid appearance due to nonliving extracellular crystals of
calcium minerals
* Bones are living tissue containing several types of cells involved in
bone formation and remodeling
* Five important functions of bone
* Support
* Protection
* Movement
* Mineral storage
* hematopiesis
- Stability
- homeostasis
Ligaments
Dense fibrous connective tissue
Attach bone and bones in a synovial joint
* Made of dense fibrous connective tissue
* Provide strength in joints yet enable movement
Cartilage
Specialized connective tissue, fibers of collagen and elastic in a
gel-like ground substance
Cushions vertebrae
Reduces friction in joints
Compact Bone
contains marrow space
Yellow bone marrow (mostly fat) in
marrow space
Spongy Bone
trabeculae form
lattice-like support in ends of long
bones
Spaces may contain red bone marrow
Red marrow contains stem cells which
produce red blood cells, white blood
cells, platelets
Periosteum
connective tissue covering of bone
– Contain Osteoblasts
– Generate new bone during growth and repair
Osteoblasts
bone-forming cells
Osteons/Haversian system
cellular arrangement found in compact
bone
– Extracellular deposits of calcium phosphate enclosing living cells
(Osteocytes)
Osteocytes
Osteocytes arranged in rings called osteons (Haversian
systems)
Central Canal
Blood Vessels
Types of Cartilage
– Fibrocartilage
Intervertebral disks between vertebrae
Menisci in knee joints
– Hyaline
Forms embryonic structure, which later forms bone
Covers and protects ends of long bones in joints, providing
protection, reducing friction
– Elastic cartilage
Flexible
Outer ear, nose, epiglottis
Bone development
- Early fetal development: cartilage models form
– Formed by chondroblasts (cartilage-forming cells) - Later fetal development: osteoblasts replace cartilage
with bone
Long bones continue to lengthen during childhood - Growth occurs at growth plate
- Bones may also grow in diameter as osteoblasts
deposit bone beneath the periosteum
How many bones does an adult
have?
206
Bone Remodeling
changes in shape, size, strength
* Weight-bearing exercise increases overall bone mass and strength
Osteoclasts
cells that degrade bone to initiate normal bone remodeling and mediate bone loss in pathologic conditions by increasing their resorptive activity
Osteoblasts
cells that form new bones and grow and heal existing bones
Osteoporosis
is loss of bone mass due to prolonged imbalance of osteoblast and osteoclast activity
Long Bones
These bones are longer than they are wide and have a shaft with two ends. Examples include the femur, humerus, and radius.
Short Bones
These bones are roughly equal in length, width, and thickness. Examples include the bones in the wrist (carpals) and ankle (tarsals).
Flat Bones
These bones are flat and often provide protection and serve as attachment points for muscles. Examples include the skull bones (such as the parietal bone), scapula, and sternum.
Irregular Bones
These bones have complex shapes that don’t fit into the other categories. Examples include the vertebrae and facial bones.
Skeleton Purpose
Protects, Supports, and Permits Movement
* Provides support for soft organs
* Protects many organs
* Joints provide flexible movement of many parts of the body
Axial Skeleton
made up of the 80 bones within the central core of your bod
* includes the skull, vertebral column (spine), and ribcage
* Axial Skeleton Forms the Midline of the Body
* Skull
* Cranial bones
* Facial bones
* Axial Skeleton: Vertebral Column
Appendicular skeleton
— comprised of the upper and lower extremities, which include the shoulder girdle and pelvis
* Includes the bones of the limbs (arms and legs) and the girdles that attach them to the axial skeleton.
