Sleep in the context of Neuroscience of sleep

The pineal gland (also known as the pineal body or epiphysis cerebri) is a small endocrine gland in the brain of most vertebrates. It produces melatonin, a serotonin-derived hormone, which modulates sleep patterns following the diurnal cycles. The shape of the gland resembles a pine cone, which gives it its name. The pineal gland is located in the epithalamus, near the center of the brain, between the two hemispheres, tucked in a groove where the two halves of the thalamus join. It is one of the neuroendocrine secretory circumventricular organs in which capillaries are mostly permeable to solutes in the blood.

The pineal gland is present in almost all vertebrates, but is absent in protochordates, in which there is a simple pineal homologue. The hagfish, archaic vertebrates, lack a pineal gland. In some species of amphibians and reptiles, the gland is linked to a light-sensing organ, variously called the parietal eye, the pineal eye or the third eye. Reconstruction of the biological evolution pattern suggests that the pineal gland was originally a kind of atrophied photoreceptor that developed into a neuroendocrine organ.

A dream is a succession of images, dynamic scenes and situations, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep. Humans spend about two hours dreaming per night, and each dream lasts around 5–20 minutes, although the dreamer may perceive the dream as being much longer.

The content and function of dreams have been topics of scientific, philosophical and religious interest throughout recorded history. Dream interpretation, practiced by the Babylonians in the third millennium BCE and even earlier by the ancient Sumerians, figures prominently in religious texts in several traditions, and has played a lead role in psychotherapy. Dreamwork is similar, but does not seek to conclude with definite meaning. The scientific study of dreams is called oneirology. Most modern dream study focuses on the neurophysiology of dreams and on proposing and testing hypotheses regarding dream function. It is not known where in the brain dreams originate, if there is a single origin for dreams or if multiple regions of the brain are involved, or what the purpose of dreaming is for the body (or brain or mind).

Leisure (UK: /ˈlɛʒər/, US: /ˈliː-/) has often been defined as a quality of experience or as free time. Free time is time spent away from business, work, job hunting, domestic chores, and education, as well as necessary activities such as eating and sleeping. Leisure as an experience usually emphasizes dimensions of perceived freedom and choice. It is done for "its own sake", for the quality of experience and involvement. Other classic definitions include Thorstein Veblen's (1899) of "nonproductive consumption of time." Free time is not easy to define due to the multiplicity of approaches used to determine its essence. Different disciplines have definitions reflecting their common issues: for example, sociology on social forces and contexts and psychology as mental and emotional states and conditions. From a research perspective, these approaches have an advantage of being quantifiable and comparable over time and place.

Leisure studies and sociology of leisure are the academic disciplines concerned with the study and analysis of leisure. Recreation differs from leisure in that it is a purposeful activity that includes the experience of leisure in activity contexts. Economists consider that leisure times are valuable to a person like wages. If it were not, people would have worked instead of taking leisure. However, the distinction between leisure and unavoidable activities is not a rigidly defined one, e.g. people sometimes do work-oriented tasks for pleasure as well as for long-term utility. A related concept is social leisure, which involves leisurely activities in social settings, such as extracurricular activities, e.g. sports, clubs. Another related concept is that of family leisure. Relationships with others is usually a major factor in both satisfaction and choice.

A bedroom or bedchamber is a room situated within a residential or accommodation unit, primarily used for sleeping. A typical Western bedroom contains as bedroom furniture one or two beds, a clothes closet, and bedside table and dressing table, both of which usually contain drawers. In dwellings with multiple stories, bedrooms are often on the upper floors. Beds range from a crib for an infant; a single or twin bed for a toddler, child, teenager or single adult; to bigger sizes like a full, double, queen, king or California king). Beds and bedrooms are often devised to create barriers to insects and vermin, especially mosquitoes, and to dampen or contain light or noise to aid sleep and privacy.

A bed is a piece of furniture that is used as a place to sleep, rest, and relax.

Most modern beds consist of a soft, cushioned mattress on a bed frame. The mattress rests either on a solid base, often wood slats, or a sprung base. Many beds include a box spring inner-sprung base, which is a large mattress-sized box containing wood and springs that provide additional support and suspension for the mattress. Beds are available in many sizes, ranging from infant-sized bassinets and cribs, to small beds for a single person or adult, to large queen and king-size beds designed for two people. While most beds are single mattresses on a fixed frame, there are other varieties, such as the murphy bed, which folds into a wall, the sofa bed, which folds out of a sofa, the trundle bed, which is stored under a low, twin-sized bed and can be rolled out to create a larger sleeping area, and the bunk bed, which provides two mattresses on two tiers as well as a ladder to access the upper tier. Temporary beds include the inflatable air mattress and the folding camp cot. Some beds contain neither a padded mattress nor a bed frame, such as the hammock. Other beds are made specifically for animals.

