Rhythms of Waking and Sleeping

Vocabulary flashcards covering the biological mechanisms of sleep, circadian rhythms, brain structures, and sleep disorders based on the lecture notes.

Curt Richter

A researcher who proposed in 1922 that the body generates its own cycles of activity and inactivity, independent of external stimuli.

Endogenous circannual rhythms

Internal mechanisms that operate on an annual or yearly cycle, such as migratory patterns or animals storing food for winter.

Endogenous circadian rhythms

Internal mechanisms that operate on an approximately $24$ hour cycle, regulating sleep, eating, body temperature, hormone secretion, and urination.

Zeitgeber

A German term meaning "time giver"; refers to a stimulus that resets the circadian rhythm, such as sunlight, tides, exercise, or meals.

Phase-delay

The shift in circadian rhythms caused by traveling west.

Phase-advance

The shift in circadian rhythms caused by traveling east.

Period 3 gene

A gene providing a basis for sleep preference; having a long gene is associated with being an early riser, while a short gene is associated with being a late riser.

Suprachiasmatic nucleus (SCN)

Located above the optic chiasm and part of the hypothalamus, it is the main control center of circadian rhythms for sleep and temperature.

Retinohypothalamic path

A small branch of the optic nerve that travels directly from the retina to the SCN to reset the biological clock via light.

Melanopsin

A special photopigment found in a specific population of retinal ganglion cells that respond directly to light without input from rods or cones.

PER and TIM

Proteins produced by the Period and Timeless genes that increase the activity of SCN neurons to regulate sleep and waking.

Pineal gland

An endocrine gland located posterior to the thalamus that is regulated by the SCN and secretes melatonin.

Melatonin

A hormone secreted by the pineal gland that increases sleepiness; secretion typically starts $2$ to $3$ hours before bedtime.

Polysomnograph

A combination of EEG and eye-movement records used to monitor the various stages of sleep.

Alpha waves

Brain waves present when an individual begins a state of relaxation.

Sleep spindles

Characteristic of Stage $2$ sleep, these are $12$- to $14$-Hz waves occurring in bursts that last at least half a second.

K-complex

A sharp wave associated with temporary inhibition of neuronal firing, occurring during Stage $2$ sleep.

Slow wave sleep (SWS)

The combination of Stage $3$ and Stage $4$ sleep, characterized by slow, large amplitude waves and synchronized neuronal activity.

Paradoxical sleep

Another name for REM sleep because it is deep sleep in some ways (relaxed postural muscles) but light sleep in others (irregular, fast EEG waves).

Ventrolateral preoptic nucleus (VLPO)

A sleep-promoting region of the hypothalamus inhibited by the SCN and activated by Adenosine; it utilizes the neurotransmitter GABA.

Reticular formation

A part of the midbrain extending from the medulla to the forebrain responsible for arousal.

Pontomesencephalon

A part of the midbrain that releases acetylcholine and glutamate to produce excitatory effects and increase cortical arousal.

Locus Coeruleus

A small structure in the pons that releases norepinephrine to arouse the cortex, increase wakefulness, and enhance attention and memory.

Orexin (hypocretin)

A neurotransmitter released by the hypothalamus that stimulates acetylcholine-releasing cells in the basal forebrain to maintain wakefulness.

PGO waves

High-amplitude electrical potentials detected in the pons, then the lateral geniculate, and then the occipital cortex during REM sleep.

Sleep apnea

A sleep disorder characterized by the inability to breathe for a prolonged period while sleeping.

Cataplexy

A symptom of narcolepsy involving muscle weakness triggered by strong emotions.

Narcolepsy

A sleep disorder characterized by frequent sleepiness and sudden attacks, caused by a lack of hypothalamic cells that release orexin.

Periodic Limb Movement Disorder

Repeated involuntary leg or arm movements during NREM sleep, occurring every $20$ to $30$ seconds for extended periods.

REM behavior disorder

A condition characterized by vigorous movement and acting out dreams during REM sleep, possibly due to inadequate GABA.

Night terrors

Experiences of intense anxiety during NREM sleep from which a person awakens screaming.

Sexsomnia

A condition similar to sleepwalking where an individual engages in sexual behavior while asleep.

Activation-synthesis hypothesis

The theory that dreams begin with spontaneous activity in the pons which the cortex then synthesizes into a story.

Clinico-anatomical hypothesis

The theory that dreams are similar to thinking under unusual circumstances, generated by internal arousal combined with memories and sensory fragments without prefrontal cortex criticism.

Parietal cortex (inferior part)

An area important for visual-spatial perception; damage to this area in the context of the clinico-anatomical hypothesis leads to reports of having no dreams.