Endogenous pacemakers/ zeitgebers

Question 1

AO1 endogenous pacemakers

Answer 1

• Main one is a tiny cluster of nerve cells called the suprachiasmatic nucleus which lies in the hypothalamus
  This plays an important role in generating the bodys circadian rhythm, acts as the master clock which links to other brain regions which control sleep and arousal
  Neurons in the SCN synchronise with each other so their target neurons in sites elsewhere in the body receive correctly time coordinated signals
• The SCN maintains a circadian rhythm for a long time because it has a built in one which only needs resetting when external light levels change, receives info about this via the optic nerve.
  SCN also regulates the manufacture and secretion of melatonin in the pineal gland via an interconnecting neural pathway