What is the difference between tonic and phasic receptors?
Give one reason why the Jendrassik maneuver may produce a response with greater amplitude than the involuntary knee-jerk. In your body you have muscles primarily designed to fight gravity (posture) and muscles to help you move; respectively called tonic and phasic. tonic muscles respond to faulty loading (over-use, under-use, disuse and abuse) by getting short and tight. On the other hand, phasic muscles respond to faulty loading by tending toward getting long and weak (actually they’re still strong, just strong in the wrong place). If you hit tendon below the person’s knee with a hammer you get the involuntary knee jerk. The elicited response is compared with the reflex result of the same action when the maneuver is not in use. Often a larger reflex response will be observed when the person is occupied with this maneuver, as the maneuver may prevent the person from consciously inhibiting or influencing his or her response to the hammer.
