Involuntary reactions to stimulus resulting with instantaneous movement are called reflexes. Reflexes are apparent from birth including blinking and sneezing. There are many types of reflexes in a healthy person.



A pain receptor in the skin is an example of a sensory neuron. The sensory neuron detects the pain and sends a signal that is intercepted by a motor neuron, which results in the withdrawal reflex. Since only one interaction occurs this is called a monosynaptic reflex. More complex reflexes, known as polysnaptic reflexes, involve interneurons and may be integrated through the brainstem, cerebrum or spinal cord.

The reflex arc is the arrangement of neurons in the structure of circuits and networks to form a pathway, which a nerve impulse travels to signal an action reflex. This signal does not pass into the brain, although the brain receives sensory input, but takes place in the spinal cord instead, which speeds the process. There are two types of reflex arcs:
· Autonomic reflex arc is associated with the inner organs.
· Somatic reflex arc influences the muscles.

Primitive reflexes are exhibited by healthy infants and begin in the central nervous system. These same reflexes should not be exhibited in healthy adults in response to a particular stimulus. The frontal lobes inhibit primitive reflexes as a child develops. There are several types of primitive reflexes including:

· Babinski Reflex – This is caused by stimulation to the sole of the foot. In a child from infancy to age two, when the sole of the foot is stroked, the big toe will move forward and the other toes fan out. A physician may attempt to elicit a Babinski reflex in an older child to test for problems of the central nervous system.

· Moro Reflex – It appears when the hand supporting an infant’s head is momentarily released, quickly supporting the head again without allowing the head to drop back far enough to cause harm. The infant’s hands will quickly jump to the side of the body, palms facing up and thumbs flexed. This is also known as a startle response or embrace reflex.

· Rooting Reflex – This occurs when an infant’s face turns and sucking motions are elicited by a stimulus to the cheek or lips. This information is especially important for nursing mothers when attempting to feed a newborn. The response generally disappears by three to four months of age.

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