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physiology
the study of living things and how they function
organization of biosphere
atom, molecule, cell, tissue, organ, organ system, organism, population of species, ecosystem of different species, biosphere
homeostasis
maintenance of a relatively stable internal environment
negative feedback loops
achieve homeostasis, feedback reduces the difference between target set point and actual value, reduces initial stimulus and regains homeostasis
negative feedback loop diagram
stimulus, receptor, sends signal to, integrating center, sends signal to, effector, output to reduce initial stimulus, homeostasis
negative feedback loop blood pressure
decrease in bp, baroreceptors sense bp changes in blood, nerve signal about decreased bp, medulla oblongata, nerve signal and hormones, blood vessels and heart, reduction to bring bp back to normal
positive feedback loop
increases the difference between the target set point and actual value, moves system away from homeostasis, increases stimulus
positive feedback loop childbirth
baby drops and presses on cervix, stretch receptors in cervix, brain releases oxytocin, smooth muscles of uterus, increases contractions and delivery of baby stops cycle
feedforward control
initiation of a response in anticipation of the stimulus
organ system
a collection of parts that work together in a predictable way to achieve a common function
lumen
interior of hollow organs
cytoplasm
interior of cells, consists of cytosol, organelles, inclusions, proteins
extracellular fluid
1/3 of total body water volume, consists of interstitial fluid and blood plasma
intracellular fluid
2/3 of total body water volume
cell membrane
provides structural support, selectively permeable, regulates exchange, regulates communication
gap junction
enables communication between adjacent cells, connexin proteins
tight junctions
adjacent cell membranes are partly fused together forming a barrier, occludin and claudin proteins
anchoring junctions
anchor cells to each other or ECM, cadherin proteins
epithelial tissue types
exchange, protective, secretory, transport, ciliated
epithelial tissue function
protects internal environment of the body, regulates exchange of materials between internal and external environment
connective tissue
extensive extracellular matrix
connective tissue types
loose connective tissue, dense connective tissue, adipose tissue, bone, blood, cartilage
connective tissue function
provides structural support, physical barrier
muscle tissue
skeletal, cardiac, smooth
neural tissue
neurons for information transfer, glial cells to support neurons
apical membrane
faces lumen or external environment
basolateral membrane
faces ECM and ECF
connective tissue matrix type
varied-protein fibers in ground substance that ranges from liquid to gelatin to firm to calcified
muscle tissue unique feature
able to generate electrical signals, force, and movement
neural tissue unique feature
able to generate electrical signals
epithelial tissue locations
covers body surface, lines cavities and hollow organs and tubes, secretory glands
connective tissue locations
supports skin and other organs, cartilage, bone, blood
muscle tissue locations
makes up skeletal muscles, hollow organs and tubes
nerve tissue locations
throughout body, concentrated in brain and spinal cord
epithelial tissue cell arrangements and shapes
variable number of layers, cells flattened, cubiodal or columnar
connective tissue cell arrangements and shapes
cells not in layers, usually randomly scattered in matrix, cell shape irregular to round
muscle tissue cell arrangements and shapes
cells linked in sheets/elongated bundles, cells shaped in elongated thin cylinders, heart cells may be branched
nerve tissue cell arrangements and shapes
cells isolated or networked, cell appendages highly branched and/or elongated
determines membrane permeability of a molecule
lipid solubility, molecular size
facilitated transport
protein-mediated transport, vesicular transport
factors affecting rate of diffusion
lipid solubility, molecular size, concentration gradient, composition of lipid layer, membrane surface area
fick's law of diffusion
rate of diffusion = surface area = concentration gradient = membrane permeability
types of membrane channel proteins
passive/leak channels, voltage-gated channels, ligand-gated channels, mechanically-gated channels
carrier proteins
open to one side of the membrane or the other
channel selectivity depends on
diameter of the pore, electrical charge of amino acids lining the pore
uniport carriers
transport only one kind of substrate
symport carriers
transport two or more substrates in the same direction
antiport carriers
transport two or more substrates in opposite directions
primary active transport
directly uses ATP as its energy source
secondary active transport
uses potential energy stored in concentration gradients from other molecules, either via symport or antiport
endocytosis/exocytosis
ligand binds to membrane receptor, receptor-ligand migrates to clathrin-coated pit, endocytosis, vesicle loses clathrin coat, clathrin returns to clathrin-coated pit to be recycled, receptors and ligand separate, ligands go to lysosomes/Golgi for processing, transport vesicle with receptors moves to cell membrane, transport vesicle and cell membrane fuse, exocytosis
vesicular transport
endocytosis, exocytosis
example of active protein-mediated transport
primary active transport = sodium-potassium pump, secondary active transport = sodium-glucose transporter
transcellular transport
transport through cells via simple diffusion, facilitated diffusion, active transport, endocytosis/exocytosis
paracellular transport
