Reflex Arc encounter

Currently I work at a primary care doctor’s office where I have been given the opportunity to see the doctor evaluate patients while I translate. Part of the examination of a physical exam reminded me of histology class, particularly the nervous system. When the doctor wants to check if the reflexes are intact, he will tap the knee joint with an instrument and analyze the response. As I watch these examinations, most of the patients are surprised by their body’s response because it was unconscious.  

            While discussing the nervous system in lecture we briefly talked about the reflex arc and its mechanism. This is only one example of your nervous system functioning through a reflex arc, there are many more instances. For example, when light suddenly hits the eye the pupils automatically constrict. Also, when your finger touches a hot surface your body automatically withdraws itself from the hazard. Our peripheral nervous system is divided into afferent and efferent pathways. The sensory afferent pathways includes the receptors which sense changes deviating from homeostasis and the nerves connected to them. These nerves relay the change information towards the spinal cord and brain. The somatic efferent pathway sends out information to the effector cells after the spinal cord and brain has integrated the information. This impulse will cause a change in the effector cells to return to homeostasis.

            Our nervous system functions at incredible speeds. However, in the case of a reflex arc the body must react almost instantly after an incident. Therefore, the integration process only happens in the spinal cord with interneurons rather than traveling to the brain. When the doctor taps your knee joint, it causes a stretch in the muscles which is detected by the stretch receptors. This information is relayed to the dorsal horn of the spinal cord via sensory afferent pathways. The interneurons relay the information through the ventral horn to the motor neurons. This signals the front leg muscles to contract and the hamstrings to relax. At the clinic Dr. Kurup analyzes the response time of each patient and judges their reflex functioning. From this exam it is possible for him to detect abnormalities in the sensory/motor pathways, the interneurons, or the neuromuscular junction.