final exam bio Flashcards
metabolism
bio chem runs that allow cell/organism to extract energy from its surroundings and use it for homeostasis, growth and reproduction
organic molecules
carbohydrates, lipids, proteins, nucleic acids
monosaccharides
main fuel cells use for work
in aqueous solns can form rings
disaccharide
consists of 2 mono linked via dehydration rxn
sucrose = glucose + fructose
lactose = glucose + galactose
maltose = 2 glucose
polysaccharides
polymers of monosaccharides
long chains of sugar units
starch: long chain of glucoses (plants)
glycogen: same but with branches (animals, muscle)
cellulose: same but with different linkage (cell walls of plants, structural component) (most abundant) (dietary fiber)
lipids
- C and H linked by nonpolar covalent bonds, so mostly hydrophobic and insoluble in water
fats, phospholipids, steroids
fats
type of lipid
- dietary fat composed mostly triglycerides
- made from glycerol + 3 fatty acids (bound by dehydration rxn)
function: energy storage, cushioning, insulation
unsaturated fats
fewer than max # of H bonded to the C resulting in a double bond (bend in fatty acid chain)
- lower melting point (oils)
- liq @ room temp (plants/fish triglycerides)
mono/poly depending on how many double bonds (trilinolein)
saturated
all C’s of the fatty acid backbone are bonded to max # of H
- solid @ room temp
- animal triglycerides
- easily stack
atherosclerosis
lipid containing deposits (plaque) build up in walls of blood vessels, reduce blood flow
- saturated fat diet leads to this
essential nutrients
differ from animal to animal,
- substances animals require in diets but can’t make for themselves
- essential amino acids, fatty acids, minerals and vitamins
human requirement:
- 8 essential amino acids
- 13 vitamins (water and fat soluble)
- large # of essential minerals (macro/micronutrients and trace elements)
8 essential amino acids
methionine
tryptophan
leucine
phenylalanine
threonine
valine
isoleucine
lysine
vitamins (water v fat soluble)
water soluble
- often precursors of coenzymes
- coenzymes: non protein organic subunits that associate with/ enzymes to aid in catalysis
riboflavin B2 -> FAD component
niacin -> NAD+
fat soluble
- variety roles
vitamin A -> visual pigment
minerals
ions (neurons, muscle contraction), structural material (calcium), parts of other molecules (iron in hemoglobin)
how does digestion work? + digestive structures common to all mammals
- food is pushed through digestive tube by peristalsis (muscular contractions of wall)
- 4 lvls of gut
- storage of food @ locations in tube allows for digestion while engaged in other activities
structures common to all mammals
- mouth, pharynx, esophagus, stomach, intestine, anus
stomach
stores food + continues digestion
secretes mucus and gastric juice
small intestine
completes digestion and begins absorption of nutrients
- nutrients absorbed many are processed in the liver
duodenum receives secretions from liver, gallbladder, and pancreas
large intestine
primarily absorbs water and mineral ions from digestive residues
- secretes mucus and bicarbonate ions, concentrates undigested matter into feces
sphincter
ring of smooth muscle form valves between major regions of digestive tract
ex.
lower esophageal sphincter: between esophagus and stomach
pyloric sphincter: between stomach and small intestine
where does digestion start?
mouth more specifically salivary glands (secrete lubricating mucus, amylase enzyme, starch digesting enzyme + lysozyme, kills bacteria, and bicarbonate ions)
liver
secretes bile, which emulsifies fats, and bicarbonate ions
gallbladder
stores and concentrates bile secreted by liver
pancreas
secretes enzymes that break down all major food molecules and bicarbonate ions that neutralize digestive contents
rectum
stores feces, distensión stimulates expulsion of feces
4 major layers of the vertebrate gut
- mucosa
- submucosa
- muscularis
- serosa
mucosa
lines inside of gut
epithelial cells that absorb nutrients, seal off digestive contents from body fluids
glandular cells: secrete enzymes, mucus, pH regulation
submucosa
elastic connective tissue, neuron network, blood + lymph vessels
neural network: local control of digestive activity
muscularis
formed by circular layer (constricts gut diameter) and longitudinal layer (shortens + widens gut)m, does peristalsis
- oblique layer (stomach only)
serosa
outermost gut layer, connective tissue that is continuous w/ mesentery (tissue that suspends dig organs in abdomen)
secretes lubricating fluid to reduce friction between organs
chyme
partially digested food
bolus
food mass from mouth
epiglottis
blocks trachea when swallowing
swallowing reflex
- elevation of soft palate to prevent food bolus from entering nasal passages
- pressure of tounge seals back of mouth and prevents bolus from backing up
- larynx moves upward, pushing glottis against epiglottis to prevent bolus from entering airway
glottis
middle part of larynx, where vocal cords are located
gastric juice
hydrochloric acid and protein digesting enzyme, pepsin + mucus (secreted by glandular cells)
chief cells
secrete pepsinogen (precursor to pepsin)
positive feedback mechanism
parietal cells
secrete H+ and Cl-
HCL can activate pepsinogen to form pepsin
gastric pits
indentations in stomach that contain
surface epithelial cells, mucous cells, chief cells, and parietal cells
what stimulates release of secretion of cells
when food enters stomach, stretch receptors in stomach wall are activated
gastrin
major hormone that regulates acid secretion in the stomach
- stimulated by stomach distension + presence of digested proteins (amino acids)
stomach pH
2: optimal pH for pepsin
- helps unfold and break down proteins
- kills unwanted bacteria
function of stomach mucus
protects stomach wall from acidity and breakdown from pepsin
how long does it take for the stomach to empty after a meal? which nutrient takes the longest to digest and where is it digested?
