Human Physiology: An Integrated Approach (8th Edition)
8th Edition
ISBN: 9780134605197
Author: Dee Unglaub Silverthorn
Publisher: PEARSON
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Textbook Question
Chapter 13, Problem 19RQ
There are several theories about how presynaptic inhibition works at the cellular level. Use what you have learned about membrane potentials and synaptic transmission to explain how each of the following mechanisms would result in presynaptic inhibition:
- a. Voltage-gated Ca2+ channels in axon terminal are inhibited.
- b. Cl− channels in axon terminal open.
- c. K+ channels in axon terminal open.
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Local anesthetic is often used in dentistry to lessen the sensation of pain during dental procedures. It prevents propagation of nerve conduction by decreasing the flow of ions.
a. Describe how depolarization of an action potential can be blocked by the use of local anesthetic. b. Your classmate explained that once the threshold potential has been reached, the inside charge of the neuron is more positive than the outside charge. Is she correct? Can you compare the inside charge to the outside charge in an axon treated with local anesthetic?
11) Compare the propagation speeds of an action potential along an axon that is 10 µM in diameter and one that is 20
uM in diameter. You must have a quantitative answer.
12) How would the velocity of action potential propagation change if you quadrupled the membrane conductance?
You must have a quantitative answer.
13) You discover a mutation in mice that causes them to suddenly lose their myelin sheaths. How would this mutation
change the speed of action potential propagation and why?
9
When a neuron reaches threshold voltage, all voltage-gated channels are triggered to make conformational changes. The order in
which this happens comes down to the timing/speed/kinetics of the different gates on the channels. Put the following events in
the order they occur after a neuron reaches threshold voltage.
1. Voltage-gated K+ channels finish closing their gate.
2. Voltage-gated Na+ channels open their activation gate, increasing Na+ permeability.
3. Voltage-gated Na+ channels close their inactivation gates, reducing Na+ permeability.
4. Voltage-gated K+ channels open their gate, increasing K+ permeability.
5. Voltage-gated Na+ channels reset to their original conformation.
Chapter 13 Solutions
Human Physiology: An Integrated Approach (8th Edition)
Ch. 13.2 - List the general steps of a reflex pathway,...Ch. 13.2 - If a cell hyperpolarizes, does its membrane...Ch. 13.3 - Prob. 3CCCh. 13.3 - Draw a reflex map of the flexion reflex initiated...Ch. 13.3 - Prob. 5CCCh. 13.3 - Prob. 6CCCh. 13.3 - Prob. 7CCCh. 13 - Prob. 1RQCh. 13 - Prob. 2RQCh. 13 - The pathway pattern that brings information from...
Ch. 13 - When the axon terminal of a modulatory neuron...Ch. 13 - Autonomic reflexes are also called _____ reflexes....Ch. 13 - Prob. 6RQCh. 13 - Prob. 7RQCh. 13 - Prob. 8RQCh. 13 - Prob. 9RQCh. 13 - Prob. 10RQCh. 13 - Prob. 11RQCh. 13 - Prob. 12RQCh. 13 - Prob. 13RQCh. 13 - Prob. 14RQCh. 13 - Prob. 15RQCh. 13 - Prob. 16RQCh. 13 - Prob. 17RQCh. 13 - At your last physical, your physician checked your...Ch. 13 - There are several theories about how presynaptic...Ch. 13 - Prob. 20RQCh. 13 - Prob. 21RQCh. 13 - Prob. 22RQ
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- Relatively high velocity (speed) action potential propagation is a feature of axons that have which of the following: a. additional mitochondria b. reduced absolute refractory period c. fewer potassium channels d. a myelin sheath Which effect listed below would characterize the drug as a serotonin agonist? a. Stimulating monoamine oxidase to reduce available serotonin b. Binding and activating a postsynaptic serotonin receptor c. Increasing the efficiency of a serotonin transporterarrow_forwardWhich of the following statements regarding polarized membranes is incorrect? a. There is a separation of the charge by a membrane, resulting in its ability to do work. b. An RMP of –60 mV indicates that there are more positive ions inside the axon than an RMP of –70 mV. c. A resting membrane potential (RMP) of –90 mV indicates the there are more positive ions inside the axon than an RMP of –70 mV. d. There is a difference in the charges found on the inside of the membrane to the