5.3.3 maintaining water and nitrogen balance in the body

What is the role of ADH?

ADH (anti-diuretic hormone) controls water balance by changing the permeability of the kidney tubules.

Where is ADH produced?

ADH is released by the pituitary gland when blood concentration is too high.

How does ADH work?

ADH increases the permeability of kidney tubules so more water is reabsorbed into the blood, producing smaller, more concentrated urine.

What happens when blood concentration is too low?

Less ADH is released, kidney tubules become less permeable, so less water is reabsorbed and more dilute urine is produced.

What type of feedback loop controls ADH release?

A negative feedback loop — when blood concentration changes, ADH secretion changes to reverse it.

What is osmosis?

Osmosis is the movement of water molecules from a region of high concentration to a region of low concentration across a partially permeable membrane.

What happens if water concentration in the blood increases?

Water moves into cells by osmosis, cells expand and may burst.

What happens if water concentration in the blood decreases?

Water moves out of cells by osmosis, cells shrink as they lose water.

What are the main roles of the kidneys?

They filter out waste products and selectively reabsorb useful substances like glucose, ions and water.

What is urea and how is it formed?

Urea is a waste product formed in the liver when excess amino acids are broken down (deamination).

How is water lost from the body besides urine?

Through exhalation from the lungs and sweat from the skin (not under conscious control).

How are ions balanced in the body?

Ions are taken in from food; excess ions are lost in sweat and urine, with kidney reabsorption ensuring blood ion levels are maintained.

What is kidney failure?

Kidney failure occurs when the kidneys stop working, leading to a build-up of waste products that can be harmful and fatal if untreated.

What is dialysis?

A treatment that carries out the function of the kidneys using a partially permeable membrane and dialysis fluid to remove waste products while keeping useful substances.

How often is dialysis needed?

Usually three times a week, each session lasting three to four hours.

What are some problems of dialysis?

It can be unpleasant, time-consuming, requires a strict diet, and can cause blood clots or infections.

What is a kidney transplant?

Replacing a diseased kidney with a healthy donor kidney to restore normal function.

What are the advantages of kidney transplants?

Patients don't need regular hospital visits like dialysis, and it is cheaper long-term.

What are the disadvantages of kidney transplants?

Risk of rejection by the immune system, need for immunosuppressant drugs, and transplanted kidneys do not last forever.