A hammock, from Spanish hamaca, borrowed from Taíno and Arawak hamaka, is a sling made of fabric, rope, or netting, suspended between two or more points, used for swinging, sleeping, or resting. It normally consists of one or more cloth panels, or a woven network of twine or thin rope stretched with ropes between two firm anchor points such as trees or posts. Hammocks were developed by native inhabitants of the Americas for sleeping, as well as the English. Later, they were used aboard ships by sailors to enable comfort and maximize available space, by explorers or soldiers travelling in wooded regions and eventually by parents in the early 1920s for containing babies just learning to crawl. Today they are popular around the world for relaxation; they are also used as a lightweight bed on camping trips. The hammock is often seen as a symbol of summer, leisure, relaxation and simple, easy living.

Cardiovascular disease (CVD) is any disease involving the heart or blood vessels. CVDs constitute a class of diseases that includes: coronary artery diseases (e.g. angina, heart attack), heart failure, hypertensive heart disease, rheumatic heart disease, cardiomyopathy, arrhythmia, congenital heart disease, valvular heart disease, carditis, aortic aneurysms, peripheral artery disease, thromboembolic disease, and venous thrombosis.

The underlying mechanisms vary depending on the disease. It is estimated that dietary risk factors are associated with 53% of CVD deaths. Coronary artery disease, stroke, and peripheral artery disease involve atherosclerosis. This may be caused by high blood pressure, smoking, diabetes mellitus, lack of exercise, obesity, high blood cholesterol, poor diet, excessive alcohol consumption, and poor sleep, among other things. High blood pressure is estimated to account for approximately 13% of CVD deaths, while tobacco accounts for 9%, diabetes 6%, lack of exercise 6%, and obesity 5%. Rheumatic heart disease may follow untreated strep throat.

A sleep disorder, or somnipathy, is a medical disorder that disrupts an individual's sleep patterns and quality. This can cause serious health issues and affect physical, mental, and emotional well-being. Polysomnography and actigraphy are tests commonly ordered for diagnosing sleep disorders.

Sleep disorders are broadly classified into dyssomnias, parasomnias, circadian rhythm sleep disorders, and other disorders (including those caused by medical or psychological conditions). When a person struggles to fall or stay asleep without an obvious cause, it is referred to as insomnia, which is the most common sleep disorder. Other sleep disorders include sleep apnea, narcolepsy, hypersomnia (excessive sleepiness at inappropriate times), sleeping sickness (disruption of the sleep cycle due to infection), sleepwalking, and night terrors.

Night sweats or nocturnal hyperhydrosis is the repeated occurrence of excessive sweating during sleep. The person may or may not also perspire excessively while awake.

One of the most common causes of night sweats in women over 40 is the hormonal changes related to menopause and perimenopause. This is a very common occurrence during the menopausal transition years. Over 80% of women experience hot flashes, which may include excessive sweating, during menopause.

Sleep deprivation, also known as sleep insufficiency or sleeplessness, is the condition of not having adequate duration or quality of sleep to support decent alertness, performance, and health. It can be either chronic or acute and may vary widely in severity. This means it can happen over both short and long periods of time. Sleep is important because adequate sleep, or restful sleep, is essential for maintaining your overall health, brain performance, emotional regulation, and metabolic balance. Persistent sleep insufficiency can contribute to cognitive decline, emotional instability, and biological wear that has effects similar to accelerated aging. Scientific research demonstrates overwhelming evidence that inadequate sleep produces chronic consequences for overall health, ranging from attentional lapses to long-term neurodegenerative changes.

The human body and most living organisms depend on sleep for neural recovery. All known animals sleep or exhibit some form of sleep behavior, and the importance of sleep is self-evident for humans, as nearly a third of a person's life is spent sleeping. Sleep deprivation is common as it affects about one-third of the population.

Sleep-learning or sleep-teaching (also known as hypnopædia or hypnopedia) is an attempt to convey information to a sleeping person, typically by playing a sound recording to them while they sleep. Although sleep is considered an important period for memory consolidation, scientific research has concluded that sleep-learning is not possible. Once a concept explored in the early history of psychology, sleep-learning appears frequently in fiction and parapsychology, and is widely considered to be pseudoscience.

