Question

Describe the mechanism of homoloqous deserisitizahar and its significane. The action potential is self proqaqating. Expoain how this takes place and why it is so important. Define and explain each of the following Local homeostatic control mechanism Epsp vs IPSP Large dense care synatptic vescicles Schwann cells Spatial summahion

Answer 1

1. The attenuation of biological effect of receptor towards its agonist is known as homologus desensitization. Upon continuous exposure of receptor, the receptor detached from the signaling cascade and no longer responds to the agonist though it is present in high concentrations. It is an important mechanism of receptor adaptation (adaptation of special senses that is very importatnt).

2. When any form of impulse strikes the cell, it causes change in membrane potential by changing the ion permeability across the membrane. If the membrane potential reaches threshold level, then the action potential is generated, and the nerve impulse propagates to the next neuron. If the stimulus fails to reach threshold level of membrane potential, the no action potential is generated. This is called all-or-none response. Without the generation of action potential imulse propagation do not occur.

3.

A) Feed mechanisms play an important role in maintenance of homeostatic conditions of the body. They are of two types namely,

1. Positive feedback mechanism

2. Negative feedback mechanism

If the release of one hormone is further triggered by its release, then it is called as positive feedback mechanism. Eg: release of oxytocin during labour pains is the best example of positive feedback regulation.

If the release of hormone inhibits the further release of the same, then it is called as negative feedback regulation. Eg: Release of noradrenaline during hypotension.

The key for maintanance of homeostasis reulation is the response of different sensors towards change in the local environment that trigger corresponding regulating mechanism.

B)

If the released neurotransmitter is excitatory and causes depolarization of post synaptic membrane, then EPSP (excitatory post synaptic potential) is generated. Or if, the released neurotransmitter is inhibitory and causes hyperpolarisation of post synaptic membrane, then IPSP (inhibitory post synaptic potential) is generated.

E) Sometimes, two or more EPSPs occur at a single synapse, one after another, but before the post synaptic membranes potential has not returned to the normal resting potential. In such cases, the EPSPs add together, and this is called