I played a little social tennis tonight on the Woodland Park tennis courts. We rained out on both Tuesday and Thursday of last week, so it was great to finally get out and play.
And hey! the muscle memory from many years of playing tennis is still there, sending signals to the old muscles and creaky bones— to run down that incoming shot, and strike it, so it goes back over the net.
Muscles need electrolytes (salty water) to function. A neuromuscular junction (or myoneural junction) is a chemical synapse (connection that allows a signal to pass), formed by the contact between a motor neuron and a muscle fiber. It is at the neuromuscular junction that a motor neuron is able to transmit a signal to the muscle fiber, causing muscle contraction. Here is what happens, all of it in a millisecond or so! (1) The electric signal’s action potential reaches the axon terminal. (2) Voltage-dependent calcium gates open, allowing calcium to enter the axon terminal. (3) Neurotransmitter vesicles fuse with the presynaptic membrane and acetylcholine (ACh), a small neurotransmitter, is released into the synaptic cleft via exocytosis. (4) ACh binds to postsynaptic receptors on the sarcolemma (membrane on the muscle fiber). (5) This binding causes ion channels to open and allows sodium and other cations to flow across the membrane into the muscle cell. [Source: Wikipedia]