The entorhinal cortex (EC) is an area of the brain's allocortex, located in the medial temporal lobe, whose functions include being a widespread network hub for memory, navigation, and the perception of time. The EC is the main interface between the hippocampus and neocortex. The EC-hippocampus system plays an important role in declarative (autobiographical/episodic/semantic) memories and in particular spatial memories including memory formation, memory consolidation, and memory optimization in sleep. The EC is also responsible for the pre-processing (familiarity) of the input signals in the reflex nictitating membrane response of classical trace conditioning; the association of impulses from the eye and the ear occurs in the entorhinal cortex.

A hormone (from the Greek participle ὁρμῶν, "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs or tissues by complex biological processes to regulate physiology and behavior. Hormones are required for the normal development of animals, plants and fungi. Due to the broad definition of a hormone (as a signaling molecule that exerts its effects far from its site of production), numerous kinds of molecules can be classified as hormones. Among the substances that can be considered hormones, are eicosanoids (e.g. prostaglandins and thromboxanes), steroids (e.g. oestrogen and brassinosteroid), amino acid derivatives (e.g. epinephrine and auxin), protein or peptides (e.g. insulin and CLE peptides), and gases (e.g. ethylene and nitric oxide).

Hormones are used to communicate between organs and tissues. In vertebrates, hormones are responsible for regulating a wide range of processes including both physiological processes and behavioral activities such as digestion, metabolism, respiration, sensory perception, sleep, excretion, lactation, stress induction, growth and development, movement, reproduction, and mood manipulation. In plants, hormones modulate almost all aspects of development, from germination to senescence.

Morpheus (Ancient Greek: Μορφεύς, romanized: Morpheús 'Fashioner', derived from Ancient Greek: μορφή, romanized: morphḗ, meaning 'form, shape') is a god associated with sleep and dreams. In Ovid's Metamorphoses he is the son of Somnus (Sleep, the Roman counterpart of Hypnos) and appears in dreams in human form. From the Middle Ages, the name began to stand more generally for the god of dreams, or of sleep.

The Shakespeare funerary monument is a memorial to William Shakespeare located inside Holy Trinity Church at Stratford-upon-Avon in Warwickshire, the church in which Shakespeare was baptised and where he was buried in the chancel two days after his death. The monument, carved in pale blue limestone, is mounted on the north wall of the chancel. It has traditionally been identified as the work of the sculptor Gerard Johnson, but this attribution is challenged by Lena Cowen Orlin, who argues that it was more likely modelled from life by Gerard's brother, Nicholas Johnson.

The monument features a demi-figure of the poet holding a real quill pen in one hand and a piece of paper resting on a cushion in the other. The style, which was popular from the early- to the mid-17th century, was most commonly used to memorialize divines, academics, and those professions with pretensions of learning. The buttoned doublet, with its ornamental slashes, was probably originally painted scarlet, the loose subfusc gown black, the eyes hazel, and the hair and beard auburn. It has been retouched many times, and was painted entirely white in 1793. This demi-figure is one of only two representations definitely accepted as accurately portraying William Shakespeare's physical appearance. The monument is topped with strapwork rising to a heraldic shield displaying Shakespeare's arms, on either side of which sits an allegorical figure: one, representing Labour, holds a spade, the other, representing Rest, holds an inverted torch and a skull.

Nightwear – also called sleepwear, or nightclothes – is clothing designed to be worn while sleeping. The style of nightwear worn may vary with the seasons, with warmer styles being worn in colder conditions and vice versa. Some styles or materials are selected to be visually appealing or erotic in addition to their functional purposes.

Ejaculation is the discharge of semen (the ejaculate; normally containing sperm) from the penis through the urethra. It is the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. After forming an erection, many men emit pre-ejaculatory fluid during stimulation prior to ejaculating. Ejaculation involves involuntary contractions of the pelvic floor and is normally linked with orgasm. It is a normal part of male human sexual development.

Ejaculation can occur spontaneously during sleep (a nocturnal emission or "wet dream") or in rare cases because of prostatic disease. Anejaculation is the condition of being unable to ejaculate. Dysejaculation is an ejaculation that is painful or uncomfortable. Retrograde ejaculation is the backward flow of semen from the urethra into the bladder. Premature ejaculation happens shortly after initiating sexual activity, and hinders prolonged sexual intercourse. A vasectomy alters the composition of the ejaculate as a form of birth control.