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Encyclopedia > Reflex

A reflex action is an automatic (otherwise called involuntary) neuromuscular action elicited by a defined stimulus.[1] In most contexts, especially involving humans, a reflex action is mediated via the reflex arc (although this is not always true in other animals, or in more casual usage of the term 'reflex'.) Reflexive may refer to: In grammar: Reflexive pronoun, a pronoun with a reflexive relationship with its self-identical antecedent Reflexive verb, where a semantic agent and patient are the same In mathematics and computer science: Reflection (computer science), the ability of a program to observe and possibly modify its high... In physiology, a stimulus is a detectable change in the internal or external environment. ... A reflex arc is the neural pathway mediating a reflex. ...

Contents

Mechanism

A reflex action or reflex is a biological control system linking stimulus to response and mediated by a reflex arc. Reflexes can be built-in or learnt. For example, a person stepping on a sharp object would initiate the reflex action through the creation of a nociceptive stimulus within specialized sense receptors located in the skin tissue of the foot. The resulting stimulus would be transmitted through an afferent nerve to the spinal cord. This stimulus is usually processed by an interneuron to create an immediate response to nociception by initiating a motor response to withdraw from the pain-producing object. This retraction would occur as the sensation is arriving in the brain and producing the subjective perception of pain, which would result in a more cognitive evaluation of the situation. A control system is a device or set of devices to manage, command, direct or regulate the behaviour of other devices or systems. ... Stimulation is the irritating action of various agents (stimuli) on muscles, nerves, or a sensory end organ, by which activity is evoked; especially, the nervous impulse produced by various agents on nerves, or a sensory end organ, by which the part connected with the nerve is thrown into a state... A response is the following: Often a response is the result of a stimulus. ... A reflex arc is the neural pathway mediating a reflex. ... Pain redirects here. ... In physiology, a stimulus is a detectable change in the internal or external environment. ... The mechanism of the reflex arc In the nervous system, afferent neurons--otherwise known as sensory or receptor neurons--carry nerve impulses from receptors or sense organs toward the central nervous system. ... The Spinal cord nested in the vertebral column. ... An interneuron (also called relay neuron,association neuron or bipolar neuron) is a term used to describe a neuron which has two different common meanings. ... A top-down view of skeletal muscle A muscle contraction (also known as a muscle twitch or simply twitch) occurs when a muscle cell (called a muscle fiber) shortens. ... Cognitive The scientific study of how people obtain, retrieve, store and manipulate information. ...


Reflexes are tested as part of a neurological examination to assess damage to or functioning of the central and peripheral nervous system. The neurological examination is the physical examination of the nervous system. ... A diagram showing the CNS: 1. ... The Peripheral nervous system resides or extends outside the CNS central nervous system (the brain and spinal cord) to serve the limbs and organs. ...


Reflexes may be trained, such as during repetition of motor actions during sport practice, or the linking of stimuli with autonomic reactions during classical conditioning. This article or section is in need of attention from an expert on the subject. ... Classical Conditioning (also Pavlovian or Respondent Conditioning) is a form of associative learning that was first demonstrated by Ivan Pavlov. ...


Reaction time

For a reflex, reaction time or latency is the time from the onset of a stimulus until the organism responds. Scientist have started to research who has the faster reflexes between men and women. Reaction time, in humans, is the elapsed time between the receiving of stimuli and the subsequent reaction. ... Life on Earth redirects here. ...


In humans, reaction time to visual stimuli is typically 150 to 300 milliseconds.[2] This article is about modern humans. ... Look up vision in Wiktionary, the free dictionary. ...


Human reflexes

The mechanism of the reflex arc. Note that this image includes an interneuron in the monosynaptic patellar reflex for purposes of illustration.

Reflex actions include: Image File history File links ReflexArc1. ... Image File history File links ReflexArc1. ... A reflex arc is the neural pathway mediating a reflex. ... An interneuron (also called relay neuron,association neuron or bipolar neuron) is a term used to describe a neuron which has two different common meanings. ... The patellar reflex or knee jerk is a monosynaptic reflex. ...


Tendon reflexes and stretch reflexes

The deep tendon reflexes provide information on the integrity of the central and peripheral nervous system. Generally, decreased reflexes indicate a peripheral problem, and lively or exaggerated reflexes a central one. Tendon reflex (or T-reflex) is an involuntary muscle contraction after its tendon is hit. ... It is reflex muscle contraction in response of its stretch. ...

While the reflexes above are stimulated mechanically, the term H-reflex refers to the analogous reflex stimulated electrically, and Tonic vibration reflex for those stimulated by vibration. Pronation A rotation of the forearm that moves the palm from an anterior-facing position to a posterior-facing position, or palm facing down. ... The tricep reflex is tested as part of the neurological examination to asses the sensory and motor pathways within the C7 and C8 spinal nerves. ... The patellar reflex or knee jerk is a monosynaptic reflex. ... The ankle jerk reflex, also known as the Achilles reflex, occurs when the Achilles tendon is tapped while the foot is dorsi-flexed. ... In medicine (neurology), the Babinski reflex or Babinski sign is a reflex that can identify disease of the spinal cord and brain. ... This reflectory reaction was first described by Paul Hoffmann (hense H-reflex) in 1910. ... Tonic vibration reflex is a sustained contraction of a muscle subjected to vibration. ...


