Cell Physiology Flashcards by Jenny Huber

Channels that span the cell membrane

Integral protein - hydrophobic interactions

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How peripheral proteins attach

electrostatic interactions

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Tight Junctions

Zona Occludens

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Attachment between cells that permit intercellular communication.

Gap Junction

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Coupling between myocardial cells

Gap Junction

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Simple Diffusion

not-carrier mediated, occurs down a chemical gradient

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Equation to measure Flow

Flow = -permeabilityarea(Conc1-Conc2)

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Factors that increase permeability

increase oil/water coefficient
decrease radius of solute
decrease membrane thickness

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3 Characteristics of Carrier Mediated Transport

Stereospecificity, Saturation, Competition

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Characteristics of Facilitated Diffusion (4)

Down an electrochemical gradient,
passive (doesn’t require metabolic energy),
more rapid than simple diffusion,
carrier-mediated so exhibits stereospecifity

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Type of transport for glucose into muscle and adipose tissue

Facilitated diffusion because it goes “downhill” and it carrier mediated and is inhibited by sugar like galactose

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Characteristics of Primary Active Transport

Against an electrochemical gradient
needs ATP to work
carrier-mediated (shows stereospecificity, saturation and competition)

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drugs that inhibits Na/K - ATPase

ouabain and digitalis (cardiac glycoside drugs)

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SERCA or Ca2+ ATPase is what type of transport?

Primary active transport

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Gastric Parietal cells use which type of pump?

H/K-ATPase pump (primary active) to transport H+ into the stomach

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Omeprazole inhibits what?

H/K-ATPase pump

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Characteristics of Secondary Active Transport

Transport of 2 or more solutes
one of the solutes is transported downhill providing energy for the other solute to go uphil
metabolic energy is provided indirectly by Na gradient

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Symport or Cotransport

solutes moving in the same direction, type of secondary active transport

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Countertransport, exchange or antiport

solutes moving in opposite directions

Na-Ca exchange or Na-H exchange

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Na-glucose cotransport in the small intestine and renal PT

Glucose is being transported uphill

Na is being transported downhill

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concentration of osmotically active particles in a solution

osmolarity

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Equation for osmolarity

osmolarity = (#particles in solution) * (concentration)

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Flow of water across a semipermeable membrane from solution with low solute to high solute concentration

Osmosis

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Eqtn for Osmotic Pressure

pi = g*C*RT
pi is osmotic pressure
g is #particles in a solution
C is concentration
R is gas constant 0.082
T as absolution temp in K

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When solute concentration increases, what happens to the osmotic pressure?

increases

osmotic pressure created by protein concentration

colloidosmotic oressure or oncotic pressure

Reflection coefficient closer to 1

solute is less permeable the closer it is to 1, | 0 means the solute is completely permeale (urea)

Conductance of an ion channel is dependent on what

probability of the channel being open

These channels are opened or closed by changes in membrane potential

VGC

These channels are open or closed by bhromones, second messengers or NTs

Ligand-gated Channels

Nicotinic receptor for ACh is what type of channel?

LIgand-gated Channel

Potential difference generated across a membrane because of a concentration difference of an ion

diffusion potential

diffusion potential that exactly balances the tendency for diffusion caused by a concentration difference

equilibrium potential

This equation is used to calculate the equilibrium potential at a given concentration difference of a permeable ion across a cell membrane.

