Neurons and Contraction

NMJ

All motor axon terminals that innervate a single muscle fiber

Tip: The starting lineup

Motor endings

Release ATP ACh at the NMJ

Calcium Channels

Voltage gated

Action potential (AP)

A change in voltage across a neurons membrane

Nicotinic receptors

Always depolarizing (excitatory)

End plate potential

Open nicotinic receptors produce a local depolarization

Can spread passively

Generated at the NMJ

Acetylcholinesterase

An enzyme in the cleft that quickly breaks down ACh down to remove stimulus effect

Depolarization

An electrical shift within a cell where the inside of the cell temporarily becomes less negative (or more positive) compared to the outside

Repolarization

Restoring the sarcolema to its initial polarized state

Negative inside and positive outside

Excitation-contraction coupling

AP stimulation (excitation) is coupled to muscle response (contraction)

Transmission of an AP along sarcolemma leads to the sliding of myofilaments, which converts an electrical process into a mechanical process

Calcium release channels

Depolarization causes the SR to open and release calcium into the sarcoplasm

Botox

Causes a temporary paralysis of muscles by preventing ACh release

Pre sympathetic

Interferes with SNARES

Myasthenia gravis

Disease of the NMJ where the receptors for ACh on muscle cells are attacked. This prevents muscle form being stimulated, making them tire easily