Human Physiology: An Integrated Approach (8th Edition)
8th Edition
ISBN: 9780134605197
Author: Dee Unglaub Silverthorn
Publisher: PEARSON
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Textbook Question
Chapter 8.3, Problem 16CC
A stimulating electrode placed halfway down an axon artificially depolarizes the cell above threshold. In which direction will an action potential travel: to the axon terminal, to the cell body, or to both? Explain your answer.
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In the laboratory, researchers can apply an electrical stimulus at any point along the axon, making action potentials travel in both directions from the point of stimulation. An action potential moving in the usual direction, away from the axon hillock, is said to be traveling in the orthodromic direction. An action potential traveling toward the axon hillock is traveling in the antidromic direction. If we started an orthodromic action potential at the axon hillock and an antidromic action potential at the opposite end of the axon, what would happen when they met at the center? Why?
You generate action potentials in a neuron bathed in solution in a petri dish by applying a threshold-level depolarizing stimulus near its axon hillock. If the solution surrounding
the neuron contained 5mM K+, 150 mM Na+, and 0 mM Ca2+ which of the following would you expect?
The neuron would not be able to propagate action potentials down the entire length of the axon
The neuron would not release neurotransmitter from the axon terminal
The neurons action potentials would have an unusually long duration
The neuron would have a resting membrane potential of zero
Which of the following would occur if a neuron was experimentally stimulated simultaneously at both ends?
The action potentials would pass in the middle and travel to the opposite ends
The action potentials would stop as they meet in the middle.
The stronger action potential would override the weaker action potential.
Summation would occur when the action potentials meet in the middle, resulting in a larger action potential.
Chapter 8 Solutions
Human Physiology: An Integrated Approach (8th Edition)
Ch. 8.1 - Organize the following terms describing functional...Ch. 8.2 - Where do neurohormone-secreting neurons terminate?Ch. 8.2 - What is the difference between a nerve and a...Ch. 8.2 - Draw a chain of three neurons that synapse on one...Ch. 8.2 - What is the primary function of each of the...Ch. 8.2 - Name the two glial cell types that form myelin....Ch. 8.3 - Given the values in Table 8.2, use the Nernst...Ch. 8.3 - Would a cell with a resting membrane potential of...Ch. 8.3 - Would the cell membrane depolarize or...Ch. 8.3 - Match each ions movement with the type of graded...
Ch. 8.3 - Prob. 11CCCh. 8.3 - What is the difference between conductance and...Ch. 8.3 - If you put ouabain, an inhibitor of the Na+-K+...Ch. 8.3 - The pyrethrin insecticides, derived from...Ch. 8.3 - When Na+ channel gates are resetting, is the...Ch. 8.3 - A stimulating electrode placed halfway down an...Ch. 8.3 - Place the following neurons in order of their...Ch. 8.4 - Prob. 18CCCh. 8.4 - Prob. 19CCCh. 8.4 - Prob. 20CCCh. 8.4 - Prob. 21CCCh. 8.4 - Prob. 22CCCh. 8.4 - Classify the H+-neurotransmitter exchange as...Ch. 8.4 - Prob. 24CCCh. 8.4 - Prob. 25CCCh. 8.4 - Is Na+-dependent neurotransmitter reuptake...Ch. 8.5 - In Figure 8.24e, assume the postsynaptic neuron...Ch. 8.5 - In the graphs of Figure 8.24a, b, why doesnt the...Ch. 8.5 - Prob. 29CCCh. 8.5 - Prob. 30CCCh. 8 - List the three functional classes of neurons, and...Ch. 8 - Somatic motor neurons control __________, and...Ch. 8 - Prob. 3RQCh. 8 - Prob. 4RQCh. 8 - Prob. 5RQCh. 8 - Prob. 6RQCh. 8 - Axonal transport refers to the (a) release of...Ch. 8 - Match the numbers of the appropriate...Ch. 8 - Arrange the following events in the proper...Ch. 8 - List the four major types of ion channels found in...Ch. 8 - Prob. 11RQCh. 8 - An action potential is (circle all correct...Ch. 8 - Choose from the following ions to fill in the...Ch. 8 - What is the myelin sheath?Ch. 8 - List two factors that enhance conduction speed.Ch. 8 - Prob. 16RQCh. 8 - Draw and label a graph of an action potential....Ch. 8 - Prob. 18RQCh. 8 - Prob. 19RQCh. 8 - Create a map showing the organization of the...Ch. 8 - Prob. 21RQCh. 8 - Prob. 22RQCh. 8 - Prob. 23RQCh. 8 - Prob. 24RQCh. 8 - The presence of myelin allows an axon to (choose...Ch. 8 - Define, compare, and contrast the following...Ch. 8 - Prob. 27RQCh. 8 - Prob. 28RQCh. 8 - Prob. 29RQCh. 8 - Prob. 30RQCh. 8 - An unmyelinated axon has a much greater...Ch. 8 - The GHK equation is sometimes abbreviated to...Ch. 8 - In each of the following scenarios, will an action...
