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BIO 203 Week Five Notes

by: Andrea Tufekcic

BIO 203 Week Five Notes BIO 203LEC

Marketplace > University at Buffalo > Biology > BIO 203LEC > BIO 203 Week Five Notes
Andrea Tufekcic

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About this Document

Covers muscle structure and contraction mechanisms
General Physiology Lec
Loretz, C A
Class Notes
Physiology, Biology
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This 3 page Class Notes was uploaded by Andrea Tufekcic on Tuesday October 11, 2016. The Class Notes belongs to BIO 203LEC at University at Buffalo taught by Loretz, C A in Fall 2016. Since its upload, it has received 12 views. For similar materials see General Physiology Lec in Biology at University at Buffalo.


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Date Created: 10/11/16
Muscle Contraction -Movement produced by generating force through energy-consuming interactions Main proteins: myosin, actin Regulatory proteins: tropomyosin, troponin Scaffolding and regulatory proteins: titin, nebulin Types Striated: skeletal: voluntary cardiac: involuntary, very regular pattern of myosin Smooth: not in regular stripes Organization muscle  tendon  bundle  single fiber (multiple nucl) multiple myofibrillayers of myosin/actin M-line Z-line Myosin/Titin connection Z-line actin Relaxed muscle diagram -multiple sarcomeres build up tiny contractions to create movement -actin and myosin slide past each other to contract, pulling z-lines together -muscle attached to bones at tendons -actin bonds in long ropes lined with tropomyosin, troponin -actin ropes binds with myosin when binding sites are exposed -Ca2+is released from sarcoplasmic reticulum (surrounding myofibrils) 2+ -Ca binds troponin and myosin binding sites on the actin -myosin heads bind to actin which releases P from ADP-P, initiates power strike -filaments slide past each other, drawing Z-lines together -ADP is released, ATP binds to myosin and causes it to release actin -ATP is hydrolyzed and myosin goes back to its original position -Ca2+flows back into the sarcoplasmic reticulum and muscle relaxes 2+ -energy is derived from hydrolysis of ATP, cycle repeats if Ca is available Force levels: passive <calcium <titin Isometric contraction: muscle generates force but doesn’t shorten (like pressing on a table) Isotonic contraction: muscle generates constant force and shortens (like making a fist) -muscle shortens fastest when unloaded load increases and velocity decreases until muscle can’t shorten at all Functional nerve muscle group: composed of motor units = {neuron and muscle fiber} | Coupled events: nerve action potential -transmission across neuromuscular junction } action pot like synapses -muscle action potential -intracellular messenger (Ca ) signal Z- line sarcoplasmic reticulum Z-line -mechanical contraction myofibril Tubule (green) muscle surface diagram -acetylcholine based action potential diffuses into muscle surface from neuron 2+ -action potential propagates down to tubules, triggers releases of Ca from SR -calcium binds to troponin, uncovers myosin binding sites on actin, triggers contraction mech -CaATPases move calcium back into SR, myosin detaches and muscle relaxes Motor unit: smallest functional unit of force development control -high force demands, low fine motor demands = quads, uses ~2000 muscle fibers -low force demands, high fine motor demands = eyes, uses ~10 muscle fibers -individual units activated as all or nothing, strength determined by number of motor units twitching Tetanic contraction: rapid delivery of stimuli = mechanical contraction -delivery of another stimuli before complete relaxation of previous response = inc response -summed twitches bring muscle to maximum contraction = tetanus EXAMPLE: Amazonian vine produces blow dart poison that is a post-synaptic receptor toxin, competes with acetylcholine @ neuromuscular junction, prevents neurotransmitter release and causes paralysis Skeletal muscle  actin based Smooth muscle  myosin based -lacks T-system (tubules) - most stimulated Ca 2+ entry across plasma mem from extracellular fluid -exhibits graded contraction (different levels of force) -exhibits myogenic activity with no neuronal input


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