Human Anatomy & Physiology (2nd Edition)
2nd Edition
ISBN: 9780134553511
Author: Erin C. Amerman
Publisher: PEARSON
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Chapter 11, Problem 1CYU
A drug that blocks
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A drug that blocks Na+ channels in neurons does so not only in the axon but also in the dendrites and cell body. What overall effect would this have on action potential generation?
In an experiment, the extracellular [Na+] surrounding a nerve cell was reduced from 145 to 45 mM. Which of the following is the most likely effect of this on action potentials?
No action potentials would occur because the concentration of extracellular Na+ is too low.
The membrane potential would become more negative so the threshold for action potential generation could not be reached.
The nerve cell would still produce an action potential but its amplitude would be reduced and the depolarisation phase would be slower.
The nerve cell would still produce an action potential but its amplitude would be reduced and the depolarization phase would be more rapid.
Consider the following three diagrams of a nerve cell membrane. They show resting potential,
depolarization, and hyperpolarization. Figure out which one is which, then draw them in the
order they occur in a cell that undergoes an action potential
outside
+
Na*
inside
K*
Na*
Nat
K Nat
K Na
potential: -80 mV
outside
+
Na
K* Na*
inside
Na+
K Nat
Na*
K+
potential: +30 mV
outside
Na Na Na Na*
K+
inside
K*
Na*
Kt
potential: -70 mV
Chapter 11 Solutions
Human Anatomy & Physiology (2nd Edition)
Ch. 11.1 - What are the organs of the CNS?Ch. 11.1 - Prob. 2QCCh. 11.1 - Describe the sensory, integrative, and motor...Ch. 11.1 - 4. What are the differences between the somatic...Ch. 11.1 - How does the somatic motor division of the PNS...Ch. 11.2 - What are the functions of the cell body,...Ch. 11.2 - What are the structural differences between...Ch. 11.2 - What are the functional differences between...Ch. 11.2 - What are the functions of astrocytes?Ch. 11.2 - Prob. 5QC
Ch. 11.2 - Prob. 6QCCh. 11.2 - 7. What is the function of the myelin sheath?
Ch. 11.2 - How does the myelin sheath differ in the CNS and...Ch. 11.2 - Are neurons more likely to regenerate in the CNS...Ch. 11.2 - Prob. 10QCCh. 11.3 - 1. What is the resting membrane potential?
Ch. 11.3 - In and around the axon, where is the higher...Ch. 11.3 - Prob. 3QCCh. 11.3 - 4. Define local potential. Why is it also called...Ch. 11.3 - Why are local potentials useful only for...Ch. 11.3 - What takes place during the depolarization phase...Ch. 11.3 - 7. What must be reached in order for...Ch. 11.3 - 8. What takes place during the repolarization and...Ch. 11.3 - 9. What are the absolute and relative refractory...Ch. 11.3 - 10. How do local potentials and action potentials...Ch. 11.3 - Which is useful for long-distance signaling, and...Ch. 11.3 - 12. How is an action potential propagated down an...Ch. 11.3 - Prob. 13QCCh. 11.4 - What are three locations where presynaptic axons...Ch. 11.4 - Define synaptic transmission.Ch. 11.4 - Prob. 3QCCh. 11.4 - How do the two types of postsynaptic potentials...Ch. 11.4 - Prob. 5QCCh. 11.4 - Prob. 6QCCh. 11.5 - Prob. 1QCCh. 11.5 - Prob. 2QCCh. 11.5 - Prob. 3QCCh. 11.5 - Prob. 4QCCh. 11.5 - Prob. 5QCCh. 11.5 - Prob. 6QCCh. 11.6 - 1. Why are neurons organized into neuronal...Ch. 11.6 - Prob. 2QCCh. 11.6 - 3. What mechanisms stabilize neural circuits?
Ch. 11 - Which of the following statements about the...Ch. 11 - 2. Regulation of heart rate, blood pressure, and...Ch. 11 - Match each type of neuroglial cell with its...Ch. 11 - 4. Mark the following statements as true or false....Ch. 11 - 5. An axon is best defined as a process that:
a....Ch. 11 - 6. Fill in the blanks: The myelinated segment of...Ch. 11 - 7. Fill in the blanks: The _______is the period of...Ch. 11 - 8. Which of the following statements best...Ch. 11 - 9. Identify the following as properties of...Ch. 11 - The trigger for exocytosis of synaptic vesicles...Ch. 11 - Match the following neurotransmitters with their...Ch. 11 - 12. Which of the following is not a method by...Ch. 11 - 13. A ________is characterized by multiple input...Ch. 11 - Mark the following statements as true or false. If...Ch. 11 - Sequence the following list of events of a...Ch. 11 - 16. Mark the following statements as true or...Ch. 11 - 1. A drug that blocks channels in neurons does so...Ch. 11 - Prob. 2CYUCh. 11 - Why must a cell body be intact for an axon to...Ch. 11 - 4. Explain how an action potential is propagated...Ch. 11 - Prob. 1AYKACh. 11 - 2. During a surgical procedure, an...Ch. 11 - Albert accidentally ingests the poison...Ch. 11 - 4. Albert, the patient in question 3, takes the...Ch. 11 - Predict the effect that tetrodotoxin would have on...Ch. 11 - Explain what would happen if depolarization of the...
