Smell: Spencer, Matt, Catt, Ashcon, and Bailey

January 18, 2010


Why don’t you take time to smell the roses? Just take a deep breath in and think about all the systems at work. That seductive scent is the result of air borne molecules, known as aromatic substances, wafting towards your eager noses. A cascade of events takes place and although the act of smelling, especially something pleasurable, seems like mere moments, a complex mechanism is at work.

Our scent molecule dissolves in the thin mucous lining deep within the nostrils and is detected by the sensory neurons that lay beneath.  These neurons send a chain of messages to the part of the brain know as the Olfactory bulb. The information is transported by Olfactory nerve and processed in another area of the brain, known as the limbic area, and the scent is identified as a flower.

An interesting fact to note about the sense of smell is that we can detect over 10 000 odors, but the ability to distinguish individual scents is unknown and could be based on stimulation of more than one receptor at a time. This being said, the association between the sense of smell and memory creation is a close one.   A common misconception that can also be note is one involving taste. The majority of what we taste, approximately 85%, is actually the result of odor stimulating the receptors at the back of the throat.

Here is a video illustrating the process:


Taste: Sarah, Milka, Braden, K, Dallas

January 17, 2010

Taste is a function of the human body’s nervous system, brought on by the release of tiny molecules upon chewing, drinking or digesting food or drink. Those molecules stimulate sensory cells located in the mouth (taste buds on the tongue, roof of mouth) and throat (lining), which are called gustatory cells. Most taste buds on the tongue contain gustatory cells – at birth we have around 10, 000, but that number declines especially around seniority.


When food stimulates the taste cells, it causes them to send messages to the brain. They do this through three taste nerves which help identify or rather distinguish flavours, since it is our mind that has named and identified the flavours as certain things. Through our own personal organization as humans, we name these flavours salty, sour, sweet, bitter, and savory. Contrary to popular belief, certain taste cells are in fact not specific to certain areas on the tongue. They are spread evenly throughout the tongue’s surface, making all flavours distinguishable no matter where they are placed on the tongue.


We distinguish between certain foods by the intensity and sensation of their flavours. Nerve endings help us perceive these things, since foods contain natural (and unnatural) chemicals which are recognized by these nerve endings. These nerve endings can be found not only in the mouth, but also in the nose, throat, and even eyes. This explains how our sense of smell contributes to the intensity of flavour we taste in such foods as mint for example. This also explains the burning sensation in our throats when we intake spicy foods. These nerve endings are also prominent in our eyes when dealing with foods like onions and hot peppers. This chemical matter that foods give off chemicals which help us almost feel what we are tasting, which contributes a great deal to the final sensation.
The other major contributing factor to our taste is our sense of smell. Without functioning smelling capabilities, our food has very little flavour at all. This is due to the flavour receptors shared between the roof of the mouth and the nasal passages.


SIGHT: Andrew, Angela, Christine, Felix, Rui

January 17, 2010


Touch: Sean, Greg, Nic, Ivan

January 16, 2010

Our group has been chosen to focus on the mental model pertaining to the sense of touch. In class, we came up with a simple way of describing how this sense works. In a nutshell, the brain starts with an electrical impulse generated by the nerve endings that act as receptors and send signals via the nervous system to the brain for interpretation and potential action. This system is similar for all aspects of the body.

Basically when a person feels something, the nerve endings in their hand/fingers receive signals. This is referred to as the somatosensory system. These signals then get sent through the nervous system to the brain to be processed. Nerves in the arm include: ulnar nerve that is connected to the hand and fingers, the Median nerve near the elbow, and radial nerves. All nerves connect to the spinal cord and the cerebellum than finally the brain. The brain is like our personal computer, and therefore interprets the signals received based on previous, and real time data. Seeing as the brain has to control the entire body it is a very complex and important organ. Most of the data relevant to touch is processed in the upper part of the brain in the Central Sulcus. The brain reacts accordingly based on this new data and previous knowledge.

When the brain needs to take action, then the system works in reverse. The brain generates a signal and is sent via the cerebellum to the nervous system, then to the nerve endings in muscles for example and action is taken to perform a given task. In this way the system is very efficient by running in both directions.

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HEARING: Danielle, Anna, Yan, Lianna

January 15, 2010

Step One: Hearing the Sound

Sound waves travel through the air to the outer, visible part of one’s ear, the PINNA. These sound waves bounce off the pinna in different ways, depending on the direction of the sound’s source. This causes the sound waves to have a distinct patter which the brain can recognize, thus determining where the original sound came from.

Step Two: Sound Changes to Vibrations via Middle Ear

After sound waves enter the outer ear, they travel through the EAR CANAL to the middle ear where they collide with the EAR DRUM, a thin piece of skin stretched tight like a drum. The eardrum then vibrates, causing the OSSICLES (the three tiniest bones in the human body) to move, sending the sound to the inner ear. These bones include:

– the malleus (aka “hammer”)
– the incus (aka “anvil”)
– the stapes (aka “stirrup”)

Step Three: Into the Inner Ear & to the Brain

Sound flows into the inner ear as vibrations and enters the COCHLEA (a small, curled tube in the inner ear). Within the cochlea is a liquid which when hit by the vibration forms waves. The cochlea also has tiny hairs lining its walls which transform the vibrations into nerve signals that are then sent to the brain by the AUDITORY NERVE and understood as specific sounds.


Exercise Two: Perception and Cognition Research

January 11, 2010


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 08:30 on Monday, January 18.