A reflex is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus. It is an automatic response that occurs via neural pathways in the nervous system called reflex arcs. A stimulus initiates a neural signal, which is carried to a synapse. The signal is then transferred across the synapse to a motor neuron, which evokes a target response. These neural signals do not always travel to the brain, so many reflexes are an automatic response to a stimulus that does not receive or need conscious thought.
Reflexes are found with varying levels of complexity in organisms with a nervous system. There are many types of reflexes, and every healthy person has them. Some examples of reflexes include:
-
Protective Reflexes: Reflexes that protect the body from things that can harm it. For example, if you put your hand on a hot stove, a reflex causes you to immediately remove your hand before a "Hey, this is hot!" message even gets to your brain. Other protective reflexes are blinking when something flies toward your eyes or raising your arm if a ball is thrown your way. Even coughing and sneezing are reflexes. They clear the airways of irritating things.
-
DTR (Deep Tendon Reflex): A reflex that the doctor tests by tapping on a tendon with a reflex hammer. The reflex that the doctor tests is controlled by a specific nerve root. The reflex can be absent, normal, or increased.
-
Short-Latency Reflex: The simplest type of reflex, which has a very short delay between the stimulus and the response.
Reflexes are fine-tuned to increase organism survival and self-defense. This is observed in reflexes such as the startle reflex, which provides an automatic response to an unexpected stimulus, and the feline righting reflex, which reorients a cats body when falling to ensure safe landing.