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- A neuron responds to adequate stimulation with _______, a type of self-propagating signal.arrow_forwardWhich of the following are the likely explanations for the failure of a postsynaptic neuron to trigger an action potential? Select all that apply. The EPSPs are neutralized by the neurotransmitter The summation of IPSPs and EPSPs is insufficient to depolarize the cell to threshold The synapses generating the EPSPs are too close to the axon hillock The synapses generating the EPSPs are too far from the axon hillockarrow_forwardExplain what happens when an action potential reaches the axon terminus (terminal) by activating the receptors on the postsynaptic membrane. Explanation addressing the question above When an action potential, or nerve impulse, arrives at the axon terminal, it activates voltage-gated calcium channels in the cell membrane. Which is present at a much higher concentration outside the neuron than inside, rushes into the cell. The Ca2+ allows synaptic vesicles to fuse with the axon terminal membrane, releasing neurotransmitters into the synaptic cleft. The molecules of neurotransmitters diffuse across the synaptic cleft and bind to receptor proteins on the postsynaptic cell. Activation of postsynaptic receptors leads to the opening or closing of ion channels in the cell membrane. This may be depolarizing, making the inside of the cell more positive, or hyperpolarizing making the inside more negative depending on the ions involved. The excitatory and inhibitory postsynaptic potentials…arrow_forward
- Which of the following is NOT true regarding the changes that occur during an action potential. Check All That Apply When stimulus is sufficient to cause the threshold potential to be reached, the area stimulated opens its voltage-gated sodium channels.When stimulus is sufficient to cause the threshold potential to be reached, the area stimulated opens its voltage-gated sodium channels. After threshold is reached, the sodium ions move into the cell via the Na+/K+ pump, the inside of the cell becomes momentarily positive.After threshold is reached, the sodium ions move into the cell via the Na+/K+ pump, the inside of the cell becomes momentarily positive. At almost the same time as Na+ channels are closing, voltage-gated potassium channels open, allowing an increased movement of potassium ions out of the cellAt almost the same time as Na+ channels are closing, voltage-gated potassium channels open, allowing an increased movement of potassium ions out of the cell The…arrow_forwardWhy does an action potential move in an all-or-nothing fashion down the length of an axon without stopping?arrow_forwardWhich of the following describe(s) the difference(s) between an EPSP and an IPSP? Select all that apply. An EPSP is actively reproduced as it travels along the axon, whereas an IPSP is a graded potential that decreases in strength with time and distance. An EPSP moves the cell closer to threshold, whereas an IPSP moves the cell away from threshold. An EPSP results from the movement of Cl- ions into the cell, whereas an IPSP results from movement of Na+ ions into the cell. An EPSP is a result of depolarization of the cell membrane, whereas an IPSP is a result of hyperpolarization of the membrane.arrow_forward
- Resting potential is a balance across the axon membrane between______forces moving ions out of the cell and ______forces operating to keep ions in the cell.arrow_forwardWhich of the following combinations of spatial summation of postsynaptic potentials (PSP) would result in an action potential in a typical neuron? The voltage given for each PSP is measured as it reaches the axon hillock. Axon A EPSP 25 mV & axon B IPSP 10 mV Axon A IPSP 25 mV & axon B EPSP 10 mV Axon A IPSP 5 mV & axon B IPSP 5 mV Axon A EPSP 5 mV & axon B EPSP 5 mVarrow_forwardYou are recording the resting membrane potential from a neuron placed in a petri dish. The following oscilloscope tracing shows the voltage measured when a microelectrode tip is placed just inside the axon. The solid line on the oscilloscope is obtained when the neuron is placed in a control solution containing 5mM K+ and 150 mM Na+. The solution is then changed and a second recording is made, shown by the dashed line on the tracing. You can reasonably conclude this new solution: a) has increased concentration of K+ b) has increased concentration of Na+ c) has decreased concentration of K+ d) has decreased concentration of Na+arrow_forward
- You are recording the resting membrane potential from a neuron placed in a petri dish. The following oscilloscope tracing shows the voltage measured when a microelectrode tip is placed just inside the axon. The solid line on the oscilloscope is obtained when the neuron is placed in a control solution containing 5mM K+ and 150 mM Na+. The solution is then changed and a second recording is made, shown by the dashed line on the tracing. You can reasonably conclude this new solution: Membrane Potential (mV) 989 20 -80 HORRETAN 0 1 2 3 4 5 6 7 8 9 10 Time (sec) has decreased concentration of K+ Ohas decreased concentration of Na+ has increased concentration of K+ 1. has increased concentration of Na+arrow_forwardIf a neuron is stimulated simultaneously by 2 stimuli at its dendrites (one generates a very large hyperpolarizing potential and the other generates a very small depolarizing potential). What would happen to this neuron? Group of answer choices The summation of these two graded potentials will generate an action potential and this action potential will travel down the axon. Summation of these two graded potentials will cause the membrane potential at the axon hillock to be more negative. These graded potentials will bring the resting membrane potential to 0 mV. These graded potentials with opposite polarity would therefore generate two action potentials and they will travel along this neuron in opposite direction.arrow_forwardImmediately after the repolarization phase of an action potential, the neuronal membrane is temporarily unable to respond to the stimulation of a second action potential, a phenomenon referred to as the refractory period. What is the mechanistic basis for the refractory period?arrow_forward
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