Actin and myosine

Thick filament myesin ATPase activity Apairheavy chain. actin hexames binding site 2pairlight chain 2pair of Apair ATPase of heavy light activity chymotripsion chain chain 2 + 4 LMM HMM ( Light mecomyosin) ( Heavy 6 masomyoin Papaine S1 S2 globular head (ATP BDP+Pi) Thin filament - Actin O myosinbinding site + Troponin + Tro pomgosin myoin head bind to actin's myoin binding site usually blocked by Tropomyosis Placed by Troponin

C . c.o ractin myoin birdingsite + of 88 Tropomyoin 8 Troposis Troponin + Tropomyoiin myoin bindingsite hydrolysis. of factin. ATP required for muscle relaxation ATP binds to myoin head. hydiolyse ATP ADP+Pi myoin head flexible (bend upto90$ 90° interact to actin Power stroke Release ADPfPi 45° Polling nowAsitin the stable confirmation ATPagain binds & myoinhead detach from binding site ADPAPi air 90 Powerstroke

require ca muscu cell Tropomyoiin & Troponin complex block myosin binding site Tpt Troponin TpI TpC TpT IpI Tpc (ca2t bindin) Ca2+ in cytoool elevates 100 times. (107 M 156M) ca2+ binds to Tpc TropanineTropomyorlo leaves Myorin head binds contraction. Skeletal muscle contraction voluntary signal intiated by nerve impolse @ axon hillock voltage gated Nat channel (depdalization of reve cellmentra Impolsemove & reach ason terminal depolarization open voltage gated ca2t channel Ca2+ @axon

synaptic cleft releasechacetyl eholine binds to receptor Na+ (ligard (Na+ + channel) Ligard gated goted Nat channel muscle volatage muscle exceled spred to "entire muste cell membrone muscle cell depotative ER source of calcium opens ca2t channel voltage gated leaztinduced calcium ca2t channel in MPM channel , open 1 1 PM Ca2t pump 2 ca2+ Ca2t ER ca2t dependent D ca2t T tubule (invagination of muscle cell 3 ER ca2t voltage dependent 3 Ca 2 t Real? inER Chanel. Ca2+/H+ ATPase pomp back ca2+ back to ER (omes). relaxation unlike other lissue muscle pocces special enzyme