Contraction and Relaxation of skeletal muscle - Nerve impulses elicit a muscle action potential in the following way.
- 1) Release of acetylcholine: Nerve impulse
- arriving at the synaptic end bulbs causes many synaptic vesicles to release ACh into the synaptic cleft
- 2) Activation of ACh receptors: Binding of ACh to the receptor on the motor end plate opens an ion channel. Allows flow of Na+
- to the inside of the muscle cell
- 3) Production of muscle action potential: The inflow of Na+ makes the inside of the muscle fiber more positively charged triggering a muscle action potential. The muscle action
- potential then propagates to the SR to release its stored Ca++
- 4) Termination of ACh activity: Ach effects last only briefly because it is rapidly broken down by acetylcholinesterase (AChE)