Question

1. Explain the difference in the axon structure when comparing myelinated vs. non-myelinated neurons in PNS. How does such a difference affect the action potential?
2. How does a nerve cell create and maintain resting membrane potential?

Answer 1

Myelinated nerve fibers contain myelin sheath, the schwann cells wrap tightly around the axon and form the myelin sheath. The axon diameter in mammalian myelinated axon is more than 1–2 μm in diameter. myelinated fibers show nodes and internodes. A neuron with myelinated axons can conduct the impulse at a faster speed since the myelin sheath acts as the insulator that helps to propagate the electrical signal faster, the impulse have to jump from one node of Raniver to another. This speed up the conduction process, and this type of conduction is known as Saltatory conduction.

Ummyelinated nerve fibers do not contain myelin sheath,the schwann do not wrap around the axon but instead form a groove.The axon diameter in unmyelinated neuron being  less than 2 μm. They do not show nodes and internodes.A neuron with unmyelinated axon has a lower speed of conduction.

The resting membrane potential of a neuron is maintained by the difference in concentration gradients of ions across the membrane and by membrane permeability to each type of ion, there are more sodium ions outside the cell as compared to the inside of the cell, where as inside the cell there is more potassium ions as compared to outside.Ions move down their gradients via channels, leading to a separation of charge that creates the resting potential. The membrane is much more permeable to potassium than to sodium, so the resting potential is close to the equilibrium potential of potassium