Blood Pressure Regulation (Baroreflex, RAAS) - Anatomy and Physiology
- Which blood pressure control mechanism acts within seconds?
- The baroreceptor reflex. The RAAS and other hormonal mechanisms take minutes to days.
- Angiotensin II stimulates which adrenal cortex hormone that increases Na+ reabsorption?
- Aldosterone, from the zona glomerulosa.
- Which enzyme converts angiotensin I to angiotensin II, and where is it most concentrated?
- Angiotensin-converting enzyme (ACE), most abundant on lung capillary endothelium.
- Which cells secrete renin?
- Juxtaglomerular (granular) cells in the wall of the afferent arteriole.
- Which cranial nerves carry baroreceptor signals from the carotid sinus and aortic arch?
- The glossopharyngeal nerve (IX) from the carotid sinus and the vagus nerve (X) from the aortic arch.
- A patient takes an ACE inhibitor. What happens to angiotensin II, aldosterone, and blood pressure?
- All three decrease. Less angiotensin II means less vasoconstriction and less aldosterone-driven sodium and water retention.
- Which reaction does renin catalyze?
- Conversion of angiotensinogen (made by the liver) to angiotensin I.
- Which brain region integrates the baroreceptor reflex?
- The cardiovascular center of the medulla oblongata.
- Which hormone, released by stretched atrial muscle cells, opposes the RAAS?
- Atrial natriuretic peptide (ANP). It promotes Na+ and water excretion, causes vasodilation, and inhibits renin and aldosterone.
- Where are the main arterial baroreceptors located?
- In the carotid sinuses and the aortic arch.
- A person stands up quickly and blood pressure briefly drops. How does the baroreflex respond?
- Baroreceptor firing falls, so sympathetic output rises and vagal output falls, raising heart rate, contractility, and vasoconstriction.
- What are the three main stimuli for renin release?
- Low renal perfusion pressure, low NaCl delivery sensed by the macula densa, and sympathetic stimulation of beta-1 receptors.