Final answer:
The glomerular filtration rate (GFR) is regulated by the renin-angiotensin-aldosterone system, the sympathetic nervous system, and autoregulation.
Step-by-step explanation:
The glomerular filtration rate (GFR) is regulated by several factors:
- Renin-angiotensin-aldosterone system (RAAS): When there is a decrease in blood pressure or blood volume, the juxtaglomerular cells in the kidney release renin. Renin initiates a cascade that leads to the production of angiotensin II, a potent vasoconstrictor that increases blood pressure. Angiotensin II also stimulates the release of aldosterone, which increases sodium reabsorption and water retention, ultimately increasing GFR.
- Sympathetic nervous system: Activation of the sympathetic nerves to the kidney constricts the afferent arterioles, decreasing blood flow and GFR. This mechanism is important during times of low blood pressure, such as during exercise or hemorrhage.
- Autoregulation: The kidneys have the ability to maintain a relatively constant GFR even when systemic blood pressure changes. The mechanism involves the contraction and relaxation of the smooth muscles in the afferent and efferent arterioles, allowing for a consistent GFR.