8. The events that occur at a neuromuscular junction are depicted below. Identify every structure provided with a leader line. Note: The pink arrows depict the propagation of the action potential.
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a
axon terminal of motor neuron
b
motor neuron axon branch
myelinated axon of motor neuron
d
muscle fiber
e
Sarcolemma of muscle fiber
synaptic cleft
synaptic vesicle containing ACH
h
terminal cistern of the SR
triad
9—
T tubule
i
gf

The structures are already listed, I will go ahead to explain the event that happens at the neuromuscular junction which is also known as the SYNAPSE ,as I do that, I will make mention of all the structures listed and represented in the picture.

In Synapse,there is always more than one neurone involves in the transmission of a nerve impulse from it's point of origin to it's destination. Whether it is a sensory nerve or motor nerve,no physical contact exist between the two neurons.

The exact point at which the neurone moves from the presynaptic neurone to the postsynaptic neurone,at the free end,the axon of the presynaptic neurone breaks up into minute branches that further terminate into small swellings that is known as synaptic knobs or the terminal buttons.

These synaptic knobs are in close range to the dendrites and the cell body of the postsynaptic neurone.

The space between them is known as the synaptic cleft.

The synaptic knobs contains membrane bound synaptic vessicles which are spherical in shape,these membrane bound vesicles store a chemical that is known as the neurotransmitter which is released into the synaptic cleft.

These neurotransmitters are synthesized in the nerve cell bodies and they are actively transported along the axons and then stores in the synaptic vesicles. In response to the action potential,they are released by exocytosis and then diffuse across the synaptic cleft.

They act on receptor sites that are specific in nature on the post synaptic membrane.Immediately they act upon the post synaptic cell,such as a muscle fibre,they either get inactivated by enzymes or they are taken back into the synaptic knobs,hence, their action is short lived.

Neurotransmitters most times exert an excitatory effect on postsynaptic receptors but sometimes they are also inhibitory.

However,some drugs that are important has a way of mimicking, neutralising (antagonise) or prolong neurotransmitter activity.

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explanation: