AP PSYCHOLOGY

Detailed explanation-1: -CELL MEMBRANE FUNCTIONS In a nerve, if the membrane potential decreases from-70 mV to-55 mV the cell fires an action potential which propagates along the axon. An action potential is propagated (i.e. ‘handed on’) with the same shape and size along the whole length of the axon or muscle cell.

Detailed explanation-2: -There are several potassium leakage channels in the human neuron; hence, potassium tends to leak out of the channels faster than sodium can enter through the channel. This causes a scenario of leaving the neuron’s interior with a high negative charge of almost-70 mV.

Detailed explanation-3: -When the depolarization reaches about-55 mV a neuron will fire an action potential. This is the threshold. If the neuron does not reach this critical threshold level, then no action potential will fire.

Detailed explanation-4: -Action potentials in mammalian neurons use the concentration gradients of sodium and potassium ions to encode and transmit information by a transient change in membrane voltage. In this process, the ionic gradients are partially dissipated and must be restored by the Na+/K+-ATPase pump, requiring metabolic energy.