Diagram and label the knee jerk reflex. What is the physiological function of this reflex? Explain how this reflex may be important during walking, if you didn't notice a dip in the sidewalk and stepped into it. What is the role of reciprocal inhibition? How would the reflex be affected if reciprocal inhibition failed? Describe the effects on the reflex of severing each structure involved in the

Question

reflex, considering one structure at a time. Describe the effects of damaging the opposite side of the spinal cord, or areas higher or lower on the spinal cord.

What will be an ideal response?

Answer 1

The diagram should resemble Figure 13.6 in the chapter. The function of the reflex is to control movement at the knee joint. If you stepped down farther than you expected, your opposite knee may bend more than it would have, activating the reflex and straightening that leg to prevent you from falling. Reciprocal inhibition allows muscles opposing extension of the leg to be inhibited. If this inhibition failed, leg extension would not occur; instead, the knee would be "locked." Severing the afferent or efferent nerve, the spinal cord at the level of the reflex, or the muscle would all prevent the reflex from occurring. Damage to the opposite side of the spinal cord or areas above or below the cells involved in the reflex should have no effect on the basic reflex. (Note to instructor: In reality, it is not so simple, but the point is to get the students to consider the basic mechanics of the reflex.)