question: Why exactly do we blink?
comment: Your eyes are wet on the surface, and all the internals of your eyes are wet— the tissues are almost all water inside. Blinking replenishes the thin coating of tears that lubricates your eyes and keeps them from drying out.
passages: Section::::Function and anatomy.:Central nervous system's control.
  
  Though one may think that the stimulus triggering blinking is dry or irritated eyes, it is most likely that it is controlled by a "blinking center" of the globus pallidus of the lenticular nucleus—a body of nerve cells between the base and outer surface of the brain. Nevertheless, external stimuli can contribute. The orbicularis oculi is a facial muscle; therefore its actions are translated by the facial nerve root. The levator palpebrae superioris’ action is sent through the oculomotor nerve. The duration of a blink is
   Blinking
  
  Blinking is a bodily function; it is a semi-autonomic rapid closing of the eyelid. A single blink is determined by the forceful closing of the eyelid or inactivation of the levator palpebrae superioris and the activation of the palpebral portion of the orbicularis oculi, not the full open and close. It is an essential function of the eye that helps spread tears across and remove irritants from the surface of the cornea and conjunctiva.
   A reflex blink occurs in response to an external stimulus, such as contact with the cornea or objects that appear rapidly in front of the eye. A reflex blink is not necessarily a conscious blink either; however it does happen faster than a spontaneous blink. Reflex blink may occur in response to tactile stimuli (e.g. corneal, eyelash, skin of eyelid, contact with eyebrow), optical stimuli (e.g. dazzle reflex, or menace reflex) or auditory stimuli (e.g., menace reflex)
  
  Section::::Types of blink.:Voluntary blink.
   Menace reflex
  
  The menace response is one of three forms of blink reflex. It is the reflex blinking that occurs in response to the rapid approach of an object. The reflex comprises blinking of the eyelids, in order to protect the eyes from potential damage, but may also include turning of the head, neck, or even the trunk away from the optical stimulus that triggers the reflex.
   The cornea has unmyelinated nerve endings sensitive to touch, temperature and chemicals; a touch of the cornea causes an involuntary reflex to close the eyelid. Because transparency is of prime importance, the healthy cornea does not have or need blood vessels within it. Instead, oxygen dissolves in tears and then diffuses throughout the cornea to keep it healthy. Similarly, nutrients are transported via diffusion from the tear fluid through the outside surface and the aqueous humour through the inside surface. Nutrients also come via neurotrophins supplied by the nerves of the cornea. In humans, the cornea has a diameter of about 11.5 mm and a thickness of 0.5–0.6 mm in the center and 0.6–0.8 mm at the periphery. Transparency, avascularity, the presence of immature resident immune cells, and immunologic privilege makes the cornea a very special tissue.
   Section::::Blinking in everyday life.:Adults.
   There are multiple muscles that control reflexes of blinking. The main muscles, in the upper eyelid, that control the opening and closing are the orbicularis oculi and levator palpebrae superioris muscle. The orbicularis oculi closes the eye, while the contraction of the levator palpebrae muscle opens the eye. The Müller’s muscle, or the superior tarsal muscle, in the upper eyelid and the inferior palpebral muscle in the lower 3 eyelid are responsible for widening the eyes. These muscles are not only imperative in blinking, but they are also important in many other functions such as squinting and winking. The inferior palpebral muscle is coordinated with the inferior rectus to pull down the lower lid when one looks down.
   Blinking also protects the eye from irritants. Eyelashes are hairs attached to the upper and lower eyelids that create a line of defense against dust and other elements to the eye. The eyelashes catch most of these irritants before they reach the eyeball.
   The precise adaptive significance behind the attentional blink is unknown, but it is thought to be a product of a two-stage visual processing system attempting to allocate episodic context to targets. In this two-stage system, all stimuli are processed to some extent by an initial parallel stage, and only salient ones are selected for in-depth processing, in order to make optimum use of limited resources at a late serial stage.
   Some animals, such as tortoises and hamsters, blink their eyes independently of each other. Humans use winking, the blinking of only one eye, as a form of body language.
  
  Section::::Function and anatomy.
  
