Final answer:
Angiotensin II affects arterioles by causing vasoconstriction, reduces GFR and renal blood flow, stimulates aldosterone release from the adrenal cortex, and indirectly affects fluid regulation in the proximal tubule.
Step-by-step explanation:
The downstream effects of Angiotensin II (ANG2) include vasoconstriction and increased systemic blood pressure, impacting various systems:
- Arterioles: ANG2 acts as a potent vasoconstrictor, particularly at the afferent and efferent arterioles of the glomerulus, which can lead to decreased glomerular filtration rate (GFR) and reduced renal blood flow, especially in situations of blood loss or dehydration to preserve blood volume.
- Cardiovascular Center (CVC): ANG2 raises blood pressure and increases the workload of the heart as part of the body's response to maintain adequate blood pressure.
- Adrenal Cortex: ANG2 stimulates the release of aldosterone, which promotes renal reabsorption of sodium (Na+) and water, further contributing to increased blood pressure over a longer term.
- Hypothalamus: While ANG2 does not act directly on the hypothalamus, it can influence the release of ADH, which has downstream effects on fluid balance and blood pressure.
- Proximal Tubule: ANG2 indirectly promotes the action of aldosterone, leading to increased reabsorption of sodium and water in the nephron, including the proximal tubule, affecting overall fluid volume regulation.