1. Nerve Supply to a Muscle

2. Nerve Supply Motor Neuron: Nerve that stimulates a muscle cell. A single nerve (motor neuron) will supply approximately 150 muscle fibers. Motor Unit: Motor neuron plus the muscle fibers= 1 motor unit.

3. Nerve Supply The outside of most plasma membranes contain a slightly positive charge sodium (Na+) The inside of this same membrane has a slightly negative charge, potassium (K+) and chlorine (Cl-) This slight difference in charge is called Resting Membrane Potential.

4. 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. Na+/K+ pumps, pump the Na+ ion back out of the cell and restore the membrane to its resting potential. This shift in charge initiates an Action Potential which propagates to the terminal end of the motor neuron.

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

6. Neuromuscular Junction Synaptic Cleft: Depression in the sarcolemma that receives the motor neuron. Motor End Plate: Portion of sarcolemma that meets with the motor neuron. Synaptic Vesicles: Tiny sacs in the motor neuron that contain neurotransmitters.

7. Neuromuscular Junction Neurotransmitter: Chemical that carries a signal from one nerve terminal to another neuron or muscle. They are found in the synaptic vesicles. Examples: Acetylcholine (ACh)

8. Neurotransmitter When action potential 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 endplate. At the motor end plate the ACh binds to receptor sites. When the Ach binds to the receptor site it initiates another action potential across the muscle fiber.

9. 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 its broken down by the Acetylcholine-esterase