GENERATION AND CONDUCTION OF NERVE IMPULSE GULNAZ KAUR

GENERATION AND CONDUCTION OF NERVE IMPULSE - GULNAZ KAUR PGT(Bio) KV Bhandup, MUMBAI

Resting Potential Neurons are in excitable state because their membranes are in a polarized state. They have different ion channels which are selectively permeable to different ions. In Resting state the membrane is more permeable to K+ and impermeable to Na+

Resting Potential The membrane is impermeable to –vely charged proteins present in the axoplasm of axon. Therefore, the outside of axon is slightly +ve and the inside is slightly –ve. This difference is polarity creates a potential difference of -6070 millivolts. To maintain resting potential Na-K pump operates. This pump is located in the axon membrane which pumps 3 Na+ from ECF to axoplasm and 2 k+ from axoplasm to ECF and this is run by a enzyme Na-K ATPase

Depolarization When a stimulus is received by the polarized membrane, the Na+-K+ pump stops operating and there is rapid influx of Na+ due to which the polarity is reversed and the membrane is then said to be depolarized. The infux of Na+ continues till the potential difference reaches to 0 and goes upto +30 m. V. This is said to be the peak of Action potential. The travelling of action potential along the membrane is a nerve impulse takes about 4 -5 msecs.

Repolarization Once it reaches +30 m. V, the polarity begins to reverse as the Na+K+pump operates again and this is known as Repolarization. The membrane becomes more permeable for Na+ as a result of which they begin to leave the axon and less permeable for K+ Hence there is accumulation of more Na+ Which makes the outside of the membrane slightly +ve and inside slightly -ve Incase of medulated neurons, transmission occurs through nodes of Ranvier The message is transmitted faster and is known as jumping or dancing action is called saltation or saltatory conduction.

RECAPITULATION What is the potential difference in a resting axon? How is the potential difference maintained in a resting axon? What is the peak of action potential? When does the Na-K exchange pump begin to operate again to restore the polarity? Does transmission of nerve impulse occur along the entire length in case of medulated neuron? What is saltation?

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