Sleep physiology

A yawn is a reflex in vertebrate animals characterized by a long inspiratory phase with gradual mouth gaping, followed by a brief climax (or acme) with muscle stretching, and a rapid expiratory phase with muscle relaxation, which typically lasts a few seconds. For fish and birds, this is described as gradual mouth gaping, staying open for at least three seconds and subsequently a rapid closure of the mouth. Almost all vertebrate animals, including mammals, birds, reptiles, amphibians, and even fish, experience yawning. The study of yawning is called chasmology.

thumb| Northern bat hibernating in [[Norway]] thumb|Bats hibernating in a silver mine

small endocrine gland found in most vertebrates, which produces melatonin; in humans, located in the epithalamus, in a groove where the two halves of the thalamus join; its shape and size resembles a pine nut, after which it is named

spontaneous sleep orgasm

phenomenon

dream where one is aware that they are dreaming

natural internal process that regulates the sleep-wake cycle

sleep disorder characterized by repeated cessation and commencing of breathing that disrupts sleep

unique phase of sleep in mammals and birds, characterized by random/rapid movement of the eyes

thumb|right|Theba pisana snails aestivating on [[Foeniculum vulgare in Montbazin, France]]

part of the brain's hypothalamus

syndrome where people perceive loud imagined noises when falling asleep or waking up

Hypnagogia is the transitional state from wakefulness to sleep, also defined as the waning state of consciousness during the onset of sleep. Its corresponding state is ‌sleep to wakefulness. Mental phenomena that may occur during this "threshold consciousness" include hallucinations, lucid dreaming, and sleep paralysis.

thumb|right|An artist's depiction of a dream

chronic mismatch between a person's normal daily rhythm, compared to other people and societal norms

brain state during sleep

family of sleep disorders which affect the timing of sleep

Oneiromancy () is a form of divination based upon dreams, and also uses dreams to predict the future. Oneirogen plants may also be used to produce or enhance dream-like states of consciousness. Occasionally, the dreamer feels as if they are transported to another time or place, and this is offered as evidence they are in fact providing divine information upon their return.

sleep in non-human beings

medical specialty or subspecialty devoted to the diagnosis and therapy of sleep disturbances and disorders

3rd and 4th sleep stage

EEG waveform that occurs during sleep

A chronotype is the behavioral manifestation of an underlying circadian rhythm's myriad physical processes. A person's chronotype is the propensity for the individual to sleep at a particular time during a 24-hour period. Eveningness (delayed sleep period; most active and alert in the evening) and morningness (advanced sleep period; most active and alert in the morning) are the two extremes with most individuals having some flexibility in the timing of their sleep period. However, across development there are changes in the propensity of the sleep period with pre-pubescent children preferring

A zeitgeber ( , ) is any external or environmental cue that entrains or synchronizes an organism's biological rhythms, usually naturally occurring and serving to entrain to the Earth's 24-hour light/dark and 12-month cycles.

cumulative effect of not getting enough sleep

sleep disorder that involves an altered circadian rhythm resulting in falling asleep in early evening and awaking very early in the morning

thumb|right|350px A K-complex is a waveform that may be seen on an electroencephalogram (EEG). It occurs during stage 2 NREM sleep. It is the "largest event in healthy human EEG". They are more frequent in the first sleep cycles.

oscillation between the slow-wave and REM phases of sleep

drowsiness just after waking up

specific actions or reactions of an organism that recur with a regularity more frequent than once in 24 hours

sleep disorder

Dreamwork is the exploration of the images and emotions that a dream presents and evokes. It differs from classical dream interpretation in that it does not attempt to establish a unique meaning for the dream. In this way the dream remains "alive" whereas if it has been assigned a specific meaning, it is "finished" (i.e., over and done with). Dreamworkers take the position that a dream may have a variety of meanings depending on the levels (e.g. subjective, objective) that are being explored.

Hypnopompia (also known as hypnopompic state) is the state of consciousness leading out of sleep, a term coined by the psychical researcher Frederic Myers. Its mirror is the hypnagogic state at sleep onset; though often conflated, the two states are not identical and have a different phenomenological character. Hypnopompic and hypnagogic hallucinations are frequently accompanied by sleep paralysis, which is a state wherein one is consciously aware of one's surroundings but unable to move or speak.

sleep in which half the brain remains alert

increased frequency of REM after sleep deprivation

physiological response when a person wakes up

awakened and sleep cycyle

overview about sleep and emotions