12.14.1 Human Regulation: The Nerve Impulse: General Events

Question 1

Human Regulation: The Nerve Impulse: General Events

Answer 1

• A nerve impulse is an electrical signal involving the flow of ions across the plasma membrane of a neuron.
• Because of differences in ion concentrations and permeability, the inside of a neuronal membrane is more negative than the outside, resulting in a voltage gradient.
• The membrane potential is the voltage measured across the plasma membrane of the cell. A typical neuron has a resting membrane potential of –70 mV, and the inside of the neuron is more negative than the outside.
• The depolarizationof a nerve cell is a reduction in the electrical gradient across the membrane. A stimulus on the receptors of the nerve cell triggers depolarization. Depolarization can trigger an action potential, a rapid and relatively drastic change in the membrane potential of the nerve cell.

Question 2

note

Answer 2

• A nerve can convert a stimulus to an impulse. The impulse
  travels down the myelinated axon to the synapse, where the
  impulse will be transmitted to the dendrite of another nerve
  cell

Question 3

membrane potential

Answer 3

• A difference in charge resulting from ion-concentration differences causes a voltage gradient between the inside and outside of the nerve cell. The membrane potential, or voltage difference across the membrane of a resting neuron, is typically –70mV.
• Notice in the diagram to the left that the outside of the cell has a higher sodium ion (Na+) and chloride ion (Cl)
  concentration than the inside, and that the inside of the neuron has a much higher potassium ion (K+) concentration than the outside.
• The sodium-potassium ATP pump maintains the difference in ion concentration across the membrane of a nerve cell. This pump uses energy from ATP to pump Na+ out of the cell and K+ into the cell. For every three Na+ that are pumped out, two K+ are pumped in.
• K+ (symbolized by squares) constantly diffuses out of the cell, and Na+ (symbolized by circles) diffuses into the cell. Notice that more K+ flows out of the cell than a+ flows in.

Question 4

Which of the following is responsible for maintaining the difference in ion concentration across the membrane of a nerve cell?

Answer 4

• the sodium-potassium pump

Question 5

Which of the following ions is involved in generating an action potential of a neuron?

Answer 5

• sodium ion
• chloride ion
• potassium ion
• All of these are involved in generating an action potential of a neuron.

Question 6

A membrane potential is

Answer 6

• the difference in charge between the inside of a cell and its exterior.
• the voltage measured across the plasma membrane.
• generally in the range of −50 to −100 in a nerve cell at rest.

Question 7

On average, the membrane potential for a neuron in its resting state is

Answer 7

• −70 mV

Question 8

Stimuli are conducted down the axon of the nerve cell to the synaptic terminal by

Answer 8

• sequential depolarizations and action potentials

Question 9

The negative charge on the inside of the neuron is mostly maintained by

Answer 9

• large negatively-charged proteins.