BPK 205 midterm 1

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