1-6 hours
fat - small intestines
where does the most digestion occur?
small intestine
how are proteins/polysaccharides/triglycerides/nucleic acids broken down in small intestine?
proteins: endopeptidases, exopeptidases
polysaccharides: hydrolysis by amylase (from pancreas), then disaccharidases
triglycerides: hydrolyzed by lipase
nucleic acids: hydrolyzed by nucleases (DNase, RNase)
absorption of nutrients in the small intestine (what structures help and why?)
starts here
optimize absorption by
intestinal villi: folds in lining of small intestine
microvilli: projections of plasma membrane of epithelial cells (brush border)
greatly increase surface area of intestine
- have capillaries and lymphatic vessels (fat goes here)
lacteal
the lymphatic vessels of the small intestine that absorb digested fats
what is the first part of the small intestine?
duodenum
- where digestive substances from pancreas and liver aid the digestive process
what digestive organ secretes enzymes? which ones?
pancreas through exocrine cells
- bicarbonate HCO3- cells
- proteolytic enzymes: (further break down proteins)
trypsin
chymotrypsin
carboxypeptidase
lipase (breaks down fat)
amylase (sugars)
nucleases
secretes into ducts that empty into the duodenum
what organ secretes bile? what is biles role
liver, stored in common bile duct in gallbladder, released through bile duct when chyme enters small intestine
- emulsifier
types of cells in pancreas
exocrine (secretes enzymes)
endocrine (secrete glucagon and insulin)
duct cells (bicarbonate ions)
endocrine alpha and beta cells in liver (what do they secrete and what do these do)
glucagon (alpha cells) released when blood glucose levels are 2 low
- causes live to convert glycogen to glucose and release into bloodstream
insulin (beta cells) causes cells in liver, muscle and fat tissue to take up glucose from blood
- stores as glycogen in liver and muscle, stopping use of fat as an energy source
bile salts
form a hydrophilic coat around fats (polar/nonpolar side)
how are fats digested?
bile and churning motion of small intestine emulsifies fat into micelles
lipase hydrolyzes fats in micelles into monoglycerides and free fatty acids
in mucosal cell cytoplasm, hydrophobic molecules packaged into chylomicrons
these are secreted into interstitial fluid of submucosa ((extracellular fluid) and taken up by lacteal (lymph nodes), transported from intestine to muscle tissue
micelle
structure that has molecules with hydrophilic head regions in contact with surrounding solvent, sequestering the hydrophobic tail regions in center
chylomicrons + what they’re made of
lipoproteins particles
- protein coat that provides hydrophilic surface that keeps droplets suspended in cytosol of mucosal cell
triglycerides, phospholipids, cholesterol, proteins
lipoproteins and 5 major groups
enable fats and cholesterol to move within bloodstream
1. chylomicrons
2. VLDL
3. IDL
4. LDL
5. HDL
absorption of fluids
small intestine reabsorbs 6-8L of 7-9L fluid release from stomach
- active uptake of salts, passive following water
- large int also absorbs
- water soluble products absorbed by intestinal mucosal cell cytoplasm
- nucleic bases active transport
- pentoses just absorbed with other sugars
protein absorption
endocytosis - large peptides/proteins
Na+ co transporters - amino acids
H+ ion dependent co trans - di/tripeptides
may reduce polypeptides to amino acids or may be carried across cell intact
where do absorbed nutrients go and how? (from small intestine)
nutrient molecules carried by capillaries in mucosal cells (intestinal villae) that collect into veins that join to form the hepatic portal vein -> capillary bed in liver
what happens to absorbed nutrients at the liver?
- excess glucose → glycogen
- fats/amino acids → plasma proteins or sugars
- lipids carbohydrates, etc. synthesize into cholesterol
- albumin made (plasma protein imp for maintaining high pressures)
- synthesizes lipoproteins that transport cholesterol
- detoxifies substances
- blood from liver carried to deliver nutrients to body
large intestine made of (subdivisions) and purpose
cecum, appendix, colon, rectum
absorbs water and mineral ions from digestive contents
- undigested remnants at end (feces) expelled from anus
digestion regulated by:
signals from autonomic nervous system
activity of neuron networks in digestive tube wall
hormones secreted by digestive system
respond to signals from sensory receptors that monitor volume (stretch) and composition (chemoreceptors) of digestive contents
ENS
enteric nervous system
subdivision of PNS directly controls the GI system
imbedded in lining of GI system, efferent/afferent/inter neurons included
sensory neurons report on mechanical and chemical conditions
motor neurons through intestinal muscles control peristalsis and churning of intestinal contents
others control secretion of enzymes
gastrin
chemoreceptors signal neuron networks to stimulate stomach to secrete hormone gastrin -> gastrin stims the stomach to secrete HCL and pepsinogen + contractions in stomach and intestine
secretin
hormone. released when chyme enters duodenum, prevents more chyme from entering till current has been neutralized by HCO3- secretion also stimed by secretin
CCK
cholecystokinin, hormone, stimulated release by fat in chyme (mostly)
inhibits gastric activity (allows time for nutrients to be digested absorbed) and stimulates secretion of pancreatic enzymes and bile from gallbladder
GIP
glucose dependent insulinotrophic peptide, hormone from pancreas
meal entering digestive tract stimulates it
triggers insulin release (insulin stims uptake and storage of glucose)
hypothalamus role in digestion
determining appetite
appetite center
satiety center
what provides input to hypothalamus centers in digestion
stop eating:
- insulin acting on cells of hypothalamus
- glucose uptake by cells of hy
- mechanoreceptor detect distention
- chemoreceptors detect food
hunger: absence of these
long term control: adipose cells
full of fat:
secrete leptin hormone -> binds receptors in hypothalamus -> stims center that red appetite, inhibits center that stims appetite
increase in met rate: oxidize fatty acids rather than convert them to fat
low in fat -> less leptin
