Neuromuscular Junctions Physiology of Muscle Fibers

This will eventually lead to a muscle contraction if the stimulus is above the threshold.

What do we have in common?

Puffer fish

Poison Arrow Frog

Blue-ringed Octopus

Neuromuscular Junction - The Real Thing!

Botulinum toxin binds to pre-synaptic membranes at neuromuscular junctions, enters the neuron, and then a component of the toxin interferes with the release of neurotransmitter. Release of acetylcholine is blocked. No acetylcholine? No muscular contraction. (flaccid paralysis)

The Transverse (T) Tubules work with the sarcoplasmic reticulum to rapidly concentrate and move calcium ions throughout the sarcoplasm

Ca2+ binds the troponin molecules on the thin actin myofilaments.

This leads to the ability of the thick myosin filaments to bind the actin. The myosin heads pull the actin molecules inward, causing the whole fiber to shorten.

What is happening when ATP binds the myosin head?

The cross-bridge is broken and the muscle relaxes!

Body Temperature

Rigor Mortis

Time since death

Warm

Not yet stiff

Dead not more than 3 hours

Warm

Stiffness starting in head

Dead 3 to 8 hours

Cold

Stiff

A Cold

Dead 9 to 36 hours

No longer stiff

Dead more than 36 hours

http://www.youtube.com/watch?v=9FF6 UKvDgeE

http://www.youtube.com/watch?v=pcay ZjTKsm8&feature=related