Muscle Contraction

ekadar's version from 2017-02-03 14:14

Skeletal muscle

Question Answer
A bandAlways the same length
H,I, Zshrink
type 1 muscleslow twitch
fiber type of type 1 musclered fibers
type 2 musclefast twitch
fiber type of type 2white fibers
aerobic metabolismtype 1
anaerobic metabolismtype 2
region of sarcomere containing only myosin thick filamentsH band
A band contains onlythin filaments
Z diskcross conections of actin thin filaments


Question Answer
Depolarization of Skeletal muscleDepolarization of cell membrane triggers opening of L-type Ca channels within the myocyte’s T-Tubule system. Interacting with ryandoine receptors in skeletal muscle the opening of RyR1 calcium channels present within the SR which then leads to a subsequent release in Ca from the intracellular stores of SR. “L-Type channel RyR mechanical coupling”
Relationship of calcium and skeletal muscleskeletal muscle does NOT require Ca to enter from the extracellular space to cause calcium release within the cell; so CCBs would have no effect. This mechanical coupling.
contraction in skeletal musclecalcium released from SR then binds troponin C allowing actin and myosin to bind; ATP bound to myosin is then hydrolyzed and contraction occurs
Cardiac muscle and ryanodine receptorsL-type Channel RyR mechanical coupling does NOT exist
Calcium and cardiac muscledepolarization causes L-type Ca channels to open and allow influx of extracellular Ca; this Ca binds to and activates RyR2 channels by a mechanism known as Calcium induced Calcium
Contraction in cardiac musclecontraction then occurs just as in skeletal muscle (binds troponin, actin and myosin then bind, myosin ATP release and contraction)
Smooth muscle and ryanodine receptorsCa enters cell from extracellular space during depolarization through voltage gated L-type Ca channels and then causes a release of Ca from SR via a calcium dependent RyR calcium channel in SR
Smooth muscle contractionCalcium then binds CALMODULIN(not troponin in smooth muscle cells) which activates myosin light chain kinase (MLC Kinase) and that leads to phosphorylation of myosin which allows it to bind to actin and cause muscle contraction