One of the Five Senses; Hearing

January 21, 2011

Mhairi Robertson, Olivia Shin & Jacky Tse

Hearing is a special sense that works differently from how we process our other senses. While other senses require chemical reactions, hearing is a mechanical process. Hearing is still very mysterious because the way the brain interprets the sound signals is very complicated. There is still a lot to be learned about how we hear. However, we do know quite a lot about how the inside of our ears work.

The ear is comprised of three main parts; the inner ear, the middle ear and the outer ear. By working together these three areas protect each other and allow us to hear sound. The most outer part of the ear or the pinnae catches sound waves and helps draw them into our ear. We can determine where noise is coming from because of the way it bounces off the pinnae. As sound waves enter the outer ear they go through an area called the ear canal or tympanic membrane. Here, the sound waves are amplified making it easier for us to distinguish complicated sounds like speech.

The sound vibrates the ear drum which is a tiny piece of skin that flaps when sound waves hit it. Interestingly, when the ear drum senses a loud noise a muscle pulls the ear drum taut stopping the sound from damaging the inner ear. When the ear drum moves it vibrates the ossicles– the three tiny bones inside your ear. Ossicles are located in the middle ear and are commonly referred to as the hammer, anvil and stirrup. These bones amplify the sound one last time before they enter the inner ear.

Once inside the inner ear the sound waves travel through canals filled with water. It is harder for sound waves to move through water, hence why the sound is amplified by the other elements in the ear. This watery area is called the cochlea and looks like a spiralling shell. The sound waves cause the water to move which stimulates tiny hair cells in the cochlea. These tiny hairs send electrical messages through the auditory nerve to the brain. How the brain interprets these signals is still a mystery.


One of the five senses : Smell

January 21, 2011

by Caroline, Alexandra, Phoebe, & Andrew

Olfaction is another word for sense of smell.

Specialized receptor cells of the olfactory epithelium detect and recognize smells.

Your nose is a huge cavity built to smell, moisten, and filter the air you breathe. When you breathe in, the tiny hairs, called cilia, act like a broom and filter everything trying to get into your nose; from dust particles to bugs.

The air passes through the nasal cavity and though a thick layer of mucous to the olfactory bulb. Each odour particle has a receptor that is recognized by a nerve cell. The cells then send signals to the brain via the olfactory nerve. The brain then interprets those molecules as the sweet flowers, or  pie.

Humans can detect over 10,000 different smells. The olfactory nerve picks up the scents from the air you breathe and translate them into nerve impulses or messages that are then sent to the olfactory bulb located in the front of the brain.

Actually, how and why we smell is still inadequately known.

Random Facts:

-Anosmia is a condition where someone can’t sense smells

-your sense of smell gets worse as you age

–dogs have 1 million smell cells/nostril which are 100x bigger than humans


One of the five senses : Sight

January 21, 2011

Nicholas Calvert, Judy (Sohyun) Chun, Sandra Frankel, Renars Dimza

How does our sense of sigh work?

Light from a source bounces off an object and enters through the eye through cornea (protective surface layer). The light then passes through the pupil controlled by the iris (muscle), into the lens. When light passes through the pupil, the size of the iris changes in order to allow a certain amount of light in.

The lens then focuses on the image, as it is squeezed by contracting muscles. The retina is filled with light sensitive cells called cones and rods; The light filters through layers of pigment in the outer layers of the cones and rods.  The rods are responsible for low light vision (black and white), and the cones are responsible for colour vision; unlike the rods, the cones require a brighter light in order to function. The rods are distributed throughout the retina, mostly along the edge of the field of vision, however there are none at the fovea and the blind spot. The cones are mostly near the fovea and far fewer are present in the retina.

The cones and rods are connected through cells in the retina to the nerve fibres in the optic nerve. When the cones and rods are stimulated by light, the nerves send off electric charges through the fibres in to the brain. The image is then projected in reverse upon the retina, and the brain interprets the image right-side up. This is done in the visual cortex. The brain does not receive a photographic image rather it constructs an approximation of what is being perceived.


Exercise Two: Perception and Cognition Research

January 19, 2011

In the first class, your Project One group developed a mental model for one of the senses, to the best of your knowledge. Expand your knowledge by researching the sense in question, and post the results of your research to the blog.

Make your post succinct. It should no more than three paragraphs, and should make use of images where appropriate. Specifically identify any misconceptions in the mental model developed in class and correct them. Informally cite any sources employed.

Only one post per group is necessary. Please include the name of all of your group members in the title of your post. Be prepared to briefly present your post next week.

Exercise Two is due at 15:30 on Friday, January 21.