01-11-07, Continuing those Anat-Physio notes

Motor neurons connect the CNS to the skeleton muscle cells (effectors). Impulses (action potentials) are responsible for starting the contraction. The nerve cell and muscle cell comes together at the neuromuscular junction.

Vesicles, or pockets, in the axon terminals of the motor neuron release molecules of the neurotransmitter acetylcholine. These molecules diffuse across the synapse junction, producing an impulse in the cell membrane of the muscle cell (myocyte).

Acetylcholine diffuses from the end of the nerve cell to the muscle cell and produces an impulse in the cell membrane of the muscle cell.

It's basically going to open a whole bunch of gates and let ions flow in and that's what starts the muscle contraction. Acetylcholine (Ach) has been referred to as a lock-and-key situation because it is essentially what opens up the holes to allow Ca²⁺ and other ions to flow through. The calcium ions are needed to work with the molecular complex at the junction between actin and myosin filaments in these long, stretched myocytes with multiple nucleus.

Some of these notes are on 01-08-07 again so go back and look at those.