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 Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter7: The Peripheral Nervous System: Efferent Division

Section: Chapter Questions

Problem 1SQE

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Recently, it has been observed that several muscle diseases and disorders are linked to problems with triad structure and function.One such disorder is called malignant hyperthermia, a dire hypermetabolic response to certain inhaled anesthetics such as halothane. Muscles become very rigid due to excessive contraction (especially the masseter muscle), the body temperature spikes, andmuscles break down. Death is certain if not treated. Given the principal symptoms of malignant hyperthermia, what is its likely cause?Propose a theoretical mechanism for a treatment that would dampen the deleterious effects of this disorder.
While the sarcoplasmic reticulum of muscle was first described by nineteenth-century microscopists, its true significance was not ap-preciated until its intricate structure was revealed much later by the electron microscope. What could you tell a nineteenth-century microscopist to enlighten him or her about the structure of the sarcoplasmic reticulum and its role in the coupling of excitation and contraction?
Why is the latent period longer during an isotonic twitch of a skeletalmuscle fiber than it is during an isometric twitch?a. Excitation–contraction coupling is slower during an isotonic twitch.b. Action potentials propagate more slowly when the fiber is shortening,so extra time is required to activate the entire fiber.c. In addition to the time for excitation-contraction coupling, it takesextra time for enough cross-bridges to attach to make the tension in themuscle fiber greater than the load.d. Fatigue sets in much more quickly during isotonic contractions, andwhen muscles are fatigued the cross-bridges move much more slowly.e. The latent period is longer because isotonic twitches only occur in slow(type I) muscle fibers.
Mr. White has cerebral palsy and suffers severe muscle spasms as a result of his condition. He is prescribed the drug dantrolene, which prevents the release of calcium ions from the SR. Explain how this will treat his muscle spasms.?
Explain how the process of skeletal muscle excitation–contraction coupling demonstrates the general principle of physiology that controlled exchange of materials occurs between compartments and across cellular membranes.
How does the neuromuscular junction illustrate the general principle of physiology that the functions of organ systems are coordinated witheach other?
Explain why reticular fibers are also termed as argyrophilic fibers and lattice fibers
Human Anatomy and Physiology Describe in detail the events at the neuromuscular junction and how these events allow for the excitation-contraction coupling event to occur. Be sure to also include in detail all the steps at the NMJ and the steps of the excitation-contraction coupling event.
Imagine that you are part of a research team that specializes in diagnosing disorders associated with malfunctioning cellular structures. Medical doctors consult your group to help diagnose particularly difficult cases. You have been presented with the following data:Patient History:o Seven year-old boyo Fatigueo Muscle weaknesso Low enduranceo Loss of coordinationo Progressive difficulty walkinPhysical Examinationo Muscle loss & deformityo Awkward gaito Difficulty breathingLaboratory Resultso Cells have abnormal shapeo Cell division is abnormalo Impaired intracellular movement of material.Explain which structures may be involved. Use the patient history data to support your conclusions.
.The poison ouabain (wah-BAY-in), or arrow poison, blocks the Na+ K+pump. What effect would this poison have on the sodium and potassium ion gradients and so on the action potentials of a muscle fiber?
Subject: Neurophysiology Would a skeletal muscle fire an AP if a single quanta of ACh was secreted? Why or why not?
A motor unit associated with the stimulation of skeletal muscle is designated as a 1:8 motor unit. Which of the following statements is correct? The motor unit consists of one somatic neuron and 8 myofibers (muscle fibers) Each of the myofibers in the motor unit is innervated by more than one neuron It is part of the autonomic nervous system The neuron in the motor unit is an afferent neuron