Nerve Supply to Skeletal Muscle

Nerve Supply

The outside of the nerve plasma membranes contain a slightly positive charge (Na+).

The inside of this same membrane has a slightly negative charge (Cl-).

This slight difference in charge is called Resting Membrane Potential.

Nerve Supply

Motor Neuron: Nerve that stimulates a muscle cell.

A single nerve will supply approximately 150 muscle cells.

Motor Unit: Motor neuron plus it’s muscle cells= 1 motor unit.

Nerve Supply Upon stimulation, the nerve cell

membrane potential is changed. Ion channels open allowing positive Ions

(Na+) to enter the cell. The inside of the cell becomes positively

charged for a split second. Ion pumps, pump the Na+ ion back out of

the cell and restore the membrane to its resting potential.

This shift in charges initiates an Action Potential which propagates down the neuron.

Neuromuscular Junction

Motor End Plate: Portion of sarcolemma that meets with the motor neuron.

Synaptic Vesicles: Tiny sacs in the motor neuron that contain neurotransmitters.

Neuromuscular Junction

Synaptic Cleft: Depression in the sarcolemma that receives the motor neuron.

Neuromuscular Junction: Motor neuron terminal end, Motor end plate, and Synaptic cleft.

Neuromuscular Junction

Neurotransmitter: Chemical that passes from one nerve to another nerve or muscle. They are found in the synaptic vesicles. Acetylcholine (ACh), for skeletal muscle contraction.

Neurotransmitter

When the A.P. reaches the terminal end of the neuron the synaptic vesicles open and release (ACh).

The ACh then diffuses across the synaptic cleft to the motor end plate.

At the motor end plate the ACh binds to receptor sites.

When the Ach binds to the receptor site it initiates another A.P. on the muscle cell membrane (sarcolemma).

Neurotransmitter

Acetylcholine-esterase: Enzyme that breaks down ACh and does not allow it to bind to receptor sites. Certain drugs can have the same

effect. Nerve gas binds to receptor sites but it

isn’t broken down by the Acetylcholine-esterase.