Reflexes Lab

A sensory neuron carries the message from the receptor to the central nervous system (the spinal cord and brain). A motor neuron carries the message from the central nervous system to the effector. For instance, in the knee-jerk reflex arc the sensory

neuron directly connects to the motor neuron in the spinal cord.

Reflexes tested:

The photopupillary reflex is a reflex that adjusts the size of the upil in order to adjust for the varying degree of light in the area. To test this, we had a classmate cover his eye and cover it. After 5 minutes he uncovered his eye and the results are as follows:

The reason the response occurred was because the eye detected the intensity of the light and corrected for it, allowing less light into the eye. This ultimately reduced the stress on the eye.

The knee jerk reflex is a sudden involuntary forward movement of the lower leg that can be produced by a firm tap to the tendon located just below the kneecap. The term is loosely applied to any muscular response or belief that is automatic rather than thought. To test this we tapped our classmates knee. The results are as follows:

The reason this response occured was due to the pressure on the tendon. Remember that the knee is like a lever, and once the tendon is pressed in, it shortens, pulling up the knee.

The blink reflex is an involuntary blinking of the eyelids elicited by stimulation of the cornea (such as by touching or by a foreign body), though could result from any peripheral stimulus. To test this reflex we had our classmate hold surran wrap up by his face and stare at us throwing cotton balls at him, the results were as follows.

The results were due to speed and direction of the objects we were throwing at him. If we were to throw the cotton balls at his chest, he would likely not blink.

The plantar reflex is a superficial reflex obtained by stroking the skin on the lateral edge of the sole of the foot, starting at the heel advancing to the ball of the foot then continuing medially to the base of the great toe. The normal response is flexion of all the toes. On our test subject, she did not flex her toes. The reason she did not flex was likely due to the absence of the nerve responsible for the action in her foot

Finally, we tested our somatic nervous system by trying to catch a ruler as it fell

Our response times were as follows:

As shown in the graph, when asked to text while trying to grab the ruler, reaction times were more than doubled. This was because we cannot physically do two things at once, instead, we can only switch off from one task to another very rapidly.