Muscle Physiology: Simple Muscle Twitch
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Questions and Answers

What characterizes a simple muscle twitch?

  • A sustained muscle contraction
  • A rapid, single muscle contraction followed by relaxation (correct)
  • The total contraction of a muscle group
  • A prolonged relaxation phase of the muscle

    • Which sequence accurately describes the phases of a simple muscle twitch?

  • Contraction phase -> Relaxation phase -> Latent period
  • Latent period -> Relaxation phase -> Contraction phase
  • Relaxation phase -> Latent period -> Contraction phase
  • Latent period -> Contraction phase -> Relaxation phase (correct)

    • If a second stimulus is applied during the latent phase of the first stimulus in a simple muscle twitch, what will occur?

  • Curve with 2 humps
  • No effect (correct)
  • Two separate twitches
  • Curve with higher contraction

    • What is represented by curve (C) in the context provided?

    <p>Simple muscle</p> Signup and view all the answers

    Which phase does curve (C1) change to curve (C2) if a second stimulus is applied?

    <p>Early relaxation</p> Signup and view all the answers

    Which of the following correctly describes Expiratory reserve volume?

    <p>The maximal volume of air that can be expired after normal expiration</p> Signup and view all the answers

    What is the definition of Tidal volume?

    <p>The volume of air that can be inspired and expired with each normal breath</p> Signup and view all the answers

    Which option represents Residual volume?

    <p>The volume of air remaining in the lungs after end of forced expiration</p> Signup and view all the answers

    Vital capacity is defined as which of the following?

    <p>The maximal volume of air that can be expired after a maximal inspiration</p> Signup and view all the answers

    What does Inspiratory capacity measure?

    <p>The amount of air that a person can breathe after the normal expiratory level</p> Signup and view all the answers

    What effect does adding warm saline to the Sinus venosus in a frog's heart have?

    <p>Increases cardiac rhythmicity</p> Signup and view all the answers

    What is the normal duration of the PR interval on an ECG?

    <p>0.12-0.20 seconds</p> Signup and view all the answers

    What is considered a hypertensive blood pressure reading?

    <p>160/100 mmHg</p> Signup and view all the answers

    Which of the following is the normal range of heart rate in an adult at rest?

    <p>60-100 bpm</p> Signup and view all the answers

    What does the term 'tachycardia' refer to when measuring the pulse?

    <p>A pulse rate more than 100 beats per minute</p> Signup and view all the answers

    Which site is most commonly used for examining pulse?

    <p>Radial artery</p> Signup and view all the answers

    In a normal ECG, what does the (P) wave represent?

    <p>Atrial depolarization</p> Signup and view all the answers

    During which phase of the cardiac cycle does the first heart sound occur?

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

    What is true about the methods for determining arterial blood pressure?

    <p>Blood pressure is most commonly measured from the brachial artery of the upper arm</p> Signup and view all the answers

    Study Notes

    Muscle Used in SMT Recording

    • Muscle and nerve used for recording of a Simple Muscle Twitch (SMT):
      • Gastrocnemius muscle, sciatic nerve

    Simple Muscle Twitch Definition

    • A simple muscle twitch is a rapid, single muscle contraction followed by relaxation.

    Sequence of Events in a Simple Muscle Twitch

    • Latent period → Contraction phase → Relaxation phase

    Effect of Second Stimulus During Latent Phase

    • If a second stimulus is applied to a muscle twitch during the latent phase, no effect is observed.

    Effect of Second Stimulus During Early Relaxation Phase

    • If a second stimulus is applied during the early relaxation phase of the first stimulus, a curve with two humps (or two separate twitches) is observed.

    Curve Representation in SMT

    • Curve C1 represents a normal simple muscle twitch.
    • Curve C2 occurs when a second stimulus is applied during the early relaxation phase of a prior stimulus.

    Curve C Representation

    • Curve C represents separate, independent contractions (not tetanus or clonus).

    Cause of Curve C

    • Curve C is due to multiple stimuli during the early relaxation phase.

    Conversion of Curve B to Curve C

    • Curve B (presumably, a sustained contraction) can be converted to curve C (separate contractions) by applying stimuli during the early relaxation phase.

    Respiratory Volumes and Capacities

    • Inspiratory Reserve Volume (IRV): The maximal volume of air that can be inspired after a normal inspiration.
    • Expiratory Reserve Volume (ERV): The maximal volume of air that can be expired after a normal expiration.
    • Tidal Volume (TV): The volume of air inspired and expired with each normal breath.
    • Residual Volume (RV): The volume of air remaining in the lungs after a forced expiration.
    • Vital Capacity (VC): The maximal volume of air that can be expired after a maximal inspiration.
    • Inspiratory Capacity (IC): The sum of tidal volume and inspiratory reserve volume; the amount of air that a person can breathe in after a normal exhalation.

    Effect of Warm Saline on Frog Heart

    • Adding warm saline to the sinus venosus of a frog's heart increases cardiac rhythmicity.

    PR Interval in ECG

    • Normal PR interval duration: 0.12-0.20 seconds

    Normal Adult Resting Heart Rate

    • Normal adult resting heart rate: 60-100 bpm

    Tachycardia Definition

    • Tachycardia refers to a pulse rate more than 100 beats per minute.

    Hypertensive Blood Pressure Reading

    • A hypertensive blood pressure reading is 160/100 mmHg or higher.

    Normal Arterial Blood Pressure Range

    • Normal arterial blood pressure: 100-140/60-90 mmHg.

    Silent Gap Phenomenon

    • Silent gap phenomenon is observed in conditions with hypertension.

    First and Muffled Sound in Auscultatory Method

    • The first sound heard in the auscultatory method is systolic blood pressure.
    • When the sound is muffled, it indicates diastolic blood pressure.

    Methods for Determining ABP

    • The auscultatory method is the most common and reliable method for determining arterial blood pressure.
    • Brachial artery is the common site for measuring blood pressure.

    Arterial Blood Pressure Characteristics

    • Arterial blood pressure decreases after hemorrhage and during sleep.
    • It increases during emotion.

    Steps for Measuring ABP

    • The auscultatory method usually follows the palpatory method

    Normal Pulse

    • Normal pulse rate: 60-100 beats/minute

    Common Pulse Site

    • Radial artery is the most common site for measuring pulse.

    ECG Wave Representations

    • P wave: Atrial depolarization
    • T wave: Ventricular repolarization
    • QRS complex: Ventricular depolarization

    PR Interval Measurement in ECG

    • PR interval is measured from the beginning of the P wave to the beginning of the QRS complex.

    First Heart Sound in Cardiac Cycle

    • The first heart sound (S1) occurs during ventricular systole.

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    Description

    This quiz explores the physiological concepts related to Simple Muscle Twitches (SMT), including the muscle and nerve involved, the sequence of events during a twitch, and the effects of additional stimuli. Test your understanding of latent periods, contraction phases, and muscle response to stimulation through various scenarios.

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