5.3.7 - Negative feedback - adrenaline and thyroxine

Question 1

Adrenaline

Answer 1

produced by the adrenal glands in times of fear or stress. Increases heart rate and boosts delivery of oxygen and glucose to the brain and muscles, preparing the body for a ‘fight or flight’ response.

Question 2

Thyroxine
inc. definition of basal metabolic rate

Answer 2

Produced by the thyroid gland in the neck and stimulates the basal metabolic rate. Plays an important role in multiple processes in the body, such as stimulating protein synthesis for growth and development.

Basal metabolic rate: the speed at which chemical reactions in the body occur whilst the body is at rest.

Question 3

How are thyroxine levels controlled by negative feedback?

Answer 3

Thyroxine is released in response to thyroid stimulating hormone (TSH), which is released by the pituitary gland.

Level of thyroxine in blood higher than normal, secretion of TSH inhibited. Reduces amount of thyroxine released from thyroid gland, so level in blood falls back to normal.

Level of thyroxine in blood lower than normal, TSH secreted. Increases amount of thyroxine released from thyroid gland, so level in blood rises back to normal.

Question 4

How is hormone release affected by negative feedback

Answer 4

Body detects that the level of a substance has gone above or below the normal level, triggers a response to bring the level back to normal again.