Do humans have more than five senses?
A common misconception that’s being propagated even by most schools is that human beings only have a total of five senses. Actually, schools are mainly responsible for spreading this outdated information, but then again, they often tend to do that. I spent most of my life believing this until one faithful day a couple of years back when I decided to do what any responsible young adult does when he or she wants to learn something new or make sure that what they know is in fact correct. I Googled it. I can’t remember why I decided to question my knowledge of the human body that day, but I’m certainly glad I did. Sure enough, my good friend Google brought up a plethora of results and among them were various articles and videos talking about more than five sense. How could this be?
Well, it turns out that I already knew some of the stuff I was reading and listening to, and you know it as well. For example, when you’re feeling cold or hot that’s another sense in and of itself called thermoreception. Aside from being able to sense temperature, your skin can also feel pain (also known as nociception), pressure, and I’m sure you’ve felt itching more than a couple of times. All of these might seem to be related to the sense of touch, but according to scientists each of them is a distinct sense, which actually makes sense (pun intended) when you think about it. So, right off the bat we can see that there are more than the five senses taught in school, namely smell, touch, hearing, taste, and sight. Speaking of the latter, researchers have found that there are three types of receptors in our eyes, two of which directly contribute to sight. Specifically, brightness is detected thanks to the rod photoreceptors while color comes courtesy of the cone photoreceptors. I’m mentioning this because it’s generally considered that each of them is technically a distinct sense.
The remaining “traditional” senses are pretty straight forward, although there are some disagreements in regards to taste. Similar to how eyes have different receptors for color and brightness, the tongue has different receptors for various flavors such as sweet, salty, sour, bitter, or umami. That said, these receptors – or taste buds – are different in the sense that they can each taste all the flavors, so they’re no specialized like the rods and cones. Granted, some taste buds are more sensitive to certain flavors than others depending on where they’re located on the tongue, but I’ll talk a more about that in a moment. Here I would just like to mention that it is generally accepted that the tongue is not responsible for four or five senses despite featuring all the different receptors. With that out of the way, let’s talk a bit about a taste-related fun fact.
Since I’ve already mentioned something about false information being taught in schools, there is yet another misconception that I would like to address. Legend has it that certain parts of your tongue are solely responsible for allowing you to taste one of the aforementioned flavors. For example, the tip of the tongue is responsible for sweet while the back of the tongue is responsible for bitter. It goes without saying that this can’t be true as that would mean that you wouldn’t be able to taste something bitter if you were to put in on the tip of the tongue, which you most certainly can. In other words, the taste map is just as false as the idea that we only have five senses.
One of the main goals of this article thus far has been to share a bit of interesting info about the “traditional five senses” in order to prepare you for some of the more less known senses you may not know about, or may not have considered to be senses before. Oh yes, we’re getting to the good stuff now. One of these senses goes by the name of proprioception and it’s being described as being your ability to perceive your own body parts, specifically arms and legs. If you want to experiment with it, just close your eyes and wave your arms a little. Now see if you can figure out where your arms are while your eyes are still closed. Of course you can. Whether you look at them or not, you always know where your arms and legs are in relation to the rest of the body.
Similar to all the other senses, there are instances when you can lose your proprioception, in which case you’ll have a very difficult time performing virtually any action. Completely losing this sense happens very rarely, but partial loss of proprioception happens on a daily basis for many people if they’re drunk or on drugs. If you’ve ever experienced one of those states you likely know that even walking straight can become problematic. In fact, that’s exactly what the cops are testing for when they tell you to walk in a straight line or touch your nose with your finger. Easy for a sober person, not so much for someone who partially lost their sense of proprioception due to alcohol or drugs. Proprioception aside, those substances, as well as various medical conditions can also affect you sense of equilibrioception, more commonly referred to as the sense of balance. Otherwise known as the vestibular sense, equilibrioception is tied to the inner ear but has little to do with hearing. Instead, it helps you sense direction, acceleration, movement, walk upright, and as its many names suggest, also helps you keep your balance while walking.
