Jaw jerk reflex

The jaw jerk reflex is a motor reflex used to test the status of a patient's trigeminal nerve(CN V). The mandible?or lower jaw?is tapped at a downward angle just below the lips at the chin. Normally this reflex is not present?that is?the jaw does not move in response to this stimulus. However if the reflex exists it indicates there is a lesion along the upper motor neurontract leading to the trigeminal motor nucleus.

the information is erroneous for the jaw jerk reflex. When the masseter is stretched, it DOES contract; in a monosynaptic reflex fashion. The afferent limb is a mesencephalic trigeminal neuron. Trigeminal motor neuron form the efferent limb.

(ref: Nolte, J. The Human Brain. Mosby Ed.4, Missouri, 1999. p.301)

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It uses material from the http://en.wikipedia.org/wiki/Jaw+jerk+reflex Wikipedia article Jaw jerk reflex.