transport between adjacent cells to get to or from lumen
concentration of potassium in ICF/ECF
140mM/4mM
concentration of sodium in ICF/ECF
15mM/145mM
concentration of calcium in ICF/ECF
0.001mM/1.8mM
concentration of chlorine in ICF/ECF
4mM/115mM
the nernst equation
61/z*log(ion)out/(ion)in, used to calculate equilibrium potential of an ion
resting membrane potential
the net charge difference between the intracellular fluid and extracellular fluid
the goldman-hodgkin-katz equation
61*log[(Pk)out+(PNa)out+(PCl)in]/[(Pk)in+(PNa)in+(PCl)out], predicts membrane potential that results from the contribution of all ions that can cross the membrane
if a cell's permeability to an ion increases
increase in flow of that ion, a change in Vm towards that ions Ex
exchange epithelium
simple layer of squamous cells, leaky junctions between cells
protective epithelium
stratified, squamous cells form outer layer, undifferentiated cuboidal cells form inner layers, cells tightly connected by gap junctions and hemidesmosomes
ciliated epithelium
single layer of columnar cells, cells connected by tight junctions
secretory epithelium
often simple, cells are cuboidal or columnar, may have tight junctions
transport epithelium
cells connected by tight junctions, single layer of thick cuboidal or columnar cells
local cell-to-cell communication
gap junctions, contact-dependent, autocrine signals, paracrine signals
autocrine signals
act on the same cell that secreted them
paracrine signals
secreted by one cell and diffuse to adjacent cells
long distance communication
hormones, neurohormones, neurotransmitters
hormones
secreted by endocrine glands/cells into the blood, only target cells with receptors for the hormone will respond to the signal, insulin
neurotransmitters
chemicals secreted by neurons that diffuse across a small gap to target cell, acetylcholine
neurohormones
chemicals released by neurons into the blood for action at distant targets, oxytocin
intracellular signal receptors
lipophilic signal molecules diffuse through cell membrane, molecule binds to receptor in cytosol, binding triggers nuclear receptors, slower responses related to changes in gene activity
extracellular (cell membrane) signal receptors
extracellular signal molecule binds to a cell membrane receptor, binding triggers a rapid cellular response
signal transduction
signal molecule/first messenger, binds to receptor protein/transducer, activates intracellular signal molecules/second messenger system, alters target proteins, creates response
kinases
phosphorylates proteins
phosphotases
dephosphorylates proteins
signal amplification
second messenger system amplifies message, receptor-ligand complex activates an amplifier enzyme
enzyme-linked receptors
ligand binds to receptor which activates associated enzyme
tyrosine kinase
surface molecule binds to surface receptor which activates tyrosine kinase on cytoplasmic side, phosphorylated protein
ATP + protein = (P)protein + ADP
G protein coupled receptors
ligand binds to a receptor that is physically coupled to a Guanosine nucleotide binding (G) protein, made up of 3 subunits
GPCR-adenylate cyclase signal transduction
signal molecule binds to GPCR, G protein activates adenylyl cyclase, adenylyl cyclase converts ATP to cyclic AMP (cAMP), cAMP activates protein kinase A, protein kinase A amplifies message
GPCR and phospholipase C
signal molecule activates receptor and associated G protein, G protein activates phospholipase C (PLC), PLC converts membrane phospholipids into diacylglycerol (DAG) which remains in the membrane and IP3 diffuses into cytoplasm, DAG activates protein kinase C, IP3 causes release of calcium from organelles creating a calcium signal
GPCR inactive form
GDP + G protein
GPCR active form
GTP + G protein
calcium can enter cells via
voltage-gated channels, ligand-gated channels, mechanically-gated channels
properties of hormones
- cell-to-cell communication molecules
- binding to target receptor initiates cellular response
- communication eventually terminated
- half-life
peptide/protein hormones
- made in endocrine cells all over the body
- made in advance and stored in vesicles
- preprohormone, prohormone, hormone
- released into ECF via exocytosis then diffuses
- short half-life
- lipophobic, binds to external membrane receptors
steroid hormones
- cholesterol, lipophobic precursor, SER, lipophilic steroid hormone
- only made in adrenal cortex, kidney, skin, gonads, placenta
- lipophilic
- cannot be stored
- made on demand
- released by simple diffusion into blood
- transported bound to carrier proteins
- longer half-life
- bind to intracellular receptors or cell membrane receptors
amine hormones
- made in pineal gland, adrenal medulla, thyroid
- mostly derived by tyrosine
- catecholamine characteristics similar to peptide hormones
- thyroid hormone characteristics similar to steroid hormones
catecholamine
- lipophobic
- stored for release
- short half life
- changes activity of target protein
- ex. dopamine, norepinephrine/noradrenaline, epinephrine/adrenaline
thyroid hormone
- lipophilic
- made on demand from lipophobic precursors stored in thyroid
- requires carrier proteins
- longer half life
- genomic responses
- ex. thyroxine
exocrine
uses a duct that secretes hormones onto epithelial tissue
endocrine
secretes hormones directly into the blood
pancreas endocrine portion
- alpha cells = glucagon
- beta cells = insulin
pancreas exocrine portion
- acinar cells = secrete digestive products
- duct cells = secrete digestive products
cellular responses regulated by hormones
- rates of enzymatic reactions
- transport of ions or molecules across cell membranes
- gene expression and protein synthesis
- helps maintain homeostasis