other: Reflex (disambiguation)

A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. In most contexts, in particular those involving humans, reflex actions are mediated via the reflex arc; this is not always true in other animals, nor does it apply to casual uses of the term 'reflex'.

Reaction time

For a reflex, reaction time or latency is the time from the onset of a stimulus until the organism responds.

In animals, reaction time to visual stimuli is typically 150 to 300 milliseconds.

Tendon 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.

• Biceps reflex (C5, C6)
• Brachioradialis reflex (C5, C6, C7)
• Extensor digitorum reflex (C6, C7)
• Triceps reflex (C6, C7, C8)
• Patellar reflex or knee-jerk reflex (L2, L3, L4)
• Ankle jerk reflex (Achilles reflex) (S1, S2)
• Plantar reflex or Babinski reflex (L5, S1, S2)

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.

Reflexes usually only observed in human infants

main: Primitive reflexes

• Asymmetrical tonic neck reflex (ATNR)
• Grasp reflex
• Hand-to-mouth reflex
• Moro reflex, also known as the startle reflex
• Sucking
• Symmetrical tonic neck reflex (STNR)
• Tonic labyrinthine reflex (TLR)

Other reflexes

Other reflexes found in the central nervous system include:

• Anocutaneous reflex
• Bulbocavernosus reflex
• Escape reflex
• Oculocardiac reflex
• Optokinetic reflex
• Photic sneeze reflex
• Mammalian diving reflex
• Muscular defense
• Scratch reflex
• Startle reflex
• Withdrawal reflex
• Crossed extensor reflex

Many of these reflexes are quite complex requiring a number of synapses in a number of different nuclei in the CNS (e.g., the escape reflex). Others of these involve just a couple of synapses to function (eg., the withdrawal reflex). 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.

Grading

The activity of a reflex is usually graded on a scale from 0 to 4:

See also

• List of reflexes (alphabetical)
• Automatic behavior
• Involuntary action
• Voluntary action
• Preflexes