Kin 292: Basic Electrophysiology

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Kin 292: Basic Electrophysiology
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2010-08-31 12:58:47
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  1. Myocardial Cells: Location, primary function, primary property
    • Location: Myocardium
    • Primary Function: Contraction relaxation
    • Primary Property: Contractility
  2. Pacemaker Cells: Location, primary function, primary property
    • Location: Electrical conduction system
    • Primary Function: Generation and conduction of electrical
    • impulsesPrimary Property: Automaticity, Conductivity
  3. Current
    the flow of electrical charge from one point to another
  4. Voltage
    measurement of potential energy (volts or milivolts)
  5. Electrolytes
    elements or compounds that break into charged particles when melted or dissolved into water or another solvent (Na, K, Ca, Cl)
  6. Action Potention
    transient depolarization and repolarization of cells that is triggered by external mechanisms
  7. Resting membrane potential
    electrical charge across a cell membrane (Ca, Na, K)
  8. Threshold membrane potential
    at which the cell will depolarize and become more positive
  9. slow response
    • because fewer channels and intercalated disks
    • SA and AV nodes (Slow calcium and sodium channels) Spontaneous action potentials
  10. fast response
    • Atria, ventricles and Purkinje system (Voltage sensitive sodium channels)
    • sensitive to sodium
  11. Polarization
    • resting membrane potential (-90mV)
    • resting state without electrical changes
  12. what leaks out during depolerization to maintain threshold?
    K+
  13. Depolarization
    • resting to positive state
    • Na+ enters the cell
    • electrical stimulus proceeds from endocardium to epicardium
  14. P wave?
    Atrial Depolarization
  15. QRS complex?
    ventricular depolarization
  16. repolarization
    • Na+ stops flowing into cell
    • K+ leaks out
    • Returns to negative state inside cell
    • relaxation of contractile proteins
    • Electrical stimulus proceeds from epicardium to endocardium
  17. Phase 0?
    Rapid Depolarization
  18. Phase 1?
    Early Repolarization
  19. Phase 2?
    Repolarization (plateau phase)
  20. Phase 3?
    Rapid Repolarization
  21. Phase 4
    Resting membrane potential
  22. What happens as cell is rapidly depolarizing?
    cells recieve impulse, Na+ comes in, Ca2+ comes in slowly, and K+ diffuses out slowly
  23. What happens as cell is in early repolarization?
    Na+ Channels partially closed (slowly come in), Cl- enters and K+ leaves
  24. What happens as cell is repolarizing?
    • Ca2+ comes in slowly, K+ leaces
    • ST segment (absolute refractory period)
  25. What is happening as a cell is in Rapid Repolarization?
    • K+ goes out fast (more negative)
    • T wave (relative refractory period)
  26. What happens to a cell when is it at resting membrane potential?
    sodium potassium pump is regulating
  27. Refractory period?
    during which cardiac cells may or may not depolarize due to an electrical stimulus
  28. Absolute Refractory Period (ARP)?
    • Onset of QRS complex to the peak of the T wave
    • Cannot be stimulated to depolarize
  29. Relative Refractory Period (RRP)
    • Peak of T wave to the end
    • Sufficient repolarization that a strong stimulus will depolarize cells
    • Vulnerable period of repolarization
  30. Supernodal Period
    End of the T-wave
  31. Automaticity of cardiac cells?
    • Ability of pacemaker cells to spontaneously initiate electrical
    • impulse without stimulation from outside source
    • SA node, AV node, Purkinje fibers
    • Normal Na+, Ca2+, and K+ necessary
  32. Irritability of cardiac cells?
    • Ability to respond to external stimulus (chemical, electrical or
    • mechanical)
  33. Conductivity of cardiac cells?
    Ability to receive stimulus and conduct to an adjacent cell (Intercalated disks)
  34. Contractility of cardiac cells?
    Ability to shorten and produce force
  35. S-A Node?
    • “Natural pacemaker" of your heart because it
    • controls your heart rate.
  36. What is the S-A node made of and where is it located?
    • Bundle of specialized cells
    • In your right atrium connected directly to atria
  37. How many electrical signals does the S-A node produce per
    minute?
    • Normally produces 60-100 electrical signals per
    • minute
  38. Internodal pathway
    • Bachmann’s Bundle: anterior internodal pathway
    • Wenckebach’s bundle: middle
    • Thorel’s pathway: posterior
    • 50 ms SA node to AV node conduction
  39. Atrioventricular Junction?
    • delays relay of impulse to allow atria time to empty
    • (includes AV node and bundle of His)
  40. What is the AV Node made of and where is it located?
    bundle of specialized cells located posterior septal wall of right atrium behind tricuspid valve near the coronary sinus.
  41. Bundle of His? (and how many bts/min bidcharge?)
    • only electrical connection between atria and ventricles.
    • Automaticity: 40 – 60 bts/min discharge
  42. What is the point of the AV delay?
    Allows the artria to empty completely
  43. Where is the His-Purkinje System located and what does it do?
    located in ventricals, makes your ventricles contract.
  44. Accessory pathway
    allows for a shortcut for impulses can become dangerous if heartrate increases or etc.
  45. The parts of the His-Purkinje system include:
    • Bundle of His (the start of the system)
    • Right bundle branch
    • Left bundle branch
    • Purkinje fibers (the end of the system)
  46. Where is the Right bundle branch located?
    right ventricle
  47. three branches of the left bundle branch?
    • o Anterior fascicle
    • o Posterior fascicle
    • o Septal fascicle
  48. What are Purkinje Fibers are branches of?
    The bundle branch that spread through the interventricular septum into the myocardium
  49. Enhanced automaticity?
    • increased firing rate from another pacemaker site other than the SA node
    • spontaneous depolarization of non-pacemaker cells
  50. What is the intrinsic rate of the bundle branches?
    20 to 40 bts/min
  51. Causes of Arrhythmias?
    • o Enhanced automaticity
    • o Reentry
    • o Escape beats (protective)
    • o Conduction disturbances (i.e.: AV block)
  52. What is Reentry?
    • Have to have Circular conduction pathway
    • o Block within the circuit
    • o Delayed conduction with the remainder of the circuit.
  53. Waveform
    positive or negative deflection from the baseline
  54. What is a segment?
    • a line between to waveforms
    • o PR segment
    • o ST segment
  55. What is an Interval?
    • waveform + segment
    • o P-R interval
    • o Q-T interval
  56. What is a complex?
    several waveforms

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