Physiology of Action Potentials and Muscle Atrophy
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Questions and Answers

What is the primary effect of increasing K+ permeability on membrane potential (Vm)?

  • Vm becomes less negative
  • Vm remains unchanged
  • Vm becomes more negative (correct)
  • Vm becomes more positive
  • Why do local anesthetics primarily produce analgesia without paralysis?

  • They affect large diameter neurons more effectively
  • They block all types of nerve fibers equally
  • They target myelinated fibers preferentially
  • They are more effective against small diameter neurons (correct)
  • How does the speed of action potential transmission relate to fiber characteristics?

  • It remains constant regardless of fiber type
  • It only depends on fiber diameter
  • It is influenced by both fiber size and myelination (correct)
  • It is faster in unmyelinated fibers
  • What role do action potentials play in sensory neurons?

    <p>They transmit sensory information to the CNS</p> Signup and view all the answers

    What characteristic of action potentials allows for information encoding?

    <p>The frequency of action potentials varies</p> Signup and view all the answers

    What is a primary cause of muscle atrophy associated with a sedentary lifestyle?

    <p>Denervation</p> Signup and view all the answers

    Which of the following consequences is typically observed in muscle performance due to atrophy?

    <p>Degeneration of contractile proteins</p> Signup and view all the answers

    How long does it typically take before fiber loss occurs due to disuse?

    <p>1-2 years</p> Signup and view all the answers

    What characterizes the neuromuscular junction (NMJ)?

    <p>It consists of motor neuron synapses with muscle fibers</p> Signup and view all the answers

    Which of the following is NOT a cause of muscle atrophy?

    <p>Active resistance training</p> Signup and view all the answers

    What is the primary cause of hypertrophy in muscles?

    <p>Near maximal force development</p> Signup and view all the answers

    How does the addition of sarcomeres in series affect the velocity of shortening?

    <p>It increases the total velocity of shortening.</p> Signup and view all the answers

    What is the effect of hyperplasia on muscle fibers?

    <p>It contributes to the formation of new muscle fibers.</p> Signup and view all the answers

    What change occurs during normal muscle lengthening?

    <p>Increase in shortening capacity.</p> Signup and view all the answers

    Which statement best describes the relationship between hypertrophy and hyperplasia?

    <p>Both contribute to increased force generation without changing velocity of contraction.</p> Signup and view all the answers

    What does myelination do to membrane capacitance and ion flow?

    <p>Decreases membrane capacitance and reduces ion flow 5,000-fold</p> Signup and view all the answers

    Which statement best describes the role of refractory periods in action potentials?

    <p>They limit the maximum frequency of action potentials.</p> Signup and view all the answers

    What is the primary function of nodes of Ranvier in myelinated neurons?

    <p>Concentrating Na+ and K+ channels for action potential propagation</p> Signup and view all the answers

    What characteristic of multiple sclerosis is highlighted in its description?

    <p>It is an immune-mediated inflammatory demyelinating disease of the CNS.</p> Signup and view all the answers

    How does saltatory conduction differ from non-myelinated conduction?

    <p>It occurs only at the nodes, leading to increased velocity.</p> Signup and view all the answers

    What is a common symptom presentation in multiple sclerosis patients?

    <p>Paresthesias followed by weakness or visual disturbances</p> Signup and view all the answers

    What is the expected frequency of multiple sclerosis in the US population?

    <p>About 1 person per 1,000</p> Signup and view all the answers

    Which of the following best describes the effect of myelination on energy conservation in neurons?

    <p>It significantly reduces energy expenditure during signal transmission.</p> Signup and view all the answers

    Which ion is primarily transported by the Na+-K+ ATPase during its operation?

    <p>Na+</p> Signup and view all the answers

    What is the main function of the beta subunit in the Na+-K+ ATPase complex?

    <p>Its function is not clear</p> Signup and view all the answers

    What is the electrogenic ratio of Na+ to K+ transported by the Na+-K+ ATPase?

    <p>3 Na+ to 2 K+</p> Signup and view all the answers

    How does the Ca2+ ATPase help in muscle cells?

