Steps of excitation and contractions (Muscle)

Step 1

Motor neuron A.P

Step 2

ACh released from motor neuron into the synaptic cleft on the NMJ.

Step 3

ACh diffuses across synaptic cleft and binds to ACh protein receptors on the motor end plate.

Step 4

Na+ channels open on MEP, Na+ rushes into sarcoplasm cause local depolarization on MEP

Step 5

Local depolarization causes action potential/ AP spreads across the sarcolemma and through t-tubules. 

Step 6

Sarcoplasmic Reticulum releases Ca++

Step 7

Ca++ binds to troponin/ troponin changes shape and pulls tropomyosin off actin filaments. 

Step 8

Cross-Bridge

Step 9

Powerstroke

Step 10

ATP binds to myosin head, breaking cross-bridge.

Step 11

ATPase on myosin head splits ATP to ADP and P to re-position myosin heads. Ending the contraction.

Step 12

Steps 8-11 repeat until no more ATP and Ca2+ is produced. And motor neuron no longer releases ACh