6.4 Regulation of Sleep-Wake Patterns by Internal Biological Mechanisms

biological rhythms

natural, repeating cycles in the body and brain

controls physical functions and behaviours

biological clocks

internal timers that regulate rhythms

found in nearly every cell

“Master Clock”

located in the brain and coordinates all the body’s clock to keep them in sync

Circadian Rhythms

approx. 24 hours

endogenous but influenced by exogeneous cues like light, clocks, meals

e.g. sleep wake cycle, body temprature, cortisol levels

Suprachiasmatic Nucleus (SCN)

strcutre in hypothalamus that regulates an individual’s sleep-wake pattern and helps to release melatonin

controls circadian rhythm

pineal gland

responsible for the production and release of melatonin

Ultradian Rhythms

less than 24 hours

e.g heart rate, breathing, eating pattenrs, hormone bursts

sleep cycle is a key rhythm

Sleep as an ultradian rhythm

• one cycle is about 90 mins

• repeates 4-6 times a night

• alternates between REM and NREM sleep

Suprachiasmatic Nucleaus Features

• located in hypothalamus

• master biological clock

• recieves light info from optic nerves

• sends signals to the pineal glands to control melatonin production

How does the SCN help to regulate sleep-wake cycle

• light is detected by the eyes

• stimulates the SCN in the brain

• SCN sends signald to the pineal gland

• melatonin hormone is released to the brain

Meltonin

• hormone that make the brain feel sleepy

• produced by the pienal gland, regulated by the SCN

• more meltonin= more drowsy

• less light= more melatonin

• morning light= melatonin drops= wakefulnes

• often referred to as “dracula of hormones”- only come out in the dark