Physiology Ch. 14

  1. Cardiac Output (CO)
    • Volume of blood pumped per min by each ventricle
    • CO = SV(Stroke volume) x HR
  2. Regulation of Cardiac Rate
    Without neuronal influences from the sympathetic/parasympathetic nervous systems, the heart beats according to the rhythm set by SA node
  3. Regulation of Cardiac Rate
    Autonomic effect:
    • Sympathetic and parasympathetic nerve fibers to the heart modify the rate of spontaneous depolarization
    • Innervate the SA node
    • NE and Epi stimulate
    • ACh depresses
  4. Regulation of Cardiac Rate
    Cardiac control center (medulla)
    Coordinates activity of autonomic innervation
  5. Regulation of Stroke Volume
    3 variables
    • EDV- (increase in EDV increases SV)
    • Total peripheral resistance (TPR)
    • Contractility
    • A change in any of these 3 will change the SV
  6. EDV (End diastolic volume)
    Volume of blood in the ventricles at the end of diastole
  7. Total peripheral resistance (TPR)
    Frictional resistance or impedance to blood flow in the arteries
  8. Contractility
    Strength of ventricular contraction
  9. End diastolic volume
    • Workload on the heart prior to contraction (preload)
    • SV directly proportional to preload
    • Increase in EDV results in an increase in SV
    • SV directly proportional to contractility
    • Strength of contraction varies directly with EDV
  10. Ejection fraction
    • EF = SV divided by EDV
    • Normally is 60% if below than this the heart is failing
    • Clinical diagnostic tool
  11. TPR(Total peripheral resistance)
    • Impedance to the ejection of blood from ventricles into arteries
    • Pressure in arteries before ventricle contracts is a function of TPR
  12. SV inversely(opposite) proportional to TPR
    Greater the TPR, the lower the SV
  13. Frank-Starling Law of the Heart
    • Relationship between EDV, contraction strength and SV
    • Just the right amount of actin and myosin, to make the greatest amount of contraction
    • Explains how the heart can adjust to rise in TPR
  14. Extrinsic Control of Contractility
    • Strength of contraction at any given fiber length
    • Depends upon sympathoadrenal system
    • NE and Epi produce an increase in contractile strength
    • Parasympathetic stimulation- does not directly influence contraction strength
  15. CO affected 2 ways
    • Contractility
    • HR
  16. Venous Return (the return of blood via veins)
    • veins have thinner walls
    • 2/3 blood volume is in veins
    • EDV, SV, CO affect venous return
  17. Skeletal muscle pump
    Aid venous return
  18. Blood Volume
    • 2/3 of total body Water within the cells
    • 1/3 total body water ( 80% interstitial fluid, 20% blood plasma)
    • Maintained by constant balance between water loss and gain
  19. Causes of Edema- excessive accumulation of tissue fluid
    • High arterial pressure
    • Venous obstruction
    • Leakage of plasma proteins into interstitial fluid
    • Decreased plasma protein
    • Obstruction of lymphatic drainage
  20. Regulation of Blood volume by the Kidneys
    • Volume of urine excreted can be varied by changes in reabsorption of filtrate
    • Adjusted according to needs of body by action of hormones
  21. Regulation of Blood Volume can be influenced by:
    • ADH
    • Aldosterone
    • Renin-Angiotension-Aldosterone System
  22. Resistance
    Influenced by the length of vessel, viscosity(thickness) of the blood and radius of the vessel
  23. Extrinsic Regulation of Blood Flow
    Controlled by autonomic nervous system and endocrine system
  24. Sympathoadrenal system
    Increases CO & TPR
  25. Parasympathetic nervous system
    Promotes vasodilation to the digestive tract, external genitalia, and salivary glands
  26. Aerobic requirements of the Heart
    Survival requires that the heart and brain receieve adequate blood supply at all times
  27. Coronary arteries supply enormous # of____
  28. Systole contracts the coronary_____
    blood vessels