* Appendicular Skeleton
* Includes body parts that attach to axial skeleton
* These are referred to as appendages
* Appendicular skeleton includes:
* Arms, hands, and pectoral girdle
* Legs, feet, and pelvic girdle
Vertebral column
– Also called the backbone or spine
– Protects spinal cord
– Column of 33 irregular bones in the following regions:
Cervical (neck): 7 vertebrae
Thoracic (chest): 12 vertebrae
Lumbar (small of the back): 5 vertebrae
Sacral (sacrum): 5 fused vertebrae
Coccygeal (coccyx): 4 fused vertebrae
– Intervertebral disks: cushion vertebrae; assist in movement and flexibility
Herniated disk
– Also referred to as a “slipped disk”
– Sudden movement or impact may cause intervertebral disks to balloon outward compressing spinal nerves
– Disk may rupture
– Surgical repair may reduce flexibility
* Injury to vertebral column may damage or sever spinal cord
– May result in complete or partial paralysis
Ribs and Sternum
Protecting the Chest Cavity
Ribs protect lungs and heart
– 12 pair
* 10 pair are attached to vertebrae in back, sternum in front
* Lowest two pair are “floating,” attached to vertebrae but Not attached to sternum
Pectoral Girdle
Lends Flexibility to the Upper Limbs
* Permits a wide range of motion
* Connected to rest of body by muscles and tendons
* Can rotate upper arms almost 360 degrees
* Elbows bend and rotate, wrist and fingers can bend and rotate
* Opposable thumbs enable grasping and manipulating objects
* Susceptible to injury
– Dislocated shoulder
– Broken clavicle: one of the most common fractures
– Repetitive stress: carpal tunnel syndrome
Pelvic girdle (hip)
– Supports weight of upper body
– Protects organs in pelvic cavity
– Attachment of legs
- Remodeling of the pelvic girdle in females is triggered by hormones at puberty
- Pelvic girdle in women
- Broader
- Shallower
- Wider opening
- These changes adapt pelvis for pregnancy and birth
Diseases and Disorders of the Skeletal
System
- Sprains
– Stretched or torn ligaments
– Heal slowly (few cells and poor blood supply) - Bursitis and tendinitis
– Inflammation of bursae or tendons - Osteoporosis: excessive bone loss
- Arthritis: inflammation of joints
– Osteoarthritis
– Rheumatoid arthritis
Osteocyte
Mature bone cell
Circulatory System Overview
- Consists of: heart (pump), blood vessels and blood
- Picks up nutrients from digestive system
- Distributes nutrients throughout the body
- Exchanges gases with respiratory system
o Delivers O2 to every cell
o Carries CO2 to lungs for removal - Carries wastes and excess water to urinary system
- Carries metabolic wastes to liver for removal
- Helps regulate body temperature
- Contains specialized defensive cells of the immune system
The Composition and Functions of Blood
- Blood is a specialized connective tissue:
o Formed elements: specialized cells and cell fragments
o Liquid component: Plasma - Volume of blood in the body
o Adult male: 5-6 L
o Adult female: 4-5 L - Blood is five times more viscous than water
Plasma
- Plasma (makes up 55% of whole blood)
o Water
o Electrolytes (ions)
o Proteins (albumins, globulins, clotting proteins)
o Hormones
o Gases
o Nutrients and Waste - Plasma: liquid portion of the blood
- 90% water
- 10% dissolved solutes
o Proteins
o Hormones
o Ions
o Amino acids
o Carbohydrates
o Vitamins
o Metabolic wastes
Formed Elements
- Formed elements (makes up 45% of whole blood)
o Red Blood Cells
o White Blood Cells
o Platelets
Red Blood Cells
- Erythrocytes (red blood cells): 5 million/mm3
- Functions: transport O2 and CO2
- Lack a nucleus and other organelles
- Packed with hemoglobin, which transports O2
- Hemoglobin molecule includes four polypeptide chains and four heme groups that each have iron atoms to O2
- Origin: stem cells in the bone marrow
- Life span: 120 days in humans
Hemoglobin
- Factors affecting binding of hemoglobin
o concentration: higher O2 promotes binding
Lungs: O2 is high, O2 binds readily to hemoglobin
Tissues: O2 is low, hemoglobin releases O2 to tissues - Hemoglobin measurement
o Men: 14–18 gm% Women: 12–14 gm%
Hematocrit
- Hematocrit: the percentage of whole blood that consists of red blood cells
o Men: 43–49% Women: 37–43% - Low hematocrit or hemoglobin may indicate anemia
- High hematocrit may be a response to high elevation. Less O2 available in atmosphere – body adapts by making more red blood cells
- Very high hematocrit is risky because of increased blood viscosity.
Stem Cells
- Stem cells in bone marrow divide continually throughout the life of an individual.
