PHGY 209 Lecture Notes - Lecture 22: Myocyte, Ryanodine, Relaxed Muscle
21 Feb 2018
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Document Summary
The action potential of the muscle fiber is coupled to the muscle fiber (excitation-contraction coupling). When the motor neuron sends an action potential, it releases neurotransmitter (acetyl-choline) into the neuromuscular synapse. The dhp receptors are then activated by the acetyl-choline which in turn allows calcium to flow into the muscle fiber. This calcium is not what actually triggers the muscle contraction, but it is rather the calcium from the. The sr is continuously pumping calcium ions into its lumen which allows it to act as a storage of calcium. When the dhp is activated, it changes its conformation. Since it is physically coupled to the ryanodine receptor (calcium channels on sr membrane), the dhp physically activates the ryanodine which allows high levels of calcium efflux into the cytoplasm. This is the calcium that triggers the cross-bridge cycling. There are two additional proteins found on the actin filaments:
