SAP - Chemical Senses Lesson

Learning Target:

  • Describe taste and smell processes, including the specific nature of energy transduction, relevant anatomical structures, and specialized pathways in the brain for each of the senses.

AP psychology course and exam description, effective fall 2020. (n.d.). https://apcentral.collegeboard.org/media/pdf/ap-psychology-course-and-exam-description.pdf

Chemical Senses Lesson

Taste and Smell

Each taste bud contains 50-100 receptor cells that catch food chemicals and send neural messages along pathways to the thalamus of the brain.

Taste and smell are linked through sensory interaction (the principle that one sense may influence another). The interaction between the two is undeniable if you have ever had a cold. When your nose is stuffed up it will also affect your sense of taste. Foods taste bland when we are sick. Smell both changes and adds to our perception of taste. The flavor of food is affected by how it smells, its texture, and its taste.

Unlike vision and hearing, taste and smell are perceived through various chemical substances. Each has specialized sensory receptors that respond to different chemicals.

Taste (Gustation)

The stimulation of special sensory receptors in the mouth causes us to taste. Chemical stimuli are produced by chemical substances in whatever you eat or drink. The substances are dissolved by saliva, activating our taste buds. Each taste bud contains 50-100 receptor cells that catch food chemicals and send neural messages along pathways to the thalamus of the brain. Taste buds are located on your tongue, your cheeks, the roof of your mouth, and in your throat. They reproduce every week or two. Therefore, when you burn your tongue on a hot dish it heals itself within a few days. As we age, the number of taste buds we have decreases as well as our sensitivity to taste.

Each taste bud has maximum sensitivity to one taste and less to others. For tastes that are complex, multiple receptors are activated. There are five basic taste sensations, each showing a maximum sensitivity to one taste and a lesser to others.

In the activity below, roll over each number to reveal the basic taste sensations.

Smell (Olfaction)

Airborne molecules from various substances provide the sensory stimuli that create the sensation of odor or smell. Like taste, smell is also a chemical sense. It is an important sense as it alerts us to danger and changes our perception of taste. Smell is also the only sense that bypasses the thalamus on its way to the brain. It is important to know this is the only one that bypasses the thalamus.

The airborne molecules travel through an opening in the palate in the back of the throat. The molecules then enter some five million receptor cells at the top of each nasal cavity. Each odor is specialized in responding to molecules of different chemical substances. The brain is alerted through axon fibers and messages are sent to the olfactory bulb, then the temporal lobes, smell cortex, and parts of the limbic system involved in memory and emotion.

 

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