The 5 senses of the human being are touch, sight, smell, vision, hearing and taste. In this Psychology-Online article we are going to focus on getting to know them better and, thus, getting to know better what the media with which we relate to the world are like. In this article you will be able to discover what are the human senses and their functions.
Taste
There are about 10,000 taste buds on the tongue, grouped in papillae (those buttons all over your tongue). Taste buds are groups of neuronal bodies that trace thin grooves in the papillae, and look like microscopic bunches of bananas.
Molecules from the food we eat mix with saliva and find their way between the grooves and on the surfaces of neurons. Like a key fitting into a lock, these molecules open small pores in cell membranes and begin the firing process in the neuron much like the way neurotransmitters do between neurons.
There is only four basic flavors – that is, only four particular molecules to which as many neurons in the tongue respond:
- Salty (mostly at the end of the tongue)
- Sweet (mostly on the tip of the tongue)
- Salty (mostly on the front sides of the tongue)
- Acid (mostly on the back sides of the tongue)
And we say “most” because there are no clear boundaries here, and all flavors can be found to some degree anywhere on the tongue, and even in some parts of the inside of your mouth and lips.
There may be a fifth taste: “Umami” (in, for example, monosodium glutamate).
Also note that your tongue is sensitive to touch (hence the idea of texture in food), and temperature and, of course, pain. Jalapeño peppers, for example, have a certain flavor in the ordinary sense, but they also provide us with a delicious (!) sensation of pain. You may find it helpful to know that if your mouth burns from eating peppers, it helps to drink milk, because dairy fats dissolve the active chemicals (capsaicin) while water merely spreads them around.
Perhaps the largest part of our sense of taste is, curiously, smell…
The sense of smell
Smell works like taste: It is also a sense of “lock and key.” This time, it’s a matter of moist air passing over a specialized coin-sized mucous membrane at the top of the nasal cavity. With smell, we seem to respond to the presence of a certain combination of seven basic molecules:
- Floral
- Mentholated
- Musky
- Pungent (like spices)
- Camphorated (like mothballs)
- Ethereal (such as dry cleaning fluids)
- Putrid (like rotten eggs)
- But we are far from knowing that these are the fundamental aromas – some researchers think there are many more.
The chemical senses are extremely sensitive, and this is especially true of smell. We can detect acetic acid (the smell of vinegar) at a concentration of 500,000,000,000 molecules per liter of air. But dogs beat us in this: They can detect it at a concentration of 200,000 molecules per liter of air!
There has been considerable debate for many years about the existence of a sense similar to smell that can detect the presence of molecules called pheromones. Many animals can clearly smell the presence of a potential mate over long distances. People can certainly smell other people – but is there a special smell that isn’t really a particular scent, but rather leads us to feel, well, those special “I love you” feelings? . I don’t think so, but there are many who disagree with me.
The touch
The skin really has three types of sensations: Pressure, temperature and pain.
Pressure is a matter of mechanical distortion, the twisting of a “hair” on a hair cell. It’s not really a hair, of course, but an extended version of a dendrite. When it is bent, its tension causes the opening of pores, the exchange of ions, and, of course, the firing of the neuron. There are, however, three different types of pressure receptors: light touch, pressure, and vibration.
The temperature seems to have a direct influence of heat or cold that opens certain ion channels. We have found three of them: one for cold, one for heat, and one for extreme heat. Maybe there is also one for extreme cold or even for mildness.
It is interesting to note that menthol can also activate cold receptors, making us think we are feeling cold when we are not. It is also peculiar that, when we touch a “thermal grill” – a surface that alternates lines of cold and heat – we feel neither cold nor heat, but pain!
We’ll talk about pain separately, but basically, pain is a matter of detecting certain chemicals that indicate tissue damage. Itching and tickling are also classified with pain. Interestingly, there is a substance called capsaicin that acts on pain receptors in the same way that it does actual damage. It has been found in things like jalapeno peppers, as mentioned above.
Ear (Hearing)
Hearing is also a matter of hair cells. You probably remember the basic structure of the ear: The outer ear canal leads to the eardrum, a thin tissue stretched from the opening. Below the eardrum, there is a sequence of three small bones that amplify the vibrations of the eardrum. These end in another thin tissue that encloses the true hearing organ, called the cochlea. It is actually a tube, first folded in half, then twisted into a spiral, and filled with fluid.
Along this tube, there is a membrane that moves according to the wave patterns of the fluid. It has hair cells growing under it, and those hair cells send messages to the brain about the wave patterns and changes it detects. This may sound quite complicated, but the description is actually very simplified.
Vision
Vision is different from all the other senses. It involves receptor neurons that are sensitive to light. Light enters through the pupil and lens of the eye and is projected onto the dark surface of the eye called the retina. The retina is made up of, among other things, receptor neurons called rods and cones.
The rods are sensitive to a wide range of light, p. Eg. they inform us about “white”. They contain rhodopsin, a substance that is sensitive to light. Note that a crucial part of this substance is derived from vitamin A. The substances break down when exposed to light and release a protein (opsin) which eventually releases a neurotransmitter to send messages to the brain (“there is light”). The released products are then reconstructed into rhodopsin.
lThe cones are similar, but they include a substance called iodopsin, which is sensitive to more specific wavelengths, depending on pigments associated with these substances. One type of cone responds to red, another to green, and another to blue. Again, a protein (retinin) leads to the release of neurotransmitters, etc.
Rods are much more sensitive than cones. This is why you see black and white when there is not much light. Nocturnal animals tend to be color blind, that is, they do not have cones, for them color is of little use while high sensitivity is. Also, nocturnal animals typically have a bright background on their retina that reflects light back to the rods called the tapetum. It is usually made of small crystals. This is why cats and other animals reflect light from their eyes!
As with all the senses, vision is much more complicated, but for now it can help us to know this.
Other senses of the human being: Kinesthetic and Vestibular Sense
He kinesthetic sense is based on receptor neurons in muscles and joints which basically work on the mechanical principle of distortion. Some of these receptors are hair cells; others are spindles that start firing when stretched.
The vestibular sense tells you where “up” is, how your body is in relation to “up”, and how your body is moving in space. Sensations are based on hair cells. In the inner ear, there is a special configuration of three semicircular canals around a central area. In the semicircular canals, the movement of fluid as you spin causes gelatinous clumps called domes to stick together, which causes hair cells to stick together as well. The three channels are oriented approximately 90º from each other, and that allows you to have rotation information in all three dimensions.
The vestibular sense is also connected to parts of the brain that tell you when it’s time to throw up. This is the cause of motion sickness.
If you spin a lot and then stop suddenly, the sensation lasts for a while, and it seems like you’re still spinning, but in the opposite direction. Your brain may try to compensate for this, causing you to fall or at least feel dizzy.
You can also confuse these channels when you shower and hot or cold water enters your ear. Changes in temperature can cause the fluids to move and feel like they are spinning, and then you may feel dizzy.
The two central areas of this organ also have hair cells. The hair cells are embedded in gelatinous clumps called macules, which will pull them in one direction or another, depending on whether you’re face up, leaning to one side or another, or doing a handstand. The tilting of the hair cells again sends signals to the brain which interprets them accordingly.
This article is merely informative, at Psychology-Online we do not have the power to make a diagnosis or recommend a treatment. We invite you to go to a psychologist to treat your particular case.
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