1Define homeostasis.
The maintenance of a constant internal environment.
2Define negative feedback.
A change triggers a response that reverses the change.
3What is excretion?
The removal of metabolic waste from the body.
4Where is urea produced?
In the liver via the ornithine cycle.
5What is the functional unit of the kidney?
The nephron.
6Define ultrafiltration.
Filtration under high pressure in the Bowman’s capsule.
7How is high pressure created in the glomerulus?
The afferent arteriole is wider than the efferent arteriole.
8What is the basement membrane?
A molecular filter preventing proteins and blood cells entering the filtrate.
9What are podocytes?
Cells in the Bowman’s capsule with filtration slits.
10Where does selective reabsorption occur?
The proximal convoluted tubule (PCT).
11Name three substances reabsorbed in the PCT.
All glucose, all amino acids, and some salts and water.
12How are PCT cells adapted?
They have microvilli and many mitochondria.
13Why might glucose be present in urine?
Blood glucose exceeds the renal threshold.
14What is the function of the Loop of Henle?
To create a low water potential in the medulla.
15Define counter-current multiplier.
The mechanism that builds up a salt gradient in the medulla.
16What hormone controls water reabsorption?
ADH.
17Where is ADH produced and released?
Produced in the hypothalamus and released from the posterior pituitary.
18How does ADH work?
It increases collecting duct permeability by adding aquaporins.
19What is osmoregulation?
Control of the water potential of blood and body fluids.
20What nitrogenous waste do birds excrete?
Uric acid.
21Why do desert animals have longer Loops of Henle?
To conserve more water by producing concentrated urine.
22What is haemodialysis?
Filtering blood using an external machine.
23What is the composition of dialysis fluid?
Normal glucose and salt levels but no urea.
24What is the role of the vasa recta?
To maintain the medullary gradient.
25What is deamination?
The removal of the amino group from an amino acid.
26Name a metabolic waste product other than urea.
Carbon dioxide or creatinine.
27What happens to urine volume when ADH is high?
Urine volume decreases and concentration increases.
28What are aquaporins?
Water channel proteins.
29Where are osmoreceptors located?
In the hypothalamus.
30Why do kidney transplant patients take immunosuppressants?
To prevent organ rejection.