Nerve impulse reaches axon terminal of motor neuron

Step 1

Calcium channels open/calcium ions enter axon terminal

Step 2

Calcium ion causes synaptic vesicles release (ACh)

Step 3

ACh diffuses across synaptic cleft / attaches to

receptors on sarcolemma of muscle cell

Step 4

If ACh is released, sarcolemma becomes more

permeable to sodium ions (Na+)

Potassium ions (K+) diffuse out of cell

Sodium ions enter / Potassium ions leave

Imbalance in interior

more positive ions (depolarization), thereby opening more Na+

channels

Step 5

Depolarization opens sodium channels allow

sodium ions to enter cell

Action potential created

Once begun, Action potential unstoppable

Conducts electrical impulse from one end of cell to other

Step 6

Acetylcholinesterase (AChE) breaks down

acetylcholine into acetic acid and choline

AChE ends muscle contraction

SINGLE nerve impulse ONE contraction

Cell returns to resting state when

1. Potassium ions (K+) diffuse out cell

2. Sodium-potassium pump moves sodium / potassium

ions back to original positions