Question

Fully explain the anatomy and physiology (the process of saltatory conduction) of a post- synaptic depolarized sensory neuron exactly as outlined in the lecture. Identify and explain the purposes of the three neurotransmitters. What happens to neurotransmitters released from the pre-synaptic terminal bulb toward the next post-synaptic polarized sensory neuron?

Answer 1

ANSWER: Post synaptic depolarised neuron is a neuron that recieves the neurotransmitter after it has crossed the synapse and may experience the action potential if that neurotransmitter is strong enough. It works through temporal summation and partial summation. The synapse contians three parts namely presynaptic terminal, synaptic cleft and the post synaptic region. The presynaptic neuronal terminal region causes the release of neurotransmitter from that region into the synaptic cleft through exocytosis which gets binded to the receptors found onthe postsynaptic membrane of the neuron. By binding of the neurotransmitter the action potential is generated in the postsynaptic neuron. The action potential can be conducted in many waves like the saltatory conduction in myelinated neuron and continuous conduction in case of nommyelinated neurons. In saltatory conduction the action potential jumps from one node of Ranvier to the next node of Ranvier thus making the conduction faster and more efficient. It is due to the rush in of sodium ions into the node of Ranvier creates an electric force which pushes the ions already inside thus producing an action potential.

The main three Neurotransmitters are the acetylcholine, norepinephrine and dopamine.

Acetylcholine is an excitatory neurotransmitter secreted by motor nerves supplying muscles. Its main function is to stimulate muscle contraction.

Dopamine is secreted by neurons of substania nigra. It is necessary for coordination of involuntary movement by inhibiting the unnecessary movement. It also inhibits the secretion of prolactin hormone.

Norepinephrine is an excitatory neurotransmitter secreted by Postganglionic sympathetic nerves. It increases the alterness and wakefulness of the person.

The neurotransmitter released from the presynaptic terminal reaches the postsynaptic neuron and binds to its receptor and cause depolarisation to elicit response on the next neuron.