What mechanisms control blood pressure in nephrons?

Blood pressure in nephrons is controlled by the renin-angiotensin-aldosterone system and the autoregulation mechanism of the kidneys.

The renin-angiotensin-aldosterone system (RAAS) and the autoregulation mechanism of the kidneys are the two primary mechanisms that control blood pressure in nephrons. The RAAS is a hormone system that regulates blood pressure and fluid balance. When blood pressure drops, the juxtaglomerular cells in the kidneys release renin, an enzyme that triggers a cascade of reactions. Renin converts angiotensinogen, a protein produced by the liver and released into the bloodstream, into angiotensin I. This is then converted into angiotensin II by an enzyme called angiotensin-converting enzyme (ACE). Angiotensin II is a potent vasoconstrictor, meaning it narrows the blood vessels and increases blood pressure. It also stimulates the release of aldosterone, a hormone that promotes sodium and water reabsorption in the kidneys, further increasing blood pressure.

The autoregulation mechanism of the kidneys also plays a crucial role in controlling blood pressure in nephrons. This mechanism ensures a constant blood flow to the kidneys, despite changes in systemic blood pressure. It involves two primary processes: the myogenic mechanism and the tubuloglomerular feedback mechanism. The myogenic mechanism responds to changes in blood pressure in the renal arterioles. When blood pressure increases, the smooth muscle in the arteriole walls contracts, reducing the diameter of the blood vessels and maintaining a constant blood flow. Conversely, when blood pressure decreases, the smooth muscle relaxes, increasing the diameter of the blood vessels and ensuring a steady blood flow. The tubuloglomerular feedback mechanism involves the macula densa cells in the distal tubule of the nephron. When these cells detect an increase in the flow of filtrate, they signal the afferent arterioles to constrict, reducing glomerular filtration rate and maintaining blood pressure.