Patellar Lab Report

Introduction There are two groups of reflexes in the human body, with two ways to categorize each of them. Reflexes can either be inborn and connected through the nervous system, or they can be learned through practice. Another way to explain a reflexive category would be autonomic reflexes or somatic reflexes. Autonomic reflexes are those which are unaware to us and act on visceral organs of the body, whereas somatic reflexes involve skeletal muscle stimulation. Both types of reflexes are put into effect via the nervous system. (1)
The Patellar reflex, or Knee-Jerk reflex, is used to test the nervous tissue in the spinal cord from L2-L4. The patellar reflex is known as a “reflex arc”. It is a negative feedback circuit that is made of three components. The first is a sensory, or afferent neuron which takes in information from a sensory stimulus, and translates it to an electrical signal, which then gets sent to the central nervous system. The second piece is an interneuron in the integration center, which is a processing center that determines the strength of the response of the incoming stimulus. The third piece is a motor, or efferent neuron. The motor neuron will take the information received from the interneuron and send it on to its effectors (muscles or glands), which will activate a response.
The patellar reflex is classified as a somatic reflex because it involves the stimulation of skeletal muscle, specifically stimulation of the Quadriceps femoris. It is also an example of a monosynaptic reflex arc, which is simply a neural pathway controlling a somatic reflex. In a monosynaptic reflex arc, there is only one motor neuron and one sensory neuron, which form a single chemical synapse. This means when the patellar tendon is tapped with a reflex hammer, there needs to only be a very brief stimulation to the muscle spindles. These muscle spindles provide the feedback that the brain needs to regulate tension in skeletal muscles. In other words, there will be