Human Physiology
15th Edition
ISBN: 9781259864629
Author: Fox, Stuart Ira
Publisher: Mcgraw-hill Education,
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Chapter 7, Problem 9RA
Summary Introduction
 To determine:
 The characteristics of an action potential.
Introduction:
An action potential or a nerve impulse is a sequence of events, which are generated by voltage-regulated or voltage-gated channels present in the cell membrane. The cell membrane in the resting phase is stimulated to cause depolarization, which results in the movement of Na+ (sodium ion) ions into the cell, where the gated channels for Na+ open. This changes the membrane potential to positive.
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Which of the following primarily reflects the opening of voltage-gated Na+ channels?
A. The resting membrane potential
B. The depolarization phase of the action potential
C. The threshold potential
D. The repolarization phase of the action potential
E. All of the above
Which of the following is TRUE regarding the absolute and relative refractory periods of the action potential (AP)?
A. The absolute refractory period may be overcome if enough excitatory stimulation is applied to the neuronal membrane.
B. The absolute refractory period is due the closing of the activation gate of voltage gated sodium channels at the peak of the AP.
C. The relative refractory period is due to the closing of the activation gate of voltage gated potassium channels during the overshoot phase of the AP.
D. The relative refractory period is due the closing of the inactivation gate of voltage gated sodium channels .
E. All of the above statements are FALSE.
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.
Chapter 7 Solutions
Human Physiology
Ch. 7 - Draw a neuron, label its parts, and describe the...Ch. 7 - Distinguish between sensory neurons, motor...Ch. 7 - Describe the structure of the neurilemma, and...Ch. 7 - Explain how myelin sheaths are formed in the CNS....Ch. 7 - Explain what is meant by the blood-brain barrier....Ch. 7 - Define the terms depolarization and...Ch. 7 - Prob. 4bCPCh. 7 - Describe how gating of Na+andK+ in the axon...Ch. 7 - Prob. 5aCPCh. 7 - Prob. 5bCP
Ch. 7 - Prob. 6aCPCh. 7 - Describe the location of neurotransmitters within...Ch. 7 - Describe the sequence of events by which action...Ch. 7 - Explain how chemically regulated channels differ...Ch. 7 - Prob. 8CPCh. 7 - Prob. 9aCPCh. 7 - Prob. 9bCPCh. 7 - Prob. 10CPCh. 7 - Prob. 11CPCh. 7 - Prob. 12aCPCh. 7 - Prob. 12bCPCh. 7 - Prob. 13aCPCh. 7 - Prob. 13bCPCh. 7 - Prob. 14aCPCh. 7 - Describe the mechanism of action of glycine and...Ch. 7 - Give examples of endogenous opioid polypeptides,...Ch. 7 - Prob. 15bCPCh. 7 - Prob. 16CPCh. 7 - Prob. 17aCPCh. 7 - Prob. 17bCPCh. 7 - Prob. 17cCPCh. 7 - Prob. 1RACh. 7 - Prob. 2RACh. 7 - Prob. 3RACh. 7 - Prob. 4RACh. 7 - Repolarization of an axon during an action...Ch. 7 - As the strength of a depolarizing stimulus to an...Ch. 7 - Prob. 7RACh. 7 - Which of these is not a characteristic of synaptic...Ch. 7 - Prob. 9RACh. 7 - Prob. 10RACh. 7 - Prob. 11RACh. 7 - Prob. 12RACh. 7 - Prob. 13RACh. 7 - Prob. 14RACh. 7 - Prob. 15RACh. 7 - Prob. 16RACh. 7 - Prob. 17RACh. 7 - Which of these may be produced by the action of...Ch. 7 - Prob. 19RACh. 7 - In a step-by-step manner, explain how the...Ch. 7 - Prob. 21RACh. 7 - Prob. 22RACh. 7 - Prob. 23RACh. 7 - Prob. 24RACh. 7 - Once an EPSP is produced in a dendrite, how does...Ch. 7 - Prob. 26RACh. 7 - List the endogenous opioids in the brain and...Ch. 7 - Explain what is meant by long-term potentiation...Ch. 7 - Prob. 29RACh. 7 - Prob. 30RACh. 7 - Prob. 31RACh. 7 - Prob. 32RACh. 7 - Prob. 33RACh. 7 - Explain the nature of the endocannabinoids....Ch. 7 - Prob. 35RACh. 7 - Prob. 36RACh. 7 - Prob. 37RACh. 7 - Prob. 38RACh. 7 - Prob. 39RACh. 7 - Use the figure below (from figure 7.34) to answer...
