THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -ATP is released and calcium increases in granular and smooth muscle cells of the afferent arteriole. This causes arteriole constriction and decreased renin release. This overall process helps decrease GFR and maintain it in a limited range, albeit slightly higher than baseline.

Detailed explanation-2: -Overall the constriction of the afferent arteriole decreases both blood flow and filtration pressure where as constricting the efferent arteriole decreases blood flow but increases filtration pressure.

Detailed explanation-3: -Falling blood pressure does the opposite: dilate the afferent arteriole and preserve blood flow to the kidney. Secondly, the renin-angiotensin-aldosterone system acts to preserve GFR. The juxtaglomerular cells in the afferent arteriole release renin in response to decreased stretch.

Detailed explanation-4: -The afferent and efferent arterioles constrict in response to -adrenergic stimulation. This vasoconstriction predominantly affects the afferent arteriole, effectively reducing hydrostatic pressure within the glomerular capillary lumen and decreasing glomerular filtration.