Sleep Stages and EEG Patterns

A sleep disorder characterized by frequent pauses in breathing during sleep. These pauses can lead to awakenings, poor sleep quality, and daytime sleepiness.

A type of sleep apnea caused by a blockage of the airway, often due to muscle spasms or relaxation.

A sleep disorder where the central nervous system fails to signal the body to breathe.

A rare and fatal genetic disorder that causes progressive insomnia leading to death.

A sleep disorder characterized by involuntary limb movements, especially during sleep.

External cues that synchronize biological rhythms with the 24-hour day-night cycle.

A disruption of the body's natural sleep-wake cycle due to travel across time zones, leading to fatigue, sleep disturbances, and cognitive impairment.

A disruption of the body's natural sleep-wake cycle due to working shifts at different times of the day or night, causing similar effects to jet lag.

The internal timing mechanism that regulates the body's 24-hour rhythm.

A brain structure located in the hypothalamus responsible for controlling the circadian rhythm.

Specialized photoreceptor cells in the retina that detect light and transmit signals to the SCN to synchronize the circadian clock.

The neural pathway that connects the retina to the SCN, allowing light information to influence the circadian rhythm.

The ability of the body to maintain a 24-hour rhythm even in the absence of external cues.

Genes responsible for determining the natural length of an organism's circadian rhythm.

The temporo-parieto junction and the medial prefrontal cortex are crucial for dreaming. Damage to these areas stops dreaming. The medial occipital lobe is important for visual imagery in dreams, and damage to this area leads to a loss of visual imagery in dreams.

During rapid eye movement (REM) sleep, the medial prefrontal cortex, medial occipital cortex, and temporo-parieto junction show increased activity. The temporo-parieto junction is active during both REM and NREM sleep, suggesting its vital role in dreaming.

The prefrontal cortex displays reduced activity during dreaming. This reflects the decreased organization and planning seen in dreams.

The idea that being awake disrupts the body's internal balance, and sleep is necessary to restore this balance. This theory highlights the restorative function of sleep.

Sleep is not solely about responding to wakefulness's negative effects but reflects an internal 24-hour cycle. This theory suggests that sleep serves a biological purpose, rather than simply responding to wakefulness's consequences.

Sleep deprivation can lead to increased sleepiness and quicker sleep onset. However, sleep deprivation is often accompanied by stress, making it difficult to isolate the effects of sleep deprivation in research.

Across many mammals and birds, sleep is common, suggesting a basic biological function. This challenges the idea that sleep is mainly for protection or energy conservation.

Noradrenergic neurons in the locus coeruleus (LC) are highly active during wakefulness, less active during slow-wave sleep, and almost inactive during REM sleep.

Serotonergic neurons in the raphe nuclei are less active during slow-wave sleep and almost inactive during REM sleep, but become very active after REM sleep ends.

Histaminergic neurons in the hypothalamus are highly active during wakefulness but less active during slow-wave and REM sleep.

The posterior hypothalamus and adjacent midbrain promote wakefulness.

The anterior hypothalamus (preoptic area) and adjacent basal forebrain promote sleep.

Destruction of the preoptic area causes total insomnia in rats. Electrical stimulation causes drowsiness and sleep.

Neurons in the preoptic area receive inhibitory inputs from some of the same regions they inhibit, creating a balance between sleep and wakefulness.

Neurons in the preoptic area become active during the transition from waking to sleep.

Low levels of activity in the reticular formation produce sleep, while high levels produce wakefulness. This is why it's called the reticular activating system.

REM sleep is controlled by several nuclei in the caudal reticular formation, each responsible for a different aspect of REM sleep, such as muscle tone reduction, rapid eye movements, and cortical EEG desynchronization.

Circadian rhythms are biological processes that occur in a roughly 24-hour cycle and are regulated by internal biological clocks, like the SCN in the brain.

The Suprachiasmatic Nucleus (SCN) is a tiny region located in the hypothalamus of the brain that acts as the body's master clock, regulating circadian rhythms.

Zeitgebers are external cues that synchronize circadian rhythms with the environment, like light and dark cycles.

Melatonin, a hormone produced by the pineal gland, influences circadian rhythms. It's secreted during darkness and plays a role in regulating sleep.

The pineal gland, located near the thalamus, acts as a neuroendocrine organ that releases melatonin, contributing to sleep regulation.

Acetylcholine (ACh) is a neurotransmitter that plays a role in arousal and REM sleep. High levels are observed during wakefulness and REM sleep, while low levels are seen during slow-wave sleep.

The locus coeruleus (LC), a brain region in the dorsal pons, releases norepinephrine, a neurotransmitter crucial for maintaining alertness and wakefulness.

Norepinephrine, a neurotransmitter released by the LC, is linked to wakefulness. Its levels are high during wakefulness, decrease during slow-wave sleep, and are almost absent during REM sleep.

During wakefulness and REM sleep, the brain exhibits high neuronal activity, reflected in high levels of ACh in regions like the hippocampus and neocortex.

Polyphasic sleep involves sleeping multiple times a day, often seen in infants and some mammals.