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Skeletal Muscle Activity

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Irritability
The ability to receive and respond to a stimulus
Contractility
The ability to shorten (forcibly) when an adequate stimulus is received
Motor Unit
One neuron and all the skeletal muscle cells it stimulates (figure 6.4)
Neuromuscular Junctions
When a long threadlike extension of the neuron, called the nerve fiber or exon, reaches the muscle, it branches into a number of axonal terminals, each of which forms junctions with the sarcolemma of a different muscle cell (figure 6.5)
Synaptic Cleft
The gap between the endings of the muscle cells' membrane.
Filled with tissue (interstitial) fluid
Neurotransmitter
A chemical released when the nerve impulse reaches the axonal terminals
Acetylcholine or ACh
The specific neurotransmitter that stimulates the muscle cell.
Defuses across the synaptic cleft and attaches to receptors (membrane proteins), which are part of the sarcolemma.
Action Potential
The "upset" caused by a rushing intake of sodium ions (Na+) through the muscle cell