Olfaction and Gustation

18. Trace the olfactory pathway from the time an odor reaches the olfactory epithelium until nerve impulses reach their final destination in the brain.

18.Axons leaving the olfactory epithelium collect into 20 or more bundles that penetrate the cribriform plate of the ethmoid bone to reach the olfactory bulbs of the cerebrum. Axons leaving the olfactory bulb travel along the olfactory tract to reach the olfactory cortex, hypothalamus, and portions of the limbic system.

19. Why are olfactory sensations long-lasting and an important part of our memories and emotions?

19.Olfactory sensations are long lasting and important to memories because the sensory information reaches the cerebral cortex by the hypothalamus and the limbic system without first being filtered through the thalamus.

Trace the olfactory pathway, beginning at the olfactory epithelium.

Axons from the olfactory epithelium collect into bundles that reach the olfactory bulb. In the olfactory pathway, axons leaving the olfactory bulb then travel along the olfactory tract to the olfactory cortex, hypothalamus, and portions of the limbic system.

When you first enter the A&P lab for dissection, you are very aware of the odor of preservatives. By the end of the lab period, the smell doesn't seem to be nearly as strong. Why?

By the end of the lab period, central adaptation has occurred. Inhibition of synapses along the olfactory pathway re- duces the amount of information reaching the olfactory cortex, even though the olfactory neurons remain active.

Define gustation.

Gustation is the sense of taste, provided by taste receptors responding to chemical stimuli.

If you completely dry the surface of your tongue and then place salt or sugar crystals on it, you can't taste them. Why not?

Taste receptors (in taste buds) are sensitive only to molecules and ions that are in solution. If you dry the surface of your tongue, the salt ions or sugar molecules have no moisture in which to dissolve, so they will not stimulate the taste receptors.

Your grandfather can't understand why foods he used to enjoy just don't taste the same anymore. How would you explain this to him?

Your grandfather is experiencing the effects of several age-related changes. The number of taste buds decreases dramatically after age 50, and those that remain are not as sensitive as they once were. In addition, the loss of olfactory receptors contributes to the perception of fewer flavors in foods.

2. A reduction in sensitivity in the presence of a constant stimulus is (a) transduction, (b) sensory coding, (c) line labeling, (d) adaptation.

d) adaptation

Define olfaction.

sense of smell