As we\'ve learned that neurotransmitters are released from pre-synaptic terminal

Question

As we've learned that neurotransmitters are released from pre-synaptic terminal into a synapse, bind to receptors on post-synaptic cells to produce their actions, and are removed from the synaptic cleft to terminate their actions.

The mechanisms of actions of various medications and drugs are based on the presence of or clearance of various neurotransmitters within the synaptic cleft. Based ont he processes of neurotransmitter release, pre-uptake, and binding, describe a mechanism that might contribute to potentiating a neutrotransmitter's synaptic effects and describe a mechanism that might contribute to limiting a neurotransmitter's synaptic's effects. Provide an example where these mechanisms might play a role in physiological role.

Explanation / Answer

The nreve cells communicate with each other through chemicals called neurotransmitters.They are synthesised by pre-synaptic neurons and stored in their vesicles at axon terminal. Once a neuron is stimulated they are relaesed and travel between pre and post-synaptic nerves. The presynaptic neuron and the postsynaptic neuron are separated by a small gap — the synaptic cleft whic is filled with extracellular fluid (the fluid bathing all the cells in the brain). Although very small, typically on the order of a few nanometers , the synaptic cleft creates a physical barrier for the electrical signal carried by one neuron to be transferred to another neuron. The function of neurotransmitter is to overcome this electrical short. It does so by acting like a chemical messenger, thereby linking the action potential of one neuron with a synaptic potential in another.

Neurotransmittes can be of two types;

1. Small molecule neurotranimitters e.g., acetylcholine (Class I), Biogenic amines like catchecolamines, serotonin, histamine (Class II), Amino acids for example,gamma aminoa butyric acid, glycine, aspartate, glutamate (Class III) or Nitrous oxide (Class IV). The small molecule neurotransmitters act rapidly and illict acute responese.

2. Nuuropeptide transmitters e.g., neuroactive peptides,pituary peptides,peptides acting on the gut and brain and neuropeptides from other tissues.

Neurotransmitters can have excitory ( acetylcholine,aspartate, dopamine, histamine, serotonin, ehinephrine, norephinephrine, glutamate) as well as inhibitory function (GABA,glycine)..

Mechanism of excitory neurotransmission (glutamate, acetylcholine, aspartic acid)

Excitory neurotransmitter ------------> Neuron (Action potential) ------> Muscle contraction of gland-------->Secretion

Excitory neurotransmitter ------------> Central nervous system ------> Depolarization of post synaptic membrane

Acetylcholine neurotransmission causes cardiac inhibition, vasodilation, gastrointestinal peristalsis,control of sleep, thought and mood.

Mechanism of inhibitory neurotransmission (GABA, glycine, dopamine)

Inhibitory neurotransmitter -----------> Reduce or block activity of postsynaptic cell

Inhibitory neurotransmitter -----------> Central nervous system --------> hyperpolarization of post synsptic membrane

Dopamine neurotransmission results in parkinsonism, induction of vomitting, inhibition of prolactin secretion and schizophrenia.

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