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23 Cards in this Set

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  • Back

Distinguish between the labeled-line and across-fiber pattern principles.
In a system relying on the labeled-line principle, each receptor would respond to a limited range of stimuli and send a direct line to the brain.

In a system relying on the across-fiber pattern principle, each receptor responds to a wider range of stimuli and contributes to the perception of each of them. In other words, a given response by a given sensory axon means little unless the brain knows what the other axons are doing at the same time.

Indicate the ways in which taste receptors resemble neurons and skin cells.
Like neurons, taste receptors have excitable membranes and release neurotransmitters to excite neighboring neurons, which in turn transmit information to the brain. Like skin cells, however, taste receptors are gradually sloughed off and replaced, each one lasting about 10 to 14 days.

Explain how you would prove the existence of the five kinds of taste receptors.
1. Sweet
2. Sour
3. Salty
4. Bitter
5. Umami (Glutamate)

Use cross-adaptation.

Describe the mechanism by which the five kinds of taste receptors work.
See study guide.

Describe the pathway taken by taste information in the brain.
When an olfactory receptor is stimulated, its axon carries an impulse to the olfactory bulb. The olfactory bulb sends axons to the olfactory area of the cerebral cortex, where neurons responding to a particular kind of smell cluster together. From the cortex, info connects to other areas that control feeding and reproduction.

Discuss gender differences in olfaction.
On average, women detect odors more readily than men, and the brain responses to odors are stronger in women than in men. Those differences occur at all ages and in all cultures that have been tested.

Women also seem to pay more attention to smells. Surveys have found that women are much more likely than men to care about the smell of a potential romantic partner. In addition, if people repeatedly attend to some faint odor, young adult women gradually become more sensitive to it, until they can detect it in concentrations 1/10000 of what they could at the start. Men, girls before puberty, and women afthe ter menopause do not show that effect, so it apparently depends on female hormones.

Compare the VNO of adult humans with that of other mammals.
The vomeronasal organ (VNO) is a set of receptors located near, but separate, from the olfactory receptors. VNO receptors are specialized to respond only to pheromones, which are chemicals released by an animal that affect the behavior of other members of the same species, especially sexually. Although the VNO is reasonably prominent in most mammals and easy to find in a human fetus, in adults humans it is tiny and has no receptors. It seems to be vestigial—that is, a leftover from our evolutionary past. Humans nevertheless do respond to pheromones. Researchers have found at least one pheromone receptor in humans. Its structure resembles that of other mammals’ pheromone receptors, but for us, it is located in the olfactory mucosa along with normal olfactory receptors—not in the VNO.

Cite evidence that pheromones play a role in human sexual behavior.
See study guide.
Labeled-Line Principle
Each receptor would respond to a limited range of stimuli and send a direct line to the brain
Across-Fiber Pattern Principle
Each receptor responds to a wider range of stimuli and contributes to the perception of each of them
taste buds
Receptors on the tongue
Structure on the surface of the tongue
Fatigue of receptors sensitive to source tastes
Reduced response to one taste after exposure to another
nucleus of the tractus solitarius (NTS)
Structure in the medulla

Transmit taste information to other brain areas (pons, lateral hypothalamus, amygdala, ventral-posterior thalamus, somatosensory cortex, and insula)
People who have the highest sensitivity to all tastes
The sense of smell

The detection and recognition of chemicals that contact the membranes inside the nose
olfactory cells
Neurons responsible for smell

Line the olfactory epithelium in the rear of the nasal air passages.

In mammals, each olfactory cell has cilia (threadlike dendrites) that extend from the cell body into the mucous surface of the nasal passages. Olfactory receptors are located on the cilia
The general lack of olfaction
specific anosmia
Inability to smell a single chemical

For example, two to three percent of all people are insensitive to the smell of isobutyric acid, the smelly component of sweat.
vomeronasal organ
Set of receptors located near, but separate from, the olfactory receptors
Chemicals released by an animal that affect the behavior of other members of the same species, especially sexually
The experience of one sense in response to stimulation of a different sense