Parkinson's disease (characterized by tremors and progressive rigidity of limbs) is caused by the degeneration of brain neurons that are involved in movement control and utilize which neurotransmitter?

Which digestive hormone inhibits both gastric secretion and motility, stimulates insulin release, and is secreted mainly when fat is present in the duodenum?

The repeated sequence of gradual onset of apnoea followed by gradual restoration of respiration is called ________.