Action 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.

Action 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.

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

Section4.3: Action Potentials

Problem 2CYU

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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 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.
Which 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) ....
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
The resting membrane potential of a neuron or muscle cell is a. equal to the potassium equilibrium potential. b. equal to the sodium equilibrium potential. c. somewhat less negative than the potassium equilibrium potential. d. somewhat more positive than the sodium equilibrium potential. e. not changed by stimulation.
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 activity
Repolarization 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+.
Action potential conduction velocity is more rapid in a myelinated axon than an unmyelinated one because in a myelinated axon: a. the action potential travels as a continuous wave. b. there is a decrease in membrane resistance. c. the action potential jumps along the axon. d. there is an increase in membrane capacitance. e. there is an increase in the ion gradients.
Post synaptic neurons membrane potentials are less negative than resting membrane potentials when this occur A. Creates a new set point for the resting membrane potential B. Has a lower propensity to produce an action potential C. Reacts by generating action potential D. Higher chance of reaching the potential 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
Threshold potential is O a. typically 10 mV to 20 mV depolarized from ("higher than") resting potential. b. the membrane potential at which a graded potential is converted to an action potential. c. both of these. d. neither of these.
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.