- These stem cells produce all of the types of blood cells.
- Stem cells that divide and produce blood cells are called hematopoietic stem cells.
Erythroblasts
Immature red blood cells
- Erythroblasts transform into erythrocytes in the bone marrow prior to release into the blood.
- Erythroblasts fill with hemoglobin, mature into red blood cells, and discard their nucleus and organelles.
Erythrocytes
Mature Red Blood Cells
Lack nucleus
- Aged RBCs are removed by macrophages (large phagocytic cells) in the liver and spleen.
- Iron and amino acids from hemoglobin are recycled.
- Heme (minus the iron), is converted to bilirubin, discarded through digestive tract.
White Blood Cells
aka Leukocytes
- Produced by division of stem cells in bone marrow
- Functions
o Protect against infection
o Regulate the inflammatory reaction
- Two major categories
o Granular: neutrophils, eosinophils, and basophils
o Agranular: lymphocytes and monocytes
- Most WBCs have a relatively short life span 1-20 days
- Circulating levels can rise quickly in response to infection
- May leave the blood for the interstitial fluid or lymph
Platelets
- Megakaryocytes arise from division of stem cells in bone marrow.
- Megakaryocytes in bone marrow break into fragments called platelets.
- Platelets play an important role in hemostasis.
o If blood vessel is injured, platelets initiate the clotting process.
o Platelets participate in the repair process.
Hemostasis
Stopping Blood Loss
1. Vascular spasm: constriction of blood vessels to
reduce blood flow
2. Platelet plug formation: sealing of the ruptured
blood vessel
3. Coagulation: formation of a blood clot
Blood changes from a liquid to a gel
Complex series of reactions involving at least 12 different clotting proteins in the plasma
Clotting Disorders
- Bleeding disorder
o Hemophilia: deficiency of one or more clotting proteins - Some medications interfere with hemostasis
o Aspirin: blocks platelet clumping
o Ibuprofen and naproxen may have a similar effect
Blood Types
- Blood transfusion: administration of blood directly into bloodstream of another person
- Success depends on matching the blood type of the donor with that of the recipient
- What are the different blood types?
o ABO Blood Types (A, B, AB, O)
o Rh (Rh-Positive) (Rh-Negative)
o 8 different blood types
Antigen
A defensive protein made by the body
- May be on a cell from another individual or on the cell of an invading microorganism
- Red blood cells from another person may have proteins on their surface (antigens) which are different than the molecules on our red blood cell surfaces
- If we receive a blood donation with blood that has these different antigens, our immune system may produce a serious potentially fatal transfusion reaction
- The antigen on the R B C surface determines the blood type
o Individuals have A and/or B or neither antigen on their red blood cell surfaces (A, B, A B, or O)
- Individuals have antibodies against the antigens N O T on their own red blood cells
Antibody
- Antibodies are gamma globulins, proteins found in the plasma
- Many antibodies are directed against infectious microbes
- Other antibodies may be directed against other antigens, such as those found on the cells of blood received in a blood transfusion
- Antibodies may clump and inactivate antigen-bearing cells
Blood Type # Can Receive…
Individual with Type A blood (has anti-B antibodies) can receive A or O
Individual with Type B blood (has anti-A antibodies) can receive B or O
Individual with Type A B blood (has neither antibody type) can receive AB, A, B, O
Individual with Type O blood (has both anti-A and anti-B antibodies) can receive O
Can donate to A, B, AB
Rh Factor
another antigen found on red blood cell surfaces
- 85% of Americans are R h-positive (have the antigen)
- 15% are R h-negative
o These individuals will respond to R h-positive blood by producing anti-R h antibodies
- Can be a problem when an R h-negative woman is pregnant with an R h-positive fetus.
- Mother may produce anti-R h antibodies that cross placenta and damage fetal red blood cells.
- Anti-R h antibodies from an R h negative mother may cause hemolytic disease of the newborn in the R h-positive baby.
- Risk is much higher for second and subsequent pregnancies.
