WJEC Biology A2 homeostasis

What is homeostasis?

Maintains a constant internal environment.

What is negative feedback?

When a change in the environment changes the system brings it back to normal.

What is the function of the kidney?

Removal of nitrogenous metabolic waste from the body and osmoregulation.

What is osmoregulation?

The homeostatic control of body water, the balance of water loss and gain.

What is the nephron made up of?

Bowman's capsule, proximal tubule, loop of Henle and a distal tubule.

What brings the blood to the glomerulus?

Afferent arteriole

What lets the blood leave the glomerulus?

Efferent arteriole

What are the capillary structures leaving the efferent arteriole?

Capillary network serving the proximal and distal convoluted tubules and a network beside the loop of Henle

What is the Vasa Recta?

A capillary network running beside the loop of Henle.

Name the three sections of the kidney.

Cortex, medulla, pelvis.

Name the three processes of the nephron.

Ultra-filtration, selective reabsorption and secretion.

What is ultrafiltration?

Filtration under pressure that separates small soluble molecules from blood plasma. They get filtered through the capillaries, glomerulus and Bowman's capsule.

The layers of cells in the capillaries in the Bowmans capsule.

Endothelium cells, basement membrane and podocytes.

Why is the efferent arteriole narrower than the afferent arteriole?

To increase the hydrostatic pressure of the blood plasma.

What happens when the hydrostatic pressure is increased?

Small soluble molecules are forced out of the plasma.

What is selective reabsorption?

The process where useful products (glucose and salts) are reabsorbed into the blood along the nephron.

What is it selective reabsorption?

It has already been absorbed in the small intestine and only some molecules are reabsorbed.

How are the walls of the proximal convoluted tubule adapted?

Microvilli for large surface area and numerous mitochondria for ATP.

What is the role of the loop of Henle?

Make sure urine is more concentrated than blood.

Which part is impermeable to water?

Ascending part of loop of Henle.

What part of the brain is responsible for detecting changes?

Hypothalamus.

What is the coordinating system in triggering ADH to be released?

Pituitary lobe.

How does ADH work?

It increases the permeability of the collecting duct and distal convoluted tubule.

How does water pass from the collecting duct?

Channel forming proteins called aquaporins. The channel is hydrophilic.

How does the hypothalamus detect changed?

Notices the change in sodium chloride concentration. A low water potential is noticed by osmoreceptors.

What activates the thirst centre?

Hypothalamus

What are the 2 types of dialysis?

Haemodialysis and Continuous ambulatory peritoneal dialysis.

What is haemodialysis?

An artificial kidney machine. Lasts between 2-6 hrs. Blood passes through tubes with semi permeable membranes, other side dialysis fluid. Pass opposite direction to each other.

What is continuous ambulatory peritoneal dialysis?

Use the peritoneum cavity as a natural filter. Floods cavity with fluid that bathes the organs so waste products pass into fluid. Catheter used to take the fluid in and out.

What adaptations do animals have for different environments?

Aquatic animals produce ammonia which is toxic but soluble. Diffused out through gills and diluted. Birds/insects excrete uric acid which is insoluble and non-toxic. Less energy and water. Mammals excrete urea. Requires energy but less toxic so can be tolerated in higher concentrations.