  29. Diastole increases blood flow to the ____ ____
    heart muscle
  30. Coronary blood flow
    Coronary blood flow is the flow of blood through the coronary vessels of the heart to supply oxygen to the heart muscle
  31. Sympathetic nervous system
    • Vasoconstriction of coronary arteries at rest (alpha receptors)
    • Vasodilation of the coronary arteries during activity (beta receptors)
  32. Blood flow through skeletal muscles
    • Sympathetic: Vasoconstrict at rest
    • Parasympathetic/Sympathetic: Vasodilate during activity
  33. Circulatory changes during exercise
    • Vascular resistance decreases to skeletal muscles
    • Blood flow to skeletal muscles increases
    • SV and CO increase-blood flow to brain stays the same
    • HR increases to maximum of 190 beats/min-ejection fraction increases due to increased contractility
  34. Vascular resistance:
    • Decreases to skeletal muscle
    • Increases to GI tract and skin
  35. Cerebral circulation
    Cerebral blood flow is not normally influenced by sympathetic nerve activity
  36. Thermoregulation
    • Blood flow through the skin is adjusted to maintain deep-body temperatures at about 37C
    • Occurs due to: Vasoconstriction/vasodilation arteries
  37. Bradykinin
    Sweat glands secrete bradykinin which increases blood flow to skin and sweat glands
  38. Blood Pressure
    • Is the pressure of arterial blood, regulated by blood volume, TPR, and cardiac rate
    • Negative feedback
  39. Blood Pressure
    3 most important variables are:
    • HR
    • SV
    • TPR
    • Increase in each of these will result in an increase in BP
  40. BP can be regulated by:
    • Kidney (SV)- amount of water to reabsorb
    • Sympathoadrenal system (HR + TPR + SV)
  41. Auscultation: Listening through stethoscope
    Art of listening
  42. Laminar flow:
    • Normal blood flow
    • Blood in the central axial stream moves faster than blood flowing closer to artery wall
    • Smooth and silent
  43. Turbulent flow and vibrations(of blood flow) produced in the artery when cuff is:
    Greater than diastolic pressure and lower than systolic pressure
  44. Blood pressure cuff is inflated above____
    systolic pressure
  45. As cuff pressure is lowered, the blood will flow only when_____ _____ is _____ cuff pressure, producing the sounds of Korotkoff.
    systolic pressure; above
  46. Korotkoff sounds will be heard until cuff pressure equals_____ _____, causing sounds to disappear.
    diastolic pressure
  47. Average arterial BP
    120/80 mm Hg
  48. Average pulmonary BP
    22/8 mm Hg
  49. Pulse Pressure
    • The expansion of the artery in response to the volume of blood ejected by the left ventricle
    • PP= systolic pressure - diastolic pressure
  50. MAP (mean arterial pressure)
    • Represents the average arterial pressure during the cardiac cycle
    • Is closer to diastolic presure, as the perois of diastole is longer than the period of systole
    • MAP = diastolic pressure + 1/3( pp)
  51. Hypertension (HTN)
    • Blood pressure in excess of normal range for age and gender
    • High BP
    • > 140/90 mm Hg
  52. Primary or essential hypertension
    • Is the result of a complex or poorly understood process
    • Naturally run high
  53. Secondary hypertension
    Is a result of a known disease process
  54. Essential Hypertension
  55. Dangers of Hypertension
    • Silent killer
    • Atherosclerosis
    • Congestive heart failure
    • Damage cerebral blood vessels- cerebral vascular accident (stroke)
  56. Congestive Heart failure
    • CO is insufficient to maintain the blood flow required by the body
    • Increase venous volume and pressure
  57. Congestive heart failure is caused by:
    • MI (most common cause)
    • Congenital defects
    • Hypertension
    • Aortic valve stenosis
    • Disturbances in electrolyte concentrations
  58. Congestive heart failure is treated with medications:
    • Digitalis
    • vasodilators
    • diuretics
Card Set
Physiology Ch. 14
Cardiac Output, Blood Flow, Blood Pressure