Patellar Reflex (Brent Shano)

Author

Brent Shano

Principles Illustrated

1. An example of a monosynaptic reflex arc.

2. Absence or exaggeration of the reaction suggests that there may be damage to the central nervous system.

3. Can be helpful in recognizing thyroid disease.

Standards

• HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multi cellular organisms.

• HS-LS4-4 Construct an explanation based on the evidence for how natural selection leads to adaptation of populations.

• HS-LS2-8 Evaluate the evidence for the role of group behavior on individual and species' chances to survive and reproduce.

Questioning Script

Prior knowledge & experience:

Students know that the central nervous system (CNS) made up of the brain and spinal cord control specific muscular movements. In this case the quadriceps and all the leg muscles. They understand the basis of electrical impulses coming from the brain and moving through varying neurons to achieve a desired result. Here the main focus are motor neurons. Students will have grasped the concept that through afferent and efferent impulses the signal will either go from the brain, through the systemic pathway of nerves to achieve the motor output OR go from a sensory input through the systemic pathway that goes to the brain and can either assimilate the data for processing or yield another motor output based on the sensory input that just took place.

Root question:

Why does the leg move when my brain consciously did not tell it to?

Target response:

This is a "reflex". The normal pathways of mechanical input to motor output are not totally in effect here. The brain is basically "bypassed" and the signal is shortened not allowing for processing of the information. A reflex occurs as the body is hardwired to generate this response upon the specific pressure applied in a specific region.

Common Misconceptions:

This specific reflex arc is found in the knee at an intersection where a joint can be found between the femur and the tibia along with the fibula. This reflex arc is not found in the elbow, hips, or shoulder girdle as one might possibly assume as they learn about intersections of bones joining together.

Photographs