So why are we able to move (or seem to move) lightning fast when we have a reflex, but we are unable to move that fast and acutely at will?
In: Biology
This is a very good question and the answer is actually very interesting, especially when you’re someone like me who loves to learn things about how to human body works.
Usually, when you make a conscious decision to move, an electrical signal is sent from your brain down your spinal cord to your muscles which causes your muscles to contract therefore performing the action you wanted to do.
A reflex is a protective mechanism designed to prevent injury. Probably one of the easiest examples of a reflex is touching something hot. When you touch something hot, heat sensors in your fingers send an electrical signal saying “this is hot”. Usually this signal would travel to your brain via the spinal cord. However, in this situation, touching something hot is going to cause injury. So instead of sending a message all the way to the brain and all the way back to the muscles, the electrical signal goes from your fingers to your spinal cord and back to your muscles bypassing the brain entirely.
For example, when your hand touches something hot, your nerves send little lightning-fast jolts to your brain. Once you’ve received these jolts your brain will pull your hand away without any conscious input
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Nerve impulses take longer to travel when there are more synapses between neurons to cross. The reflex arc in your arm would travel to the spine then back to muscles in the arm with few synapses, so a stimulus would cause a reletavely immediate reaction. If you consciously wanted to move your arm, youd need to send a signal thriugh many more synapses in the brain and spine to get to finally get to the arm muscles, delaying the movement.
You can think of your brain as the boss, your spine as the overseer and your muscle (+ some local nerves) as the worker.
If the boss decides he wants the worker to do something, he tells the overseer, who tells the worker, who does the task. This takes some time.
A reflex is like the worker seeing something going wrong, so he just screams at the overseer, who screams some instructions back. The whole process is very quick *because* the boss is not involved.
Reflexes can be totally involuntarily or close to it and bypass a lot of the higher thought processes. Since we’re not wasting time deciding if we should do something a lot of time is saved. Your brain can go straight from “object flying at face” to “close eyes” without considering anything else
When your body does a reflex the nerve impulse is sent in the nerve system in the spine which is basically a highway with no traffic and that’s why it goes faster when you do a reflex
A reflex bypasses ‘you’. The interesting thing is that although you can’t be that fast at will, you can create reflexes. For example, returning a 100mph tennis serve happens too fast for the higher functions to be called into play.
A reflex is when you choose to grab a cookie yourself. You see a need. You make it happen.
A choice to move is like when you ask mom for a cookie. You have to send the information to mom that you want a cookie. She needs to consider what all is involved with getting you a cookie. Then she has to send out the message that it’s ok to get a cookie.
As you can see, a reflex is much faster because mom is not involved and no thinking is needed.
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