Humans are said to have 5 basic senses. They are as follows: Touch, Sight, Smell, Hearing and Taste. Now senses themselves are simply signals being relayed to the brain, so that the brain can then interpret them. It allows us to perceive our reality in different forms. This is done a number of ways, but essentially, specialized cells, which we learnt about in the previous class, are responsible for receiving stimuli, whether it be light (through your eyes) or sound (through your ears) for example, and translating them into signals that the brain can then make sense of.
Let’s see if we can gain more of an understanding below
Sight – Sight is what is known as the process of perceiving images through your eyes. The process itself it perhaps a little more complicated than you might expect. Below is a video demonstration of how the eye works.
So as we can see, it is a process that is based fundamentally on the light touching your pupils and the brain calculating and processing from the signals it receives, so you can have a solid perception of your surroundings in a visual form. This includes turning the image the right way up, as when received, the image is upside down.
On a cellular level, we have specialized cells that sit within the eye, known as rods and cones. These cells translate light into nervous signals, which are then carried to the brain by the optic nerves. The brain processes them in order to form visual images. Please note that whilst cones deal more with translating light into colours, and maintaining your central vision, rods help with peripheral vision and giving humans vision when there is limited light available, like there is in the night time.
Hearing – The same way the light must be transformed into image signals for the brain, sound waves must be translated into sound signals. Again the brain must process and interpret. Have a look at the diagram below.
Whatever the sound might be, whether its music, or the voice of someone close by, the sound waves in the air reach the ear. The sounds waves are funnelled down the ear canal by the outer ear, towards the ear drum. The sound waves then beat against the ear drum, which then transfers these vibrations to the three small bones called the malleus, incus and stapes. These bones carry the vibrations to the inner ear. As these three bones knock away, with the vibrations, specialized cells in the inner ear detect the pressure and activate nervous receptors, sending signals towards the brain.
Smell – Smell really starts with the nerve receptors located in your nasal or nose. When we breathe in, or inhale through the nose, the chemicals in the air make contact with these receptors. Again a signal is then triggered and sent up to what is called the olfactory bulbs. This is where you’ll find neuron cell bodies that transmit information along cranial nerves and towards the brain for interpretation.
Research in recent times has indicated the humans can smell over a trillion different scents.
Taste – This is a sense that involves what we call taste buds, which we find on our tongue. There are tiny little bumps on the top of the tongue, and many of these bumps contact these taste buds. When we eat, chemicals from the food make contact with the taste buds, and as we see with all senses, this contact triggers a response. The response is specialized cells inside the buds activate nervous receptors, which yet again send signals towards nearby nerves, which then carry those signals to the brain for interpretation.
Touch – Again, it is specialized cells within the different layers of your skin which detect sensations, such as touch, pressure and vibrations. So as your epidermis (outer skin layer) comes into contact with different materials, these cells relay signals based on that detection, through peripheral nerves and towards the brain. Different body parts will contain different forms of receptor cells, which is why some body parts are more sensitive than others. It is also different types of detectors which allow you to feel different sensations, such as pain, pleasure, itching or tickling.
