Urine 3L

Flashcards covering GFR regulation, tubular reabsorption, PCT functions, nephron function, and countercurrent mechanisms.

What is GFR (Glomerular Filtration Rate)?

The rate at which the kidneys filter blood to form filtrate; controls urine volume and composition.

What are the two main ways GFR is regulated?

Intrinsic control (renal autoregulation) by the kidney itself;

Extrinsic control via nervous system and hormones.

How does the kidney adjust GFR?

Changes diameter of the afferent arteriole; Alters the surface area of the filtration membrane.

What does the nervous system do to GFR?

It can lower GFR (e.g., during stress or low BP).

What can hormones do to GFR?

Some hormones can raise GFR (e.g., atrial natriuretic peptide).

What is tubular reabsorption?

Movement of substances (water, nutrients, ions) from kidney tubules back into the blood.

What processes are involved in reabsorption?

Diffusion, osmosis, and active transport.

What is transport maximum (Tm)?

The highest rate at which a substance can be reabsorbed, depending on the number of transport proteins.

What happens if glucose exceeds its transport maximum (~375 mg/min)?

Not all glucose is reabsorbed; the excess remains in the urine.

What does the PCT reabsorb?

About 65% of filtered sodium and water; Nearly all glucose and amino acids; Other ions like potassium, calcium, and bicarbonate.

What does the PCT secrete?

Wastes, drugs, and hydrogen ions into the tubule for excretion.

How does the PCT help maintain homeostasis?

It stabilizes fluid and electrolyte balance by reclaiming solutes and water.

Why is tubular reabsorption important?

Prevents the loss of vital substances like water, glucose, and ions;

Maintains proper fluid and electrolyte balance;

Ensures waste products stay in the tubule for excretion.

What are the general functions of the nephron?

Filter blood (in renal corpuscle);

Reabsorb vital substances (in tubules);

Secrete waste/excess substances into tubules;

Concentrate urine (using loop of Henle & collecting duct).

What is the countercurrent multiplier?

A mechanism in the nephron loop that creates a salt gradient in the medulla to allow for water reabsorption and urine concentration.

Why is the countercurrent multiplier important?

It helps the body conserve water, especially during dehydration.

What is the countercurrent exchanger?

The vasa recta, which preserves the salt gradient established by the multiplier.

Why is the countercurrent exchanger significant?

It prevents the salt gradient from being washed away by blood flow, ensuring proper urine concentration.