Excretion as an example of homeostatic control

Question 1

What types of products need to be excreted?

Answer 1

• CO2
• Nitrogen- containing compounds – urea (nitrogenous waste
• other compounds

Question 2

What do the lungs excrete?

Answer 2

Carbon dioxide

Question 3

Carbon Dioxide as a waste product

Answer 3

CO2 is transported in the blood as hydrogencarbonate ions
(CO2 + H2O -> H2CO3 (carbonic acid)
H2CO3 -> H+ + HCO3- )
The H+ produced from dissociation can reduce the pH of the blood plasma ~(proteins in the plasma usually acts as buffers)
change in pH can be detected by the medulla oblongata which causes an increase in breathing rate

Question 4

How can too much CO2 be harmful?

Answer 4

Can cause:
* Drowsiness
* headaches
* restlessness
* confusion
Can also cause respiratory acidosis

Question 5

What is the livers role in excretion?

Answer 5

Liver directly involved in excretion due to its many metabolic roles.
Also involved in converting excess amino acids to urea (in a process called deamination)

Question 6

What does the skin excrete?

Question 7

What do the kidneys excrete?