Cell Physiology Flashcards
Channels that span the cell membrane
Integral protein - hydrophobic interactions
How peripheral proteins attach
electrostatic interactions
Tight Junctions
Zona Occludens
Attachment between cells that permit intercellular communication.
Gap Junction
Coupling between myocardial cells
Gap Junction
Simple Diffusion
not-carrier mediated, occurs down a chemical gradient
Equation to measure Flow
Flow = -permeabilityarea(Conc1-Conc2)
Factors that increase permeability
increase oil/water coefficient
decrease radius of solute
decrease membrane thickness
3 Characteristics of Carrier Mediated Transport
Stereospecificity, Saturation, Competition
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
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
Characteristics of Primary Active Transport
Against an electrochemical gradient
needs ATP to work
carrier-mediated (shows stereospecificity, saturation and competition)
drugs that inhibits Na/K - ATPase
ouabain and digitalis (cardiac glycoside drugs)
SERCA or Ca2+ ATPase is what type of transport?
Primary active transport
Gastric Parietal cells use which type of pump?
H/K-ATPase pump (primary active) to transport H+ into the stomach
Omeprazole inhibits what?
H/K-ATPase pump
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
Symport or Cotransport
solutes moving in the same direction, type of secondary active transport
Countertransport, exchange or antiport
solutes moving in opposite directions
Na-Ca exchange or Na-H exchange
Na-glucose cotransport in the small intestine and renal PT
Glucose is being transported uphill
Na is being transported downhill
concentration of osmotically active particles in a solution
osmolarity
Equation for osmolarity
osmolarity = (#particles in solution) * (concentration)
Flow of water across a semipermeable membrane from solution with low solute to high solute concentration
Osmosis
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
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
NE
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
- no ATP bound to myosin and myosin is attached to actin
- ATP binds myosin and myosin releases actin
- myosin moves to + end of actin and ATP -> ADP
- Mysoin reattaches “powerstroke”
- 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