The next sense I want to talk about can be just as useful as all the others that were already mentioned, although it’s a bit more situational. Magnetoreception is being described as one’s ability to sense magnetic fields around them. A number of animals use magnetoreception for the purposes of navigation as it gives them a better sense of direction and altitude. Some examples include bats, homing pigeons, and various species of invertebrates. Generally speaking, this sense is most useful for flying animals, however, some land ones are known to use it as well. Humans also have this sense to a lesser extent, although only some can make good use of it. Just like some people are able to see or hear better than others. those with a strong sense of magnetoreception are better at knowing where North is without looking at a compass, which can come in handy if you’re lost in the woods and don’t have a map. As mentioned, it’s pretty situational.
Unlike magnetoreception, thirst and hunger are not a mystery to most human beings and they count as senses, too. Generally speaking, you can sense when your body needs food or water and you can also sense when you’ve had enough. There is some debate regarding this seeing as how you can often ignore this sense and go days without eating or eat even some more after your body tells you that you’re full. Although sometimes enjoyable, I don’t advise the last past as it lead to vomiting, which comes as a result of yet another sense called the chemoreceptor trigger zone. Sure enough, that was just as example as this sense can be triggered by various other factors as well. Aside from all of those, there are a few other non-traditional senses according to my other good friend Wikipedia, such as the sense that controls your breathing frequency, or the one that causes your cheeks to blush. I’ll skip a couple of them in order to touch upon something that’s a little bit more interesting.
An often debated topic when it comes to the senses is time, or rather, how we perceive it. Scientists have come to the conclusion that our ability to sense the passage of time is governed not by one, but multiple mechanisms that can be found throughout various parts of the brain. Though we’ve yet to fully understand these mechanisms, we do know that one of the components is responsible for our circadian rhythms, or 24-rhythms. Known as the suprachiasmatic nucleus, this component is located in the hypothalamus. Much like all of our other senses, the sense of time – or chronoception – can also be distorted by a variety of factors such as drugs or medical conditions like Parkinson’s disease and schizophrenia. Interestingly, our perception of time can also change based on our emotional states or when we’re in a fight-or-flight situation. Age also plays an important role when it comes to chronoception, with young people generally being better than older ones at estimating time intervals. The reason why many young adults often complain that some days seem to last “forever” is because they do in fact experience time at a slower rate. By comparison, older people are often heard saying things like “where have the years gone?”. In short, if you feel like time is running faster as you get older, it’s because it does. Tick tock.
The bottom line is that humans do have more than five senses even though some are less obvious while others are not yet fully understood. The traditional five senses model is believed to have been proposed by Greek scientist Aristotel or one of his contemporaries back in the day. Aristotel was undoubtedly a smart guy, but he also lived between the years 384–322 BC, so many of his theories have become a bit outdated by now. We’ve learned a lot about the human body in the meantime and we’ll continue to learn even more as time passes. Perhaps some day we’ll even come up with ways of adding even more senses, or enhancing the ones found in our already impressive repertoire. I don’t know about you, but I could really go for some better hearing or vision, especially in the dark. Echolocation would be nice to have, too.
Chinese Dinosaur Might Have Been as Iridescent as a Hummingbird
Earlier this month, I wrote an article on a toy line of scientifically accurate Velociraptor action figures with plumage inspired by modern birds. I mused how impressive it would be if prehistoric raptors had been covered by feather patterns not unlike those in the toy line. Little did I know that two weeks later, researchers would reveal that some theropods had iridescent feathers that outshine David Silva’s velocifigures.
