Question

Describe how graded potentials are regulated and how they regulate action potential firing. In your answer, specifically identify where on a neuron each event occurs.

Answer 1

Ans. Graded potential is brough out through the passive electrical property of neuronal membrane, by external stimulli or by neurotransmitters released in synapses. The Graded potential occurs in post-synaptic cell in dendrites or soma. They can be depolarizing or hyperpolarizing depending on the nature of stimulus. The action potential is generated by the change in the neuron resting potential, depolarizing from negative resting potential to more positive potential using infux of cations through ion channel. During this process the part of neural membrane opens to allow the entry of positive charge ion and exit of negative ions out of cell, only muscle and neuron are capable of generating action potential. The action potential occurs in plasma membrane regions where concentration of voltage-gated Na+ and K+ channels are high. The graded potential initiates the action potential, as graded potential summate at the specific location on axon beginning to initiate action potential. The axon hillock is where the summation takes place as they have a high density of voltage-gated Na+ channels that initiate the depolarizing phase of the action potential. Thus the graded potential lead to initiation of action potential.