Health Science 2211- Lecture 2

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Health Science 2211- Lecture 2
2014-01-14 01:59:36
heart physiology

heart physiology
Show Answers:

  1. what is the cardiac muscle called that forms the wall of the heart?
  2. how are the muscles arranged in the myocardium?
    spiral and circular bundles
  3. The heart's four chambers must beat in an ______________.
    organized manner
  4. When does a chamber of the heart contract?
    when an electrical impulse moves across it
  5. Concentric layers of cardiac muscle cells are called?
  6. Describe the structure of cardiomyocytes.
    short, fat, branched, striated cells with a central nucleus interconnected by intercalated discs
  7. what are intercalated discs?
    areas where the plasma membranes intermesh
  8. what are the 2 ways that intercalated discs connect adjacent cardiac muscle cells?
    • desmosomes
    • gap junctions
  9. Define desmosome.
    tight seals that weld the plasma membranes together
  10. Define gap junctions.
    ionic channels responsible for propagation of electrical signal from cell to cell during muscle contraction
  11. what does intercalated discs enable?
    enable synchronized contraction of muscle fibers (atria and ventricles contract at the same time)
  12. what is the sarcolemma?
    plasma membrane of muscle cell
  13. what are T (transverse) tubules?
    tiny invaginations of the sarcolemma that quickly spread electrical signal to all parts of the muscle fiber during contraction
  14. Muscle fibers are filled with bundles of threads called?
  15. what do myofibrils consist of?
    consist of thick and thin filaments which are the contractile structure of muscle
  16. what is a sarcomere? (structure in myofibrils) Where is it found? (2)
    • group of overlapping thin and thick filaments
    • each sarcomere is found between 2 Z discs
  17. what are striations?
    when a thick and thin filaments overlap each other in a pattern
  18. what happens to filaments during contraction and relaxation of the muscles?
    they slide past each other
  19. what is the heartbeat?
    single sequence of atrial contraction followed by a ventricular contraction
  20. what controls the heartbeat? Describe it.
    • special tissue called nodal tissue
    • has characteristics of both nerve and muscle tissue
  21. Cardiac muscle cells in nodal tissue are authorthytmic, what does this mean?
    • self-excitable
    • can generate electrical impulses without an external stimulus
  22. where are the authorthytmic nodal cells located?
    in the cardiac conduction system
  23. What is the Sinoatrial (SA) node and where is it located?
    • it's the pacemaker of the heart
    • cluster of cells in wall of right atrium
  24. what is the function of the SA node?
    begins an action potential followed by contraction of both atria, expelling contents into ventricles
  25. What is the atrioventricular (AV) node? and where is it located?
    • transmits electrical signals to AV Bundle (bundle of His)
    • located in atrial septum
  26. what is the atrioventricular (AV) bundle?
    • Bundle of His
    • only place where signal can be transmitted from atria and ventricles
  27. what is the difference between systole and diastole?
    • systole: contraction
    • diastole: relaxation; filling
  28. what is the ECG or EKG?
    a recording of the electrical changes that accompany the cardiac cycle
  29. what does the P wave indicate?
    atrial contraction
  30. what does the QRS complex indicate?
    rapid ventricular contraction
  31. what does the T wave indicate?
    ventricular relaxation
  32. ______________ system can increase or decrease heart rate.
  33. what 5 things influence heart rate?
    • hormones (epinephrine)
    • age
    • gender
    • physical fitness
    • body temperature