Reflexes involving cranial nerves

Name Sensory Motor
Pupillary reflex II III
Accommodation reflex II III
Corneal reflex, also known as the blink reflex V VII
Caloric reflex test/Vestibulo-ocular reflex VIII III, IV, VI +
Gag reflex IX X

In medicine, pupil constriction (also known as the pupillary reflex) is reduction of pupil size. ... Human eye The Accommodation Reflex is a reflex action of the eye, in response to focusing on a near object, then looking at distant object (and vice versa). ... Corneal reflex This is an automated involuntary blinking of the eyelids (See : Reflex) elicited by stimulation (such as touching or a foreign body) of the eyeballs cornea. ... Example of a blinking eye (slow-motion) Blinking is the rapid closing and opening of the eyelid. ... In medicine, the caloric reflex test is a test of the vestibulo-ocular reflex. ... Figure 3 Three-neuron arc, during a head movement to the right. ... This article does not cite any references or sources. ...

Reflexes in infants only

Main article: Primitive reflexes
grasp reflex
grasp reflex

Newborn babies have a number of other reflexes which are not seen in adults, referred to as primitive reflexes.[3] These include: Primitive reflexes are reflex actions originating in the brain stem that are exhibited by infants but not adults in response to particular stimuli. ... Image File history File linksMetadata Size of this preview: 450 × 600 pixel Image in higher resolution (960 × 1280 pixel, file size: 545 KB, MIME type: image/jpeg) Permission see below This image needs to be cleaned up, because: blurry For help, see Commons:Images for cleanup. ... Image File history File linksMetadata Size of this preview: 450 × 600 pixel Image in higher resolution (960 × 1280 pixel, file size: 545 KB, MIME type: image/jpeg) Permission see below This image needs to be cleaned up, because: blurry For help, see Commons:Images for cleanup. ... A human infant The word Infant derives from the Latin in-fans, meaning unable to speak. ...

The asymmetrical tonic neck reflex (ATNR) is a primitive reflex found in newborn humans, but normally vanishes by the childs first birthday. ... The grasp reflex is the tendency of an infant to clutch its hands into fists, grabbing tightly around whatever crosses their palms. ... The hand to mouth reflex is when you put your finger down your throat in order to induce vomiting or cough. ... The Moro reflex, also known as the startle reflex, is one of the infantile reflexes. ... Suction is the creation of a partial vacuum, or region of low pressure. ... The tonic labyrinthine reflex (TLR) is a primitive reflex found in newborn humans. ...

Other reflexes

Other reflexes found in the human nervous system include:

Processes such as breathing, digestion, and the maintenance of the heartbeat can also be regarded as reflex actions, according to some definitions of the term. The anal wink or anocutaneous reflex is the reflexive contraction of the external anal sphincter upon stroking of the skin around the anus. ... This involves a withdrawal reflex—the flexors on the withdrawing side are contracting and the extensors are inhibited. ... Escape reflex, a kind of a escape response, is a simple reflectory reaction in response to stimuli indicative of danger, that initiates an escape motion of an animal. ... The jaw jerk reflex is a motor relfex used to test the status of a patients trigeminal nerve (CN V). ... Submerging the face into water causes the mammalian diving reflex, which is found in all mammals (including humans, although it is less pronounced), but especially in marine mammals (as, for example, whales and seals. ... The oculocardiac reflex, also known as Aschner phenomenon, Aschner reflex, or Aschner-Dagnini reflex, is a decrease in pulse rate associated with traction applied to extraocular muscles and/or compression of the eyeball. ... Horizontal optokinetic nystagmus. ... ACHOO syndrome is inherited in an autosomal dominant fashion. ... The scratch reflex is a reflex transmitted by very sensitive nerve endings near the surface of the skin via the spinal cord, and is a reflex frequently inherited by mammals. ... The nociceptive withdrawal reflex (NWR) is a spinal reflex intended to protect the body from damaging stimuli. ... Breathing transports oxygen into the body and carbon dioxide out of the body. ... For the industrial process, see anaerobic digestion. ... Heart rate is a term used to describe the frequency of the cardiac cycle. ...


See also

Automatism, from the Greek automatismos or self action, is the spontaneous production of often purposeless verbal or motor behavior without conscious self-control, self-conceptualization or self-censorship. ... A voluntary action is a motor response induced by a processed response to external stimulus. ...

References

  1. ^ Purves (2004). Neuroscience: Third Edition. Massachusetts, Sinauer Associates, Inc.
  2. ^ Human Benchmark: Reaction Time Statistics. Retrieved on 2007-10-11.
  3. ^ NIC27 at FPnotebook

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