The anal wink, anal reflex, perineal reflex, or anocutaneous reflex is the reflex

Reflex

A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...

ive contraction of the external anal sphincter upon stroking of the skin around the anus.

A noxious or tactile stimulus will cause a wink contraction of the anal sphincter muscles and also flexion. The stimulus is detected by the nociceptor

Nociceptor

A nociceptor is a sensory receptor that responds to potentially damaging stimuli by sending nerve signals to the spinal cord and brain. This process, called nociception, usually causes the perception of pain.-History:...

s in the perineal

Perineal

Perineal can refer to:* The perineum* Perineal artery* Perineal nerve...

 skin to the pudendal nerve

Pudendal nerve

The pudendal nerve is a sensory and somatic nerve in the pelvic region which is a large branch of the sacral plexus that innervates the external genitalia of both sexes, as well as sphincters for the bladder and the rectum...

, where a response is integrated by the spinal cord

Spinal cord

The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

 sacral segments S2-S4.

The absence of this reflex indicates that there is an interruption of the reflex arc

Reflex arc

A reflex arc is a neural pathway that controls an action reflex. In higher animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord...

, which may be in the sensory afferent

Afferent

Afferent is an anatomical term with the following meanings:*Conveying towards a center, for example the afferent arterioles conveying blood towards the Bowman's capsule in the Kidney. Opposite to Efferent.*Something that so conducts, see Afferent nerve fiber...

 limb or the motor efferent

Efferent

Efferent is an anatomical term with the following meanings:*Conveying away from a center, for example the efferent arterioles conveying blood away from the Bowman's capsule in the kidney. Opposite to afferent....

 limb. The synapse

Synapse

In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell...

 between the afferent and efferent limbs occurs in the lowest sacral segments of the spinal cord

Spinal cord

The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

.

External links

• Testimony by Dr. Bruce Woodling — Expert testimony in McMartin Child Abuse Case.
• False allegations of child abuse — Expert opinion on false allegations of child abuse, with mention of "anal wink" testimony.