increase in appetite
ghrelin
tiggers hunger hormone
PYY
peptide YY secreted by small int after meals suppresses appetite
infection
condition in which pathogenic microorganisms penetrate host defenses, enter the tissues, and multiply
viruses are (characteristics)
obligate intracellular parasites (multiply by taking control of host cells genetic material)
not living (unable to generate energy)
potential for rapid, large scale proliferation
facts:
classified on size, shape, chem comp, structure of genome, mode of replication
fully assembled inf virus = virion
RNA viruses compose 70% of all, error rate of enzymes in RNA rep, these show higher mutation rates than DNA virus
basic structure of virus
protein shell (capsid, made of capsomeres) surrounding nucleic acid core (DNA or RNA)
3 types:
enveloped: outer phospholipid/glycoprotein coat) CoVs HIV
naked: no envelope (papilloma)
complex: extra structures (pox virus)
only have enough genes to invade host cells genetic material and redirect its activity
retrovirus
single stranded RNA virus that stores its nuc acid in form of mRNA genome (HIV)
provirus
when DNA gets incorporated into the host cells genome by an integrase enzyme
special case with multiplication of dsDNA viruses (chickenpox)
viral DNA can stay dormant and be reactivated later
CPEs
cytopathic effects, indicate viral damage to cells
syncytium and inclusion
virions , what damage can viruses do to cells
viruses released by infected cells
- destruction of cell mem, organelles
shut down metabolism genetic expression
release lysosomes
cell death
latency
syncytium
mass of cytoplasm containing several nuclei and enclosed in a membrane but no internal cell boundaries
inclusion
body suspended in cytoplasm such as a granule
how do bacteria cause damage
can produce toxins that disrupt normal cell func
- done by damaging specific cells -> blocking transmission of signals, over stimulating cells so they malfunction
cholera toxin -> disrupts ionic balance of cell membranes -> cells in small intestine secrete large amts of water into intestine -> diarrhea -> dehydration
penicillins
inhibit formation of bacterial cell wall by blocking cross-linking of cell wall structure
tetracyclines
inhibit protein synthesis by binding to the subunit of the bacterial ribosome (305 subunit)
quinolones
blocks DNA syn by inhibiting bacterial enzyme (DNA gyrase) needed in this process
first line of defense (nonspecific)
physical (barrier), chemical, genetic
-skin: resist pathogen penetration, replication
mucous membranes: (chem) prevent attachment to cell, directly inactivate virus
lysozyme: damage bac cell walls, abundant in secretions
acidic env of stomach (pH 2)
specificity of viruses to host cell receptors (genetic)
second line of defense, nonspecific
innate immune system
key players: inflammatory response, phagocytosis, complement, interferons, cytokines
3rd line of defense (specific)
adaptive,/acquired immune system
key players: antibodies, T cells, B cells, accessory cells, cytokines
innate immune system characteristics
nonspecific
acts sooner
responses broad spectrum
no memory of lasting protective immunity
activation can occur in response to general components of pathogens or factors released by damaged cells
PAMPs DAMPs PRRs
PAMPs
pathogen associated molecular patterns
- found on pathogens
lipopolusaccharide (LPS) (found on outer membrane of bacteria)
DAMPs
damage ass mol patterns
cell components released during cell damage/death
(presence of DNA in other than nucleus/mitochondria, triggers responses mediated by TLR9)
PRRs
pattern recognition receptors
id PAMPs and DAMPs
found on some immune cells (phagocytic)
(Toll-like receptors) TLRs (drosophila christine nelson nobel prize)
cytokine
any # of subs, that are secreted by certain cells of immune system and have effect on other cells (Interferon, TNF(alpha and beta), Interleukins or growth factors)
pyrogen
polypeptide that produces fever by causing metabolic changes in hypothalamus (raise set point of hypothalamic thermostat)
fever inhibits x of temp sensitive viruses (polio, cold, herpes zoster) and stims immune rxns (phagocytosis)
exogenous (prod by inf agents)
endogenous (prod by cells in body such as macrophages)
stem cells in bone marrow can become:
granulocytes
monocytes
lymphocytes
granulocytes
class of wbc, granules in cytoplasm (neutrophils, eosinophils, mast cells, basophils)
monocytes
clear cytoplasm, larger, migrate to site of inf and divide /diff into macrophages and dendritic cells
lymphocytes
agranulocytes (no granules in cytoplasm)
found in lymph
term for any 3 types
NK: natural killer
T cells
B cells
during development:
B cells stay in bone marrow
T cells migrate to the thymus
NK cells
function mostly in innate immunity but also in adaptive
T cells
cell-mediated, cytotoxic adaptive immunity
antigen receptors of T cells bind only to antigens that are displayed
B cells
for humoral, antibody driven adaptive immunity
antigen receptors of B cells bind to epitopes of intact antigens on pathogens OR circulating free in body fluids
wbcs
leukocyte, white blood cells
inflammatory response
activated by cell and tissue damage induced by pathogen
interferes with further pathogen replication/multiplication
characteristics/stages
- vascular changes
- inc circulation
- vasodilation
- redness, warmth - swelling: leakage of vascular fluid
- pus is exudate, typically white-yellow, yellow, or yellow brown
- pain=stimulation of nerve endings - prod of chem mediators (molecules) that
- cause fever, stim wbcs
- TNF (chemotaxis, phagocytosis), IFN (inhibits virus replication), IL (activate wbc)
chemokine
type of cytokine that induces directed chemotaxis in nearby responsive cells
mast cells role in inflammation
activate when break in skin introd bacteria, release histamine, histamine and cytokines dilate local blood vessels, chemokines attract neutrophils
histamine
prod by basophils and mast cells found in nearby connective tissues
increases the permeability of the capillaries to wbcs and some proteins, to allow them to engage pathogens in the infected tissues
chemotaxis
tendency of cells to migrate in response to a chemical stimulus
phagocytosis
