Question

As a result of very low arterial blood pressure, what happens to glomerular hydrostatic pressure?

Answer 1

The glomerular filtration rate (GFR) describes the total amount of blood filtered by the glomerulus into the Bowman's capsule of all the nephrons per unit of time in the kidneys. It depends upon the hydrostatic pressure and osmotic pressure of both glomerulus and Bowman's capsule.

Complete answer:
Hydrostatic pressure is defined as the pressure formed by a fluid against the surface; thus, glomerulus hydrostatic pressure can be defined as the pressure formed by the blood against the glomerular capillary walls through which it flows. It is the opposing force to osmotic pressure, which prevents osmosis.
The hydrostatic pressure of the glomerulus forces fluid out of the glomerulus into the glomerular capsule, and this capillary pressure is regulated by the afferent and efferent arterioles. The afferent arterioles supply blood to the glomerular capillaries, while those that converge from the glomerulus are known as efferent arterioles. These are branches of the renal artery. To elaborate, the renal artery enters the hilum of kidney branches to form the interlobar arteries, which give rise to interlobular arteries, which finally branch to form afferent arterioles.

The constriction of the efferent arteriole and dilation of the afferent arteriole result in the increase of glomerular hydrostatic pressure and thereby increases the glomerular filtration rate. Conversely, dilation of the efferent arteriole and constriction of afferent arteriole will decrease the glomerular filtration rate and the hydrostatic pressure of these capillaries will reduce when glomerular blood flow decreases as a result of low arterial blood pressure or reduced cardiac output.

Thus, very low arterial blood pressure will reduce glomerular hydrostatic pressure significantly.

Note:
Bowman’s capsule hydrostatic pressure is the opposing pressure acting against the hydrostatic pressure of the glomerulus. An increased Bowman's capsule hydrostatic pressure will decrease the glomerular filtration rate, while a decrease in Bowman's capsule hydrostatic pressure will increase the glomerular filtration rate.