Unformatted text preview: Neuromuscular Junctions (NMJ) The synapse between a motor neuron and a muscle cell is a neuromuscular junction . At the NMJ, the motor neuron releases a neurotransmitter that stimulates a muscle cell. The neurotransmitter released by motor neurons is acetylcholine and it causes the skeletal muscle to contract. Before release, the ACh molecules are packaged in small vesicles in the synaptic terminal . When stimulated, the neuron releases the ACh by exocytosis into the synaptic cleft . The motor end plate is the specialized region of the muscle cell that has ACh receptors . The ACh released from the neuron diffuses across the synaptic cleft and binds to ACh-Rs; the receptors open and let Na + into the cell. Thus, ACh-Rs are both receptors and channels. Also found in the NMJ is the protein acetylcholinesterase . This enzyme breaks down ACh and ultimately causes relaxation of the muscle. Special glial cells called Schwann cells envelope and isolate the NMJ....
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- Fall '10
- Anatomy, Neuromuscular Junctions