type of endocytosis: cell membrane actively engulfs large particles or cells into vesicles
ingestion
phagolysosome formation
destruction
excretion
phagocyte
class of wbc capable of engulfing other cells and part
types:
neutrophils: type of granulocytes, short lived
monocytes- large, a granulated
macrophages- diff from monocytes
interferon (IFN)
glycoprotein prod primarily by fibroblasts, lymphocytes, macrophages, epithelial cells, T cells
binding of a virus to a host cell initiates IFN synthesis
IFN secreted by cell into extracellular space
binds to another host cell:
induces prod of proteins
degrades viral RNA or prevents translation of viral proteins
not virus specific, activates NK cells, macrophages, enhances phagocytosis
complement
nonspecific group of proteins found in plasma
forms membrane -> attack complex that kills cells by creating holes in membrane (disrupts osmotic balance, intermembrane proteins)
involved in both types of immunity
complement cascade
3 different complement pathways (as determined by activator)
- classical: C1 binds antigen antibody complex
- lectin: mannose-binding lectin (MBL) binds forgein surface
- alternative: starts with complement protein C3
result: make complement proteins C6-C9 = membrane attack complex
other nonspecific defenses to viruses
RNAi (interference): cellular mech, destroys viral dsRNA, inhibits virus life cycle
NK cells (lymphocytes not phagocytes)
can be activated by interferon
- secrete perforin: cretes pores in target cell, ruptures infected cells
- secrete enzymes to degrade DNA, trigger apoptosis
adaptive/aquired immune response (specific)
keep players
antigens
immunoglobins (antibodies + receptors)
lymphocytes (B and T)
two types of adaptive immune responses
antibody mediated immunity (humoral)
plasma cells (derived from B cells) secrete antibodies that circ in blood, bind to antigens, clear them
cell mediated
specific T cells activated attack and kill forgein pathogens and inf cells
antigen
viruses, forgein cells, molecules that are capable of triggering immune rxns by lymphocytes
can originate from within body (self antigen) or external environment (non self)
- immune system doesn’t usually react to self antigens under normal homeostatic conditions due to neg selection of T cells in thymus (killing)
epitope
precise molecular group of an antigen that defines its specificity and triggers the immune response
gene segment rearrangement
gene segments: encode for receptors on surface of T and B cells, also encode for variable region on antibodies
rearranged extensively, this leads to assortment of receptors on T and B cells
each T or B lymphocyte has a protein receptor of unique config and is specific and reactive to a specific antigen
V(D)J recombination
unique mechanism of genetic recombination that occurs only in developing lymphocytes during the early stages of T and B cell maturation
involves recombination, results in highly diverse repertoire of antibodies/immunoglobulins and t cell receptors found on B cells and T cells
during B cell diff, random V and J DNA segments join with C -> functional light chain gene
DNA between V and J deleted
assembly of heavy chains and formation of T cell receptor occurs similarly
V(D)J recombination
unique mechanism of genetic recombination that occurs only in developing lymphocytes during the early stages of T and B cell maturation
involves recombination, results in highly diverse repertoire of antibodies/immunoglobulins and t cell receptors found on B cells and T cells
polypeptide encodes for variable region in antibody molecule
clone definition
clone: each genetically unique line of lymphocytes arising from the gene segment rearrangement
millions of genetically different clones of T and B cells are generated, each responds to 1 specific antigen
T and B cells then migrate to lymphoid tissues
thymus
spec organ of immune system where T lymphocytes mature
each T cell attacks a different antigen (the receptor is specific to the antigen)
T cells that attack the body’s own proteins are eliminated in the thymus
clonal selection theory
- hematopeietic stem cell undergoes diff and genetic rearrangement to prod immature lymphocytes with diff antigen receptors
- those that bind to antigens from the body’s own tissues are destroyed, rest mature into inactive lymphocytes
- those that encounter matchin forgein antigen are activated to prod many clones of themselves
hematopeietic stem cell
give rise to all other blood cells through process of haematopoiesis located in red bone marrow
immunoglobulins
large glycoprotein molecules
serve as both:
1. antibodies (aka lg; are secreted by plasma cells (wbcs that are derived from B cells and secrete large vol of antibodies) , these reside in blood plasma
-
2. membrane receptors of mature B cells (IgD)
5 classes of antibodies
IgM
IgG
IgA
IgE
IgD
IgM
surface of unstim B cells (as monomer), free in circulation (as pentamer) ‘
1st antibodies sec by B cells in primary response, activates agglutination rxn, complement system and phagocytic activity of macrophages
IgC
blood + lymphatic circulation
most abundant antibody in 1ry and 2dry responses,
crosses placenta (passive imm to fetus)
stim phagocytosis and complement system
IgA
body secretions
blocks attachment of path to mucous membranes, confers passive immunity for breastfed infants
IgE
skin + tissue lining GI and reps tracts (sec by plasma cells)
stims mast cells and basophils to release histamine; triggers allergic responses
IgD
surface of unstim B cells
membrane receptor for mature B cells, probably imp in B cell activation (clonal selection)
allergic rxns
excessive activation of wbcs (mast, basophils) by antibody IgE
- result in inflammatory response
dendritic cells
type of antigen presenting cell (APC) present in tissues in contact with the external environment, such as skin, lining pf nose, lungs stomach intestines
once acti, migrate to lymph nodes + interact w/ T + B cells to initiate adaptive immune response
helper T cells
nearly all antigens elicit helper T response
trigger both a humoral (makes antibodies) and cell mediated response CMI
cytokines from helper T cells:
1. initiate antibody prod (to neutralize pathogens)
2. activate T cells to kill inf cells
(INF, IL, TNF, chemokines)
