Final answer:
The homeostatic mechanism for controlling glomerular filtration rate involves the arteriole myogenic mechanism and the tubuloglomerular feedback mechanism.
Step-by-step explanation:
The homeostatic mechanism for controlling glomerular filtration rate involves two main mechanisms: the arteriole myogenic mechanism and the tubuloglomerular feedback mechanism.
Arteriole Myogenic Mechanism:
When blood pressure increases, smooth muscle cells in the wall of the afferent arteriole contract to resist the pressure, resulting in little change in flow. Conversely, when blood pressure drops, the smooth muscle cells relax to lower resistance, allowing a continued even flow of blood.
Tubuloglomerular Feedback Mechanism:
Specialized macula densa cells in the tubule respond to changes in fluid flow rate and sodium concentration. When glomerular filtration rate (GFR) increases, the macula densa cells release ATP and adenosine, which stimulate the myogenic juxtaglomerular cells of the afferent arteriole to constrict, reducing blood flow and GFR. Conversely, when GFR decreases, the release of ATP and adenosine is decreased, allowing the afferent arteriole to dilate and increase GFR.