(a)[5]
Describe the main stages of cell signalling involving ACTH.
(b)[1]
If the concentration of cortisol in the blood rises above its set point, it inhibits the production of ACTH by the anterior pituitary gland. Name this type of homeostatic mechanism.
(c)[2]
The domestic dog, $Canis\ lupus\ familiaris$, is a mammal. A dog can develop Cushing’s disease, which results from excessive cortisol being secreted by the adrenal glands. The most common cause is increased secretion of ACTH due to a tumour in the anterior pituitary gland. Explain how a tumour develops.
(d)[1]
One symptom of Cushing’s disease in a dog is that the dog will want to drink far more than usual. Suggest one other reason why a dog would want to drink far more than usual.