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02:50What happens when a resting neuron's membrane depolarizes? a. There is a net diffusion of Na+ out of the cell. b. The equilibrium potential for K+(EK) becomes more positive. c. The neuron's membrane voltage becomes more positive. d. The cell's inside is more negative than the outside.
A common feature of action potentials is that they a. cause the membrane to hyperpolarize and then depolarize. b. can undergo temporal and spatial summation. c. are triggered by a depolarization that reaches threshold. d. move at the same speed along all axons.
Why are action potentials usually conducted in one direction? a. Ions can flow along the axon in only one direction. b. The brief refractory period prevents reopening of voltage-gated Na+ channels. c. The axon hillock has a higher membrane potential than the terminals of the axon. d. Voltage-gated channels for both Na+ and K+ open in only one direction.
Which of the following is the most direct result of depolarizing the presynaptic membrane of an axon terminal? a. Voltage-gated calcium channels in the membrane open. b. Synaptic vesicles fuse with the membrane. c. Ligand-gated channels open, allowing neurotransmitters to enter the synaptic cleft. d. An EPSP or IPSP is generated in the postsynaptic cell.
Suppose a particular neurotransmitter causes an IPSP in postsynaptic cell X and an EPSP in postsynaptic cell Y. A likely explanation is that a. the threshold value in the postsynaptic membrane is different for cell X and cell Y. b. the axon of cell X is myelinated, but that of cell Y is not. c. only cell Y produces an enzyme that terminates the activity of the neurotransmitter. d. cells X and Y express different receptor molecules for this particular neurotransmitter.
