A dehydrated patient with reduced renal perfusion shows activation of which system that increases renin and angiotensin II?

A dehydrated patient with reduced renal perfusion shows activation of which system that increases renin and angiotensin II?

• A. Renin-angiotensin-aldosterone system (RAAS)
• B. Hypothalamic-pituitary-adrenal axis
• C. Sympathetic nervous system
• D. Natriuretic peptide system

Answer: (A)

When renal perfusion falls as part of dehydration, the kidneys activate a hormonal system that starts with renin release from the juxtaglomerular cells. This initiates the renin-angiotensin-aldosterone system, where renin cleaves angiotensinogen to angiotensin I, and then ACE converts that to angiotensin II. Angiotensin II constricts blood vessels and stimulates aldosterone release, promoting sodium and water reabsorption to raise blood volume and pressure. This cascade directly increases renin and angiotensin II levels, making the renin-angiotensin-aldosterone system the primary driver in this situation. The sympathetic nervous system can boost renin release via beta-1 receptors, but the main system responsible for the rise in renin and angiotensin II here is RAAS. Natriuretic peptides would oppose this response, promoting natriuresis rather than retention.

When renal perfusion falls as part of dehydration, the kidneys activate a hormonal system that starts with renin release from the juxtaglomerular cells. This initiates the renin-angiotensin-aldosterone system, where renin cleaves angiotensinogen to angiotensin I, and then ACE converts that to angiotensin II. Angiotensin II constricts blood vessels and stimulates aldosterone release, promoting sodium and water reabsorption to raise blood volume and pressure. This cascade directly increases renin and angiotensin II levels, making the renin-angiotensin-aldosterone system the primary driver in this situation. The sympathetic nervous system can boost renin release via beta-1 receptors, but the main system responsible for the rise in renin and angiotensin II here is RAAS. Natriuretic peptides would oppose this response, promoting natriuresis rather than retention.