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Sarcolem membrane of muscle cell.
sarcoplasmic reticulum is where Ca2+ is stored.
Sliding filament theory: Rigor state position 1. myosin head has tight grip on actin. and no ATP present
Resting state ATP is present, myosin detaches and weakly rebinds to actin at 90 degree (position ). however, no yet move actin.
Power stroke Ca2+ presents. Myosin returns to 45 degree angle crossbridge while still bounds to position 2. This action, actin is moved toward M-line. ADP leave the myosin head and temporary returns to rigor state.
Present of Ca2+ the continuous present of Ca2+ will keep pushing the actin toward the M-line. if ca2+ drops or no more ca2+ actin is pulled back to original position with titin and nobulin ( elastic fiber)
Death state rigor state, no ATP present, myosin tight grip on actin.
sleep resting state, ATP present ( not being used, but hang around), no Ca2+ present, therefore, no power stroke.
running Lots of ATP and Ca2+ is present, therefore power stroke occur.
How does lack of Ca2+ prevent power stroke? There are two regulating protein: tropomysin and Troponin
Tropomysin elongated protein that wrap around actin. it blocks myosin binding site, which prevent myosin from moving actin.
Troponin: Ca2+ binding protein that control the position of tropomysin Ca2+ present, it binds to troponin ( changes its conformation) to move tropomysin out of the way from blocking the binding site, power stroke can now occur.if Ca2+ level drops, tropomysin go back to blocking. nebulin + titin are used during relaxation.
How a somatic motor neuron stimulate skeletal muscle to conract? Excitation -contraction coupling. 1. exocytosis of acetylcholine (Ach) into synaptic cleft.2. Ach binds to Ach gated Na+channel causes Na+ influx and K eflux lead to action potential. 3. Act.pot. sweep across sacolema in both direction and down T-tubule.
continued ADP receptor in T-tubule change conformation due to action potential. Mechanically gated Ca2+ channel on Sarcolema opens.5. Ca2+ flood cytoplasm and binds to troponin, which move tropomysin----toward the M-line (power stroke)
No Ach No Ach, the stimulation of neuron would stop, Ca2+ ATPase pumps Ca2+ back into SR--back to resting state
cycle twitch a single action potential from neuron causes a single excitation contraction.
Aerobic respiration made about 36 ATP/glucose. provide 95% of our ATP
Anaerobic respiration 2ATP/glucose. last 30-60 second worth of ATP
phophocreatin Donate its P to make ATP and provide about 20-30 second
Lipolysis breaking fat for energy of no glucose around to use to make ATP
Created by: katzz