two req needed for helper T cell to activate the adaptive immune response
- an antigen fragment must be displayed in an APC (antigen presenting cell) (ex. dendritic cells, macrophages, B cells)
having MHC class I + II proteins distinguishes an APC from other cells ( most body cells have MHC class I proteins) - antigen must bind to T cells receptor on the helper T cell
plasma cells
specialized B cells, secrete antibodies to surrounding tissues
antibody activities to antigen
unite with: opsonization (coat virus/pathogen)
immobilize: agglutinate (aggregate): antibodies can cross link
call attention to: binding of Ab enhances phagocytosis
recognition
neutralize: Abs fill receptor site on virus, prevents attachment to host cell
destroy: int of Ab with complement (complement fixation) ruptures some viruses
T cell response in CMI
antigen must be processed and presented by specific apcs (dendritic, b cells, macrophages) or by other infected cells
antigen is complexed with other proteins (MHC) and transported to the cell membrane
CD4+ cells
expressed on mature helper T cells (Th) (also monocytes, macrophages, dendritic cells)
- copreceptor for T cell receptor (TCR)
- specific for the class II MHC protein
- HIV infects them
CD8+ cells
predom expressed on surface of cytotoxic T cells (can also be found on others ex. NK cells, dendritic)
- co receptor for TCR
- CD8 is specific for class I MHC protein
T cell development
initially, some thymocytes express both CD4 and CD8 proteins
Thymocytes
immature cells in the thymus
MHC
major histocompatability complex
group of genes that encode proteins (MHC antigens) found on the cell membrane
in humans MHC genes -> HLA human leukocyte antigen genes
all tissue cells (except mature rbcs) are marked w a characteristic combo of histocompatibility antigens on the surface of the cell membrane, have mechanisms for processing and presenting antigens in association with MHC molecules (this signals immune system if cell is normal or inf)
APCs
i professional antigen presenting cells
immune cells that specialize in presenting a forgein antigen to a helper T cell
main types:
dentritic DC
macrophages
B cells
have both MHC I and II
MHC I role
- occur on all nucleated cells (except rbcs) present epitopes to cytotoxic T lymphocytes (CTL’s)
signal to immune system that cell is normal self cell
in normal cell, proteins found in cytoplasm are degraded by proteasomes and processed into self antigen epitopes
these bind within the MHC I antigen binding cleft and are presented on the cell surface
what role do MHC antigens play in transplants?
greater variance in MHC antigens between the donor and recipient, greater chance of transplant rejection
MHC class II molecules
normally occur on APCs (macrophages, dendritic cells, B lymphocytes
- CD4 (on helper T cell) docks to a n APCs MHC class II molecule
- this binding promotes sec of cytokines by APC
- cytokines stimulate proliferation of helper T cells
helper T;s secrete other cytokines to initiate both humoral response (sec of antibodies by plasma cells) and CMI (attack on infected cells)
CTL
cytotoxic T lymphocytes
expresses CD8+ receptors and T cell receptors TCRs
CTL’s CD8 receptor docks to a MHC class I molecule, if it fits the epitope, triggers cell death
T cell activation process
- antigen/MHC complex binds to T cell receptors (plus co-receptor)
- co-stimulation (ex. cytokines released from APC can activate T cells)
- cells undergo mitosis
diff into
memory t cells
t helper
cytotoxic
T cells (all types)
- distinguished from other lymphocytes by presence of T cell receptors on surface
- originate as precursor cells in bone marrow, develop in thymus gland
- immature cells in thymus: thymocytes (can be double positive sometimes (CD4 and CD8)), eventually down regulate expression of CD# cell surface receptors
- differentiation continues after leaving thymus, in secondary lymphatic organs and tissues (lymph nodes, spleen, tonsils), which is where lymphocytes interact w each other and interact with APCs
naive T cells: not need exposed to an antigen
memory T cells: interact later w antigen
t helper: (CD4 and MHCII)
- B and T cell growth and activation
- release chemical factors: IL, TNF, IFN
cytotoxic T cells (CD8 and MHCI)
- kills specific cells
- perforins: proteins that punch holes in membranes (osmotic gradients)
- granzymes: enzymes that attack proteins of target cells
how t cells are activated (2 steps)
- have to bind their T cell receptors to the MHC protein that is presenting the antigen to them (MHC and antigen are on APC)
- have to have co stim. can be caused by:
- cytokines released from APC
- binding of other molecules like CD28 on T cell with B7 molecule on APC
helper T cells different functions
- release cytokines to make clones (will have T cell receptors spec spec for antigen)
- stim B cells to make memory B cells (have B cell receptors spec to antigen) and plasma cells (that will make antibodies spec to that antigen)
- secrete cytokines that can help activate cytotoxic T cells (among other things, like stim macrophages)
steroids
class of lipids
diffuse readily across cell membrane
structure of steroid s
fused ring system 3 cyclohexanes and 1 cyclopentane
many carbon hydrogens (makes nonpolar)
many functional groups can be attached
ergosterols
fungus steroid
- same function as cholesterol in animals: build and maintain membranes, regulates membrane fluidity over temperatures
phytosterols
plant steroid
- structural comp of cell membrane
brassinosteroids
plant steroid
pollen tube formation, cell expansion and elongation, vascular differentiation
cholesterol
classified as a modified steroid (sterol/steroid alcohol)
essential structural comp of mammalian cell membranes (permeability + fluidity)
- disturbs close packing of phospholipids (lipid bilayer)
- imp comp for manufacture of bile acids, steroid hormones and vitamin D
- can get from body or synthesized in body from carbs, proteins, fat
- carried though blood in lipoproteins (HDL,LDL)
- build up leads to atherosclerosis
steroid
steroid hormone: steroid that acts like hormone
- can be grouped into 5 types by receptors to which they bind
- glucocorticoids (corticosteroid) (cortisol)
