Regulation of Blood Pressure

on 7.7.06 with 0 comments

  1. Nervous System Control
    • control of arteriole diameter
    • directs blood flow to proper organs and tissues that need it
      • baroreceptors/chemoreceptors/brain --> afferent nerve fibers --> medulla (vasomotor center) --> vasomotor (efferent) nerve fibers --> smooth muscle of arterioles
  2. Vasomotor Fibers to Smooth Muscle of Arterioles
    • sympathetic fibers that release norepinephrine (NE); cause vasoconstriction of arterioles
  3. Vasomotor Center of the Medulla
    • sympathetic neuron cell bodies in the medulla
    • receive input from baroreceptors, chemoreceptors, and brain
    • vasomotor tone - general constricted state of arterioles set by vasomotor center
  4. Baroreceptors
    • blood pressure receptors large arteries (carotid sinuses, aortic arch, neck/thorax arteries)
    • send blood pressure information to vasomotor center of medulla
      • increased pressure --> decreased pressure --> inhibits vasomotor center -> stimulates vasomotor center -> vasodilation vasoconstriction
  5. Chemoreceptors
    • located in aortic arch and carotid arteries
      • carotid and aortic bodies
    • monitor OXYGEN and pH levels of the blood
      • low OXYGEN or ------------> increase blood pressure, return blood to lungs quickly
      • low pH
  1. Higher Brain Centers Control on BP
    • hypothalamus & cortex also effect vasomotor area
  2. Chemical Controls of Blood Pressure
    • hormones of adrenal medulla - "fight-or-flight" response to fear; release of norepinephrine and epinephrine from adrenal medulla; causes vasoconstriction and increased BP
    • atrial natriuretic factor (ANF) - secreted by the atria of the heart, promotes general decline in blood pressure kidney releasing more Na+ and water, reducing fluid volume
    • antidiuretic hormone (ADH) - released by the hypothalamus, causes increase in blood pressure by getting the kidneys to conserve water in the body; eg. during hypotensive situations
    • endothelium derived factors
      • endothelin - strong vasoconstrictor
      • endothelium derived relaxing factor - vasodilation
    • alcohol - causes vasodilation
  3. Renal (Kidney) Regulation
    • direct regulation - fluid loss through urine
      • a. low pressure/volume --> conserve water
      • b. high pressure/volume --> release more water
    • renin-angiotensin mechanism
      • low blood pressure --> release of renin --> formation of angiotensin II --> vasoconstriction
      • release of aldosterone --> Na+/water reabsorption (by kidney)

Category: Physiology Notes



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