Communication and Homeostasis M5

Question 1

Describe how an endotherm, like a mammal, normally prevents its body temp from increasing when the external temperature increases (5 marks)

Answer 1

1. Thermoreceptors 2. Hypothalamus 3. Vasodilation 4. increased heat loss by conduction, convection or radiation. 5.decrease in metabolic rate. 6. decrease in the release of adrenaline/thyroxine. 7. sweating and erector pili muscles flatten hair.

Question 2

Describe how insulin is involved in the regulation of blood glucose concentration.

Answer 2

1. receptors in pancreas detect high BG 2. beta-cell in the islet of Langerhans secrete insulin. 3.INSULIN binds to protein receptors in the plasma membranes of TARGET CELLS of the effectors. 4. This stimulates the uptake of glucose, especially muscle and liver cells that increase the number of GLUTs on their surface. 5. more glucose is taken in by facilitated diffusion 6. respiration rate increases 7. Insulin activates Glycogensis that converts glucose to glycogen or fats. 8. Lowers BG levels

Question 3

Describe how glucagon is involved in the regulation of blood glucose concentration.

Answer 3

1. receptors in pancreas detect low BG 2. alpha cells in the islet of Langerhans secrete glucagon. 3. glucagon binds to target cells of the liver where glucagon activates the enzymes that cause glycogenolysis where glycogen is hydrolysed to glucose. 4. Glyconeogensis also occurs where amino acids and fats are converted in glucose. 5 Glyconeogensis inhibits the release of insulin. 6 . this raises BG levels