5.11 Adrenaline and thyroxine
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Name the gland that produces thyroxine and give one effect of thyroxine.
Mark scheme
- thyroid (gland) (1)
- stimulates / increases (basal) metabolic rate / controls growth and development (1)
Model answer
The thyroid gland. Thyroxine increases the basal metabolic rate.
Explain how adrenaline prepares the body for "fight or flight".
Mark scheme
- increases heart rate (1)
- increases blood pressure / blood flow to muscles (1)
- liver converts glycogen to glucose / raises blood glucose (1)
- more oxygen and glucose delivered to muscles / brain (1)
- for (faster) respiration / to release more energy (for contraction) (1)
Max 4
Model answer
Adrenaline increases the heart rate and blood flow to the muscles, and makes the liver convert glycogen into glucose, raising blood glucose. This delivers more oxygen and glucose to the muscles and brain, so they can respire faster and release more energy for fighting or running.
Describe how negative feedback keeps the level of thyroxine in the blood constant.
Mark scheme
- low thyroxine stimulates the hypothalamus to release TRH (1)
- TRH causes the pituitary to release TSH (1)
- TSH stimulates the thyroid to release thyroxine (1)
- when thyroxine is normal / high it inhibits release of TRH and TSH (1)
- so less thyroxine is released (1)
Max 4
Model answer
When thyroxine is low, the hypothalamus releases TRH, which makes the pituitary gland release TSH. TSH stimulates the thyroid to release more thyroxine. When the thyroxine level returns to normal, it inhibits the release of TRH and TSH, so less thyroxine is made and the level stays constant.
Explain why the release of adrenaline is not an example of negative feedback.
Mark scheme
- it is released in response to fear / stress / a stimulus (detected by the nervous system) (1)
- its effect does not reverse the change that caused it / it does not reduce its own release (1)
Model answer
Adrenaline is released because of fear or stress, and its effects do not reverse that stimulus or switch off its own release, so it is not controlled by negative feedback.
A person's thyroid gland makes too little thyroxine.
Suggest two symptoms they might have. Explain your answer.
Mark scheme
- low metabolic rate (1)
- any two symptoms linked: tiredness / lack of energy; weight gain; feeling cold (less energy released by respiration) (1 each)
- allow: slow growth / development in children
Model answer
Their basal metabolic rate would be low. They might feel tired and cold, because their cells release less energy by respiration, and they might gain weight.
Which hormone is released by the pituitary gland and stimulates the thyroid gland?
Choose one answer.
Correct Not quite: the answer is TSH
Mark scheme
B (TSH)
Model answer
B: TSH, thyroid stimulating hormone.
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