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Cell and Muscle
Physio Review - BRS
32
Medical
Graduate
08/20/2012

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Term
Integral proteins vs. Peripheral Proteins
Definition
Peripheral proteins are not embedded in the membrane nor are they covalently attached. Held by electrostatic interactions.
Term
Diffusion equation
Definition
J = -PA (C1-C2)
J = flux (mmol/sec); P = permeability (cm/sec); A = area; C1,C2 = concentration
Term
Carrier-mediated transport exhibits three characteristics:
Definition
Stereospecificity, saturation, competition
Term
Osmolarity equation
Definition
O = g x C
O = concentration (osm/L)
g = number of particles
C = concentration
Term
Osmotic Pressure equation
Definition
pi = g x C x RT
pi = osmotic pressure (mmHg or atm)
Term
Reflection coefficient, sigma
Definition
Describes permeability of a solute. 1 = impermeable, 0 = permeable. Multiply by osmotic pressure to get effectice osmotic pressure
Term
Diffusion potential
Definition
Potential difference generated across a membrane by a concentration difference of an ion.
Term
Equilibrium potential
Definition
Diffusion potential at which no more net ion movement happens.
Term
Nernst equation
Definition
E = 60mV log [Ci]/[Co]
Term
Action potential
Definition
Depol = opening of Na activation gates, slow closing of Na inactivation gates and slow opening of K channels. Repol = high K conductance returns cell to resting potential w/ undershoot.
Term
Refractory periods
Definition
Absolute = no AP can occur; Relative = requires a larger than usual stimulus to elicit an AP. Also see Effective
Term
Accommodation
Definition
Membrane potential is held at a depolarized level higher than threshold without APs because Na inactivation gates are closed. Happens in hyperkalemia when high serum K depolarizes cells.
Term
Events at neuromuscular junction
Definition
Choline acetyltransferase makes ACh from acetyl-CoA and choline. AP opens Ca channels at presynaptic terminal. Ca causes ACh to be released, which binds nicotinic receptors. Receptor is both an Na and K channel, so membrane is depol. to 0mV (mini EPP). Summation of MEPP is an EPP. Acetylcholineesterase degrades ACh.
Term
Myasthenia gravis
Definition
Antibodies to ACh receptor cause skeletal muscle weakness. Treat with AChE inhibitors.
Term
EPSPs and IPSPs
Definition
EPSPs are caused by opening of Na and K channels bringing potential to 0mV, ACh, norepi, epi, dopa, glu, serotonin. IPSPs open Cl channels bringing potential to -90mV, GABA and gly.
Term
Summation at synapses
Definition
Spatial occurs when two inputs arrive simultaneously. Temporal occurs when two inputs arrive in rapid succession. Both produce greater depol.
Term
Norepinephrine
Definition
Released from post. sym. neurons. Removed by reuptake or metabolized by MAO and COMT. Pheochromocytoma, tumor or adrenal that produces catecholamines is detected by increased urinary VMA, a metabolite.
Term
Epinephrine
Definition
Synthesized from norepi by phenylethanolamine-N-methyltransferase.
Term
Dopamine
Definition
Prominent in midbrain neurons, inhibits prolactin release. Metabolized by MAO and COMT. D1 receptors are Gs protein, D2 receptors are Gi. Parkinson's is degeneration of neurons with D2 receptors; Schizo is increased levels of D2 receptors.
Term
Serotonin
Definition
In high concentrations in brain stem. Made from trp, converted to melatonin in pineal gland.
Term
Glutamate
Definition
Most prevalent excitatory transmitter in brain. Has four subtypes of receptor, three are ionotropic including the NMDA receptor, one is metabotropic.
Term
GABA
Definition
Inihibtory, synthesized from glutamate by glutamate decarboxylase. GABAa receptor increases Cl conductance, is hit by benzos and barbiturates, GABAb receptor increases K conductance.
Term
Nitric Oxide
Definition
Short acting inhibitory transmitter, made by NO synthase.
Term
Transverse tubules
Definition
Invaginations of plasma membrane in skeletal muscle. Contains dihydropyridine receptor in the membrane, important for initiating excitation-contraction coupling.
Term
Thick filaments
Definition
Myosin, composed of two heads and a tail, which include one pair of heavy chains and two pairs of light chains. The heads bind ATP and actin to form cross-bridges.
Term
Thin filaments
Definition
Actin, troponin and tropomyosin.
Term
Sarcomere
Definition
Z line to Z line, where thin filaments attach. M line at middle of thick filaments. I band has only thin filaments, A band has thick filaments (w/ or w/o thin), and H band has no thick filament heads.
Term
Troponin
Definition
Three proteins: Troponin I inhibits the interaction of actin and myosin, C binds calcium and T that attaches to tropomyosin.
Term
Dihydropyridine receptor
Definition
In skeletal muscle, a voltage sensor that changes conformation with depolarization, opening the ryanodine receptor, releasing calcium.
Term
Excitation-contraction coupling (skeletal muscle)
Definition
DhP receptor senses depolarization, opens ryanodine receptor, Ca flows out of SR and binds troponin. Myosin hydrolyzes bound ATP and displaces toward plus end of actin, then binds actin and "power strokes" back to position and releases ADP. When Ca is taken up by the SR, troponin moves tropomyosin back into place to block actin-myosin interaction.
Term
Multi-unit vs. unitary smooth muscle
Definition
Multi-unit smooth muscle is not coupled and behaves as separate units, such as iris, ciliary muscle of the eye and vas deferens. Unitary smooth muscle is spontaneously active, is electrically coupled and is the most common type, in the uterus, GI tract and ureter.
Term
Excitation-contraction coupling (smooth muscle)
Definition
No troponin. Ca is let in from outside the cell (from voltage or ligand-gated channels, which can bind hormones and neurotransmitters). Ca then binds calmodulin which binds to and activates myosin light chain kinase. Phosphorylated myosin can bind to actin and start cross-bridge cycling.
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