Question

in the patellar tendon reflex arc, the patellar ligament is stretched, which stretches the quadriceps femoris muscle of the thigh. this reflex will cause the quadriceps femoris to ____ and the hamstrings to ____. multiple choice contract; relax contract; contract relax; contract relax; relax relax then contract; contract then relax

Explanation:

In the patellar tendon reflex arc, when the patellar ligament is stretched (stimulating the quadriceps femoris), the quadriceps femoris contracts (as it is the effector muscle being stimulated in this reflex). At the same time, reciprocal innervation occurs, which means the antagonist muscle (the hamstrings) relaxes to allow the movement caused by the contracting quadriceps femoris.

Answer:

contract; relax