Describe the signal transmission across a myoneural junction. define polarity and describe how the polarity of a neuron changes when an action potential is being produced.

The signal transmission process of the myoneural junction involves the following parts: axon terminals, pre-synaptic cell, synaptic cleft, receptors, and post-synaptic cell. Firstly, a nerve impulse will go to the axon terminals. Once it reaches the terminals, a molecule, called the neurotransmitter will be released. This neurotransmitter is stored in the pre-synaptic cell, which is attached to the axon terminals. For this process, the specific neurotransmitter ejected is called acetycholine or Ach. This Ach will then proceed to the synaptic cleft, the gap between the pre-synaptic cell (motor neuron) and the post-synaptic cell (muscle cell), and then bind to the receptors of the muscle cell. 

Acetylcholine will diffuse and once adequate amount of Ach is ejected, the sarcolemma, or the membrane of the muscle cell, will be open to positive sodium (NA+) ions to enter the cell and positive potassium (K+) ions to be excreted out from the cell. Since NA+ enter more into the muscle cell than K+ leaving out of the cell, the sarcolemma will have a plethora of positive ions thus changing the electrical state of the sarcolemma causing it to have additional pathways solely for NA+ entrance. This occurrence would generate an electric current called action potential. When this current goes out of hand, the entirety of the sarcolemma would be conducted by electric impulses which results to muscle contractions.