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- During an action potential, the inside of the cell membrane becomes more positive than the outside. Why does this happen? a. During depolarization, the sodium ions rush in and the potassium ions have not begun rushing out, making the inside more positive. b. During depolarization, the sodium ions rush in and the potassium ions have not begun rushing out, making the outside more positive. c. During depolarization, the potassium ions rush in and the sodium ions have begun rushing out, making the inside more positive. d. During depolarization, the sodium ions rush in and the potassium ions have begun rushing out, making the outside more positive.arrow_forwardAction potentials are normally initiated at the axon hillock because a. there is a particularly high density of voltage-gated sodium channels there. b. threshold potential is lower there than at other sites along the plasma membrane. c. activation of sodium channels at the axon hillock results in a particularly strong inward current and consequent depolarization. d. all of these. e. none of these.arrow_forwardWhich of the following situations correctly illustrates the all-or-none principle? Select one: o a. A smaller voltage change will result in a smaller nerve impulse. o b. A stronger impulse can be generated by increasing the number of open voltage-gated sodium channels during depolarization. O C. A greater voltage change and a smaller voltage change will result in the same action potential as long as the threshold potential has been reached. o d. A faster impulse can be generated with a voltage change that is greater than the threshold potential.arrow_forward
- The resting membrane potential results fromA. uneven distribution of ions across the cell membrane only.B. differences in membrane permeability to Na+ and K+ onlyC. activity of the sodium/potassium pump only.D. uneven distribution of ions across the cell membrane, differences in membrane permeability to Na+ and K+, and sodium/potassium pump activityarrow_forwardWhich of the following statements is TRUE of the action potential? A. At the peak of the action potential there are approximately an equal amount of open voltage gated sodium and potassium channels B. To reach threshold the action potential requires the activity of sodium potassium pump C. During the rising phase (prior to the peak) of the action potential more voltage gated sodium channels are open than voltage gated potassium channels D. None of the choice options are TRUE of the action potential E. The overshoot phase (below resting membrane potential) is a result of voltage gated sodium channels taking a long time to close.arrow_forwardVoltage-gated Na+ channels open upon reaching what state? a. resting potential b. threshold c. repolarization d. overshootarrow_forward
- Both potassium and sodium channels located along the nerve membrane are voltage-gated. This means that they respond to the changes in the voltage by opening and closing the gates to allow the ions to flow in or out of the membrane. When the threshold level is reached and depolarization occurs, how come only the sodium ions begin to rush in? a. The threshold levels for both sodium and potassium channels are equal, but sodium channels are slower to open. b. The threshold levels for both sodium and potassium channels are equal, but potassium channels take longer to open. c. The threshold level for the potassium channels is lower than the sodium channels. d. The threshold level for the potassium channels is higher than the sodium channels.arrow_forwardDepolarization and repolarization changes that occur during the action potential are produced by a. Negative feedback loops b. Channel mediated transport c. Simple diffusion of ions down their concentration gradient d. Active transport pumps along the neuron membranearrow_forwardWhich of the following statements is FALSE? a. graded potentials can sum over time and space, action potential cannot b. action potentials have refractory periods, graded potentials do not c. action potentials are all-or-none, graded potentials are not d. graded potentials and action potentials are caused by ions moving through open channels e. all of the above statements are true (if all of the above are true this is the correct answer) ....arrow_forward
- The presence of an electrical gradient is responsible for both the resting membrane potential and the action potential in the neuron.a. In this case who is responsible for maintaining the electric gradient to produce a potential for the resting membrane?b. Explain what is meant by an electrical gradient in the context of a cell (neuron)!arrow_forwardRepolarization of an axon during an action potential is produced by a. inward diffusion of Na+. b. active extrusion of K+. c. outward diffusion of K+. d. inward active transport of Na+.arrow_forwardThe figure below may help in answering some of the questions. 1. What ions are flowing (and in which direction) both during the rising phase and the falling phase of the action potential? 2. What are the values of both the 'y' (vertical) axis and the 'x' (horizontal) axis. 3. If extracellular levels of K+ rose (a condition called hyperkalemia), how would that affect the resting membrane potential? 3arrow_forward
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