Answer:
To bind neurotransmitters and generate an action potential in the sarcolemma
Explanation:
A Myoneural junction is also known as A neuromuscular junction that basically is a chemical synapse which is created when a motor neuron contacts a muscle fiber. This synapse made between a spinal motor neuron and skeletal muscle cell has a specific structure due to which it is called the motor endplate.
Now what is the function of this motor endplate?
We already know that in response to a stimuli a series of events start in nervous system which lead to the production of a response. For example, when we touch a hot object a signal travels through Central nervous system and the response occurs when we move our hands away from the hot object.
Now, taking this same example, what happens is that when a response has to be produced , for example muscle contraction, the neurons which act there are called motor neurons. When the motor nerve is stimulated due to arrival of a nerve impulse in the motor nerve terminals, the first response occurs with the help of motor endplate.
The arrival of motor neuron causes an action potential at presynaptic neuron terminal that opens up calcium channels and Ca2+ ions into the presynaptic neuron's cytosol causing several neurotransmitter molecules to fuse with the presynaptic neuron's cell membrane
Here, the neurotranmsitters like acetylcholine binds with the receptors present in the motor end plate. As soon as they bind with the receptors on motor end plate, an influx of Na+ ions occurs that triggers an action potential. When action potential is triggered it travels along the sarcolemma and into the muscle fiber which initiate the muscle contraction. This muscle contraction is the response to a certain stimuli and in the example we discussed it will be bringing our hand away from the hot object.
This is a long and complex mechanism which i tried to summarize, You can get a better idea by looking at the diagram attached.