- Can be prevented by giving mother R h o-G A M (anti-R h antibodies) during pregnancy and at delivery
Arteries
o Transport blood away from the heart
o Transport blood under high pressure
o Are thick-walled
Veins
o Store blood and return it to the heart
o Are thin-walled
Blood flows through venules and
veins to the heart
* Serve as blood volume reservoir
* One-way valves permit only one-way blood flow
Capillaries
o Exchange solutes and water with cells of the body
o Are microscopic
Where Blood Exchanges Substances with Tissues
* Structure
o Smallest blood vessels, microscopic
o Thin-walled: one cell layer thick
o Porous
Arterioles
Smallest Arteries
Precapillary Sphincters
Control blood flow from arterioles into capillaries
Vasodilation
Relaxation of vascular smooth muscle
Increases blood flow to capillaries
Vasoconstriction
Contraction of vascular smooth muscle
Decreases blood flow to capillaries
Capillary beds
extensive networks of capillaries
* Function: selective exchange of substances with the interstitial fluid
o Beginning of capillary bed, fluid is filtered out of capillary to interstitial fluid, including oxygen, nutrients; urea and diffuse from cells back into the blood Driven by blood pressure
* Later in capillary bed, most fluid is reabsorbed by diffusion
o Driven by presence of protein in plasma but not in the interstitial fluid
Heart Stats
- Pump composed entirely of living cells and cellular materials
- Output can vary from 5 liters to 25 liters of blood/minute
- Heart rate at rest: 75 beats/minute
- Heart rate can accelerate to over 200 beats/minute with exertion
- Heart can beat on its own, yet heart rate can be modified by the nervous system
Pericardium
Fibrous Sac that surrounds the heart
o Protects and anchors the heart
Epicardium
outermost thin layer of epithelial and connective tissue
External Layer
Myocardium
Thick layer of cardiac muscle (sandwiched by the epicardium and endocardium)
Electrical signals flow directly from cell to cell
This layer contracts when the heart beats
Middle Layer
Endocardium
Innermost thin layer of endothelial tissue
Continuous with lining of blood vessels
INNer layer
Heart 4 Chambers
- Four chambers
o Two atria: upper chambers
o Two ventricles: lower chambers
o Septum: muscular partition separating right and left sides of the heart
Heart 4 Valves
prevent backflow
o Two atrioventricular (AV) valves
Tricuspid valve (right side)
Bicuspid (mitral) valve (left side)
o Two semilunar valves
Pulmonary valve
Aortic valve
Pulmonary Circuit
Lungs
Blood picks up O2 gets rid of CO2
1. Deoxygenated blood from the body travels through the vena cava to the right atrium of the heart.
2. Through the right A V valve into the right ventricle
3. Through the pulmonary semilunar valve into the pulmonary trunk, which divides into the right and left pulmonary arteries and travels to right and left lungs
4. Blood is oxygenated and CO2 is given up within pulmonary capillaries
5. Oxygenated blood travels through the pulmonary veins back to the heart, entering the left atrium
Systemic Circuit
Rest of body
O2 is delivered, CO2 waste is picked up
1. Oxygenated blood flows from left atrium through left A V valve into left ventricle
2. Oxygenated blood continues from the left ventricle through the aortic semilunar valve into the aorta
3. Through branching arteries and arterioles to tissues
4. Through the arterioles to capillaries
5. Within capillaries, nutrients and oxygen are delivered and wastes are picked up
6. From capillaries into venules and veins
7. To the vena cava and into the right atrium
Atrial Systole
(0.1 second)
o Both atria contract
o A V valves open, semilunar valves are closed
o Ventricles fill
Ventricular Systole
(0.3 second)
o Both ventricles contract
o A V valves close, semilunar valves open
o Blood is pushed into pulmonary trunk and aorta
Diastole
(0.4 second)
o Both atria and ventricles relax
o Semilunar valves close
LUB
closing of both A V valves during ventricular systole
DUB
closing of both semilunar valves during ventricular diastole
Sinoatrial node
small mass of cardiac cells in upper right atrium
o Cardiac pacemaker
o Initiates the heartbeat spontaneously
o Pace can be modified by nervous system
* Atrioventricular (A V) node
o Located between atria and ventricles
o Relays impulse
Electrocardiogram (E K G/E C G)
- A record of the electrical impulses in the cardiac conduction system
- ECG involves placing electrodes on the skin at the chests, wrists, and ankles. The electrodes transmit the hearts electrical impulses, which are recorded as a continuous line on a screen or moving graph.
