When sodium ions enter a neuron through chemically gated channels, they always cause depolarization, and thus firing of the cell. The same effect occurs when we contract skeletal muscle cells because they also contain

Calcium ions

Explanation:

This is because the contraction of skeletal muscle occurs as a result of the release of Calcium ions from internal stores which is a result of the function of a neural signal.

So, skeletal muscles contract when calcium ions are released. There is also an action potential which is generated which causes the muscle to contract. This action potential is present in both skeletal muscle cells and neurons and is as a result of the movement of sodium ions in neurons and calcium ions in skeletal muscle cells.

albert einstein retrieved guacamole from the galapagos islands in africa

1. efficient use of space

2. elimination of groundwater contamination

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4. lower carbon footprint