    <p>By maintaining a low cytosolic Ca2+ concentration</p> Signup and view all the answers

    What type of transporter is involved in secondary active transport utilizing sodium as a driver ion?

    <p>Symporter</p> Signup and view all the answers

    Which of the following best describes the action of antiporters in secondary active transport?

    <p>They transport substances in opposite directions to Na+</p> Signup and view all the answers

    What effect do cardiac glycosides like digoxin have on intracellular Na+ levels?

    <p>They increase intracellular Na+ concentration</p> Signup and view all the answers

    What is the outcome of decreased activity of Na+/Ca2+ antiporters due to glycoside action?

    <p>Increased intracellular Ca2+ concentration</p> Signup and view all the answers

    What causes the c wave in the atrial pressure changes during aortic regurgitation?

    <p>Contracting ventricles causing A-V valves to bulge backward</p> Signup and view all the answers

    Which phase of the cardiac cycle occurs when the aortic valve opens?

    <p>Ventricular ejection</p> Signup and view all the answers

    Which statement accurately describes the Frank-Starling mechanism?

    <p>It facilitates optimal interdigitation of actin-myosin filaments.</p> Signup and view all the answers

    What occurs during isovolumic relaxation of the left ventricle?

    <p>The ventricle volume remains constant while pressure decreases.</p> Signup and view all the answers

    Which effect occurs when moving from point A to point B on a cardiac function curve?

    <p>Indicates an increase in preload only</p> Signup and view all the answers

    What happens during moderate exercise in relation to the cardiac function curve?

    <p>There are shifts from point D to point C on the curve.</p> Signup and view all the answers

    What does the term myocardial contractility refer to?

    <p>The ability to develop force at a given length of sarcomere.</p> Signup and view all the answers

    What physiological change occurs during beta-1 blockade according to the cardiac function curve?

    <p>Decreased contractility.</p> Signup and view all the answers

    Study Notes

    Course Information

    • Fall 2024 course offerings include Physiology for Dental Students (DENT 625) and Fundamentals of Physiology (PHYSIOL 725).
    • Course Director: Tom Adair, PhD, [email protected]
    • Course Coordinator: Jennifer Duckworth, G251, [email protected]
    • Contact hours: ~17 hours testing, ~80 hours lecture.
    • Clinical correlation hours: 6 (online).
    • Credit hours: DENT 625 – 7 Credit hours, PHYSIOL 725 – 7 Credit hours.
    • Required Text: Hall JE and Hall ME. Guyton and Hall Textbook of Medical Physiology. 14th ed. Philadelphia, PA: Elsevier, 2021.

    What is Physiology?

    • Physiology studies the normal function of living organisms and their parts, including physical and chemical processes involved in maintaining life.
    • Human physiology focuses on how the human body functions.
    • Physiology relates to various fields like:
      • Genes
      • Gene Expression
      • Cell Function
      • Biochemistry
      • Proteomics
      • Bioinformatics
      • Clinical Medicine
      • Integrative Physiology

    Course Information (continued)

    • Class meeting times: Monday/Wednesday/Friday, 10:00-11:50 AM, Upper Amphitheater, R354.
    • Additional Resources:
      • Pocket Companion to Guyton and Hall Textbook
      • Guyton and Hall Physiology Review

    Assessment Method

    • Grades based on daily quizzes, block exams (7 total, ~312 points), and a final exam (100 points).
    • Quizzes: ~0.5 points per hour of lecture
    • Block exams: approximately four questions per hour of lecture

    Course Information (continued)

    • Online testing software (ExamSoft) used for block exams and the final exam.
    • Daily quizzes are administered using Nearpod.
    • Nearpod quiz access instructions provided at the start of the course.
    • Students may submit quiz answers on paper but no more than 3 times per quiz.
    • Grading scale: A=90%-100%, B=80%-90%, C=70%-80%, F=<70%

    Dental School Attendance Policy

    • Adherence to the dental school attendance policy is essential.
    • Course coordinators may require in-person attendance for lectures or topics.
    • Arriving late or leaving early considered an absence.
    • Students required to contact course coordinator promptly, prior to next class, to make up missed class via UMMC email.
    • Missed class assignments incur a 3-point penalty on the final course grade for each case.
    • Failure to complete a missed-class assignment results in a failing grade (50).
    • No make-up tests or daily quizzes offered regardless of whether an absence is excused.