  Blinking provides moisture to the eye by irrigation using tears and a lubricant the eyes secrete. The eyelid provides suction across the eye from the tear duct to the entire eyeball to keep it from drying out.
   Section::::Overview.
   Section::::Fictional character biography.:Dark Reign.
  
  When Hercules travels to the Underworld, Blink is among the dead characters seen in Erebus gambling for their resurrection. Unlike the others, Blink just stands there watching them gamble.
  
  Section::::Fictional character biography.:Necrosha.
   Corneal reflex
  
  The corneal reflex, also known as the blink reflex, is an involuntary blinking of the eyelids elicited by stimulation of the cornea (such as by touching or by a foreign body), though could result from any peripheral stimulus. Stimulation should elicit both a direct and consensual response (response of the opposite eye). The reflex occurs at a rapid rate of 0.1 seconds. The purpose of this reflex is to protect the eyes from foreign bodies and bright lights (the latter known as the optical reflex). The blink reflex also occurs when sounds greater than 40–60 dB are made.
   Blinking may have other functions since it occurs more often than necessary just to keep the eye lubricated. Researchers think blinking may help us disengage our attention; following blink onset, cortical activity decreases in the dorsal network and increases in the default-mode network, associated with internal processing. Blink speed can be affected by elements such as fatigue, eye injury, medication, and disease. The blinking rate is determined by the "blinking center", but it can also be affected by external stimulus.
   BULLET::::- Blinking - Blinking is also a natural response that can occur for no other reason than having dry eyes. It can also be the result of a person feeling greater levels of stress. Rapid blinking can indicate arrogance while reduced blinking can move towards a stare.
  
  BULLET::::- Winking - Winking can indicate that two people understand something without using words. It can mean "hello" or it can be a sign of flirtation.
   Spontaneous blinking which is done without external stimuli and internal effort. This type of blinking is conducted in the pre-motor brain stem and happens without conscious effort, like breathing and digestion.
  
  Section::::Types of blink.:Reflex blink.
   Section::::Fictional character biography.:New Mutants.
   Voluntary blink is larger amplitude than Reflex blink, with the use of all 3 divisions of the orbicularis oculi muscle.
  
  Section::::Blinking in everyday life.
  
  Section::::Blinking in everyday life.:Children.
   Section::::Immune responses of the Cornea.
  
  "Innate immune responses" defend against pathogens and toxin in a non-discriminatory manner. They provide an inherent barrier against corneal infection while also serving as a primary mode of defense that is present from birth. For instance, the orbit and the eyelid can guard against both traumatic events and exterior debris that may contain microorganisms. Other components of the ocular innate immune system include tears, epithelial cells, keratocytes, corneal nerves, the complement system, and interferons.
   In "Think!: Why Crucial Decisions Can't Be Made in the Blink of an Eye" (Simon and Schuster, 2006), Michael LeGault argues that "Blinklike" judgments are not a substitute for critical thinking. He criticizes Gladwell for propagating unscientific notions:
   Section::::Other versions.:Age of Apocalypse/Exiles Blink.:Miniseries.
   In a study done by and his colleagues students had to watch a movie. One group did so with a pen between their teeth while the other group had to hold the pen with their lips. The first group interpreted the movie funnier than the second, because the muscles responsible for smiling were used and then made the brain release hormones related to being happy. These studys show that facial expressions are not only the result of emotions but can also be their cause. 
  
  Section::::Reception.
   Section::::History.
   Associated pathology, such as a lesion of the facial nerve seen in Bell's palsy results in the inability to blink or close the ipsilateral eyelid. Subsequent lack of irrigation increases the risk of corneal inflammation and ulcers.
  
  Section::::Other muscles involved.
  
  Section::::Other muscles involved.:Levator palpebrae superior.
   on average 100–150 milliseconds according to UCL researcher and between 100–400 ms according to the Harvard Database of Useful Biological Numbers. Closures in excess of 1000 ms were defined as microsleeps.
  
  Greater activation of dopaminergic pathways dopamine production in the striatum is associated with a higher rate of spontaneous eye blinking. Conditions in which there is reduced dopamine availability such as Parkinson's disease have reduced eye blink rate, while conditions in which it is raised such as schizophrenia have an increased rate.
  
  Section::::Types of blink.
  
  There are three types of blink.
  
  Section::::Types of blink.:Spontaneous blink.
  