How good would you say your reflexes are? And how many reflexes do you even have? Strictly speaking, a reflex is an action your body performs in response to some kind of stimulation but without any conscious effort on your part. Most of us will get tested at a doctor when they tap our knee with that little hammer to see if you kick out, but that’s just one of many reflexes the human body makes use of. Some reflexes are much more unusual and exist for some unpredictable reasons.
10. Hippos Have a Reflex That Lets Them Sleep in Water Without Drowning
Humans certainly can’t claim to have sole dominion over reflex action as most living things possess a variety of reflexes for one reason or another. In some animals they’re quite specialized as well, as can be witnessed in the hippopotamus.
Because a hippo spends so much of its life in water but cannot breathe water, it needs to be careful about not drowning. Hippos will even sleep in the water, which makes breathing even more difficult if you think of it as a totally conscious effort. Luckily for the hippos they have a reflex that takes care of that.
A hippopotamus can fall asleep under the water where they are able to hold their breath for just five minutes. The animal will surface, breathe, and then go back under the water again all while asleep thanks to reflex action.
9. The Rectoanal Inhibitory Reflex Can Determine the Difference Between Gas and Stool
Many reflex actions exist to provide us with a kind of security. They do things for us that need to be done. Things that, if they were left up to our conscious mind to control, we would probably not be able to get done fast enough or often enough to make use of them. Arguably, if none of your reflex actions worked, you probably wouldn’t live very comfortably. Case in point, the rectoanal inhibitory reflex.
There aren’t a lot of delicate ways to put this, so let’s not beat around the bush. This reflex is what allows you to judge whether you’re about to pass gas or pass something else. You can imagine how valuable this reflex is when you’re asleep. In so many words, the muscles in your rectum are able to determine when you need to go to the washroom or if you can safely work the problem out with a simple fart. It’s a necessary function for the maintenance of continence and without it you’d have to be taking precautionary trips to the washroom far more often.
8. The Arnold Reflex Causes You To Cough When the Ear Canal is Stimulated
There are a number of causes for coughing that can range from viral or bacterial infections to inhalation of irritants to allergies and so on. Figuring out what is causing someone to have a chronic cough can be much harder than you might expect as a result of the numerous potential causes. One cause that you can look to when all other potential reasons are ruled out is the Arnold reflex.
The Arnold reflex causes you to cough when the vagus nerve passing through your auditory canal is stimulated. That means if you had something stuffed in your ear, or something was impacted, it could push against this nerve and produce symptoms of a chronic cough that can last weeks as a result. You may have experienced this yourself if you ever tried to clean your own ear too aggressively, and found yourself coughing once or twice as a result of pushing a little too deep. Something as simple as irrigating the ear to clean it out can fix the problem.
7. The Glabellar Reflex Allows You To Get Used to Being Tapped on the Forehead
Here is a weird one that you can test on your own without any negative consequences. The Glabellar Reflex can be demonstrated by using one finger and tapping a person lightly between the eyebrows above the nose. The person being tapped should blink every time your finger taps them, but only for a short period. This blinking is involuntary, and as you continue to tap, the reflex action will cease and the person will be able to keep their eyes open while you’re tapping.
So what is the point of this reflex, and why would anyone care? It’s actually a useful tool. Habituation to the tapping, meaning the ability to get used to it, should occur in a short period. In an otherwise healthy adult if the person is not able to habituate the response, and they continue to blink, that can be used as an early sign of various conditions that affect the brain including dementia and Alzheimer’s.
6. Prune Fingers are a Reflex Action
Have you ever been in a swimming pool or the bathtub for so long that your hands and your feet got a little pruney? And did you think that the reason your hands and your feet got pruney was just because they were too wet? Like perhaps he just absorbed too much water? Turns out that’s not true at all, and science has been aware of this for about a hundred years now.
If you have a certain kind of nerve damage in your hands, you can’t get prune fingers. What that means is that the effect has nothing to do with the water itself. Instead, it’s actually a function of your autonomic nervous system. Blood vessels constrict below your skin and cause the wrinkly, pruney effect to occur. It’s a reflex action. But what’s the point?
It had been theorized for some time that the pattern of wrinkles on your skin served a purpose. The wrinkles form tiny channels which allow drainage of water and to improve your grip when your hands are wet.
Research conducted to help prove this theory showed that subjects who had prune hands were better able to grip wet objects than people with dry hands. There was no benefit to gripping dry objects with pruney hands, which seems to indicate the purpose of prune fingers is to help you grip wet things in a wet environment.
