Question
Changes in membrane potential during nerve transmission along an axon involve the movement of sodium and potassium ions across the axon membrane.
What explains the membrane potential at Y in the trace?
A. Potassium channels open and allow potassium ions to move to the outside of the axon membrane.
B. Potassium channels allow potassium ions to enter the axon.
C. When the threshold voltage is reached, the sodium pump begins to pump sodium ions to the outside of the axon membrane.
D. Potassium and sodium channels are closed, so there is no movement of ions across the axon membrane.
▶️Answer/Explanation
Ans. A
Question
The graph shows changes in the membrane potential in an action potential.
What is the approximate value of the threshold potential?
A. −88 mV
B. −70 mV
C. −50 mV
D. +45 mV
▶️Answer/Explanation
Markscheme
C
Question
The image shows a neuron.
What is the function of X?
A. Increases the speed of transmission along the axon
B. Increases the rate of exchange of sodium and potassium ions
C. Holds bundles of neurons together to form a nerve
D. Determines the direction of the action potential
▶️Answer/Explanation
Markscheme
A
Question
How does potassium move across the membrane of a neuron during repolarization?
A. Simple diffusion
B. Facilitated diffusion
C. Endocytosis
D. Active transport
▶️Answer/Explanation
Markscheme
B