steps of muscle contractionste

step 1

action potential arrives at axon terminal

step 2

Voltage-gated calcium channels open and calcium floods into axon terminal

step 3

calcium causes vesicles containing acetylcholine (Ach) to release their contents via exocytosis

step 4

Ach diffuses across the synaptic cleft and binds to receptors on sodium channels within the sarcolemma

step 5

Sodium channels open, causing a large influx of sodium into the muscle cell

step 6

This influx of sodium causes depolarization, immediately followed by potassium channels opening for a large efflux from the cell, causing repolarization

step 7

The action potential is now generated on the sarcolemma, where it travels down t-tubules

step 8

voltage-gated calcium channels open, causing a release of calcium from the sarcoplasmic reticulum into the sarcoplasm

step 9

calcium binds to troponin, causing it to change shape and shift

step 10

the shift causes tropomyosin to move, exposing the myosin-binding sites on the actin filament

step 11

ATP hydrolyzes to ADP, allowing the attachment of myosin to actin, forming a cross-bridge

step 12

the myosin head pivots, pulling actin towards the center of the sarcomere, causing the muscle to contract

step 13

ATP hydrolyzes to ADP again, which causes the detachment of actin and myosin

step 14

This process repeats for as long as an action potential is being sent

step 15

when the action potential is no longer sent, Ach is removed from the synaptic cleft via acetylcholinesterase, and calcium is actively pumped back into the sarcoplasmic reticulum

step 16

everything is now reset and waits for the next action potential