Explain the factors that contribute to the formation of filtrate and what might happen in the event of changes in blood pressure

Angiotensin II

In response to low Na+ filtrate levels, via tubuloglomerular feedback, angiotensin II will act on changing efferent arterioles diameter

Renin-Angiotensin Aldosterone System

regulates blood pressure and fluid balance. It works to increase blood pressure by increasing sodium reabsorption, water retention, and vascular tone

Baroreceptors

Carotid and aortic baroreceptors are responsible for detecting changes in blood pressure

GFR

measures how well your kidneys are filtering waste from your blood and specifically measures how much blood passes through the glomeruli in your kidneys each minute

autoregulation of GFR

High NaCl levels in the tubules, as sensed by the macula densa cells, will primarily induce vasoconstriction of the afferent arteriole and a decrease in the GFR, also known as tubuloglomerular feedback. Additionally, high NaCl levels will inhibit renin release

what drives filtration

Net driving force pushes fluid out of capillary and into the Bowman’s capsule. Volume of fluid that filters into the Bowman’s capsule per unit time = GFR 125mL/min or 180L/day

Hydrostatic Pressure (in capillaries)

55 mmHg - drives water and solutes out of glomerulus (main force that drives fluid out of the capillaries and into the Bowman’s capsule)

Colloid osmotic pressure (in capillaries)

30 mmHg - acts against filtration

Fluid pressure (in capsule)

15 mmHg - acts against filtration

increased BP

Higher blood pressure increases glomerular capillary hydrostatic pressure, leading to a greater driving force for filtration and thus a higher GFR

Decreased BP

Lower blood pressure reduces glomerular capillary hydrostatic pressure, decreasing the driving force for filtration and potentially leading to a lower GFR

renal autoregulation

The kidneys have intrinsic mechanisms that can help maintain a stable GFR despite changes in systemic blood pressure by adjusting the diameter of the afferent and efferent arterioles, which control blood flow into and out of the glomerulus

extrinsic regulation

The body also uses extrinsic mechanisms, such as the renin-angiotensin system and sympathetic nervous system, to regulate blood pressure and, indirectly, GFR

High GFR

If blood pressure is too high, the GFR can increase significantly, potentially leading to excessive fluid and electrolyte loss in the urine

low GFR

If blood pressure is too low, the GFR can decrease significantly, potentially leading to a buildup of waste products in the blood and impairing kidney function

Role of afferent and efferent arterioles

Constriction of afferent arteriole: decreased GFR

Constriction of efferent arteriole: increased GFR