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What Are Reflex Actions?

Tapping the petellar tendon with a reflex hammer will trigger the knee jerk reflex.
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  • Written By: Jacob Queen
  • Edited By: Lauren Fritsky
  • Last Modified Date: 26 September 2014
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Reflex actions are loosely defined as any action that the body performs unconsciously. There are several different kinds of reflex actions, including some that are responses to external stimuli and others that regulate body organs and functions. There is also a theoretical class of reflex actions that can be learned, but the existence of these and the mechanism behind them is debated.

Many reflex actions happen in response to external stimuli, and most of these actually work without any involvement from a person’s brain. For example, if a person trips at a campsite and his hand falls into the campfire, he will quickly retract it without even thinking. This happens because the nerve signal from the injury travels through the body—when it reaches the spinal cord, it triggers an automatic response before the brain can ever get involved. The spinal cord reacts by sending back another signal that causes the person to automatically pull his hand away from the fire.

This kind of response is also responsible for the well-known knee-jerk reflex that doctors use to test a person’s nervous system. In that case, the purpose of the reflex is to help a person stay balanced when walking. Most of these kinds of reflexes exist to protect people from injury or deal with things that require immediate action. For example, people blink when something is flying towards their eyes, and this sometimes happens so fast that people don’t even realize they’re doing it.

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Another kind of reflex involves the body’s ability to regulate basic functions like the heart beat and breathing. The brain keeps track of all this and keeps it going without a person’s awareness, and this is generally necessary for survival. The main thing that separates this type of reflex action is that the there is no requirement for external stimulation.

Some scientists have theorized about another kind of reflex action called a conditioned reflex. These involve a learning process where people experience something enough times and eventually develop a reflexive response to it. Unlike most reflexes involving external stimulation, these would involve the brain directly. The idea for this came from a Russian scientist named Ivan Pavlov who figured out that it was possible to make a dog salivate when it hears the sound of a bell by consistently ringing a bell right before feeding it. Scientists are generally in agreement that these sorts of reactions exist, but there is some debate about whether or not they should be called reflexes.

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pastanaga
Post 2

@Iluviaporos - It's really annoying when that happens. I'm not sure if it would count as the same level of conditioning as the dogs who salivate when they hear the bell though.

Reading this made me try the blinking reflex. It's weird that you can't really control it at all. They say that's why you can't kill yourself by holding your breath. Even if you can hold it long enough to pass out, your body will automatically begin to breathe again once you are unconscious and unable to control it. I guess it makes sense that you should have that reflex. Apparently dolphins don't have it and they have to sleep with one side of the brain awake all the time to bring them to the surface to breathe. If they had a reflex that made them breathe, they could drown.

lluviaporos
Post 1

One thing that I've always thought of as a conditioned reflex which seems to happen to a lot of people involves typing. I find that if I am really used to writing a word like "forget" and I write that word a lot, if I have to write a word like "forgery", while I am touch typing and not paying strict attention to my fingers I might later read back and realize that I typed "forget" instead of "forgery" automatically.

That's not the best example, but it does tend to be words that are similar. For example, I just started to write "doesn't" instead of "does" and had to erase it.

I've heard that similar things can happen when people are playing the piano. I mean, when I think about it, I am just typing completely by reflex, I'm not seeking out each key, or looking at the keyboard, I'm just letting my fingers do the typing. Maybe that's why it allows me to develop a kind of conditioned reflex to the starts of some words.

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