Physiology Midterm 2 Part 1

  1. function of troponin
    work with tropomyosin as a switch for muscle contraction & relaxation
  2. Troponin must work with __ to move tropomyosin in order for cross bridges to attach to actin
  3. In skeletal muscle, calcium release receptors (ryanodine receptors) are
    • released from sarcoplasmic reticulum by passive diffusion through calcium release channels
    • stimulated by action potentials that open voltage-gated Ca++ channels, which is mechanically coupled to Ca++ release channels to stimulate contraction
  4. Myosin
    thick filament

    • - does not move
    • - Actin slides over it.
  5. HCN channels
    main channel involved in making depolarization occur

    • - voltage & chemical gate
    • - Na enters same time K leaves
    • - When Na enters faster than K leaves, excitatory effect occurs
    • - have a hyperpolarizing threshold
  6. HCN (funny) channels are activated during __ to allow influx of __ and efflux of __ resulting in __
    • Repolarization;
    • Na+; K+;
    • slow accumulation of positive charge (slow depolarization)
  7. HCN channels are activated by __ binding to beta 1 receptor through a 2nd messenger
  8. The HCN channel stays open briefly as the membrane __ to a threshold value for __ channels.
    depolarizes; T-type Ca2+
  9. As the pacemaker potentials spread away from the SA node, they become __
    cardiac action potentials
  10. Phases of cardiac action potential
    • phase 0: rapid depolarization
    • phase 1: early rapid repolarization
    • phase 2: plateau
    • phase 3: final rapid repolarization
    • phase 4: diastolic depolarization

    (figure 13.19)
  11. The rapid depolarization phase (of cardiac action potential) is due to activation of __ voltage channels

    - phase 0: Na+ channels open
  12. The early rapid repolarization phase (of cardiac action potential) is due to inactivation of __ & activation of __ voltage channels.
    Na+; K+to (transient-outward K+)

    - phase 1: Na+ channel closes, K+to channel opens & closes rapidly
  13. The plateau phase (of cardiac action potential) is due to influx of __ through __ channels
    Ca2+; L-type

    - phase 2: L-type Ca2+ channels fully open; K+ channels open
  14. The final rapid repolarization phase is due to closure of __ channels and activation of __ channels.
    L-type Ca2+; K+

    - phase 3: L-type CA2+ channels close; K+ channels stay open for efflux of K+
  15. Diastolic depolarization (of cardiac action potential) is due to spontaneous depolarization of __
    SA node (due to pacemaker cells generating a new potential)

    - phase 4: heart chamber fills
  16. The P-R segment represents the length of time __
    the depolarizing wave takes to pass through the AV node & the bundle of His
  17. The P-R segment represents conduction through __
    AV node & AV bundle
  18. What converts the myosin head into the high-energy state?
    hydrolysis of ATP
  19. The release of an inorganic phosphate from the myosin molecule directly results in
    power stroke
  20. FEV1
    Forced expiratory volume in 1 second, measured during spirometry lab to test lung volume and performance

    (decreased during obstruction)
  21. In order for crossbridge cycling to occur, the actin-myosin complex must be broken by which of the following?
    ATP binding to myosin head
  22. The sequence of events that links the action potential to changes in skeletal muscle force development is called what?
    Excitation-contraction coupling
  23. Increases in the amount of cytoplasmic calcium required to initiate a muscle contraction are mediated by the coupling between a ________ on the T tubule and a ________ on the membrane of the sarcoplasmic reticulum.
    Dihydropyridine receptor; ryanodine receptor
  24. As skeletal muscle is further stretched beyond the length where optimum force is developed, ________.
    • Thin filaments are pulled away from the thick filaments, thereby reducing actin's ability to interact with myosin.
    • strength of contraction is decreased because of fewer actin and myosin cross bridge interactions
    • As a result, we cannot generate any muscle tension.
  25. As the sarcomere length of skeletal muscle is reduced beyond the length where optimum force is developed, ________.
    • There is interference between the thin filaments. (They are overlapping because they have nowhere else to go). There is no ability to generate any muscle tension.
    • The muscle contraction force is decreased because the sarcomere is short and cross bridge cycling is ineffective and actin may overlap
  26. What is an increase in the number of active motor units that would increase the force developed by a skeletal muscle called?
  27. ________ is composed of multiple globular molecules polymerized to form long chains or filaments
  28. Each myosin head has a binding site for __
    actin & ATP
  29. The molecular event that occurs immediately after the power stroke is the __
    release of ADP from myosin
  30. The relaxation of skeletal muscle relies on the activity of the ________, which decreases cytoplasmic calcium concentration.
    • SERCA
    • Ca2+ ATPase
  31. The brief period of time between the beginning of the action potential in the muscle and the beginning of contraction is referred to as the __
    latent period
  32. Slow depolarization in the SA node
    • from HCN channels activated during repolarization
    • allow influx of Na+ and efflux of K+ simultaneously
    • resulting in slow accumulation of positive charge in the cell
    • T-type Ca++ voltage channels open and allow for brief influx of Ca++
  33. gap junctions
    • how action potentials travel from one cell to the next cardiac cells
    • Tube-like proteins
    • Can change diameter to minimize damage to other cells; larger diameter has less resistance
    • Cardiac cells that are NOT pacemaker cells.
  34. The property of cardiac tissue that results in greater current flow along the length of a fiber than along its width
  35. The opening and closure of the atrioventricular and semilunar valves is driven by ________.
  36. Closure of the atrioventricular valve occurs when ________.
    • Atrial pressure is low and ventricular pressure is high
    • (beginning of systole)
  37. What are the two major regions of the heart containing pacemaker cells?
    SA and AV nodes
  38. Which of the following is the correct conduction pathway through the heart?
    SA node →  AV node→ bundle of His→ bundle branches→ Purkinje fibers
  39. The rapid depolarization phase of a pacemaker cell action potential is caused by which of the following types of ion movement?
    Na+ and small amount of L-type CA2+
  40. Which of the following ion channels must open for a cardiac pacemaker cell to depolarize to threshold for an action potential?
    • HCN (funny) channels
    • T-type Ca++ channels
  41. What is the role of ryanodine receptors in cardiac muscle?
    • release calcium from the sarcoplasmic reticulum
    • Opens to release Ca++ for muscle contraction
  42. Which of the following components of an ECG represents ventricular depolarization?
    QRS complex
  43. Which of the following components of an ECG represents ventricular repolarization?
    • ST segment
    • T wave
  44. If damage to the AV node slowed down conduction through this tissue, what would be observed on an ECG?
    longer PR interval, heart block
Card Set
Physiology Midterm 2 Part 1
muscle & heart