During resting potential, the axonal mem | Class 11 Biology Chapter Neural Control and Coordination, Neural Control and Coordination NCERT Solutions

Neuron’s membranes are in a polarized state. Different types of ion channels are present in neuron membrane which are selectively permeable to different ions. When a neuron is not conducting any impulse (resting) the axonal membrane is comparatively more permeable to K⁺ ions and nearly impermeable to Na⁺ ions and negatively charged proteins present in axoplasm. The axoplasm inside the axon contains high concentration of K⁺ and negatively charged proteins and low concentration of Na⁺. The fluid outside the axon contains a “low concentration of K⁺, a high concentration of Na⁺ and thus form a concentration gradient. These ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium- potassium pump which transports 3Na⁺ outwards for 2K⁺ into the cell. As a result, the outer surface of the axonal membrane possesses a positive charge while its inner surface becomes negatively charged and therefore is polarized. Resting potential is the electrical potential difference across the resting plasma membrane.