A 48-year-old man has hepatic cancer that is unresponsive to standard therapy. He enrolls in a clinical study of a novel chemotherapeutic agent that, as a side effect, blocks kinesin, a component of the cellular microtubular transport system. One week later, he develops skeletal muscle weakness An alteration in which of the following components of the neuromuscular junction is the most likely cause of the muscle weakness? (A) A decrease in the number of postsynaptic neurotransmitter receptors (B) A decrease in the number of presynaptic neurotransmitter vesicles (C) A decrease in the presynaptic neuron calcium permeability (D) Impaired a-motoneuron action potential conduction (E) Impaired skeletal muscle action potential conduction

A 48-year-old man has hepatic cancer that is unresponsive to standard therapy. He enrolls in a clinical study of a novel chemotherapeutic agent that, as a side effect, blocks kinesin, a component of the cellular microtubular transport system. One week later, he develops skeletal muscle weakness An alteration in which of the following components of the neuromuscular junction is the most likely cause of the muscle weakness? (A) A decrease in the number of postsynaptic neurotransmitter receptors (B) A decrease in the number of presynaptic neurotransmitter vesicles (C) A decrease in the presynaptic neuron calcium permeability (D) Impaired a-motoneuron action potential conduction (E) Impaired skeletal muscle action potential conduction

Human Anatomy & Physiology (11th Edition)

11th Edition

ISBN:9780134580999

Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

Section: Chapter Questions

Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...

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Describe a Junctional Escape Rhythm, and explain why it occurs.
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Please answer all questions Following death, muscles enter a period of sustained contraction called rigor mortis. This develops because: a) the Na+/K+ active transport pump fails. b) there isn't any more neurotransmitter secretion. c) there isn't any ATP to break actin-myosin bonds. d) calcium is not returned to the cisternae. If a muscle is stimulated to contract at maximum tension yet brief periods of relaxation are possible, the muscle is demonstrating: a) twitch. b) summation. c) incomplete tetany. d) complete tetany.
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1. Draw and label the steps of the sliding filament mechanism in skeletal muscle. This should be four parts (Cross- bridge, power stroke, disassociation, reactivation). On each part, be sure to include the following structures: actin, myosin, troponin, tropomyosin. Also include ATP, myosin ATPase, ADP, Pi, and H* (where important). • Cross-bridge: . Powerstroke: ● Disassociation: ● Reactivation:
Which of the following is a correct sequence (in chronological order of occurrence) within excitation-contraction coupling? a. Synpatic vesicles fuse with the pre-synaptic membrane, Neurotransmitter binds to receptors in the post-synaptic membrane, Neurotransmitter diffuses across the synaptic cleft b. Neurotransmitter binds to receptors in the post-synaptic membrane, Synpatic vesicles fuse with the pre-synaptic membrane, Neurotransmitter diffuses across the synaptic cleft c. Synpatic vesicles fuse with the pre-synaptic membrane, Neurotransmitter diffuses across the synaptic cleft, Neurotransmitter binds to receptors in the post-synaptic membrane
When an action potential arrives at the neuromuscular junction, acetylcholine is released into the synaptic cleft and binds to receptors in the postsynaptic membrane. Which of the following represents the correct order of the next series of events? A. An action potential travels down the T tubules, depolarization spreads through the T tubules, Ca2+ is released from the sarcoplasmic reticulum, and myosin binds to actin. B. Ca2+ is released from the sarcoplasmic reticulum, an action potential travels down the T tubules, depolarization spreads through the T tubules, and myosin binds to actin. C. An action potential travels down the T tubules, depolarization spreads through the T tubules, Ca2+ is taken up by the sarcoplasmic reticulum, and myosin binds to actin. D. T tubules are depolarized, Ca2+ is released from the sarcoplasmic reticulum, an action potential is created in the muscle cell, and myosin bonds to actin. E. An action potential travels…
Muscle motor unit recruitment follows the pattern of the SO (I) fibers being recruited first followed by the FOG (IIa) and then ultimately by the FG (IIb) if and when workloads require this. Muscle fatigue follows the order that the FG fibers fatigue first, followed by the FOG fibers and finally (maybe never) the SO fibers. Explain how it makes sense physiologically that the last fibers to be recruited to contract are the first to fatigue, while the first fibers to be recruited to contract would be the last to fatigue.
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