How does a human hear? When an object makes a noise, it sends vibrations (betterknown as sound waves) speeding through the air. These vibrations are then funneled intoyour ear canal by your outer ear. As the vibrations move into your middle ear, they hityour eardrum and cause it to vibrate as well.
This sets off a chain reaction of vibrations. Your eardrum, which is smaller and thinner than the nail on your pinky finger, vibratesthe three smallest bones in your body: first, the hammer, then the anvil, and finally, thestirrup. The stirrup passes the vibrations into a coiled tube in the inner ear called thecochlea. The fluid-filled cochlea contains thousands of hair-like nerve endings calledcilia. When the stirrup causes the fluid in the cochlea to vibrate, the cilia move.
The ciliachange the vibrations into messages that are sent to the brain via the auditory nerve. Theauditory nerve carries messages from 25,000 receptors in your ear to your brain. Yourbrain then makes sense of the messages and tells you what sounds you are hearing. While you are sitting in the meadow, you might hear a calm breeze,some beesbuzzing around and maybe some birds chirping. The wind rustles through grass andcreates sound waves.
Your ears collect these sound waves and causes your eardrum toalso vibrate. The eardrum the makes your hammer, anvil, and stirrup. The stirrupsvibrations move the liquid in your inner ear and the cilia translate those vibrations intosomething the brain can understand. The brain processes the messages and realizes thatyou are hearing a calm breeze. The same thing would happen if you heard a bee buzzingaround, except the different sound waves that it makes would cause the ear to process amessage that would tell the brain that it is hearing a bee.
Likewise for the birds, unless ofcourse its a bird you have never heard before, but we will assume you have. Since wehave experienced these sensations before, its like the noise comes in, its processed andmatched up to see if we have ever heard anything like it before. Its sort of like pullingopen a filing cabinet and looking for something. What happens if we have never heard a sound before.
Lets say while you were inthe meadow and you heard some hideous shrieking noise. You think to yourself, “What’sthat?” You would probably have to use your other senses to establish exactly what wasmaking the noise, but after that your mind knows what that particular sound represents. Using the filing cabinet analogy again, it would be just like adding another folder. How does our body feel? Our body feels by getting messages from receptors inour skin. But its not the same for all sensations.
For touch and pressure, the skin receptorsget pressed on the transmit a signal to the medulla and the thalamus, then it goes to thesensory cortex into the parietal lobe of the brain then the brain translates it into a conceptthat it can understand. By the characteristics in the signal the brain can tell the differencebetween a feather in our palm to being tackled by a lineman. If the sensation is a heat, orlack there of, is passed directly to the thalamus and then to the reticular formation. Mytheory on why it does that is that a change in outside temperature could change our inner-body temperature, thus unbalancing our homeostasis. But no matter whether its pressureor temperature, if the sensation is painful our body reacts completely differently.
If thereis an instance of pain the brain tells the body to do something to stop it, fast. While we are laying in the meadow on a mid-June day our skin senses are verybusy. Since it is sunny and in June, I am assuming that it is warm if not hot. Our skinfeels the suns rays burning our delicate skin.
It picks up a warmer feeling than when wewere in our car with the AC on. It sends a signal to the brain, via the thalamus to thereticular formation, that it warm out here. Not only that but you are laying on the ground. By laying on the ground you are putting pressure on your backside.
Your skin can feel thedifference, the side of you facing up is not feeling this pressure. Let’s