    Graduate Student Attendance Policy

    • Dr. Casey Boothe ([email protected]) manages excused absences for Graduate students.
    • Graduate students must inform course coordinator, Jennifer Duckworth, of any absence or query, copying the communication to Dr. Boothe.

    Testing Policies

    • All students required to study and agree with the Examination Honor Code before testing.
    • ExamSoft practice testing of honor code provided.
    • Specific procedures and seating arrangements applied on exam days.
    • Students given personalized scratch paper which includes seat number.
    • Students required to present student ID to proctors for bar code reading.
    • Designated seating locations provided.
    • All electronic devices stored at the front/back of the room (not aisles or seating rows).
    • Proctors randomly check assigned seating during exams.
    • Test question challenges accepted within one week of each test by contacting the course coordinator.
    • Students may make appointments to review missed questions in the same time frame.

    Course and Instructor Evaluations

    • Opportunity to evaluate instructors (including pre and post block exams).
    • Course evaluation after final exam.
    • A cash award and plaque given to the student with the highest grade in dental and graduate classes.
    • Absence from any test (excused or unexcused) disqualifies from receiving an award.

    Physiology Course Schedule (partial)

    • Course schedule included with specifics regarding days, time, session topics, and faculty.

    Course Coordinator

    Instructors (partial)

    • Several instructors presented: Tom Adair, PhD, and others
    • Instructor responsibilities outlined for each block covering different physiology topics.

    Unit 2 (Chapters 4-6)

    • Topics specific to the chapters in unit 2

    Unit 2 (Chapter 4)

    • Transport of Substances through cell membranes discussed
    • Includes discussion on the fluid-mosaic model, lipid bilayer, cell membrane, permeability coefficients (cm/sec), Molecular Gradients across cell membrane, Simple diffusion, Active Transport, Facilitated diffusion, diffusion of a molecule in water, facilitated diffusion of water through cell membranes, ion channels, Selectivity of potassium channel, Selectivity of sodium channel, How to study ion channels (Patch Clamp Method), Operation of Voltage-gated sodium channel, Simple vs. Facilitated Diffusion, what limits maximum rate of facilitated diffusion(Vmax), what is net diffusion, Electrical potential(EMF).

    Unit 2 (Chapter 5)

    • Membrane potentials and action potentials, active transport of Na+ and K+, simple diffusion of Na+ and K+, membrane potential(Vm), simplest case scenario for K+, simplest case scenario for Na+, The Sodium Nernst Potential, Resting Membrane Potential, Why is the cell membrane so permeable to K+, The Goldman-Hodgkin-Katz Equation, The effect of changing permeability of Na+ and K+ on membrane potential, functions of action potentials, resting and action potentials.

    Unit 2 (Chapter 6)

    • Contraction of skeletal muscle. includes: physiological anatomy of skeletal muscle, cellular organization, physiological anatomy of skeletal muscle detailed organization - molecular organization - Dystrophin, physiological anatomy of skeletal muscle—molecular organization—sarcomere, The Sarcomere, Titin, Function of Titin, what are the striations?, relaxed and contracted states - Which band shortens?, which band shortens - I or A?, Overall mechanisms of muscle contractions, the actin filament, Calcium triggers contraction by exposing active sights on actin filaments, The myosin filament, 'Walk-Along Theory of Muscle Contraction', Myosin-Actin Cycling in the presence of Ca2+, and ATP, Muscle Mechanics, Tension as a function of sarcomere length, Relationship of Contraction Velocity to Load, Isometric and isotonic contractions, muscle lever system, a single muscle twitch.

    Unit 3 (Chapters 7-10)

    • Topics related to unit 3, including specialized sections for chapters 7-10

    Study Questions (partial)

    • Study questions related to the physiology course content presented.

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    Description

    This quiz explores key concepts in physiology related to action potentials and muscle function, focusing on mechanisms of analgesia, the effects of K+ permeability, and implications of muscle atrophy. It also examines the role of the neuromuscular junction and factors influencing muscle hypertrophy and hyperplasia.

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