EKB-Lecture 4

•After an action potential, there is a short period of time when another action potential cannot be generated. What is this period of time called?

Refractory period
Depolarization period
Inhibitory stage
Pause stage

•Which of the following statements about nerve impulses is true?

Nerve impulses are divided into weaker impulses when transmitted to multiple neurons at once.
Nerve impulses start strong and degrade while propagating down the axon.
Only a stimulus with sufficient strength can produce an action potential in neurons.
Neurons amplify weak stimulations in order to be able to produce an action potential.

•Neurons are excitable because a difference of potential exists between the extracellular and the intracellular sides of the plasma membrane. Which of the following creates the separation of charges that sets the difference of potential at rest?

The potassium channels
The sodium–potassium pump
The passive flow of ions through the membrane
The sodium channels

•Complete the following: At rest, the concentration of …………….. ions outside of a neuron is …………….. than inside the neuron.

potassium, higher
sodium, lower
potassium, no different
sodium, higher

•Which of the following is the phase during which the neuron becomes unable to generate a second action potential regardless of stimulus strength?

Repolarization phase
Depolarization phase
Resting state
Refractory period

•The repolarization of neurons is one of the phases of an action potential. Which of the following best describes the repolarization phase?

It is the phase when sodium ion channels open and sodium ions flow back to the outside of the cell.
It is the phase when sodium ion channels close and potassium flows out of the cell.
It is the phase when chloride ions flow out of the cell and sodium ions flow into the cell.
It is the phase when sodium ion channels open and the sodium flows into the cell.

• In neurons at resting potential, the concentration gradient of positively charged sodium ions and potassium ions would dictate that sodium ions move into the cell and potassium ions move outside the cell. How do neurons maintain the ion distribution across their membrane despite that?

By means of Na+/Cl- pumps
By means of positively charged membrane proteins
By means of Na+/K+ pumps
By means of voltage-gated Na+ channels
By means of Cl- channels

• Hyperkalemia is an abnormally elevated level of potassium in the blood. Which of the following effects will the hyperkalemia most likely have on the resting membrane potential of a neuron?

Due to the high concentration of the extracellular potassium, the outflow of potassium and the resting potential will increase, causing a prolonged repolarization state.
Due to the high concentration of the extracellular potassium, the outflow of potassium and the resting potential will decrease, causing a prolonged depolarization state.
Due to the high concentration of the extracellular potassium, the outflow of potassium and the resting potential will increase, causing a prolonged depolarization state.
Due to the high concentration of the extracellular potassium, the outflow of potassium and the resting potential will decrease, causing a prolonged repolarization state.

•When the resting potential is being maintained, are the voltage-gated sodium ion channels open or closed?

Closed
open

•The graph shows how an axon membrane’s permeability to ions changes during an action potential.

•Which ion is represented by the blue line?

Hydrogenv
Sodium
Potassium
Calcium

•What is a typical value for resting potential in human axons?

70mV
-70mV
-65mV
65mV

EKB-Lecture 4

Quiz Summary

Information

Results

Results

Categories

1. Question

2. Question

3. Question

4. Question

5. Question

6. Question

7. Question

8. Question

9. Question

10. Question

11. Question