outside.arrow_forwardJose measures membrane potential in two neighboring cells. He notices that when the membrane potential changes in one cell, the membrane potential of the neighboring cell changes in a similar manner. For example, if one cell hyperpolarizes, the neighboring cell also hyperpolarizes. He concludes the cells are electrically coupled. Which of the following is the most likely to cause the electrical coupling? a.) The electrical coupling is most probably due to integrins that connect the two cells. b.) The electrical coupling is most probably due to tight junctions that connect the two cells. c.) The electrical coupling is most probably due to desmosomes that connect the two cells. d.) The electrical coupling is most probably due to gap junctions that connect the two cells.arrow_forward
- GABA is an example of an inhibitory neurotransmitter. Drugs that increase the level of GABA are used to treat diseases such as epilepsy where the signal transmission needs to be impaired. The effect of the inhibitory neurotransmitter on the postsynaptic membrane is to: Select one: a. decrease the threshold level b. hyperpolarize the postsynaptic membrane c. depolarize the postsynaptic membrane d. maintain the resting potentialarrow_forwardWhich of the following statements correctly describes the function of mitochondria found in axon terminals? a. They synthesize enzymes, which are required to break down the neurotransmitters. b. They synthesize vesicles, which transport sodium and potassium ions across the synapse. c. They synthesize ATP, which is required for the production of neurotransmitters. d. They synthesize ATP, which is required to bond the axon terminal to the dendrites.arrow_forwardWhich of the following is NOT an example of communication that happens from one neuron to another neuron? A. Endocrine signaling (ex. hormones secreted into the blood stream travel and bind to receptors on dstant cells). B. Retrograde neurotransmission (ex.the dendrite releases a neuroactive substance that binds to receptors on the axon terminal of a presynaptic neuron). C. Electrical communication via propagation of action potential from one node of ranvier to the next node of ranvier. D. Volume transmission (ex. neuropeptides diffuse away from the synapse and bind to receptors on adjacent cells) E. Electrical communication through gap junctions.arrow_forward
- Depression is a condition in which sufferers may feel low mood, lack of motivation and sleep. It is caused by a lack of serotonin in the synaptic cleft of neurone pathways. Serotonin is a neurotransmitter. a) Describe how serotonin acts as a neurotransmitter. Using your understanding of synaptic transmission, explain how communication between neurones in serotonin pathways of the brain would be affected in someone with depression. b) Doctors use tubocurarine drug as an anaesthetic as it temporarily paralyses muscles. It blocks receptors at neuromuscular junctions. Why does this lead to paralysis?arrow_forwardWhich 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.arrow_forwardHelp mearrow_forward
- The presence of an electrical gradient is responsible for both the resting membrane potential and the action potential in the neuron.a. In this case who is responsible for maintaining the electric gradient to produce a potential for the resting membrane?b. Explain what is meant by an electrical gradient in the context of a cell (neuron)!arrow_forwardClostridium tetani toxin blocks the exocytosis of GABA. A. What anatomical part of a pre-synaptic neuron would be affected by this? B. How would a post-synaptic neuron’s likelihood of experiencing an action potential be affected by this toxin? C. Explain, using at least TWO of the following terms: threshold, depolarization, repolarization, hyperpolarization, summation, IPSP, EPSP, exocytosisarrow_forwardWhich of the following statements does NOT correctly describe the repolarization of a neuron? a. The potassium channels are slower to open, allowing the potassium ions to leave after depolarization. b. The potassium ions leave the cell, thereby returning the neuron to its resting potential. c. The neuron becomes more polarized and more negatively charged than its original resting membrane potential. d. The sodium and potassium channels open, allowing the positive ions to move out of the cell.arrow_forward
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