Question

which mechanism regulating blood flow within the kidney depends upon a characteristic shared by most smooth muscle cells of the body?
a.) renin - angiotensin - aldosterone - system
b.) myogenic mechanism
c.) paracrine signalling
d.) tubuloglomerular feedback

Explanation:

The myogenic mechanism is a property of smooth muscle cells. When the blood pressure (and thus stretch) in the afferent arteriole of the kidney changes, the smooth muscle in the arteriole wall responds. If blood pressure increases (stretching the arteriole), the smooth muscle contracts (a characteristic of smooth muscle - responding to stretch by contracting) to constrict the arteriole and reduce blood flow to the glomerulus. If blood pressure decreases (less stretch), the smooth muscle relaxes (another smooth - muscle characteristic - relaxing when less stretched) to dilate the arteriole and increase blood flow.

• The Renin - Angiotensin - Aldosterone System (RAAS) is a hormonal system that regulates blood pressure and fluid balance, not directly dependent on a smooth - muscle - cell characteristic.
• Paracrine signaling involves local chemical messengers (e.g., in the kidney, adenosine in tubuloglomerular feedback can act as a paracrine signal), but it is not based on a general smooth - muscle - cell property.
• Tubuloglomerular feedback is a paracrine - mediated mechanism (involving macula densa cells and juxtaglomerular cells) that helps regulate glomerular filtration rate, not a smooth - muscle - cell - characteristic - based mechanism.

Answer:

B. Myogenic mechanism