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2011-01-15 13:49:05

Chapter 9
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  1. Difference between cardiac contraction and skeletal muscle contraction
    cardiac contraction lasts for a much longer duration
  2. What separates individual muscle fibers
    intercalate disk, specialized cell membranes with gap junctions that present small amounts of resistance to electrical impulses
  3. cardiac muscle contracts as a
    • syncytium
    • when one becomes excited they all become excited
  4. milivolts of a ventricular AP
    • 105
    • -85 to +20
  5. Plateau phase
    • allows cardiac muscle contraction to last 15x longer then skeletal muscle
    • last about 0.2 seconds
    • immediately after the onset of the AP the cardiac muscle membrane permeability for K decreases, can occur due to Ca influx, prevents early depolarization
    • K permeability returns to normal when the Ca channels close
  6. Cause of cardiac muscle action potentials
    • opening of fast Na channels and slow calcium channels (calcium-sodium channels)
    • slow channels are slower to open and remain open for a longer duration, these cause the plateau phase
    • the entering calcium ions are what cause the contraction of cardiac muscle
    • The SA node's fast channels are inactivated because of its less negative resting state, The AP here is slower.
  7. Length of the normal ventricular refractory period
    .25 - .3
  8. Relative refractory period
    • about .05 seconds in cardiac muscle
    • muscle can be excited but it takes a much larger stimulus
    • the atrial muscle is mush shorts refractory period then ventricular muscle, about .15 sec
  9. How does the AP spread to the interior of cardiac muscle
    • T tubules
    • also release Ca ions into the muscle, determines the strength of contraction
    • 5 times larger in cardiac muscle then in skeletal muscle
    • calcium is made available in the T tubules by a large quantity of mucopolysaccharides that bind and store calcium
  10. Storage of calcium in different muscle tissues
    • in skeletal muscle it is stored in the cistern of SR
    • on cardiac muscle calcium is in the extracellular fluid
  11. length of time for ventricular muscle contraction
  12. Atrial pressure waves; A, V, C
    • A is atrial contraction
    • V is the passive flow of fluid into the atria while the AV valve is closed
    • C is ventricular contraction causing a slight back flow of blood before the AV valves close increasing the pressure of the atria
  13. The ventricle contraction is over after the T wave
  14. Priming feature of atrial contraction
    • about 80% of blood passively flows from the atria to the ventricle
    • the remaining 20% is forced into the ventricle by atrial contraction
    • The body can function without this priming action while at rest, during exercise it can become pathological
  15. Period of rapid ventricular filling
    • as soon as ventricular contraction is over the AV valves open
    • flow is due to the amount of blood that has accumulated in the atria while the AV valve is closed
  16. Isovolemic contraction
    period of ventricular contraction when the AV valves have closed and the ventricle must build up enough pressure the open the Ao valve
  17. period of slow and fast ejection
    • fast ejection is during the first third of ventricular contraction, 70% of volume
    • slow ejection is last two thirds, 30% of volume
  18. calculation of mean BP
    • systolic + 2x diostolic divided by 3
    • diostolic + 1/3 pulse pressure
  19. volume of ventricle
    • 110-120 ml
    • end diastolic volume
  20. Normal EF
  21. other name for moderator band
    septomarginal trabeculea
  22. semilunar valves lack
    chordae tendineae
  23. Incisura
    • occurs in the aortic pressure wave when the aortic valve closes
    • dicrotic notch
  24. First heart sound
    • when the ventricles contract the AV valves close causing the sound
    • low in pitch and long lasting
  25. second heart sound
    • closing of the semilunar valves
    • rapid snap
  26. Stroke work output of the heart
    • the amount of energy that the heart converts to work during each heartbeat
    • Minute work output is how much energy is converted each minute, stroke work times heart rate
  27. Volume pressure work, external work
    work done to move the volume from the veins to the arteries
  28. Kinetic energy of blood flow
    • work done to propel the blood
    • increases during aortic stenosis
  29. Amount of blood in the LV before diastolic pressure rises greatly
    • 150ml
    • fibrous tissue can not stretch much more
  30. max pressure that can be generated by LV
  31. max pressure of RV
  32. Phases of the volume pressure loop
    • phase 1: period of filling, volume of LV increases by about 70ml and pressure rises from 0 to ~5
    • Phase 2: isovolemic contraction; no volume change but pressure rises to equal the diastolic pressure of the aorta
    • Phase 3: ejection; systolic pressure open Ao valve, volume of LV decreases, pressure continues to rise but then peaks and falls
    • Phase 4: isovolemic relaxation; Ao valve closes, pressure falls to level of atrial pressure and mitral valve opens
    • area within this loop is external work, this will increase when the heart pumps more volume
  33. Preload
    end diastolic pressure
  34. Afterload
    the pressure of the aorta
  35. MAin energy sources for cardiac muscle
    oxidation of fatty acids
  36. efficiency of contraction
    • ratio of energy converted to heat to energy converted to work
    • normal heart this is 20-25%
  37. Two system that regulate heart pumping
    • intrinsic, heart pumps out what it receives,
    • control by the autonomic nervous system
  38. Frank starling mechanism
    • the greater the heart muscle is stretched during filling the greater the force of contraction and the greater the quantity of blood pumped into the aorta
    • actin and myosin filiments are brought to a more optimal length
  39. Stretch of the rt atrial wall
    • directly increases heart rate 10-20 percent
    • bainbridge reflex
  40. sympathetic stimulation
    • increase heart rate as well as contractile strength
    • normal conditions has 30% stimulation
  41. distribution of parasympathetic fibers
    SA and AV nodes and atrial muscle
  42. Excess potassium ions in the extracellular fluid
    • causes the heart to become dilated
    • can block conduction
    • decreases the resting membrane potential
  43. Excess calcium ions
    spastic contractions
  44. Effects of body temp on the heart
    increase rate
  45. cardiac output os mainly controlled by
    • the ease of flow through organs, venous return
    • arterial pressure does not diminish CO until mean rises above 160