- mineralocorticoids (corticosteroid) (aldosterone)
- androgens (sex steroid)
- estrogens (sex steroid)
- progestins (sex steroid)
corticosteroid: syn in adrenal cortex (adrenal gland atop of kidneys)
hormones
signaling molecule secreted by cell that can alter activities of any cell with receptors for it
- prod by 1 tissue and trans through bloodstream (not always) to another tissue to alter its physiological activity
- hormones and local regulators grouped into 4 classes based on chem structure
- reg by feedback pathways
- effective in low concentrations (amplification)
- can be either hydrophilic/phobic
- target cells may respond to more than one hormone, and different target cells may respond differently to the same hormone
involved with controls of:
- development and function of gonads
- metabolism (thyroid hormone)
- inflammation
- salt and water balance in body fluids
- molting in insects and crustaceans (ecdysone)
vertebrate steroid hormones
steroid hormones are lipid soluble
1. sex steroids
2. corticosteroids
- glucocorticoids and mineralocorticoids
sex steroids
subset of sex hormones that produce sex differences or support reproduction
- androgens estrogens and progestins
corticosteroids
most medical steroid drugs (prednisone)
- syn from cholesterol within adrenal cortex
- include glucocorticoids and mineralocorticoids
glucocorticoids
maintain normal blood glucose lvls
- stims glucose syn from fats and proteins
- inhibition of glucose uptake in muscle + adipose
- stims breakdown of fats and proteins -> amino acids + fatty acids used as alt energy
-
mineralocorticoids
maintain blood volume and control electrolytes + water lvls by promoting Na retention in kidney (aldosterone)
anabolic steroids
class of steroids that interact with androgen receptors to inc muscle and bone synthesis
- can be natural or synthetic
- inc prod of actin and myosin proteins, these can be incorporated into existing myofibrils and add to muscular strength
- block fx of stress hormone cortisol on muscle tissue
- affect # of cells that develop into fat storage cells, by favoring cellular diff into muscle cells instead
endocrine system includes 60 major hormones that control:
growth (HGH: somatotropin)
reproduction (LH: lutenizing hormone: stims ovulation)
sexual development (testosterone: sperm prod)
use and storage of energy (glucagon: converts stored glycogen into glucose)
response to physical stress/trauma: cortisol
lvls of fluids/salt/sugar in blood: ADH, aldosterone
endocrine system
- controls activities that involve slower, long acting responses
- works in parallel with nervous system
- collection of glands that secrete hormones usually passed through bloodstream to arrive at target organ, with cells possessing appropriate receptor
- includes 4 major types of cell signaling
exocrine glands
not part of endocrine system
- secrete prod usually passed outside body (sweat glands, salivary glands)
- pancreas has exocrine glands
tropic hormone
hormone that regulates hormone secretion by another endocrine gland (ex. thyroid stimulating hormone)
4 major types of cell signaling
- classical endocrine signaling: endocrine glands secrete hormones (over a distance)
- neuroendocrine signaling: neurosecretory neurons release neurohormones into circulatory system
- paracrine regulation: cells release local regulators that diffuse through extracellular fluid to regulate nearby cells
- autocrine regulation: cells release local regulators that regulate the same cells that produced it
4 molecular classes of hormones
characterized by mol structure
1. amines
- based on tyrosine
- ex. epi, norepinephrine, thyroxine
2. peptides
- amino acid chains
- ex. growth factors, PYY (suppresses appetite)
3. steroids
- can be gen from cholesterol
- ex. aldosterone, cortisol, sex hormones
4. fatty acids
- paracrine and autocrine regulation
- ex. prostaglandins
prostaglandins
- act on array of cells and have variety of fx:
cons/dilation vascular smooth muscle cells
agg/disagg of platelets
sensitize spinal neurons to pain
dec intraocular eye pressure
reg inflammatory mediation
reg Ca movement
control cell growth - potential, short half-life before being inactivated and excreted
- sometimes defined as hormone like lipid compounds
- bind to cell surface 7-transmembrane receptors: G-p coupled receptors
- autocrine and paracrine type mediators
- prod by ox of chemicals by cyclooxygenases (COX-1 and COX-2)
- NSAIDs (aspirin, ibuprofen) inhibit cyclooxygenase
amplification
binding of a hormone to a receptor activates many proteins, which activates even more proteins etc.
- reason why hormones effective in low concentrations
- 1 molecule epi acting on liver cell liberates 10^6 glucose molecules
hydrophilic hormone action mechanism
bind to surface receptors activating 2nd messenger pathways inside cells to elicit a cellular response
(epinephrine)
- usually amines, peptides
hydrophobic hormone mechanism action
bind to receptors inside cells, activating/inhibiting genetic reg proteins
(aldosterone)
- usually steroids
aldosterone hydrophobic hormone action
- inc reabsorption of Na and water and secretion of potassium in the kidneys
- part of RAAS- raises BP (higher water=higher blood volume)
major endocrine cells and glands of vertebrates
glands:
pineal
pituitary
thyroid
parathyroid
hypothalamus
adrenal medulla
adrenal cortex
testes and ovaries
islets of langerhans (pancreas)
pineal gland
produces melatonin: hormone that fx the mod of wake/sleep patterns and seasonal functions
melatonin
int w/ hypothalamus to set body’s daily biorhythms
in some vertebrates (fish, amphibians, reptiles) helps animal change skin color
hypothalamus
review: under thalamus, has centers for apetite control, osmoreceptors, prod ADH (released by pituitary gland), temp reg, releases TRH (stims release of LH and FSH)
- prod and secretes releasing/inhibiting hormones that reg secretions by anterior pituitary
- prod ADH and oxytocin (stored and released by posterior pituitary)
- produces tropic hormones that control secretion of anterior pituitary hormones
other hormones: TRH, CRH, GnRH GHRH, somatostatin (GHIH) (also secreted at locations in digestive system, suppresses release of gastrin, CCK, GIP, secretin, etc.)
