Reflexes are the body's involuntary responses to various stimuli. They are controlled in large part by the human nervous system which has three main functions: sensory input, integration, and motor output. Sensory input is due to sensory receptors throughout the body collecting information about one's external surroundings and internal environment, and relaying them to various information centers. A sensory receptor recognizes some form of stimulus in the external or internal environment and responds by creating graded potentials or action potentials in the cell or in the cell adjacent to it. These action potentials consequently lead to integration. Integration is mainly carried out within the Central Nervous System, which consists of the brain and spinal cord in humans. (Campbell, 1024) Motor output is what occurs when the central nervous system makes sense of the sensory input due to integration, and sends information to effector cells in the body. Effector cells are the gland cells or muscle cells that make sure the body's responses to certain stimuli are carried out. (Campbell, 1024) Nerves conduct these signals. Specifically speaking, the particular nerves that relay the motor and sensory information from the central nervous system jointly make up what is called the peripheral nervous system.
[...] Our angle deflection, using the standard angles given in the lab manual, never exceeded two degrees, so no further calibration was necessary. Table 2 shows the results of the first test, during which we delivered a tap to the patellar tendon with the hammer. We measured the latency and the amplitude of the response on the computer screen. Some of our trials had identical latency results, but generally ranged from .09 to .16. The magnitude of the response did, indeed, fluctuate. [...]
[...] by the body. A reflex is therefore initiated when a stimulus is applied to a sensory receptor. The sensory receptor converts a chemical or physical stimulus into an electrical signal that can be interpreted by the body. It links certain stimuli to a certain response, hence even before sensory receptors can send a message to the brain about the environment, the spine picks it up and automatically sends back the information to the muscle, causing a spasm. The brain is only aware of the response after the reflex has taken place. [...]
[...] This change in reflex response can be attributed to the fact that when the subject was otherwise occupied with the Jendrassik maneuver, they were not consciously concentrating as much on the experiment. Consequently, the possibility of the subject consciously inhibiting or influencing the responses was much smaller. This is similar to a situation where one is absolutely unaware of a coming danger and sometimes unnecessarily sometime necessarily greatly exaggerates their reflexive motion. An example of this could be coming too close to a stove without realizing and jumping back, when obviously all that had to be done was to move your hand away. [...]
[...] The Jendrassik maneuver should increase amplitudes yet have no significant effect on the latency of a reflex response We hypothesized that the latency of the voluntary knee jerks would be longer than involuntary knee jerks because of the longer distance that neurons must travel to reach the brain and return. We also hypothesized that the knee jerk utilizing the Jendrassik maneuver would have higher amplitude than the normal knee jerks. We also made the assumption that the voluntary knee jerk amplitude is irrelevant because of the thought controlled nature of the kick. [...]
[...] Even though sources of error do exist, our results closely mimic our hypothesis. The first trial with involuntary knee jerks set the standard for amplitude and latency for the two subsequent trials. The next trial involved the voluntary knee jerk and was performed by hitting the hammer on the table as opposed to on the knee. The difference between an involuntary reflex response and a voluntary knee jerk is that the involuntary reflex doesn't have to go all the way to the brain in order to be processed. [...]
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