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.
I find this concept so interesting because I am also learning about it in my anatomy and physiology class. Essentially, a neural circuit allows the body to monitor the environment (or itself) and decide on an appropriate response to maintain homeostasis. The spinal cord is the major structure that connects the PNS and CNS is a neural circuit. Afferent nerves start in the PNS and travels to the CNS, while the Efferent nerve send signals from the CNS to effectors (targets) such as muscles, organs, and glands. My professor explained it to the class as if you’re walking on the beach and step on a piece of glass, your body isn’t just going to keep walking and ignore the pain. These nerves allow the brain to trigger a response that tells the body “ouch let me pick up my foot to stop the pain.” This happens frequently and without thought. These pathways communicate with electrical and chemical signals (action potential). It is helpful to break these systems down then put it all together to fully understand how they work individually and as a whole. But these nerves are so helpful and are a crucial neural circuit- like the majority.
Reflexes have always been a mind boggling idea for me personally. The fact that we can, without thinking, pull our body away from pain is something only science can explain, but as I was reading this, a new idea came to mind: reflexes without pain. This idea particularly came to mind because over the years I have involved myself in many sports, and for those who play sports they know that reflexes can play a big part. Our body knows how to instantly respond to pain, but how does our body know to put a hand up if a ball is being hurled at you and is a foot away from hitting you in the face. For instance, when I played a lot of baseball in middle and high school, there were numerous instances when I was not paying attention, then I turn around and a baseball is eye level and about to knock me out. Then, the reflexes kick in and without me thinking, my body acts and either ducks or catches it. Clearly there is no pain here, at least yet, so what happens with our brain and body connection here?