oxytocin
uttering contractions during birth, breast milk release, bonding
pituitary 2 major lobes
posterior: contains neurosecretory nerve endings from hypothalamus
- secretes 2 hormones
anterior: non neuronal endocrine cells
- sec 8 hormones
anterior pit hormones
- prolactin (PRL) prod milk - mammary glands
2-3. gonadotropins (FSH (egg dev, female sex hormones, sperm prod) and LH (ovulation, male sex hormones)) prod gametes and hormones - testes/ovaries - TSH inc rate of metabolism - thyroid gland
- ACTH (adrenocorticotropic) reg fluid balance, helps body cope w stress - adrenal cortex
- GH promotes growth - muscle, bone , etc. glucose metabolism, stims IGF (insulin growth factor) release in liver
- melanocyte stim hormone (MSH) promotes skin darkening - melanocytes in skin (prod by cells in intermediate lobe)
- endorphins inhibit pain perception - pain pathways of PNS
posterior pit hormones
ADH/vasopressin inc permeability- nephrons in kidneys
oxytocin - uterus (stims contractions), mammary glands (stim milk release)
adrenalcorticotropin hormone (ACTH)
causes inc prod and release of corticosteroids (glucocorticoid and mineralocorticoids)
- stims glucocorticoid sec in adrenal cortex
- glucose + cortex + steroid (role in metab of glucose, synthesis in cortex and steroid structure)
- dampen immune response
- aldosterone sec mediated by angiotensin II but also by ACTH by lesser extent
thyroid gland
thyroid hormone stim metabolism, growth and development and maturation (also T3 and T4 inc catecholamine fx)
- sec thyroxine (T4) (major hormone, longest half life) triiodothyronine (T3) calcitonin (calcium homeostasis)
- negative feedback from thyroid hormones over hypothalamus as well as anterior pituitary (TRH and TSH)
hypothyroidism
low thyroid output
- physically + mentally sluggish
- low HR, weak pulse
- children: cretinism (stunted growth, diminished intelligence)
hyperthyroidism
overprod of thyroid hormones
- irregular, rapid HR
- irritable
- insomnia
- weight loss
- emotional instability
graves’ disease
cause of hyperthyroidism
- exopthalamos
- enlarged thyroid
autoimmune disease: antibodies activate TSH receptors which stim prod of T3 and T4. thyroxine receptors in pituitary are activated by surplus of T3/T4, suppressing release of TSH.
HIGH lvls circulating thyroid hormones (T3 T4) LOW TSH lvls
goiter
enlargement of thyroid due to insufficient iodine in diet
- iodine needed for T3 and T4 to be prod in response to stim by TSH
no T3/T4, TSH not negatively feedbacked -> thyroid growth
calcitonin
peptide hormone
- secreted by parafollicular cells (C-cells) in thyroid gland
- acts to red blood Ca by:
1. stim Ca deposition in bone (inhibits osteoclast activity)
2. inhib dissolution of Ca from bone
3. in kidney, inhibits reabsorption of Ca allowing it to be excreted in urine
- secretion is stimulated when Ca lvls in blood above normal
- Ca release from bones regulated by parathyroid hormone PTH
bone remodeling/metabolism
lifelong process.
- mature bone tissue removed from skeleton (bone resorption) and new bone tissue is formed (ossification)
in adults, ~10% bone remodeled each yr
bone resorption
process by which osteoclasts break down bone and release minerals, resulting in transfer of Ca from bone fluid to blood
ossification
osteoblasts secrete new bone
ossification
osteoblasts secrete new bone
parathyroid glands
secrete parathyroid hormone
4 parathyroid glands reg Ca lvl in blood
PTH acts to increase concentration of calcium in blood (opp of calcitonin)
- calcium sensing membrane receptors in parathyroid gland monitor Ca lvls in extracellular fluid
- low lvls stim release of PTH
- stims activation of vitamin D, which promotes Ca absorption into blood from food in small intestine
- enhances active reabsorption of Ca from kidney
- stims Ca release from bone
adrenal glands
- on top of kidney
medulla (inner)
secretes: epi and norepi
- catecholamines (der from tyrosine)
- sec in response with sympathetic fight or flight system
cortex (outer)
-secretes: cortisol, aldosterone and androgens
epinephrine
preps body for handling stress/physical activity
HR inc
break down of glycogen, fats -> glucose, fatty acids for energy
can bind to 3 diff receptors (alpha, B1, B2)
- alpha receptors on smooth muscle of blood vessels: vessels constrict -> less blood flow to peripheral regions (pale)
- bind B1 on heart cells: cont inc -> blood flow inc
- bind B2 on liver cells: glycogen breakdown to glucose
overall increases energy
- dilates vessels in skeletal muscles, heart, lungs, constricts others (raised BP)
- red blood flow to kidneys -> red water loss
- inhibits smooth muscle cont inc break intestine -> slow digestion
hormones of adrenal cortex
glucocorticoids: normal glucose lvls (anti-inflammatory cortisol, dampens immune system)
mineralocorticoids: reg Na balance, extracellular fluid volume (aldosterone)
androgens: stim/control development + maintenance of male characteristics (sec in small amts)
cortisol
(cortisol: stress hormone; inc BP + blood sugar and red immune responses (anti inflammatory), decreases amino acid uptake by muscle and inhibits protein synthesis)
aldosterone
adrenal cortex hormone
- reg amt of Na+ reabsorbed from fluids in kidney
- reg amt of Na+ absorbed from foods in intestine
- red amt of Na+ secreted by salivary and sweat glands
- inc K+ secretion into kidney tubule (and resulting excretion) (Na/K pumps)
renin angiotensin system
renin: enzyme that converts a protein to angiotensin
angiotensin: peptide hormone that raises BP by constricting vessels and stim release of aldosterone
- low blood volume -> kidneys sec renin
- renin stims prod of angiotensin I (converted to angiotensin II by ACE)
angiotensin II: causes constriction of vessels -> inc BP - angiotensin stims sec of aldosterone (inc reabsorption of sodium and water in kidney) from adrenal cortex
this inc volume of fluid in body -> inc BP
hormones of islet of langerhans
