PSYC111

Lecture 8: Sleep

Lecture 9: Sleep

Circadian Rhythm: internal body clock of that regulates physiological processes according to a 24 hour cycle

Free running sleep wake cycle: Without entrainment an animals internal body clock is found to cycle around 25 hours instead of 24. Consequently, when sleep/ activity is plotted on an attogram, activity is found to start later by an hour each day.

Suprachiasmatic nucleus: "master" internal clock that regulates physiological activity. Is activated by light

Theories for why we sleep

Examples: Body temperature, melatonin, sleep propensity

Wake Maintenance zone: The period before bed where alertness is at its peak. Evolutionary theory is that animals that are alert just before bed are more likely to survive as they can make arrangements that ensure they are safe during the night.

Melatonin is a naturally occurring hormone that increases sleepyness. Levels are low during the day but increase in the evening and during the night. Peak in melatonin is around 3am in the morning.

Supra - superior

Chiasma - referring to optic nerve/chiasma

Melanopsin Receptors: located in the eye. Respond to light and activate the SCN. Light induced activation of the SCN prevents the pineal gland from producing melatonin. L

Zeitgebers

Evolutionary: So we are asleep in times when we are most unlikely to be successful in finding food

Repair and Recouperation

Conserves energy when it would otherwise be excessively expended

Forces animals to be quiet when they are most vulnerable

Problem with this theory is that lying down, unconscious is not as safe a lying down conscious where the animal can be aware of predators

Sleep deprivation cases: Pater Tripp and Rande Gardiner

Animal studies

Sleep disruption: linked to cancer, diabetes, obesity , cardiovascular risk, mood disorder. Link is through disruption of sleep wake cycle.

Phase delay & phase advance

Quantifying Sleep