5. The Bulbocavernous Reflex Can Test for Spinal Cord Injury
Using a little hammer to tap somebody’s knee is a pretty non-invasive way to test a reflex action. But a lot of our reflex actions are more difficult to gauge than that one. Testing them requires some techniques that are quite unexpected, and may put you off the idea of getting tested at all. One such reflex is the bulbocavernous reflex which is used to test for spinal cord injuries. So it sounds like it’s important, but it takes a bit of work to do.
With certain kinds of spinal cord injuries, the bulbocavernosus muscle will not contract when stimulated, thus offering an injury diagnosis or prognosis. But testing this muscle requires two hands in uncomfortable places. The muscle itself can be reached through a rectal examination, which means a doctor needs to use their finger to locate it. Then, stimulation of the muscle requires them to pinch the patient’s sexual organs with the other hand to see if the muscle contracts.
4. Goosebumps Are a Vestigial Reflex Action
Goosebumps is the name we give to a physical reaction that occurs typically when you either get cold, or potentially when you get scared. One of the most common signs of goosebumps is the hair on a person’s arm standing up, and the actual little bumps which we call goosebumps becoming visible on the skin. It looks like the actual skin of a goose if you ever seen one without his feathers and that’s where the name comes from.
Goosebumps are considered a vestigial reflex action that dates back to our primitive ancestors. Each little hair on your arm has an arrector pili muscle beneath it and nerve signals can constrict those muscles, raising the hairs.
Many mammals have a similar reaction and it serves one of two purposes. The hairs either stand up to create an insulating layer against the elements, or an animal like a cat will puff up when in danger to look more dangerous to potential predators. Since this reaction happens in humans most often when they’re either cold or scared, there is a clear correlation between the two, even if the results don’t accomplish much and humans anymore.
3. REM Atonia Suppresses the Reflex Action that Causes Sneezes
Have you ever stopped to think about how often you sneeze in a day? Probably not, so in the interests of clarity you should know that most people sneeze about four times a day. That’s a good deal of sneezing going on. Now, can you ever remember sneezing while you were asleep? Presumably if you did such a thing you would wake up. Or maybe you saw somebody else sneeze themselves awake. Odds are you’ve never experienced that, and it’s thanks to another reflex action.
REM atonia is the reason most people can’t sneeze while they sleep. It’s also the reason you don’t act out your dreams while you’re sleeping. You can imagine the chaos that would be caused if everything that was going on in your head played out with your body while you weren’t even conscious to realize it.
REM atonia is meant to prevent your brain from sending signals to your body when you’re not conscious. It’s a kind of self-inflicted paralysis that holds you still and doesn’t allow you to put yourself in danger or do things that you don’t need to do while you’re not awake.
That’s not to say it’s impossible to sneeze when you’re sleeping. There are two ways this can work. One is that the REM atonia effect isn’t working. You’ve probably heard of people sleepwalking or even sleep driving before. The effect doesn’t work on them. The other way this could play out is that something is physically necessitating you to sneeze and if that was the case your brain would actually cause you to wake up first and then you would sneeze.
2. Nerve Impulses Can Cause The Severed Head of a Dead Snake to Bite You
If you know anything about wilderness survival, then you may know that if you kill a venomous snake in the wild, you need to be cautious of its head, even if you cut the head off. Reflex action in the snake’s head can cause it to bite and inject venom, even if the head isn’t attached to the body anymore.
1. The Lazarus Reflex Causes Braindead Patients to Raise Their Arms
There is no reflex response more suited for a horror movie than the Lazarus reflex. The name itself gives some small indication of what’s in store. This reflex action has convinced people in the past that victims of serious brain trauma resulting in brain death were perhaps not as badly injured as they seemed.
The way the Lazarus reflex works is that a person who has suffered brain death may still raise their arms and then cross them over their chest in that classic “vampire in a coffin,” fashion. You can imagine how creepy it would be to walk in on a patient who is supposedly braindead and see that their arms have moved and been crossed over their own chest like they’re dead already. And even more creepy if you happen to be in the room and watch it happen yourself.
The Lazarus sign is extremely rare, which also makes it more unsettling because it’s likely not many people have heard of it. In many cases of brain death the patient will only survive for a short time afterwards. However, in two of the only recorded cases of Lazarus sign, the patients had survived over 100 days after being diagnosed as braindead.
All evidence indicates this is just nerve activity and that the brain is not involved in the function whatsoever. After patients who demonstrate Lazarus sign have completed the action, the arms tend to flop by their sides again.