islet of langerhans: where endocrine cells of pancreas are located
insulin (beta cells): lowers blood glucose conc, inhibits conv of non carb molecules into glucose
glucagon (alpha cells): raises glucose by stim glycogen, fat and protein degradation
reg blood glucose lvls
insulin
hormone: facilitates glucose uptake from blood into cells, storing it as glycogen in liver and muscle
when insulin is absent/low: glucose not taken up and body begins to use fat as energy source (ketoacidosis, lower pH bc of end product acetones)
diabetes mellitus
low insulin production/action
symptoms
freq urination (using water to tru to excrete excess glucose)
inc thirst (replace excreted water)
inc apetite (low glucose = proteins + fats broken down for energy, replace)
type 1: pancreatic beta cells destroyed by autoimmune rxn (need insulin injections)
type 2: insulin secreted, but target cells have alteres insulin receptors
complications:
protein breakdown (use for energy) weakens blood vessels (poor circulation = tissue degeneration)
- blindness, kidney failure, neuropathy
diabetes insipidus
characterized by excessive thirst + urination (diuresis)
- several types of DI
- most common is neurogenic DI caused by deficiency in antidiuretic hormone (ADH)
- nephrogenic DI caused by insensitivity of kidneys to ADH
male and female gonads hormones
ovaries
sec estrogen progesterins
testes
androgens
gonadal sex hormones
prod in gonads (testes, ovaries)
reg development of reproductive systems, sexual characteristics and mating behavior
androgens: anabolic steroids (testosterone)
estrogens (estradiol-principal estrogen)
progestins (progesterone- principal) (natural/syn steroid hormone that maintains pregnancy and prevents further ovulation during pregnancy inc endometrium)
homeostasis
based on neg feedback regulation d
stable internal condition of the body resulting from the body’s
ability to elicit responses to counteract changes, thereby restoring stasis, or balance.
ex.
pH of the blood is
normally maintained within the narrow range of 7.35 to 7.45, whereas the gastric fluid in the stomach
has a pH that generally ranges from 1 to 2.
ions in ECF regulated (osmotic balance)
maintaining conc of O2 and CO2
Chemoreceptors
-sensors that detect changes in chemical content, such as the amount of O2 in
the blood. They are found in the aorta and carotid arteries and can also send signals to the cardiac
centers in the brainstem where the information they provide is integrated with the information from
the baroreceptors.
-can also detect levels of plasma H+, and thus are important for pH regulation. To help
tightly regulate the pH of the ECF, the body often employs the bicarbonate buffering system which can
be described by the equation:
CO2+H2O H2CO3(carbonic acid) HCO3
- (bicarbonate) + H+
Respiratory acidosis
may result when one’s ability to breathe is debilitated
COPD ( amyotrophic lateral sclerosis or myasthenia gravis)
when decreased
respiration causes an increase in the blood CO2 levels. shift the equation above to the right, producing relatively more
H+ and decreasing blood pH.
metabolic acidosis
can occur if the kidneys are not adequately removing enough acid from the
body, or if other compensatory mechanisms (such as the bicarbonate buffering system, or respiratory
compensation, whereby the rate and depth of breathing is increased in order to exhale more CO2) are
insufficient
ketoacidosis: body’s inability to control prod of ketone bodies by fatty acid breakdown -> accumulation of molecules red PH
diabetic ketoacidosis/ alcoholic ketoacidosis
diabetic: lack of insulin to break down glucose leads body to switch to fatty acid breakdown
alcoholic: alcohol can inhibit the process of
gluconeogenesis, which reduces glucose production. This, in turn, directs the body to metabolize fatty
acids for energy, again resulting in the production of ketones.
(smell of acetone due to ketones)
hyperventilation
pH abnormally high
CO2 lvls fall (paper bag)
bicarbonate buffering shifted to left
CO2 + H2O H2CO3 (carbonic acid) HCO3
- (bicarbonate) + H+
osmoreceptors
hypothalamus
1. stim thirst
2. directs posterior pit to secrete ADH
ectotherms
obtain heat energy from environment by controlling rate of heat exchange with surroundings
- lower metabolic rate (inc with temp)
- invert fish and amphibians
- small surface to volume ratio (retain more body heat)
torpor
period of inactivity aligned w variations in temp
1. hibernation
2. estivation (summer)
endothermic
obtains heat energy from int rxns
- modifying insultation, minimizing heat uptake, evaporative cooling (panting + sweating), redirecting blood flow, vasodilation/constriction
heat conservation/release using blood vessels
In response to lower environmental temperatures, an organism can conserve body heat by constrict-
ing blood vessels near the body surface and enlarging more proximal blood vessels that are nearer to
the body core. This redirects blood flow away from the body surface where the heat carried by the blood
would be dissipated to the environment. Similarly, blood vessels that reside adjacent to the surface of
the body can be dilated, while those residing more internally can be constricted, thereby shunting warm
blood to the body surface, where heat can be released to the surrounding air.
counter current exchange
, a temperature gradient is established between the warm arterial
blood flowing outward in the body’s extremities and the cooler venous blood returning inward from the
extremity to the body core. At any given point, heat is transferred between an artery and an adjacent
vein, resulting in the conservation of heat.
thermoreceptores
located in the skin and the hypothalamus of the brain.
Baroreceptors
neurons/neuronal endings in walls of atria of heart, aortic arch and carotid sinuses
mechanical stretch receptors detect stretch in vessel walls
send APs to brain stem
4 basic tissues
epithelial
connective
muscle
nervous
