Stimulation of skin in certain regions of the body causes contraction of underlying muscles. This occurs reflexly, the reflex being mediated through the spinal cord. Some of these superficial reflexes are described below.
1. The abdominal reflexes consist of contraction of underlying muscles on stroking the skin of the abdomen in its upper (T6,7), middle (T8,9) and lower (T10 to T12) parts.
2. The cremasteric reflex consists of elevation of the scrotum on stroking the skin of the medial side of the thigh (T12 to L2).
3. The gluteal reflex consists of contraction of the glutei on stroking the overlying skin (L4 to S1).
4. The normal plantar reflex consists of plantar flexion of the toes on stroking the skin of the sole (L5 to S2). When there is an injury to the corticospinal system an abnormal response is obtained. There is extension (dorsiflexion) of the great toe and fanning out of other toes. This response is referred to as Babinski’s sign. Such a response may also be seen in newborn infants, and sometimes in sleeping or intoxicated adults.
5. The anal reflex consists of contraction of the external anal sphincter on stroking the perianal region (S4,5, coccygeal).