The axon hillock of a neuron reaches the threshold of excitation and the membrane potential becomes completely reversed. Then, suddenly, the membrane potential begins to return to resting membrane potential. What is the event that triggers this return to resting potential? A. Na+ channels close in a voltage-dependent manner B. Na+ channels close in a time-dependent manner C. Na+ channels close in a chemically-dependent manner D. Na+ channels open in a voltage-dependent manner

The axon hillock of a neuron reaches the threshold of excitation and the membrane potential becomes completely reversed. Then, suddenly, the membrane potential begins to return to resting membrane potential. What is the event that triggers this return to resting potential? A. Na+ channels close in a voltage-dependent manner B. Na+ channels close in a time-dependent manner C. Na+ channels close in a chemically-dependent manner D. Na+ channels open in a voltage-dependent manner

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter4: Principles Of Neural And Hormonal Communication

Section: Chapter Questions

Problem 2SQE

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Assume presynaptic excitatory neuron A terminates on a postsynaptic cell near the axon hillock and presynaptic excitatory neuron B terminates on the same postsynaptic cell on a dendrite located on the side of the cell body opposite the axon hillock. Explain why rapid firing of presynaptic neuron A could bring the postsynaptic neuron to threshold through temporal summation, thus initiating an action potential, whereas firing of presynaptic neuron B at the same frequency and the same magnitude of EPSPs may not bring the postsynaptic neuron to threshold.
Sequence the following list of events of a neuronal action potential by placing 1 next to the first event, 2 next to the second event, and so on. a. _____ The activation gates of voltage-gated Na+ channels open, Na+ flood the cytoplasm, and depolarization occurs. b. _____ K+ continue to flow out of the axon until the membrane is hyperpolarized. c. _____ Local potentials cause the membrane to depolarize to threshold. d. _____ The inactivation gates of voltage-gated Na+ channels close as voltage-gated K+ channels open, K+ begin to exit the axon, and repolarization begins. e. _____ Repolarization continues and Na+ channels return to resting
Which of the following is true about the conduction of action potentials? a. Thicker axons are faster because there is more surface area on thicker axons. b. Myelin speeds conduction because the glial cells add voltage gated Na+ channels to the neuron. c. Diffusion of Na+ ions between the Nodes of Ranvier happens faster than the wave of opening and closing membrane proteins can travel. d. Neurons that don’t have myelin sheaths undergo saltatory conduction e. Action potentials move slowly.
The nerve impulses always travel in one direction from dendrites to axon terminals. What prevents an action potential from travelling backward? a. Hyperpolarization of the neuron makes the membrane more positive and prevents another action potential. b. After repolarization, the refractory period occurs, where the sodium ions are found outside the cell. c. After repolarization, the reversal of ions prevents another action potential as there would not be enough sodium ions outside the cell to rush in. d. The refractory period prevents another action potential by lowering the threshold potential.
There is a type of toxin found in the liver of the puffer fish that prevents the opening of voltage-gated Na+ channels in neurons. The effect of this toxin is to: Group of answer choices A. prevents the initiation of the action potential B. depolarizes the membrane potential and maintains it depolarized C. prolongs the return of the membrane potential to the resting level D. increases the duration of the action potential
Which of the following statements does NOT correctly describe the repolarization of a neuron? a. The potassium channels are slower to open, allowing the potassium ions to leave after depolarization. b. The potassium ions leave the cell, thereby returning the neuron to its resting potential. c. The neuron becomes more polarized and more negatively charged than its original resting membrane potential. d. The sodium and potassium channels open, allowing the positive ions to move out of the cell.
A neuron must reach threshold to fire an action potential. In this context, threshold refers to which event? a. voltage at which damage occurs to the membrane because of the electrical charge b. the voltage at which potassium ions begin to flow in and out of the cell c. the voltage at which voltage-gated sodium channels open d. the voltage at which the neuron can no longer produce an action potential According to studies in developing rodents, testosterone treatment causes detectable changes in: a. the sex region Y gene b. the thalamus c. the hypothalamus d. alpha-fetoprotein
What membrane protein of the neuron is responsible for briefly increasing the Na+ permeability of the membrane during the rising phase of the nerve impulse? a. the sodium-potassium pump b. the voltage gated potassium channel c. the voltage gated sodium channel d. the stimulus gated sodium channel e. the ligand gated ion channel
Any change in a neuron's membrane potential that moves the membrane potential to a value more negative than the resting potential (e.g. -120mv) is: a. Hypopolarization b. Depolarization c. An action potential d. HyperpolarizationNOTE: A IS INCORRECT
Charge from depolarization along the axon reaches the axon terminal, but there is a lack of neurotransmitter release. Which of the following would cause this? Group of answer choices A. Lack of Na+ in the synaptic cleft B. Lack of Ca2+ in the synaptic cleft C. Reduced amount of K+ at the axon terminal D. Lack of voltage-gated sodium channels in the axon terminal
Voltage-gated Na+ channels open upon reaching what state? a. resting potential b. threshold c. repolarization d. overshoot
On what part of the neuron are NT receptors typically located? If the activated NT receptors cause channels to open or change thus changing the diffusion of ions, what type of potential will this initially produce? A.Resting B.Graded C.Action D.Homeostatic

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	A.	Na+ channels close in a voltage-dependent manner
	B.	Na+ channels close in a time-dependent manner
	C.	Na+ channels close in a chemically-dependent manner
	D.	Na+ channels open in a voltage-dependent manner