BIOLOGY:THE ESSENTIALS (LL) W/CONNECT
3rd Edition
ISBN: 9781260670929
Author: Hoefnagels
Publisher: MCG CUSTOM
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Chapter 24, Problem 4WIO
Summary Introduction
To determine:
The event on artificially stimulating an axon so that the threshold potential is reached midway along its length.
Introduction:
A short reversal in the membrane potential that propagates like a wave along the membrane of the axon is known as the action potential. It will arise only if a cell’s threshold potential is reached. Once the action potential begins, additional Na+ flows into the cell using the sodium channels and the membrane get a positive charge on the inside.
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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
You prepare a squid giant axon and inject it with a tiny volume of solution containing 0.1 M NaCl and 0.1 M KCl in which both the Na+ and K+ ions are radioactively labeled. The two labeled ions are now inside the axon. You place this axon in a beaker containing seawater medium. The voltage gated sodium and voltage gated potassium channels are completely blocked using specific inhibitors - so they are closed.
Under resting conditions (no stimulation of axon), would you expect any movement of the two radiolabeled ions across the cell membrane of the axon? please explain
If you now remove the voltage gated sodium channel inhibitor, and keep the voltage gated potassium channel blocked, which of the radioactively labeled ions would you expect to appear within the seawater medium, while the neuron remained at rest (no stimulation of axon). please explain
Chapter 24 Solutions
BIOLOGY:THE ESSENTIALS (LL) W/CONNECT
Ch. 24.1 - Prob. 1MCCh. 24.1 - Prob. 2MCCh. 24.1 - Distinguish between the central and peripheral...Ch. 24.2 - Describe the parts of a typical neuron.Ch. 24.2 - Prob. 2MCCh. 24.2 - Prob. 3MCCh. 24.3 - Prob. 1MCCh. 24.3 - How does an axon generate and transmit a neural...Ch. 24.3 - Prob. 3MCCh. 24.4 - Describe the structure of a synapse.
Ch. 24.4 - Prob. 2MCCh. 24.4 - Prob. 3MCCh. 24.5 - Prob. 1MCCh. 24.5 - How do the sensory and motor pathways of the...Ch. 24.5 - Prob. 3MCCh. 24.5 - Prob. 4MCCh. 24.6 - Prob. 1MCCh. 24.6 - What are the major structures in the hindbrain,...Ch. 24.6 - Prob. 3MCCh. 24.6 - Prob. 4MCCh. 24.6 - Prob. 5MCCh. 24.7 - Prob. 1MCCh. 24.7 - Prob. 2MCCh. 24.7 - What are the major types of sensory receptors?Ch. 24.7 - Prob. 4MCCh. 24.7 - What is sensory adaptation, and how is it...Ch. 24.8 - Prob. 1MCCh. 24.8 - Prob. 2MCCh. 24.9 - Prob. 1MCCh. 24.9 - Prob. 2MCCh. 24.9 - Prob. 3MCCh. 24.10 - Prob. 1MCCh. 24.10 - Prob. 2MCCh. 24.10 - Prob. 3MCCh. 24.11 - What is the role of mechanoreceptors in the sense...Ch. 24.11 - Prob. 2MCCh. 24 - Prob. 1MCQCh. 24 - Prob. 2MCQCh. 24 - Prob. 3MCQCh. 24 - Prob. 4MCQCh. 24 - Prob. 5MCQCh. 24 - In what way are the senses of smell and taste...Ch. 24 - Prob. 1WIOCh. 24 - Prob. 2WIOCh. 24 - Prob. 3WIOCh. 24 - Prob. 4WIOCh. 24 - How does myelin alter the conduction of a neural...Ch. 24 - Prob. 6WIOCh. 24 - Prob. 7WIOCh. 24 - Prob. 8WIOCh. 24 - Prob. 9WIOCh. 24 - Prob. 10WIOCh. 24 - Prob. 1SLCh. 24 - Prob. 1PITCh. 24 - Prob. 2PITCh. 24 - Prob. 3PIT
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- A neuron responds to adequate stimulation with _______, a type of self-propagating signal.arrow_forwardWhen action potentials arrive at a synapse between a neuron and another cell, they stimulate the release of molecules of a ________ that diffuse over to that cell.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
- A voltmeter is used to measure the potential difference across a neuron’s membrane. A change in potential difference will occur when an action potential is generated. A neurologist uses a giant squid neuron to study the propagation of an action potential. She places two voltmeters on the axon membrane to measure the potential difference: one near the dendrite and the other at the axon terminal. A stimulus is then applied. Often, the stimulus is applied at one end of the neuron. In this experiment, the scientist decides to stimulate the middle of the neuron. Which statement describes what the scientist would observe at the voltmeters? Select one: a. Both