Discuss briefly the mechanisms that regulate arterial blood pressure including the sympathetic nervous system, the renin-angiotensin-aldosterone system (RAAS), and renal function?
What will be an ideal response?
• The brain integrates information from sensors called baroreceptors that continually measure blood pressure.
• Various hormones such as norepinephrine and epinephrine control resistance of the blood vessels.
- Norephinephrine acts as a vasoconstrictor. When the diameter of blood vessels is decreased (either by norepinephrine or by a disease process such as atherosclerosis), blood pressure will increase.
- Vasodilation will decrease blood pressure.
• Other hormones including aldosterone and vasopressin (ADH) also assist in blood pressure control.
- Aldosterone is released to increase sodium reabsorption and, with vasopressin, will increase water resorption and blood volume, leading to an increase in blood pressure.
• Additionally, the kidneys respond to their own baroreceptors.
- If blood pressure is low, renin is released, which in turn controls the levels of angiotensin II, which causes vasoconstriction and thus also increases blood pressure.
• Proper renal function is necessary for the actions of RAAS and thus abnormalities in BP can be seen in conditions like chronic kidney disease and acute kidney injury.
• All of these responses cause an overall increase in heart rate, stroke volume, and, ultimately, blood pressure.
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