Endogenous pacemakers and exogenous zeitgebers

Endogenous pacemaker:

Internal body clocks that regulate many of our biological rhythms

SCN:

Located in the hypothalamus, this is one of our primary endogenous pacemakers, this maintains our circadian rhythm such as the sleep wake cycle, receives info about light through eyes (even when closed).

It passes information of light to the pineal gland which increases the production of melatonin, inducing sleep. (SAD)

Decoursey:

Destroyed SCN connection in 30 chipmunks and the sleep wake cycle disappeared in them. A significant portion had been killed by predators (most likely because they were awake when they shouldn’t have been).

Exogenous pacemakers:

External cues that affect our biological rhythms

Campbell and Murphy:

Light may be detected but doesn't always have to be through the eyes. They shone light pad onto the back of pps knees, sleep wake cycle could be changed by up to 3 hours, showing light doesn't have to be detected in the eyes.

Social cues:

Parents regulate when babies eat and go to sleep, this has an effect on their biological rhythms because it’s an external factor that is controlling it. Also, adapting to local times for eating and sleeping can help overcome jet lag.

Not generalisable

Decoursey performed the experiment on chipmunks, they have very different brain structure to us and we are more complex, low generalisability.

Ethical issues

Destroying parts of their body, most dying or will die soon. Therefore they were not protect from harm, discredits findings.

Real-world application

Can help those who struggle with sleep or insomnia. By reducing light intake before bed the brain will detect this and help you go to sleep quicker and easier.