voltmeters will indicate changes to the potential difference. b. No changes to the potential differences will be registered at the voltmeters. c. The voltmeter at the dendrite will indicate a change to the potential difference. d. The voltmeter at the axon terminal will indicate a change to the potential difference.arrow_forwardA voltmeter is used to measure the potential difference across a neuron’s membrane. A change in potential difference will occur when an action potential is generated. A neurologist uses a giant squid neuron to study the propagation of an action potential. She places two voltmeters on the axon membrane to measure the potential difference: one near the dendrite and the other at the axon terminal. A stimulus is then applied. Often, the stimulus is applied at one end of the neuron. In this experiment, the scientist decides to stimulate the middle of the neuron. Which statement describes what the scientist would observe at the voltmeters? a. Both voltmeters will indicate changes to the potential difference. b. No changes to the potential differences will be registered at the voltmeters. c. The voltmeter at the dendrite will indicate a change to the potential difference. d. The voltmeter at the axon terminal will indicate a change to the potential difference.arrow_forwardYou prepare a squid giant axon and inject it with a tiny volume of solution containing 0.1 M NaCl and 0.1 M KCl in which both the Na+ and K+ ions are radioactively labeled. The two labeled ions are now inside the axon. You place this axon in a beaker containing seawater medium. The voltage gated sodium and voltage gated potassium channels are completely blocked using specific inhibitors - so they are closed If you now remove the voltage gated potassium channel inhibitor and keep the voltage gated sodium channel blocked, which of the radioactively labeled ions would you expect to appear within the seawater medium, while the neuron remained at rest (no stimulation of axon). Please explain If you now remove both the sodium and potassium voltage gated channel inhibitors - which of the radioactively labeled ions would you expect to appear most rapidly within the seawater medium, after the neuron had been stimulated to conduct a number of action potentials? Please explainarrow_forward
- A neurotoxin was delivered to a patient that prevented sodium channels from opening at the axon level. How does this affect a neuron's ability to communicate to other neurons? Explain in terms of action potential conductance, and neurotransmitter exocytosis at the axon terminal.arrow_forwardThe purpose of an action potential (AP) is to propagate a signal down the axon to the axon terminal. What happens once it reaches the axon terminal? Using the experiment showing recordings from the post-synaptic cell (endplate potentials), describe what happens when an AP reaches the axon terminal and subsequently transmits the signal to a neighboring cell. What does this tell us about chemical neurotransmission?arrow_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
- When an impulse arrives at the synapse, the synaptic vesicles open and release neurotransmitters into the cleft within a thousandth of a second. Within another ten thousandth of a second, these molecules have diffused across the cleft and bound to receptor sites in the effector cell. In what two ways is transmission across a synapse terminated so that the neuron’s signal is concluded?arrow_forwardLet’s say the synapses of a neuron’s dendrites are filled with glutamate-gated channels which, when activated by glutamate, cause an excitatory postsynaptic potential (EPSP) in the neuron. In one instance, glutamate is released at all of the synapses simultaneously and this leads to an action potential in the neuron. A) What type of summation of PSPs is this? Why? B) List the sequence of steps that occur starting from binding of glutamate to the glutamate-gated channels at the synapses and ending with the membrane potential at the axon hillock returning to resting potential at the end of the action potential. (Include all the changes in voltage-gated channels underlying the action potential.)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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