The Caihong juji, Mandarin for “rainbow with a big crest” (or just Caihong for short), was a “paravian theropod,” a clade commonly known for its winged forelimbs (even though many weren’t capable of flight) and enlarged sickle foot claws. In 2014, a farmer in the Qinlong County in the Hebei Province of Northeastern China gave a nearly complete Caihong fossil, feathers included, to The Paleontological Museum of Liaoning. Finding a complete skeleton is rare in paleontology and proved very helpful to the researchers. However, you might wonder just how scientists were able to determine the iridescent nature of the Caihong’s plumage. Two words: fossilized melanosomes.
Melanosomes are organelles that create, store, and transport melanin, which determines the pigments/colors of animal hair, fur, skin, scales, and feathers. Upon examining the Caihong’s head, crest, and tail feathers with an electron microscope, scientists discovered platelet-shaped structures similar in shape to the melanosomes that give hummingbirds their iridescent coloring. The rest of the body feathers had melanosome structures similar to those in the grey and black feathers of penguins, which would have made for an odd sight: a duck-sized dinosaur with body feathers as drab as a raven’s and head and neck feathers more colorful than a peacock’s.
The inferred feather coloration of the Caihong is not its only unusual feature, though. The dinosaur had longer arm and leg feathers than its relatives, and its tail feathers created a “tail surface area” that was larger than the famous proto-bird the Archaeopteryx. Furthermore, the Caihong had bony crests, which while common among most dinosaurs, are almost unheard of among paravian theropods. But, more importantly, it had proportionally long forearms, which is a feature of flight-capable theropods, even though scientists believe the Caihong didn’t fly. While this dinosaur apparently has the earliest examples of proportionally long forearms in the theropod fossil records, it still falls in line with the belief that the evolution of flight-capable feathers outpaced the evolution of flight-capable skeletons. The melanosomes, however, are the more intriguing discovery, since they are the earliest examples of “organized platlet-shaped nanostructures…in dinosaurian feathers.”
While paleontologists are confident the Caihong’s platelet structures are melanosomes, the researchers understand that their discovery is based partially on inference and could potentially be incorrect. If the structures aren’t melanosomes, well, that invalidates this entire article. But that’s what paleontology is all about: examining the evidence, creating inferences supported by that evidence, and changing those inferences when new information becomes available. Still, the concept of dinosaurs with iridescent feathers is pretty cool. If you want to learn more about the Caihong juji, you can read the original article on Nature.
Scientists Discover Velociraptor’s Cousin, and It Looks Like a Swan
When we hear the word Velociraptor, we usually think about the clever girls from Jurassic Park/World. In my case, I think about Dinobot from Beast Wars, but that’s neither here nor there, because after you’re done reading this article, you won’t be able to get the following thought out of your head: Velociraptors are related to a dinosaur best described as a prehistoric swan. Good luck ever seeing ol’ sickle claw the same way again.
Say hello to the Halszkaraptor essuilliei (Halszka for short), a dinosaur recently discovered at Ukhaa Tolgod (part of the Djadochta Formation in the Gobi Desert in Mongolia) by a team of paleontologists led by Andreau Cau of the Geological Museum Capellini in Bologna, Italy. Halszka’s around 75 million years old, which means he was alive during the late Cretaceous period during what is known as the Campanian age. And if you’re wondering why he looks like a swan, that’s because, according to a 3D synchrotron analysis (a process that uses x-rays so powerful they can only be produced in facilities the size of football stadiums), he’s semi-aquatic. Doesn’t he just look adorable?
Halszka belongs to the suborder therapod, known for specimens such as Tyrannosaurus Rex, the Velociraptor, and the ostrich. Therapods are known for their efficacy on land, but until the Halszkaraptor’s discovery, scientists thought they were exclusive to solid ground. Sure, some therapods might have eaten fish from time to time, but Halszka is the only known therapod with aquatic tendencies.
