1. Motor Unit: A motor neuron and all the muscle fibers it innervates. *Powerful movements use more fibers *Fine movements use fewer fibers

2. Neuromuscular Junction ( NMJ): What is a NMJ? –Connection between motor neuron and muscle fiber. Label Pic: –1- Motor Neuron –2- Synaptic Cleft –3- Synaptic Vesicle –4- Receptor –5- Mitochondria in muscle cell

3. Neuromuscular Junction ( NMJ): Synaptic Vesicles: –Holding chambers for neurotransmitters. –Each vesicle stores about 10,000 molecules of Acetylcholine (Ach) –About 30,000 vesicles at each end plate

4. Neuromuscular Junction ( NMJ): Neurotransmitters (NT’s) –chemicals that aid in the transmission of nerve impulses. –Example: Acetylcholine (Ach)

5. Neuromuscular Junction ( NMJ): Steps at NMJ: 1.motor neuron receives signal to stimulate movement 2.synaptic vesicles move to end of neuron and release Acetylcholine 3.Ach attaches to receptors 4.Generic cation (+) channels open, stimulating contraction 5.Enzyme (Acetylcholinesterase) breaks down Ach stopping contractions