- E K G s can detect
o Arrhythmias
o Ventricular fibrillation (rapid irregular ventricular contraction)
Blood Pressure
- The blood exerts force on the wall of the blood vessels
- Blood pressure is highest in arteries, much less in capillaries, lowest in veins
- Sphygmomanometer device used to measure blood pressure
o Inflatable cuff is positioned over the brachial artery
o Gauge or digital screen reports the pressure - Units: m m H g (millimeters of mercury)
Systolic
highest pressure, as blood is ejected during ventricular systole
high point of pressure during cardiac cycle
o Systolic pressure <120 m m H g
Diastolic
lowest pressure, as blood returns to the heart during ventricular diastole
low point of pressure during cardiac cycle
o Diastolic pressure <80 m m H g
Hypertension
High Blood Pressure Can Be Dangerous
* Sustained elevation in blood pressure
o Systolic pressure ≥ 140 mm Hg
o Diastolic pressure ≥ 90 mm Hg
* Risk factor for cardiovascular disease
o Higher blood pressure causes greater strain on cardiovascular system
o Blood vessels react by becoming hardened and scarred
o Strain on heart from having to work harder
Hypotension
When Blood Pressure Is Too Low
* Low blood pressure
* If low enough, may cause dizziness or fainting
* May follow abrupt changes in body position
o Standing up suddenly
* May result from excessive blood loss or fluid loss from burns
Heart Attack
- If blood flow to an area of the heart is impaired long enough – sudden death of an area of heart tissue due to oxygen starvation
- Sudden death of the affected myocardium
- Symptoms
o Intense chest pain, sense of tightness or pressure on the chest that makes it hard to breath, and pain radiated down the left arm. Women tend to experience nausea and jaw and back pain. - Requires immediate medical attention
- Treatment and/or prevention
o Control of arrhythmias
o Clot-dissolving medications
o Coronary artery bypass graft (C A B G)—vein from leg is grafted in order to bypass obstructed coronary artery
Congestive heart failure
weakness of heart causes fluid back-up in interstitial spaces
o Out of breath, swollen ankles, legs, neck veins
* Why does the heart weaken?
o Age, prior heart attacks, leaky heart valves, lung disease, uncontrolled hypertension
* Treatment
o Improve cardiac performance, efficiency
o Prevent accumulation of interstitial fluid
o Medications:
Diuretics: remove excess fluids
Medications to cause heart to beat more forcefully
Embolism
- A sudden blockage of a blood vessel by material floating in the bloodstream
- Often a blood clot breaks away from a larger clot elsewhere
- May be cholesterol deposits, tissue fragments, cancer cells, clumps of bacteria, bubbles of air
- Locations
o Pulmonary embolism—chest pain, shortness of breath
o Cerebral embolism—may cause a stroke
o Cardiac embolism—may cause a heart attack
Stroke
- Damage to part of brain caused by an interruption in blood supply
- Two common causes
o Embolism blocking a vessel
o Rupture of a cerebral artery - Symptoms: depend on area of brain affected
- Immediate medical care is crucial
o If embolism, patient receives clot-dissolving drugs
o If rupture, surgical repair is sometimes possible - Recovery may require extensive rehabilitation
Pathogens
A subset of these microorganisms and viruses that cause disease
o Cancer cells
VIruses
o Extremely small, much smaller than bacteria
o Living? …..
