Signals Passing Through Neuromuscular Junction 4 th Period: Breanne Gomez, Haleigh Eary, Hanna Hollman, Yazmin Baldonado

Terms Axon is a long threadlike extension of the neuron. Axon terminal are branches of and axon that forms junctions with the sarcolemma. Neuromuscular junction is the region where a motor neuron comes into close contact with a skeletal muscle cell. Synaptic is a gap between nerve endings and muscle cells that is filled with tissue fluid. Neurotransmitter is a chemical released when nerve impulses reach axon terminals. Acetylcholine (ACh) is the neurotransmitter that stimulates skeletal muscle cells specifically.

Axon Skeletal muscles cells have to be excited or irritated by nerve impulses to contract. One neuron and all the skeletal muscle cells it excites or irritates are a motor unit. Axons branch off into numbers of axon terminals when they reach the muscle. Junctions with the sarcolemma of a different muscle cell are formed(neuromuscular junction).

Neuromuscular Junction Axons branch into a number of axon terminals when they reach the muscle. Junctions with the sarcolemma of a different muscle cell are formed.(neuromuscular junction) Nerve endings and muscle cell endings get close but never touch. The gap, or synaptic cleft, is filled with tissue fluid.

Neurotransmitter When nerve impulses reach axon terminals, a neurotransmitter (acetylcholine for muscle cells) is released. Acetylcholine (Ach) diffuses (scatters) across a synaptic cleft and attach to receptors that are part of the sarcolemma. When enough ACh is released sarcolemma temporarily lets sodium pass through it, which rushes into the cell, and potassium which diffuses out of the cell. More sodium enters than potassium leaves.

This reverses electrical conditions of the sarcolemma and allows only sodium to pass through because there are already enough potassium ions. This generates an electrical current called an action potential, which is unstoppable. The action potential travels over the entire surface of the sarcolemma, conducting electrical impulses, which results in a muscle contraction.