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- 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.arrow_forwardA common membrane-bound intermediary between the receptor and the effector protein within the plasma membrane is the __________________.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_forward
- In the figure to the left, name the 4 phases of the action potential (Note: you have to write in where phase 4 occurs). Describe what happens in each phase with a focus on Na+ and K+ flow through channels and the membrane potential. Discuss the importance of threshold. How does this relate to the concept of APs being all or none?arrow_forwardExplain the following; If a drug partly blocks a membrane’s potassium channels, how does it affect the action potential? Suppose the threshold of a neuron were the same as the neuron’s resting potential. What would happen? At what frequency would the cell produce action potentials?arrow_forwardThe graph shows a tracing of membrane potential change during the course of an action potential in a typical neuron. Predict the effect of exposure to the following neurotoxins. Briefly explain how you would expect the action potential to change in the presence of each toxin and why. A toxin produced by puffer fish which specifically binds to voltage-gated sodium channels and blocks the flow of sodium ions through the channel. A toxin found in scoprion venom which slows the closure of voltage-gated sodium channel inactivation gates. Assume that the cell is normally brought to threshold by an electrical stimulus applied to it, so that any change is due only to the presence of the toxin Precise values for voltage and duration are not important, just a general trend in how the action potential may differ from the typical trace shown is expected.arrow_forward
- Acetylcholine is a neurotransmitter that, when bound to its receptor, causes the receptor to open a channel that allows the flow of Na+ ions into neurons. When the Na+ ions begin to flow into the neuron, this change in the net charge across the neuronal cell membrane often triggers Ca2+ ion channels to open. In this scenario, the acetylcholine receptor would be acting as a channel, and the Ca2+ channels would be classified as voltage-gated; leaky ligand gated; voltage-gated symporter; antiporter None of the above. ionarrow_forwardWhich of the following events correctly ranks steps in an action potential? 1. Voltage-gated sodium and potassium channels transition from closed to open states allowing sodium ions to enter and potassium ions to exit. 2. Voltage-gated sodium channels transition from open to inactivated states. 3. Ligand-gated sodium channels are triggered to open. 4. Peak potassium permeability. 5. Peak sodium permeability. 6. Membranes hyperpolarize due to more potassium ions exiting cell and neuron enters refractory period. 7. Critical threshold is achieved. O 3, 1, 7, 5, 2, 4, 6 O 3, 7, 1, 5, 4, 6, 2 O 3, 4, 1, 2, 6, 7,5 O 6, 7, 3, 2, 5, 4, 1 O 7, 5, 3, 1, 4, 6, 2 4, 6, 3, 7, 5, 2, 1arrow_forwardYou 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 zeroarrow_forward
- An undisclosed drug (Drug A) is a drug that can block voltage-gated K+ channels when being introduced into the bloodstream. Explain the effects of Drug A on the action potentials produced by a neuron. If Drug A could be applied selectively to a presynaptic neuron that releases an excitatory neurotransmitter, analyse how would it alter the synaptic effect of the neurotransmitter on the presynaptic cell. Remark: The word count limit (250 words only), no less than 100 wordsarrow_forwardFigure I shows a schematic of an action potential. How do voltage-gated sodium channels contribute to stages 1, 3 and 6? In your answer, state what happens to the activation and inactivation gates at these three stages. Membrane Potential (mV) 50 -50 -100 -2 t 1 T T 2 3 Time (milliseconds) T 0 1 Figure 1 1 4 51 T T 5 6 7arrow_forwardAfter discussing his case with his physician, he learned that he had probably been the victim of pufferfish poisoning. The active toxin in the tissues of this fish is a chemical called tetrodotoxin (TTX). Tetrodotoxin is in a class of chemicals known as neurotoxins because it exerts its effects on neurons. The specific action of tetrodotoxin is that it blocks voltage-gated sodium ion channels. Define the following phrases and terms associated with the signs and symptoms of Dr. Westwood’s TTX poisoning: diaphoresis motor dysfunction paresthesias cyanotic hypoventilating bradycardia gastric lavage oxygen saturation As mentioned in the case description, tetrodotoxin is a molecule that blocks voltage-gated sodium ion channels. What is a voltage-gated sodium ion channel and what is its function? When nerve cells are at rest, there is an unequal amount of positive and negative charges on either side of a nerve cell membrane. This charge difference creates an electrical potential.…arrow_forward
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