Question

1. Describe what resting potential is and how neurons maintain it.

2. Explain the events that occur during an action potential, being sure to describe what causes depolarization and repolarization. How do Schwann cells (glial cells) aid in the movement of depolarization along an axon?

Answer 1

There are two questions asked here. As per the Chegg Q&A Guidelines, I am answering the first question.

Neuron, like other cells, has a cell membrane. This separates the interior of the cell from the extracellular environment. The cell membrane is composed of a lipid bilayer. As a result, hydrophilic and charged molecules are unable to cross the barrier. Additionally, the membrane is embedded with lots of protein complexes. These protein complexes include ion channels which allow selective movement of ions across the membrane. There are also transporter molecules which permit the movement of molecules against the concentration gradient at the expense of energy. The energy is obtained by the release of phosphate from adenosine tri-phosphate (ATP).

The ion pumps maintain a potential difference across the membrane by maintaining the concentrations of specific ions across the membrane. A major ionic pump involved in neurons is Na+/K+ pump. The Na+ concentration outside the cell is much higher compared to its concentration inside the cell. Similarly, the concentration of K+ is much higher inside the cell compared to its concentration inside the cell. This is maintained by the Na+/K+ pump. It pulls in K+ ions inside while pushing Na+ ions outside. For 3 Na+_ion thrown outside, two K+ ions are taken inside. This creates a charge imbalance. As a result the resultant potential inside the cell is negative compared to the outside. This is called as the resting membrane potential. In majority of neurons it ranges from -65 to -90mV. This gives the basis for the electrical activity in the neurons and eventually to the higher order brain processes like learning, memory, attention and so on.