muscle contractiom progression steps

step 1

action potential 1 arrive down to axon in axon terminal

step 2

calcium enters axon terminal

step 3

acetylcholine released from axon terminal to synaptic cleft

step 4

acetylcholine binds to ACh receptors on sarcolemma (muscle membrane)

step 5

ACh channels open allowing sodium go rush into =simple diffusion/no energy muscle cell (depolarization)-inside of muscle cell becomes less negative

step 6

sodium channels open on sarcolemma allowing more sodium in cell further depolarizing muscle cell

step 7

once enough sodium enters muscle cell threshold is reached and action potential 2 is created in muscle cell

step 8

action potential, travels along T tubules causing calcium to be released from terminal cisterns

step 9

calcium binds to troponin on actin molecules

step 10

tropomyosin shifts exposing active sites on actin molecule

step 11

myosin binds to active site shifts to power stroke causing muscle contraction and sarcomere to shorten

step 12

after contraction ATP is used to detach myosin head from active site

step 13

calcium is back in sarcoplastic reticulum

step 14

acetylcholinesterase breaks down ACh out of synaptic cleft