BIO: Endogenous Pacemakers

Question 1

endogenous pacemakers

Answer 1

internal stimuli for biological rhythms

Question 2

what is the SCN known as?

Answer 2

the ‘master circadian clock’

Question 3

what is the SCN?

Answer 3

• it contains neurons that fire in a synchronised pattern
• these neurons communicate with other pacemakers all over the body
• all pacemakers ‘keep time’ but the SCN sets them all

Question 4

Hamster study (Ralph et al. 1990)

Answer 4

• researchers took hamsters with 2 different circadian cycle lengths.
• they implanted the SCN of one hamster type into another
• in all cases the donor’s SCN’s clock was followed

Question 5

Pineal gland role in SCN

Answer 5

the pineal gland receives signals from the SCN to produce melatonin according to light levels

Question 6

role of melatonin:

Answer 6

• melatonin is derived from serotonin. it too is an inhibitory NT
• melatonin inhibits many areas of the brain (mesencephalon & limbic system) that are responsible for wakefulness
• inhibition of these areas leads to sleep

Question 7

Evaluation 1 (Research support)

Answer 7

P- research support for EPs and EZs - internal validity
E- Role of SCN supported by hamster transplant studies - donor SCN always determined the circadian rhythm (Ralph et al., 1990).
E- Furthermore, using lamps that mimic daylight allowed researchers to manipulate participants’ circadian rhythm in laboratory conditions (Vetter et al., 2011)
L- While this evidence shows the importance of EPs and EZs in setting biological rhythms, there is an issue of determinism. Animal models exposed to surgery lack external validity when applied to human functioning, and the artificial environment in the light study means these findings cannot be considered entirely ecologically valid due to factors outside labs (suggest).