Open to debate
Unable to reproduce outside of a host cell
No metabolic activity
o Structure
Contain D N A or R N A, not both
Nucleic acid is surrounded by a protein coat (capsid)
o Diseases caused by viruses include
AIDS, COVID-19, hepatitis, encephalitis, rabies, influenza, colds, warts, chicken pox, Ebola hemorrhagic fever
Epidemic
large outbreak of infectious disease in a particular community, population, or region
Pandemic
epidemic that spreads to many countries or worldwide
* Example: COVID-19
Lymphatic System
1. Maintenance of blood volume in cardiovascular system
2. Filtration of foreign material to defend against infection
Lymphatic Vessels
o Network of vessels, similar in structure to veins
Drain into cardiovascular system through right lymphatic duct and thoracic duct
o Lymph is a milky fluid containing
White blood cells
Proteins
Fats
Occasionally bacteria and viruses
Lymph Nodes
o Lymph nodes are located at intervals along lymphatic vessels
o Nodes remove microorganisms, debris, and abnormal cells from lymph
o Small, 1 m m to 2.5 m m in size
o Nodes are composed of connective tissue, macrophages, and lymphoctyes
o Nodes act as filters
Spleen
o Largest lymphatic organ
o Located in upper left abdominal cavity
o Two regions of spleen
Red pulp
* Removes old and damaged red blood cells
* Temporary blood storage
White pulp
* Contains lymphocytes, searching for pathogens
o Diseases that cause spleen enlargement
Infectious mononucleosis, leukemia
o Spleen can be removed with minor medical impact
Thymus Gland
Located behind sternum, above heart
Site of maturation of T cells (T lymphocytes)
Largest, most active during childhood
Atrophies with age
Tonsils
Masses of lymphatic tissue near the entrance to the throat
Filter food and air entering the throat
Sometimes become infected: tonsilitis
Adenoids
Lymphatic tissue near back of nasal passages
Filter air
First line of defense to keep pathogens out
Skin—an effective deterrent
Tears and saliva—contain lysozyme (antibacterial enzyme)
Ear wax—entraps microorganisms
Mucus—entraps microorganisms
Coughing, sneezing
Stomach—highly acidic, inhibits microorganisms
Vomiting, urination, and defecation—remove microorganisms
Probiotics
dietary supplements that contain living microorganisms, intentionally consumed to establish or restore beneficial microbiota
Prebiotics
dietary supplements or foods that are consumed to encourage the growth of beneficial microbes in the gut
Second Line of Defense
o Varied group of defenses that attack pathogens that have breeched the physical and chemical barriers of the first line of defense
o Include:
Complement proteins
Phagocytic cells
Inflammation
Natural killer cells
Complement system
o Includes at least 30 proteins that circulate in the blood in an inactive state
* When activated by invading microorganisms, the activated complement proteins defend by:
o Creating holes in the invading microorganisms
o Enhancing inflammation, which attracts phagocytes
o Directly lysing invading microorganisms
Phagocytes
o Phagocytes are white blood cells that engulf and digest foreign cells through the process of phagocytosis
o Some phagocytes are constantly on the move seeking out invaders; others take up residence in lymph nodes, spleen, lungs, other tissues
Neutrophils
- “first reponders”
- Initiate inflammatory cascade
- Self destruct after eating microorganisms (pus)
Macrophages
Form monocytes that leave the vascular system and enter tissue fluids
* Can be fixed or free in the body
* Can eat microorganisms over and over
Inflammatory response
- Inflammation: Redness, Warmth, Swelling, Pain
- triggered by tissue injury
o Signs: Redness, Warmth, Swelling, Pain
o Purpose: dispose of cellular debris and pathogens, and initiate tissue repair
o Process:
Injured cells release histamine and other inflammatory mediators
Inflammatory mediators cause increased blood flow to the area and attract phagocytic cells
Phagocytic cells engulf invading microbes and clean up debris
Repair mechanisms are initiated
o Mass cells: in connective tissues
Natural Killer Cells
are a type of lymphocytes
o Able to recognize:
Virus-infected host cells
Tumor (cancer) cells (they can kill your own cells that become cancerous)
o Contact their target cells:
Make a hole in the target cell membrane or can engulf them
Release enzymes into the target cell to destroy it
Pyrogens
substances that produce a fever
o Pyrogens cause the brain to reset the body’s thermostat at a higher temperature
o Fever’s defensive properties:
Makes the body less hospitable to pathogens
Enhance body’s defenses
Third line of defense
The immune response
Characteristics:
* Recognizes and targets specific pathogens and foreign substances
* Has “memory”—“remembers” initial exposure and responds more quickly and aggressively on subsequent exposures