“The first time I examined the specimen, I even questioned whether it was a genuine fossil,” explained Cau. “This unexpected mix of traits makes it difficult to place Halszka within traditional classifications.” Given the long, swan-like neck, dinky flippers, and sickle-shaped claws reminiscent of the Velociraptor, I can’t blame him for being confused. Zoologists went through the same problem when they examined the first known platypus back in 1799; who wouldn’t be confused by such disparate features? “When we look beyond fossil dinosaurs, we find most of Halszkaraptor‘s unusual features among aquatic reptiles and swimming birds,” Cau continued. “The peculiar morphology of Halszkaraptor fits best with that of an amphibious predator that was adapted to a combined terrestrial and aquatic ecology: a peculiar lifestyle that was previously unreported in these dinosaurs. Thanks to synchrotron tomography, we now demonstrate that raptorial dinosaurs not only ran and flew, but also swam!”
Halszka now proudly sits as the first of a new genus of amphibious dinosaurs, capable of using its legs to walk on land and swim through the water and with a posture likely similar to those of modern day ducks and swans. Since the Gobi Desert, especially the Djadoctha Formation, appears to be a hotbed of important paleontological finds, many of which are therapods related to Halszka, who knows how many other amphibious dinosaurs are waiting to be discovered? Halszka could either be one of many previously undiscovered swimming raptors or as unique as the Mesonychid; nature’s first and only attempt at a hoofed predator.
If you are interested in reading Cau’s paper on the Halszkaraptor essuilliei, you can read the article on Nature. However, if you do not have a subscription, you should either read the Science Daily article or Andreau Cau’s personal blog (it is in Italian but an English translation is readily available on the page).
Researchers Use Stem Cells to Help Rats with Paraplegia Walk Again
Spinal cord injuries (SCIs) harm the nerves housed in the spinal cord, often causing irreversible damage to the body and its functions. Normally, physicians and other clinicians can only help people adapt to their SCIs instead of healing them, but researchers at Tel Aviv University and the Technion-Israel Institute of Technology might have discovered an essential key in the search for a possible cure. Just a word of warning: this article contains descriptions of animal experimentation, so some information might not be suitable for some readers.
Dr. Shulamit Levenberg of the Technion-Israel Institute of Technology recently led a multi-university study to determine if lab rats with simulated complete spinal cord injuries could regain the use of their hind legs with the introduction of stem cells and tissue engineered scaffolds. Some stem cells had been induced to differentiate (i.e., develop into different type of cells such as support cells), while others hadn’t been induced at all. And, the scaffolds were designed to “provide a 3D environment in which cells can attach, grow and differentiate, maintain cell distribution, and provide graft protection following transplantation.” In other words, the scaffolds made sure the stem cells grew as intended and weren’t accidentally damaged.
Researchers took lab rats and surgically removed a small portion of the lamina (the bony plates of the vertebrae that protect the spinal column and the vulnerable nerves) and cut through all of the nerves. Since incomplete spinal cord injuries only damage some nerves and can, for example, leave people unable to move their legs but capable of feeling through them or vice versa, the researchers had to sever all the nerves to simulate a complete spinal cord injury. Some rats were then implanted with the scaffold and stem cells (some of which were induced and some of which were not) to bridge the severed nerves. Other rats were implanted only with the scaffold, and a control group received neither scaffold nor stem cells.
After the scaffolds and stem cells were implanted, the researchers stitched up all the rats, including the control group, and observed them for any improvements. Rats that received both the scaffold and induced stem cells recovered better than the other groups; 42% of these rats were able to walk and support their body weight with their hind legs after three weeks. Furthermore 75% of this group reacted to stimuli in their hind legs and tail. Fewer rats with the non-induced stem cells recovered as fully as the rats with the induced stem cells. Furthermore, researchers found the scaffold-only group could not respond to any stimuli in their hind legs or tail, and rats in the control group did not improve at all.
While the study demonstrates that induced stem cells coupled with tissue engineered scaffolds could potentially help people with SCIs walk again, the number of rats who fully recovered was fairly low. Still, the results are promising and lay the groundwork for future studies that might one day develop a cure for SCIs. The full article on Levenberg’s study can be found on Frontiers.
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