Endogenous pacemakers

Question 1

What is an endogenous pacemaker?

Answer 1

Internal body clocks that regulate many of our biological rhythms

Question 2

What is the superchiasmatic nucleus?

Answer 2

Tiny bundle of nerve cells
Located in the hypothamalus in each hemisphere of brain
Influential in maintaining circadian rhythms

Question 3

How does the Superchiasmatic nucleas work?

Answer 3

Nerve fibres connected to the eye
Cross in area called optic chiasm
On way to left and right visual area of the cerebral cortex
SCN lies just above optic chiasm
Receives info about light directly from this structure
Continues even when eyes are closed, enabling biological clock to adjust to changing patterns of daylight whilst we are asleep

Question 4

What did DeCoursey et al study?

Answer 4

Destroyed SCN connection of
30 chipmunks
Who were then returned to natural habitat
Observed for 80 days

Question 5

What did DeCoursey et al find?

Answer 5

Sleep/wake cycle of chipmunks disappeared
By end of study significant portion of them had been killed by predators

Question 6

What did Ralph et al study?

Answer 6

Bred mutant hamsters with a 20 hour sleep/wake cycle
When SCN cells from the foetal tissue of mutant hamsters were transplanted into brains of normal hamsters
The cycles of the second group defaulted to 20 hours

Question 7

Explain the pineal gland and melatonin

Answer 7

SCN passes the information on day length and light that it receives to pineal gland
During night - pineal gland increases production of melatonin (chemical that induces sleep and is inhibited during periods of wakefulness)

Question 8

What is a negative of endogenous pacemakers?

Answer 8

May obscure other body clocks
Numerous circadian rhythms in many organs and cells in the body
These peripheral oscillators are found in the organs including the lungs, pancreases and skin
Influenced by the actions of the SCN but also act independently

Question 9

What is a negative of endogenous pacemakers?

Answer 9

Darniola et al
Demonstrated how changing feeding patters in mic could alter the circadian rhythms of cells in the liver by up to 12 hours
Whilst leaving the rhythm of the SCN unaffected
Suggesting other complex influences on the sleep wake cycle

Question 10

What is a negative of the endogenous pacemakers?

Answer 10

Cannot be studies in isolation
Extremely rare
The more researchers attempt to isolate the influence of internal pacemakers the lower the validity of the research