Regulation of Sleep Wake Patterns

Biological rhythms

repeated biological processes that are regulated by internal mechanisms

Circadian Rhythms

biological and behavioural changes that occur as part of a cycle that lasts around 24 hours

Sleep-wake cycle

a 24-hour-cycle that is made up of time spent sleeping and time spent awake and alert

Ultradian rhythms

biological and behavioural changes that occur in a cycle that lasts less than 24 hours

suprachiasmatic nucleus (SCN)

an area of the hypothalamus that is responsible for regulating an individual's sleep-wake patterns

How does the SCN regulate the sleep-wake cycle?

The SCN receives information from both external and internal cues to help modulate the circadian rhythm.

External cues

external cues involve information from the environment, such as the presence or absence of light

internal cues

internal cues involve information that originates within the body (such as the expression and supression of particular genes, known as clock genes)

Pineal Gland

a gland in the brain responsible for the production and release of melatonin

Melatonin

a hormone released by the pineal gland typically at night time to indicate sleep as part of the sleep-wake cycle

Process of inducing sleep

Input to the SCN (internal and external) --> SCN receives cues --> SCN sends appropriate signals to pineal gland --> pineal gland releases hormones based on SCN signalling --> the hormone melatonin is released at night time to induce sleep

Cortisol (in terms of sleep-wake patterns)

a hormone that is responsible for increasing alertness and maintaining arousal

Melatonin in the sleep wake cycle

released from pineal gland: low levels in the body when its morning; high levels in the body at night

Cortisol in the sleep wake cycle

released from adrenal cortex: high levels in the body when its morning; low levels in the body at night

Types of brain waves

Beta, alpha, theta, delta

characteristics of NREM 1

-transition of being awake to being asleep

-light sleep

-some muscle twitches, hypnic jerks

-alpha and theta waves

characteristics of NREM 2

-moderate sleep

-amount increases each successive cycle

-theta waves and sleep spindles/k-complexes

characteristics of NREM 3

-moderate-deep sleep

-20-40 mins at a time

-amount decreases each successive cycle

-delta waves

characteristics of REM

-paradoxical sleep

-dreams occur

-amount increases each successive sleep cycle

-beta-like waves

-beta-like waves