taste and smell exercise 25 bi 232. taste and smell both are examples of chemoreceptors in which...
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Taste and Smell
Exercise 25BI 232
Taste and Smell Both are examples of
chemoreceptors in which specific chemical compounds are detected by the sense organs and interpreted by various regions of the brain
Gustation Sensory receptors for
gustation are located in taste buds
Located mainly on the top of the tongue but also in other areas of mouth
Innervated by cranial nerves facial (VII), glossopharyngeal (IX) and Vagus (X)
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Taste Receptors
Taste buds contain spindle-shaped cells Basal cells: produce daughter cells that
mature in stages Gustatory cells: extend microvilli into the
surrounding fluids through a taste pore Contain the taste receptors
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Taste Bud Histology
Taste Determination of Solid Materials Gustatory receptors
are stimulated by specific chemicals in solution
Dry your tongue Put some sugar
crystals on tongue Keep mouth open Can you determine
what the sample is? Close mouth Can you determine
what the sample is?
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Gustatory Discrimination
1. Umami: “Beef”2. Salty3. Sweet4. Bitter5. Sour Substances must be dissolved (saliva) for
the chemically gated ion channels to open
Olfaction is very important in taste
Mapping the Tongue for Taste Receptors We have varying degrees of sensitivity to the
five tastes. People with allergies, migraines or heart
problems should avoid the tasting of umami. Select a dropper bottle labeled “sweet”, “sour”,
“salty”, “bitter” or “umami” Use a sterile cotton-tipped applicator, apply one
of the tasting solutions to the cotton tip. Dab the entire surface of your partner’s tongue Map your tongue with all of the taste substances Do not contaminate the solutions by
reusing the applicator sticks or use the same applicator stick in different solutions
Olfaction Sensory receptors for
olfaction are located in the olfactory epithelium consists of:
Olfactory receptor cells
Supporting cells Basal cells
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Olfactory Reflex Take a small bottle of
ammonia and place it under the nose of your lab partner.
Have partner take a brief sniff from the bottle.
If there is visible movement of the head in the posterior direction then an olfactory reflex occurred.
Visual Cues in Smell Interpretation Determine whether the
color of a substance has any effect on what you perceive the smell to be.
Lab partner shows you a small vial labeled “almond” and then smell it
Examine and smell the small red vial labeled “Wild Cherry”
Close your eyes and have lab partner choose a vial for you.
Can you tell which one it is?
Olfactory Discrimination Obtain four vials of
different scents Peppermint, almond,
wintergreen and camphor
Lab partner closes their eyes and try to determine the name of each scent
Record how many of the smells you got correct out of the four.
Testing olfactory adaptation Adaptation refers to
a decreasing sensitivity to a stimulus over time.
Sensitivity to an odor diminishes over time.
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Adaptation to Smell Have partner close eyes
and plug one nostril Inhale scent until the
smell degreases significantly
Have lab partner record time it takes.
Now smell the wintergreen or peppermint vial.
Does the adaptation of one smell cause the olfactory receptors to adapt to other smells?
Taste and Olfaction Tests Demonstrates the dependence of the sense of smell
on taste Obtain 4 or 5 small cups Label each with the name of the juice it will contain. Pour juice into the labeled cups Have lab partner sit with eyes and closed and nose
plugged Give samples of juice to partner Partner should taste the sample and try to name it Test all samples with nose closed and then open
nose and taste samples again Record your results.
The End View Slide of taste buds Make sure that you understand the tests
performed in lab