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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.
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.
For a reflex, reaction time or latency is the time from the onset of a stimulus until the organism responds.
In humans, reaction time to visual stimuli is typically 150 to 300 milliseconds.
Reflex actions include:
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.
Reflexes involving cranial nerves
Reflexes in infants only
Newborn babies have a number of other reflexes which are not seen in adults, referred to as primitive reflexes. These include:
Other reflexes found in the human nervous system include:
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Reflex". A list of authors is available in Wikipedia.|