Exam 1 Review:  Chapter 19:  Other Regulation of Blood Pressure/Blood Volume

myogenic control of blood pressure - A localized smooth muscle cellular reflex in which the stimulus of stretching in the smooth muscles in the walls of small arterioles (as a result of increased blood pressure to the region) causes an immediate response causing vasoconstriction and a decrease in blood flow; this control adjusts local blood flow to maintain adequate blood supply for local metabolic needs (especially O₂ consumption).

autoregulation (of blood pressure) - A series of local mechanisms (independent of the nervous system) which control local blood flow and blood pressure to insure adequate blood supply to specific capillary beds in the face of systemic blood pressure changes:  (1) temperature -- dermal capillary beds respond with vasoconstriction to environmental cold and with vasodilation to environmental heat; (2) myogenic control of blood pressure -- see definition above; and (3) smooth muscle response to local hormones and metabolites -- see definition of vasoactive factors, parts (3) and (4) below.

vasoactive factors - A diverse group of regulatory substances which can affect the degree of vasomotor tone including (1) neurotransmitters:  norepinephrine (↑ = vasocontriction) and acetyl choline (↓ = vasodilation); (2) hormones:  atrial natriuretic peptide = ANP (↓) and epinephrine = adrenalin (↑), aldosterone (↑), ADH = vasopressin (↑), angiotensins I & II (↑); (3) local hormones:  serotonin (↑), and prostaglandins (↓), histamine (↓) and endothelium derived relaxation factor (EDRF) =  nitrous oxide (NO) (↓); and (4) metabolites:   H⁺ (↓), K⁺ (↓), CO₂ (↓).

endothelium derived relaxation factor (EDRF)  = nitrous oxide (NO) - A local  vasoactive hormone, which is a gas, released in response to the increased blood flow (shear stress = increased friction of blood against endothelial cells) and stimulates a corresponding vasodilation in nearby vascular smooth muscle cells.

List:

4. the chemicals monitored by the CNS chemoreceptors for making short term adjustments in blood pressure by autonomic reflexes.

          metabolites:   H⁺, K⁺, CO₂ stimulate local vasodilation; O₂ stimulates local vasoconstriction.

          [and local hormone:  endothelium derived relaxation factor (EDRF) =  nitrous oxide (NO) stimulates local vasodilation.]

Describe:

12. the autoregulation of blood pressure.

The autoregulation of blood pressure is controlled by a series of local mechanisms (independent of the nervous system) which control local blood flow and blood pressure to insure adequate blood supply to specific capillary beds in the face of systemic blood pressure changes.  These local mechanisms include: 

(1) temperature:  dermal capillary beds respond with vasoconstriction to environmental cold and with vasodilation to environmental heat.

(2) myogenic control of blood pressure:  A localized smooth muscle cellular reflex in which the stimulus of stretching in the smooth muscles in the walls of small arterioles (as a result of increased blood pressure to the region) causes an immediate response causing vasoconstriction and a decrease in blood flow; this control adjusts local blood flow to maintain adequate blood supply for local metabolic needs (especially O₂ consumption).

(3) smooth muscle response to local hormones and metabolites:

          (3a)  local hormones:  serotonin stimulates local vasoconstriction, while prostaglandins, histamine and endothelium derived relaxation factor (EDRF) =  nitrous oxide (NO) stimulate local vasodilation;
          (3b)  metabolites:   H⁺, K⁺, CO₂ stimulate local vasodilation; O₂ stimulates local vasoconstriction.