Nernst Equation

What is the Nernst Equation

``` E = -2.3((RT)/(zF))log10 (conc ions inside/outside) E is equilibrium potential z is charge on ion RT is usually 60mV at 37C F was not explained in book ```

At rest, nerve membrane is more permeable to what ion?

K+

Depolarization

makes membrane potential less negative (interior of cell less negative)

Hyperpolarization

Makes cell membrane potential more negative

Inward Current

Flow of positive charge into the cell, depolarizes the membrane

Outward current

Flow of positive charge out of the cell, hyperpolarizes the membrane

All-or-none

Action potential

Threshold

membrane potential at which AP is inevitable

At rest, Na+ channels are

Closed, Na conductance is therefore LOW

Upstroke of AP

Na channels open and more Na conductance than K+ (inward Na current)

These block voltage sensitive Na channels and abolish AP

Tetrodotoxin and lidocaine

Depolarization

slowly closes Na-gates, and slowly opens K-gates | outward K current

Period during which another AP cannot be elicited, no matter how large the stimulus

Absolute refractory period | this is because inactivation gates of NA channel are closed

AP can be elicited if larger than usual inward current is provided

Relative refractory period

Accommodation

Occurs when the cell memrbane is held at a depolarized level such that the threshold potential is passed without firing an AP occurs because depolarization closes inactivation gates on Na channels seen in hyperkalemia

spread of local currents to adjacent areas of membrane, which are then depolarized to threshold and generate Aps

Propagation of AP

Conduction velocity is increased with

increased fiber size, myelination

Saltatory conduction

APs only generated at nodes of Ranvier (gaps in myeline sheath)

Chemical Synapses

an AP in the presynaptic cell > Ca enters presynaptic terminal causing release of NT into synaptic cleft > NT into synaptic cleft > NT attaches postsynaptic mem > ions permeable on post synaptic cleft

catalyzes Ach from CoA and choline in presynaptic terminal

Choline acetyltransferase

uptake of this ion causes release of ACh into synaptic cleft

Calcium

ACh binds muscle end plate (nicotinic receptors) to open what channels?

ligand gated channels to let Na in and K out

smallest possible EPP

miniature end plate potential - these summate to prudce a full-fledge EPP

Location of AChE

muscle end plate (post synaptic membrane)

Action of Neostigmine

Inhibits AChE which prolongs and enhances action of ACh at muscle end plate

Hemicholinium

blocks reuptake of choline into presynaptic terminal, depletes ACh stored from presynaptic terminal

Curare

Competes with ACh at motor end plate thus decreasing size of EPP Max dose = paralysis of respiratory muscles and death

Botulinum Toxin

Blocks release of ACh from presynaptic terminals

Antibodies to ACh receptor

Myasthenia Gravis - skeletal muscle weakness and fatigability

Tx classification for Myasthenia Gravis

AChE inhibitors like neostigmine

Inputs that depolarize a postsynaptic cell

Excitatory post synaptic potentials (EPSP) | they open Na and K channels

Excitatory NTs

Ach, NE, epinephrine, dopamine, glutamate, and serotonin

inputs that hyperpolarize that post synaptic cell

inhibitory postsynaptic potentials (IPSP) | they open Cl channels

Inhibitory NTs

GABA and glycine

when two excitatory inputs arrive at a postsynaptic neuron stimultaneously to produce a greater depolarization

spatial summation

2 excitatory inputs that arrive at postsynaptic neuron in rapid succession. Add in stepwise fashion.

Temporal summation

depolarization of postsynaptic neuron is greater than expected because greater than normal amounts of NT are released

Facilitation, augumentation, and post-tetanic potentiation

Primary NT released from postganglionic sympathetic neurons

How NE is removed from synapse

MAO, COMT or by reuptake

Increased Vanillylmandelic acid in urine

Pheochromocytoma

phenylethanolamine-N-methyltransferase

enzyme to make NE into Epi

NT prominent in midbrain neurons

Dopamine

inhibitrs prolactin secretion

Dopamine

dopamine-beta-hydroxylase

enzyme that converts DA into NE

D1 receptors

activate adenylate cyclase via Gs protein

D2 receptors

inhibit adenylate cyclse via Gi

degeneration of D2

Parkinsons

increased levels of D2 receptos

Schizophrenia

NT high in the brain stem

Serotonin

converted to melanin in pineal gland

Serotonin

present in neurons of the hypothalamus

histamine

most prevalent excitatory NT in the brain

glutamate

GABA-A receptor

increases Cl conductance and is the site of action of benzodiazepines and barbituates

GABA-B receptor

increased K conductance

Inhibitory NT found primarily in the spinal cord and brain stem

Glycine

short acting inhibitory NT in the GI tract, BVs and CNS

Nitric Oxide

NO synthase

converts arginine to citrulline and NO

A band

myosin, thick filament

myosin heads bind

ATP and actin

Permits cross-bridge formation when it binds Calcium

troponin

TroponinT

attaches troponin complex to tropomyosin

Troponin I

inhibits the interaction of actin and myosin

Troponin C

calcium binding site for troponin, permits the interaction of actin and myosin

H band

just thick filament (no thin filament with it)

I band

just thin filament (no thick filament with it)

Z line

attachment for thin filaments

M line

attachment for thick filaments

Voltage-sensitive protein of the T-tubule, located at jx of A and I bands

Dihydropyridine receptors

site of calcium storage and release for EC coupling

sarcoplasmic reticulum

Ca-ATPase pump in SR

keeps the intracellular calcium low

calsequestrin

keeps calcium loosely bound inside SR

for calcium release from SR

Ryanodine receptor

Cross bridge cycling steps

1. no ATP bound to myosin and myosin is attached to actin 2. ATP binds myosin and myosin releases actin 3. myosin moves to + end of actin and ATP -> ADP 4. Mysoin reattaches "powerstroke" 5. ADP is release

Muscle does not relax, can occur with too much calcium intracellularly

Tetanus

No shortening of muscle, increase in tension

Isometric Contraction

Load is held constant and muscle is shortened

Isotonic Contraction

Tension developed by stretching the muscle to different lengths

Passive tension

Active tension is proportional to

number of cross bridges formed | tension will be max when there is max overlap of thick and thin filaments

Multi-unit smooth muscle

iris, ciliary muscle of lens, and vas deferens

unitary (single-unit) smooth muscle

uterus, GI tract, ureter and bladder

No troponin found in these muscles

Smooth Muscles

myosin light-chain kinase

Smooth Muscles

No striations

Smooth Muscles

Striated Muscle

Skeletal Muscle and Cardiac Muscle

Upstroke of AP in Skeletal Muscle

inward Na current

Upstroke of AP in Smooth Muscle

inward Ca current

Upstroke of AP for SA node

inward Ca current

Upstroke AP for atria, ventricles, Purkinje

inward Na current

Plateau in AP

Atria, Ventricles, Purkinje fibers - due to inwards calcium current

Molecular basis for contraction in smooth muscle

calcium-calmodulin increase myosin light-chain kinase

What's turnt up mean?

the act of getting high or drunk to the highest degree