Essays

How Does The Brain Perceive

How Does the Brain Perceive 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 also say you are laying down on a rock, a sharp squarish rock. The rock is applying a pressure to your back also, but is applying more pressure to a smaller area which creates the sensation of pain. When your brain feels pain it normally would tell your muscles the roll over or sit up and remove the rock from where you were laying, unless of course you are too lazy and just deal with the pain. You are also laying in grass, so some of your skin is exposed to it.This might cause irritation or itchiness.

This might cause your brain to want to scratch. How does our body know where were are, if we are moving or not? How does it know which way is up and down? We know this because our two types vestibular senses. The first is our sense of body rotation. This is monitored by the semicircular canals. Like the inner-ears cochlea the canals are filled with a fluid which depending on the movement of the head bends hair bundles that in turn trigger hair cells to send a message to the brain and the brain interprets the message as at what speed and direction is the body turning.

The second of the vestibular senses is the gravitation and movement of the body. This is calculated by the vestibular sacs, located between the semicircular canals and the cochlea. Each sac is filled with fluid and millions of crystals. When your body moves up, down, left or right the crystals move hair bundles which also trigger messages to the brain. But even when the body is not moving the gravitational force pulls some of the crystals down giving you a sense of where your head is located relative to the rest of your body. No mater which of the two types of the vestibular senses are used the ultimate destination inside the brain is unknown. While you are laying down your vestibular systems are always checking to see how your body is moving, but remains mostly still. If you are laying down the crystals in your vestibular sacs are being pulled towards the back of your head, therefore telling your brain that down is on your back side and that you are looking up.

The semicircular canals are telling your brain that your body is not spinning or rotating in any fashion. With all these senses our brain can see, hear, smell, etcetera, but it does not just “hear” a bird. It hears a noise and interprets it as a bird, this is perception. Perception is what our brain does to all the information it receives form all our senses. That is a lot of information. Think about as if you were at a store and you heard a noise that your brain perceives to be a horse.

Is it really a horse, probably not. It could just be some guy who is good at making animal noises. Now what if you were at a comedy club and you heard the same noise, but you also saw the comic producing the noise. Your brain would perceive that it was indeed a horse noise, but the man was making it. This just shows that the more senses involved in helping the brain to perceive a situation usually increases the chances that a assumption is correct.

So by your brain seeing light, hearing a breeze, feeling pressure and heat, smelling things it perceives that you are laying in a meadow on a bright sunny mid-June day.