Cardiovascular System

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Author:
bosebenj
ID:
244130
Filename:
Cardiovascular System
Updated:
2013-10-31 15:42:31
Tags:
Physiology
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Description:
This set is mainly for Montemayor
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  1. Wolff-Parkinson-White (WPW) Syndrome-
    Common Accessory Pathway
    • -Alternate path around AV node(Bundle of Kent)
    • -AP conducted directly: atria--> ventricle
    • -Faster than normal AV nodal pathway
    • -Ventricular depolarization is generally slower than normal
  2. Purkinje fibers
    • -Arise from RBB and Ant + Post. LBB
    • -Complext netowrk of conducting fibers spread out over subendocardial surfaces of R and L ventricles
    • -Largest diameter cardiac cells
    • -Fastest conduction velocity in the heart!
  3. In what order does repolarization occur.
    • Opposite depolarization:
    • Last Cells to depolarize are the first to repolarize.
  4. Fastest conduction
    • Purkinje fibers
    • (larger diameter equals less resistance
  5. Slowest Conduction
    • AV node, SA node
    • (small diameter=more resistance)
  6. Cardiac Muscle
    • -Striated
    • -mononucleated (sometimes binucleated)
    • -intercalated disks(Gap Junctions)
    • -Many Mitochondria
    • -T-tubules and SR (CA2+ stores in ECF and SR)
    • -Ca2+ regulation of contraction (binds troponin)
    • -Relatively slow speed of contraction (~250 ms)
  7. Biomarkers of Myocardial Injury
    • Troponin (cTnT, cTnI)
    • -Increasingly utilized as biomarker for cardiac damage
    • CK-MB
    • -Creatine kinase isoform specific to cardiac muscle.
  8. Functional Syncytium
    • -Electrical Syncytium
    • -Intercalated disks
    • -All or None Law for the Heart
  9. Electrical syncytium
    All cardiac m. cells contract in a synchronous manner
  10. Intercalated disks
    • Connect cardiac cells through mechanical junctions and electrical connections.
    • -Desmosomes
    • -Gap junctions
  11. All or None Law for the Heart
    • Either all cardiac cells contract or none do
    • -no variation in force production via motor unit recruitment
    • Due to functional syncytium and conduction system
    • Contractility (modified by altering sympathetic N.S. input) ((increase Ca2+ permeability)
  12. Extracellular Ca2+ in Cardiac Contraction
    • -Influx of extracellular Ca2+ is required for additional Ca2+ release from the SR.
    • -Ca2+ influx from ECF via voltage gated channels
    • -Release of Ca2+ from the SR also required
    • --Ca2+ induced ... not finished...
  13. Relaxation
    • -Removal of Ca2+ to the ECF
    • -Sequestering Ca2+ into the SR
  14. Removal of Ca2+ to the ECF
    • -Sarcolemmal 3Na+ -1Ca2+ antiporter
    • -Sarcolemmal Ca2+ pump
  15. Sequestering Ca2+ into the SR
    • SR Ca2+ pump (SERCA)
    • -Regulated by phospholamban
  16. Can we have tetanus in the heart?
    No, it would be fatal
  17. Pacemaker cells
    • -no resting potential
    • -Spontaneous slow depolarization phase
  18. Non-pacemaker cells
    True resting potential (~-80 to -90 mV)
  19. Fast Response AP
    • Atrial, ventricular myocytes, and Purkinje fibers
    • -Fast upstroke
    • -Early, partial repolarization
    • -Plateau
    • -Final repolarization
    • -Resting potential
    • Threshold -70 mV
  20. Slow response AP
    • SA and AV nodes
    • -Gradual upstroke
    • -Absent: early repolarization
    • -Absent: Plateau is less prolonged and flat or absent
    • -Transition from plateau to final repolarization is less distinct
    • -no true resting potential
    • Threshold -40mV
  21. 4 Major Time-dependent and Voltage-gated Currents
    • 1. Na+ current
    • -rapid depolarization
    • 2. Ca2+ current
    • -rapid depolarization
    • 3. K+ current
    • Repolarization
    • 4. Pacemaker ("funny") current
    • -slow depolarization phase in SA and AV nodal cells
  22. Pase 0 Upstroke
    Slow vs Fast
    • Fast if upstroke is due to both Ina and Ica
    • Slow is upstroke is only due to Ica
  23. Phase 1: Early, rapid (partial) repolarization
    • Activation of minor K+ current
    • Inactivation of Ina or Ica
  24. Phase 2: Plateau phase
    Continued influx of Ca2+ countered by small K+ current
  25. Phase 3: Final Repolarization
    Depends on Ik in all cells
  26. Phase 4: Electrical diastolic phase
    • Changes in Ik, Ica, and If produce pacemaker activity in SA and AV nodal cells
    • Atrial and ventricular muscle have no time-dependent currents during phase 4
  27. Conduction Velocity
    • 1. Amplitude of action potential
    • 2. Rate of change of potential during phase 0 (Slope of depolarization)
  28. Anatomic variables which can alter conduction velocity
    • -Congenital accessory pathways
    • -Degeneration of conduction system
  29. Ectopic Foci
    • Generate action potentials that do not follow normal conduction pathways.
    • -
  30. Causes of Ectopic Foci
    • -Local areas of ischemia
    • -Mildly toxic conditions can irritate fibers of the A-V node, Purkinje system, or myocardium. (ie various drugs, nicotine, caffeine, alcohol.
    • - Calcified plaques irritating adjacent cardiac fibers
    • -Cardiac catheterization( mechanical initiation of premature contractions.)

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