Adrenaline and Thyroxine

Question 1

State the function of adrenaline.

Answer 1

To prepare the body for ‘fight or flight’

Question 2

Give the effects of adrenaline.

Answer 2

• Increased heart rate / blood pressure
• Increased blood flow to the muscles
• Increased conversion of glycogen to glucose

Question 3

Explain how adrenaline causes increased respiration.

Answer 3

• It binds to receptors in the heart, causing heart muscle to contract more, so heart rate and blood pressure increase
• This increases blood flow to muscles, so cells receive more oxygen and glucose for respiration

Question 4

Explain how adrenaline contributes to raised blood glucose levels.

Answer 4

• It binds to receptors in the liver, causing it to break down glycogen stores to release glucose
• Therefore, there’s more glucose in blood to be transported to cells

Question 5

State the function of a negative feedback system.

Answer 5

To trigger a response so that the level of hormones or other substances is brought back to normal

Question 6

State the function of thyroxine.

Answer 6

It regulates metabolic rate, the speed at which chemical reactions occur in the body

Question 7

Describe the negative feedback system that increases blood thyroxine levels when they are low.

Answer 7

• The hypothalamus is stimulated to release TRH
• TRH stimulates the pituitary gland to release TSH
• TSH stimulates the thyroid gland to release thyroxine, so the blood thyroxine level rises

Question 8

Describe the process that lowers blood thyroxine levels when they are higher than normal.

Answer 8

• The release of TRH from the hypothalamus is inhibited, reducing the production of TSH from the pituitary gland
• Therefore, the blood thyroxine level falls