Dr Gawad Physiology Course Online Exam - CVS – Course Lecture 1- Introduction, Rhythmicity

11 Questions | Total Attempts: 1467

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Dr Gawad Physiology Course Online Exam - CVS  Course Lecture 1- Introduction, Rhythmicity

11 MCQs (Only one correct answer) Each MCQ: 1 mark, Total mark: 11 Allowed time: 10 min Good Luck dr Mohammed Abel Gawad


Questions and Answers
  • 1. 
    The cardiac muscle fibres :
    • A. 

      Are unstriated muscle fibres.

    • B. 

      Form true syncytiutn.

    • C. 

      Are poor in mitochondria.

    • D. 

      Have low resistance bridges and tight gap junctions.

  • 2. 
    About the pacemaker potential, all the following is true except:
    • A. 

      Its amplitude is -80 to -90 mV.

    • B. 

      It is unstable during rest.

    • C. 

      Its slope is decreased by increased permeability to K.

    • D. 

      The firing level occurs at a potential difference of about -45 mV.

  • 3. 
    S.A.N. is the normal pacemaker because:
    • A. 

      The fastest impulse discharge.

    • B. 

      Location in the atrium.

    • C. 

      Neural control.

    • D. 

      Relative position to the A.V.N.

  • 4. 
    The pacemaker potential un-stability is due primarily to:
    • A. 

      Slow decrease in K+ permeability

    • B. 

      Slow increase in K permeability.

    • C. 

      Hyperpolarization stimulating voltage gated Na channels.

    • D. 

      Rapid increase in Ca permeability.

  • 5. 
    The steepest prepotenial normally occurs in the:
    • A. 

      Atrioventricular node (AVN).

    • B. 

      Bundle of His.

    • C. 

      Purkinje fibres.

    • D. 

      Sinoatrial node (SAN).

    • E. 

      Ventricular muscle cells.

  • 6. 
    Intrinsic heart rate refers to:
    • A. 

      Heart rate that is produced by AVN

    • B. 

      Heart rate that is produced due to the permeability of SAN to Na

    • C. 

      Heart rate that is produced by atrial muscles

    • D. 

      None of the above

  • 7. 
    The main cause of plateau in cardiac muscle action potential:
    • A. 

      Out flux of K in exchange of Na

    • B. 

      Outflux of K

    • C. 

      Influx of Ca in exchange to efflux of Na

    • D. 

      The balance in influx of and out flux of positive ions along the membrane

  • 8. 
    Which of the following is considered as an ectopic pacemaker:
    • A. 

      SAN

    • B. 

      AVN

    • C. 

      Bundle of His

    • D. 

      Ventricular muscle

  • 9. 
    Regarding the differences between cardiac muscle and pace maker action potentials, which of the following is true:
    • A. 

      Cardiac muscle action potential has lower magnitude than pacemaker

    • B. 

      Both have fast depolarization

    • C. 

      Both have 2 parts repolarization

    • D. 

      Pacemaker action potential is unstable while cardiac muscle potential is not.

  • 10. 
    Regarding pacemaker action potential which is true:
    • A. 

      Ca is not important for its maintenance

    • B. 

      Na is important to initiate it, but not important for its maintenance

    • C. 

      Repolarization is due to out flux of K in exchange of Na

    • D. 

      None of the above

  • 11. 
    Regarding the cardiac muscle action potential, which of the following is not true:
    • A. 

      The initial repolarization is due to K efflux

    • B. 

      The plateau is due to balance between the Ca, K mobility

    • C. 

      The complete repolariztion is at the end of phase 3 when all K is effluxed

    • D. 

      Na is an important ion for depolarization

    • E. 

      None of the above

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