Reflexes are the automatic response of a muscle, caused by a stimulus and does not involve consciousness. The stimulus could be a hot stove or something sharp that excites an afferent nerve causing the muscle movement. Afferent nerves are sensory neurons which carry information from the stimuli to the central nervous system (CNS). In the case of reflexes, the afferent nerve carries the impulse to the spinal cord, where instead of just traveling up the spinal cord and to the brain, an efferent nerve (which transmits information from the CNS to out muscles) carries a signal straight from the spinal cord back out to the muscle, causing a response to the stimulus–without thought. At the same time, the signal is sent up the spinal cord to the brain, where the information of the stimulus is then processed. Because the signal takes more time to get to the brain, by the time the brain has processed that you’ve burned your hand, for example, you’ve pulled it away. The image displayed below is called a reflex arc, as described above, it involves a stimulus to the skin, the information moving via an afferent nerve to the spinal cord, straight back out via an efferent nerve to the muscle.
In my experience, I can think of many times my reflexes have prevented severe injury. Over the summer, I cooked for my family. While in the kitchen, I went to move a tray of roasted veggies to make space for the dish I was holding and forgot that the tray was still hot from the oven. Before I knew it, I had quickly taken my hand away from the tray. At that point, I registered the pain of my hand and the burn. This is a good example of how the reflex arc works faster than your brain in registering the stimulus.
Works Cited
Noback, Charles R, and Graham Ratcliff. “Human Nervous System.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 19 June 2019.
Helixitta. “Two Neuron Reflex Arc.” Wikipedia, 11 May 2019.