PHYSL210A Lecture 6: Muscle
22 Oct 2018
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Isotropic (i) band thin actin filaments fixed to z line at the center of the i band. Anisotropic (a) band thick myosin filaments fixed to a centrally connective tissue membrane, thin filaments composed mainly of globular actin molecules. Basic unit of myofibril sarcomere (between 2 z lines: contraction of sarcomere. Overlap between the thin actin and thick myosin filament increases. At rest, cross-bridge binding sites on actin filaments are blocked by tropomyosin. Ca ion binds with troponin which causes the tropomyosin chain to turn and revel the crossbridge binding site. Binding cause conformation change and pull the actin filaments towards the center of the sarcomere and away from the z line. Atp binding to crossbridge removes it from actin. Atp hydrolyses returns it to its energised state (adp +pi) If not atp (cid:373)us(cid:272)les (cid:272)a(cid:374)(cid:374)ot (cid:271)e retra(cid:272)ted to origi(cid:374)al shape as (cid:272)ross(cid:271)ridge (cid:272)a(cid:374)"t (cid:271)e removed. Rigor mortis no atp rigor state death after a few hours.
