and Muscle Contraction
Muscle contraction is controlled by motor
neurons that release that neurotransmitter a
acetylcholine at neuromuscular junctions.
Acetylcholine the diffuse across the narrow
synaptic cleft, and binds to acetylcholine
receptors on the membrane of the muscle cell.
This results in the opening of ion channels
within the receptor molecules, in such a way
that a depolarizing, synaptic ion current can
flow. This current triggers an all or nothing
response in the form of an action potential
across the plasma membrane of the muscle cell.
The action potential moves out in all directions
from the neuromuscular junction, resulting in
stimulation of the entire muscle fiber. Within a
few milliseconds, the contractile mechanism
responds and fiber contractile.