Suppose you depolarize an axon midway between its initial segment and its terminus. А. In which direction would the action potential travel? В. What would happen if simultaneously with the activation to threshold midway between the initial segment and the terminus you also depolarized the neuron to threshold at the initial segment?

Suppose you depolarize an axon midway between its initial segment and its terminus. А. In which direction would the action potential travel? В. What would happen if simultaneously with the activation to threshold midway between the initial segment and the terminus you also depolarized the neuron to threshold at the initial segment?

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter39: Information Flow And The Neuron

Section: Chapter Questions

Problem 8TYK: Which of the following statements best describes saltatory conduction? a. It inhibits direct...

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Which of the following statements best describes saltatory conduction? a. It inhibits direct neurotransmitter release. b. It transmits the action potential at the nodes of Ranvier andthus speeds up impulses on myelinated axons. c. It increases neurotransmitter release at the presynapticmembrane. d. It decreases neurotransmitter uptake at chemically gatedpostsynaptic channels. e. It removes neurotransmitters from the synaptic cleft.
An example of a synapse could be the site where: a. neurotransmitters released by an axon travel across a gap and are picked up by receptors on a muscle cell. b. an electrical impulse arrives at the end of a dendrite causingions to flow onto axons of presynaptic neurons. c. postsynaptic neurons transmit a signal across a cleft to apresynaptic neuron. d. oligodendrocytes contact the dendrites of an afferent neurondirectly. e. an onoff switch stimulates an electrical impulse in apresynaptic cell to stimulate other presynaptic cells.
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.
View the University of Michigan Webscope (http://openstaxcollege.org/l/nervefiber) to see an electron micrograph of a cross-section of a myelinated nerve fiber. The axon contains microtubules and neurofilaments, bounded by a plasma membrane known as the axolemma. Outside the plasma membrane of the axon is the myelin sheath, which is composed of the tightly wrapped plasma membrane of a Schwann cell. What aspects of the cells in this image react with the stain that makes them the deep, dark, black color, such as the multiple layers that are the myelin sheath?
1.) In an experiment you artificially cut in half (~50% reduction) the number of voltage gated sodium channels that are located on the membrane of the axon hillock. Which of the following is the most likely result of this experimental manipulation? A. Summation of more IPSPs would be required for an action potential to occur B. This change would have no effect on the value required to reach threshold C. Even with a very large number of summating EPSPs it would be impossible for an action potential to occur D. The value to reach threshold would be higher (more positive) making it less likely for an action potential to occur E. All of the above statements are FALSE
1. Action potentials are generated in a region called the _______ which includes the axon hillock and the initial segment of the axon. 2.According to the all-or-nothing principle a.once the electrical impulse reaches a certain level of intensity (its threshold), it fires and moves all the way down the axon without losing any intensity. b.the amount of time a neuron must “rest” in between firing episodes is stable. c.as a person ages, his or her neurological system slows down and the intensity of neural impulses decreases significantly. d.if all the neurons in a network are not integrated, the “message” carried by the neurons will be lost.
6. Identify the following structures on an image of a synapse: Postsynaptic neuron Presynaptic neuron Neurotransmitter Synaptic cleft Synaptic vesicles Receptor for neurotransmitter Cell adhesion molecules Axon terminal 7. hore CAFE Describe the actions of sodium and potassium during action potential generation as it relates to depolarization, repolarization, and hyperpolarization. State the directional flow of each ion and the state of the gated channels for each stage. See figure 12.15 in the textbook.
4.3. After the rising phase, which ion channel is responsible for action potential returning to its resting V and why? Na channels, because positive Na* ions are at higher concentration outside the axon than inside, and so they enter the axon and raise V O Na* channels, because positive Na* ions are at higher concentration inside the axon than outside, and so they leave the axon and raise V, m O K* channels, because positive K* ions are at higher concentration outside the axon than inside, and so they enter the axon and raise Vm U K* channels, because positive K* ions are at higher concentration inside the axon than outside, and so they leave the axon and lower Vm
2) If potassium channels in a neuron were blocked, would it be possible to produce an action potential? If so, describe the probable appearance of these parts of a graph: threshold, rising phase, peak, falling phase, undershoot. If not, explain.
A. Is an action potential more or less likely when the consumption of the Fugu toxin and is stimulated with a neuron with a supra-threshold stimulus? B. Which (flaccid or tonic) is the result in this case? What would be the associated physical symptoms of this condition? C. Briefly describe the pharmacological/clinical/commercial uses of this toxin and its derivatives.
14) Review the process by which an action potential is conducted across a synapse. Suppose that in the future you become a researcher that is trying to cure a new neurological disorder. This disorder causes some post-synaptic neurons to fire action potentials to intrequently in response to the excitatory neurotransmitter dopamine. You want to design a medication that will target the cellular mechanisms that are causing this to happen at the synapse. List (no explanation required) four different things that vour medication could do at the synapse to increase the rate of firing of action potentials, *(Note that each different thing you list should produce an effect by targeting a different part of the process by which conduction of an action potential across a synapse is regulated).
1) A 100-um diameter nerve axon has the following properties: rm = 2.5 x 104 ohm x cm, ri = 1 x 105 ohm/cm, r0 = 0, cm = 3 x 10-8 F/cm. The permeability to Cl- is very high and Cl- ions are at resting potential Vm. A steady inward current is injected into the axon resulting in a Vm of -110 mV at the site of current injection. If the Vm 3 mm from the site of injection is -94.5 mV, what is the resting Vm?