Able to distinguish between:
* “Self” cells and foreign, “nonself” invaders
* Healthy cells and abnormal (tumor) cells
Antigen Immune Response
foreign substance that triggers an immune response
Usually protein or polysaccharide
* Often on outer surface of an invading bacteria or virus
M H C (major histocompatibility complex) proteins
* Self-antigens that are on human cell surfaces, enabling recognition of “self”
* Enable immune system to distinguish “self” from “nonself”
* Your body recognizes these as uniquely “you” but they would appear foreign (antigenic) to someone else’s immune system
Lymphocyte
a type of white blood cell, originating from stem cells in the bone marrow
B Lymphocyte
Antibody-mediated immunity
Antibodies
proteins made by descendants of B lymphocytes that bind with specific antigens
* Have after first infection
Active against viruses, bacteria, and soluble foreign molecules
Identify microorganisms
B memory cells remember these organisms
Tag the specific microorganism, can have multiple antibodies on the same organism
* Can clump multiple of the microorganisms together “big blob”
Circulate in blood and lymph, also found in mucous secretions and breast milk
Bind to the specific antigen that triggered their production forming antigen-antibody complexes
* May cause agglutination (clumping) of antigens
* May “tag” the antigen and promote its recognition and removal by phagocytic cells
* May activate complement, which then lyses the antigen-bearing cell
* May neutralize viruses, bacteria, and toxins by blocking their ability to bond to host cell receptors
T Lymphocyte
Cell-mediated immunity
Directly attack foreign cells or infected “self” cells
Active against cancer cells, cells with “nonself” M H C
Responsible for cells, typically tumor causing or cancer causing “cells gone rogue”
T Cells
Originate from stem cells in the bone marrow
Mature in the thymus
o T-cells located in the plasma
Helper T Cells
Secrete cytokines, which stimulate other immune system cells
Play a key role in directing the immune response
Are targets of H I V infection
Cytotoxic T Cells
Directly attack and destroy abnormal (tumor or viral-infected) cells and foreign cells
Host cells that are cancerous (tumor cells)
Transplanted organs or tissue (if not appropriately matched)
o Cytotoxic T cell binds to target cell
o Cytotoxic T cell secretes two proteins which together destroy the target cell
Perforin: forms a pore in the target cell plasma membrane
* Perforin pokes a hole in the target cell
o Granzyme: enters the pore and digests and kills the target cell
Memory T Cells
Reactivate during later exposures
Protects against future infections
Remembers infections from before so can protect better in the future
Primary immune response
Occurs on first exposure to antigen
Characteristics:
* Lag time (delay) of 3-6 days for antibody production
* Antibody production peaks at 10-12 day
Secondary Immune Response
Occurs on second or subsequent exposures to antigen
* Minimal lag time (hours)
* Antibody level (titer) rises much more quickly
* Much more antibody is produced
* Antibody levels stay elevated longer
Due to long-lived memory cells produced during primary response
Active Immunization
- Intentionally expose individual to a form of the antigen that doesn’t produce disease (vaccine) – weakened or dead
- Also known as vaccination
- Vaccine may be:
o Killed or inactivated pathogen
o Attenuated (weakened) pathogen
o Some part or component of the pathogen (subunit)
o Piece of nucleic acid (D N A or R N A) that encodes an antigen from a pathogen - Recipient will develop a primary immune response including memory cells
- Recipient is now primed for a strong secondary response when exposed to the pathogen in the future
Passive Immunization
- No vaccines
- Administer protective antibodies to an individual from a doner
Antibiotics
o Antibiotics kill bacteria or inhibit their growth
Antibiotics are selectively toxic for bacteria by targeting features of bacterial cells that are different from eukaryotic cells
* Example: penicillin inhibits bacterial cell wall synthesis
Narrow spectrum antibiotics: effective against a small group of bacteria
Broad spectrum antibiotics: effective against a wider variety of bacteria
* May have negative impact on normal microbiota
Antibiotics are not effective against viruses
Allergies
hypersensitivity reactions
Inappropriate response to an allergen
Allergen: any substance (antigen) that causes an allergic reaction (not a pathogen, but the body reacts as though it is a pathogen)
Examples of allergens
* Pollen
* Mold spores
* Dust mites
o Treatment of allergies
Antihistamines – treatment of mild to moderate reactions
Epinephrine injection – treatment of anaphylactic shock
Allergy shots
