Lesson 1.1.4

1.1.4 page 2

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Crash Course  - Taste and Smell

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senses: specialized mechanisms or functions by which an organism is receptive and responsive to a certain class of stimuli which are typically external as in the senses of sight, hearing, touch, and pain but also internal as in sensing the temperature of the blood, or the levels of carbon dioxide

 

sensory receptor: a cell or a group of cells located in various parts of the body that is specialized to receive stimuli that provide information about the body’s external conditions (through sight, hearing, taste, smell, or touch) and internal conditions (such as temperature, pH, glucose levels, and blood pressure)

 

photoreceptors: sensory receptors that respond to light stimuli, allowing people to see images as well as colours

 

mechanoreceptors: a sensory receptor that detects physical deformations in the body’s environment associated with pressure, touch, stretch, motion, and sound

 

chemoreceptors: a sensory receptor that transmits information about the solute concentration in a solution or about individual kinds of molecules in solution

 

thermoreceptors: a sensory receptor that detects heat or cold

 

sensation: the reception and processing by the brain of a nerve impulse sent by an activated sensory receptor

 

perception: the interpretation of sensory information by the cerebral cortex

You can undoubtedly name the five basic senses that allow you to gather information about your environment—sight, smell, touch, hearing, and taste. To begin this lesson, read pages 406 to 409 of the textbook to explore the special type of cells, sensory receptors, that responds to stimulation from the environment.

 

You may choose to summarize this information as notes, as a mind map, as a chart, as a diagram, or as a podcast. Store your work in your course folder.

 

The senses are classified by the type of energy that stimulates the sensory receptors. You will discover how each sense has unique receptors for detecting changes. Types of sensory receptors include photoreceptors, mechanoreceptors, chemoreceptors, osmoreceptors, and thermoreceptors. These special nerve endings—or specialized nerve cells—convert the energy stimulus into electrochemical energy, a nerve impulse. You will study the electrochemical transmission of nerve impulses in Lesson 7 of this module.

 

These changes, called sensations, are communicated to specific areas of your brain, including the occipital, temporal, parietal, or frontal lobes of the cerebrum; the hypothalamus; and the cerebellum. As you saw with your friend, your brain doesn’t interpret information the same way to produce a perception.

 

 Try This

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Prepare three bowls of water—one with ice water, one with room temperature water, and one that has hot water as you would prepare for a hot bath. Put one hand in the ice water for several minutes and then put it into the room temperature water. How does the room temperature water feel in comparison to the ice water? Put the other hand into the bowl with the hot bathwater for several minutes. Now put this hand into the room temperature water. How does the room temperature water feel in comparison to the hot bathwater, and how does it compare to what you felt after the ice water? Did the temperature feel different? Was your perception of the room temperature water different after the immersion of your hand in the ice water and the hot bath water?

 

After holding your hand in ice-cold water for several minutes, the pain of the cold does not seem so excruciating. If the sensory receptors are repeatedly stimulated, sensory adaptation occurs where the brain filters out these sensations—this is why factory workers no longer notice the hum of machinery after working for a period of time. If you worked in a feed lot, do you think you would get used to the smell to the point where you would no longer notice the odour? Sometimes the brain perceives information differently from the sensory information it receives. Look at “Figure 12.4” on page 408 of your textbook for examples of some optical illusions.