Reflex Arcs!

Patellar Reflex- animation (first one)1) Choose one member of your group to be the subject. Have the subject sit on the edge of a table or tall lab chair with the knees off the table or chair and the legs dangling and relaxed.2) Palpate (feel under the surface of the skin) the patella and the tibial tuberosity. The patellar tendon, the insertion of the quadriceps femoris, is between those two structures. To be sure you have found the tendon, have the subject flex the quadriceps muscles, but not move the leg while you palpate the tendon.3) Gently but firmly tap the patellar tendon with the reflex hammer.4) Now ask the subject to clasp both hands in front of the chest and isometrically pull in opposite directions. This action leads to an enhancement of spinal reflexes causing an enhanced patellar reflex. 5) While the subject is pulling, tap the patellar tendon again and see if there is a difference in the reflexual response.

Biceps Jerk- animation

1) Have the subject sit at a desk and lay one arm on the desktop. The arm should be at a 90o angle and completely relaxed. 2) Ask the subject to isometrically contract the biceps brachii so you can palpate the tendon in the antecubital fossa (front side of the elbow).3) After locating the tendon, have the subject relax and place your thumb over the tendon.4) Tap your own thumb with the reflex hammer.5) If the reflex is absent ask the subject to clench his or her teeth for a reinforced reflex and try the test again.

Achilles Reflex (Ankle Jerk)- animation 1) Have the subject put one foot on the floor and place the knee of the other leg on a chair with the foot dangling over the edge.2) Ask the subject to slightly dorsiflex the foot to stretch the tendon a little, but remain relaxed.3) Tap the calcaneal tendon with the reflex hammer and observe the response of the foot.

Plantar Flexion- animation1) Have the subject seated with a foot propped up and relaxed.2) Using the metal end of the reflex hammer, stroke the plantar surface of the foot starting at the heel, moving up the lateral side of the foot, and then under the toes.3) Observe the reflexual response of toes.

Testing the Pupillary Reflex- animation (stop at 55sec)

1) In a dimly-lit room, have the subject look out toward a wall and hold a green card on the bridge of his or her nose to separate each eye’s field of vision. 2) Bring a penlight from the side to within 5 to 10 cm of ONE of the subject’s eyes.3) Stimulate the eye for 3 to 5 seconds. Observe the response of the pupil in both eyes.4) After allowing the subject’s eyes to return to the pre-dilated state, repeat with the subject’s other eye. Again, note the response in both eyes.