tential? embrane pot 31. If the potassium leak channels are blocked, what will h
ID: 303231 • Letter: T
Question
tential? embrane pot 31. If the potassium leak channels are blocked, what will happen to the mem (a) The interior of the cell will become less negative (b) The interior of the cell becomes less positive (c) The exterior of the cell becomes less negative (d) The exterior of the cell becomes less positive their c 32. What would happen to the membrane potential if sodium ions were allowed to flow down gradient? (a) The interior of the cell will become less negative (b) The interior of the cell becomes less positive (c) The exterior of the cell becomes less negative (d) The exterior of the cell becomes more positive 33. How can a presynaptic neuron increase the intensity of the signal it is transmitting? (a) Increase the amount of neurotransmitters secreted (b) Change the type of neurotransmitter released (c) Increase the frequency of the action potential (d) Initiate a passive spread signal 34. What is the effect of opening the voltage gated sodium channels on the membrane potential? (a) Makes the interior of the cell less negatively charged (b) Makes the interior of the cell more negatively charged (c) Makes the interior of the membrane less positive (d) None of the above 35. When an action potential starts at one end of an aroExplanation / Answer
31. Potassium leaky channels allow potassium to leak outside the cell through the membrane based on the concentration gradient. These channels maintain the membrane potential in neurons, which are created due to the differences in electrical charge on the two sides of the membrane. The sodium potassium pump transports three sodium ion out of the cell and two potassium ions inside the cell. As a result, a chemical gradient is created. K+ will then move across the membrane to the outside of the cell via the potassium leaky channels. Finally, equilibrium is reached between the electrical and chemical K+ gradients. This is known as resting membrane potential. This potential is around -70mV with the inside of the cell being more negative than the outside.
When these potassium leaky channels are blocked, the resting membrane potential is reduced as the potassium ions remain in the inside of the cell. Hence, the cell will become less negative inside.
Right answer is a. the interior of the cell will become less negative.
32. The sodium ions are actively pumped by the sodium potassium channel outside the cell. Hence, the cell will have more sodium ions present on the outside of the cell. If sodium ions were allowed to move down their concentration gradient, these ions will now move into the cell. As a result, the interior of the cell will have more positive charges as Na ions are positively charged. Hence, the interior of the cell will become more positive.
Right choice is a. The interior of the cell will be less negative.
33. The presynaptic neurons cannot alter the size of the action potential. However the number of action potentials that are generated in a specific time can be increased. Thus, frequency of the action potential can be increased which will then increase the intensity of the signal that it transmits. Neurotransmitters are released when actions potentials are generated. They act on postsynaptic neurons. Hence, changing or altering the type and amount of neurotransmitter will have an effect on post synaptic neurons.
Right choice is c. increase the frequency of the action potential.
34. When a cell is at rest, the interior of the cell is more negative as compared to the outside of the cells due to movement of potassium ions too outside of the cell. Voltage gated sodium channels cause influx of sodium into the cell. Hence, they cause depolarization of action potential leading to generation of action potential. The opening of voltage gated sodium channel will make the cell interior less negative or more positive. This creates a positive membrane potential.
Right choice is a. It makes the cell less negatively charged.
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