Final answer:
The myogenic mechanism in arterioles regulates blood flow by responding to changes in blood pressure. The tubuloglomerular feedback mechanism involves the release of ATP and adenosine to stimulate vasoconstriction of the afferent arteriole. Hydralazine works on the arterioles by causing vasodilation and decreasing vascular resistance.
Step-by-step explanation:
The myogenic mechanism in arterioles regulates blood flow by responding to changes in blood pressure. When blood pressure increases, smooth muscle cells in the arteriole constrict to resist the pressure and maintain blood flow. Conversely, when blood pressure drops, the smooth muscle cells relax to lower resistance and allow for continued flow.
The tubuloglomerular feedback mechanism, involving the juxtaglomerular apparatus (JGA) and paracrine signaling, also plays a role in regulating blood flow. Macula densa cells in the distal convoluted tubule detect changes in fluid flow rate and Na+ concentration, and release ATP and adenosine in response. These molecules act locally to stimulate vasoconstriction of the afferent arteriole, reducing blood flow and glomerular filtration rate (GFR).
In summary, hydralazine works on the arterioles by causing vasodilation and decreasing vascular resistance, leading to decreased blood pressure. It primarily affects the afferent arterioles, which regulate blood flow to the glomerulus and play a role in controlling GFR.