How does a human hear? When an object makes a noise, it sends vibrations (better
known as sound waves) speeding through the air. These vibrations are then funneled into
your ear canal by your outer ear. As the vibrations move into your middle ear, they hit
your 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, vibrates
the three smallest bones in your body: first, the hammer, then the anvil, and finally, the
stirrup. The stirrup passes the vibrations into a coiled tube in the inner ear called the
cochlea. The fluid-filled cochlea contains thousands of hair-like nerve endings called
cilia. When the stirrup causes the fluid in the cochlea to vibrate, the cilia move. The cilia
change the vibrations into messages that are sent to the brain via the auditory nerve. The
auditory nerve carries messages from 25,000 receptors in your ear to your brain. Your
brain 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 bees
buzzing around and maybe some birds chirping. The wind rustles through grass and
creates sound waves. Your ears collect these sound waves and causes your eardrum to
also vibrate. The eardrum the makes your hammer, anvil, and stirrup. The stirrups
vibrations move the liquid in your inner ear and the cilia translate those vibrations into
something the brain can understand. The brain processes the messages and realizes that
you are hearing a calm breeze. The same thing would happen if you heard a bee buzzing
around, except the different sound waves that it makes would cause the ear to process a
message that would tell the brain that it is hearing a bee. Likewise for the birds, unless of
course its a bird you have never heard before, but we will assume you have. Since we
have experienced these sensations before, its like the noise comes in, its processed and
matched up to see if we have ever heard anything like it before. Its sort of like pulling
open a filing cabinet and looking for something.
What happens if we have never heard a sound before. Lets say while you were in
the meadow and you heard some hideous shrieking noise. You think to yourself, “What’s
that?” You would probably have to use your other senses to establish exactly what was
making 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 in
our skin. But its not the same for all sensations. For touch and pressure, the skin receptors
get pressed on the transmit a signal to the medulla and the thalamus, then it goes to the
sensory cortex into the parietal lobe of the brain then the brain translates it into a concept
that it can understand. By the characteristics in the signal the brain can tell the difference
between a feather in our palm to being tackled by a lineman. If the sensation is a heat, or
lack there of, is passed directly to the thalamus and then to the reticular formation. My
theory 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 pressure
or temperature, if the sensation is painful our body reacts completely differently. If there
is 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 very
busy. Since it is sunny and in June, I am assuming that it is warm if not hot. Our skin
feels the suns rays burning our delicate skin. It picks up a warmer feeling than when we
were in our car with the AC on. It sends a signal to the brain, via the thalamus to the
reticular 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 the
difference, the side of you facing up is not feeling this pressure. Let’s