Please answer thoroughly and detailed With respect to the physiology of the syna
ID: 80447 • Letter: P
Question
Please answer thoroughly and detailed
With respect to the physiology of the synapse, a model system such as the neuromuscular junction and acetylcholine is typically used. Because of this learning paradigm, we often think of a synapse as a single-neurotransmitter system. That is, only a single type of neurotransmitter is packaged within vesicles at the axon terminus. However, is this strictly true? Can more than one type of neurotransmitter be found within the vesicles of an axon terminus? Or, can an axonal terminal have two or more different populations of vesicles, each with its unique neurotransmitter? Provide specific examples with appropriate references. What sorts of physiological advantages and problems might such a system pose?
Explanation / Answer
1. Only a single neurotransmitter is packaged within a single vesicle at a presynaptic ending.
2. However two or three neurotransmitters can be present in different sets of synaptic vesicles at the same pre-synaptic ending as per recent research. These neurotransmitters are called co-transmitters.
3. Example ; It was long believed that motor neurons secrete only acetyl choline at synapses. but it has now been shown that they secrete glutamate too. Auditory neurons have also been shown to release more than one neurotransmitter in early stages. Another example is the co-release of GABA and glycine
4. The physiological impact can be judged on a case to case basis and there cannot be a generalisation for the same. There are three classes of co-transmitters : both fast acting, both slow acting, one fast and one slow. each class has a different effect on transmission. The phenomenon also has a role in explaining behavior in injury and disease. Example : Majority patients with parkinsonism show reduced sense of smell much beofre they develop motor symptoms.