Question

A polarized neuron is the one that is
A. Conducting stimulus
B. At resting potential
C. Having action potential
D. None of the above

Answer 1

Hint: Human body has a specialized cell called neurons which respond by sending an electric impulse. Neurons have three parts; dendrites, cell body and axons. The conduction of impulse is based on the charge difference inside and outside the cell.

Complete answer: The cell membrane of a neuron contains thousands of tiny molecules known as channels. These channels allow either sodium or potassium ions to pass through. Generally, channels of neurons are closed and the membrane is said to be in a resting state. In this state, the charge of the inside of the cell membrane is more negative than the outside (approximately -70 millivolts). Because of the electrical difference across the cell membrane, the cell membrane of the neuron is polarized. The nerve impulse is initiated when pressure or any other sensory inputs disturbs a neuron plasma membrane to point that the threshold reaches -55 millivolt. This causes many sodium channels of that region of the membrane to open that in turn allows positively charged sodium ions to flow inside the cell membrane. Now for a temporary basis, the inside of the cell becomes more positive compared to the outside. This is known as the depolarizing state of the cell membrane. As the impulse passes further, the potassium channels begin to open allowing the positively charged potassium ions to flow out which causes the inside of the axon to resume the net negative charge. This is known as the repolarized stage of the membrane.
Hence, the correct answer is option B.

Note: The depolarization and repolarization of the cell membrane of a neuron or specifically the axon are known as the action potential of the neuron. The action potential is nothing but the nerve impulse passed through the neuron cell. Even after an impulse is passed, few potassium channels remain open causing the passage of more potassium ions out of the membrane which increases the negative charge inside the cell, also known as hyperpolarization.