Biology 9700/41 — May/June 2020
Cambridge A-Level · A Level Structured Questions · worked solutions for every part, with the mark scheme
Topics Genetic Technology · Inheritance · Energy and Respiration · Control and Coordination · Classification, Biodiversity and Conservation · Homeostasis · +3 more
In mammals, the hormone ACTH is released from the anterior pituitary gland. ACTH stimulates the cells of the adrenal glands to synthesise the hormone cortisol. This is an example of cell signalling.
The main stages of cell signalling involving ACTH are similar to the main stages of cell signalling by adrenaline.
Describe the main stages of cell signalling involving ACTH.
If the concentration of cortisol in the blood increases above its set point, it will inhibit the production of ACTH by the anterior pituitary gland.
Name this type of homeostatic mechanism.
The domestic dog, Canis lupus familiaris, is a mammal. A dog may develop a condition called Cushing’s disease, which is a result of too much cortisol being secreted by the adrenal glands. The most common cause of this is an increased secretion of ACTH because of a tumour in the anterior pituitary gland.
Explain how a tumour develops.
One symptom of Cushing’s disease in a dog is that the dog will want to drink much more than normal.
Suggest one other reason why a dog would want to drink much more than normal.
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