Sensation & Perception: Smell

9 flashcards · Biology · by lakesare

1. What's neurogenesis?

   Process in which neurons are generated from neural stem cells. Because the receptors that serve taste and smell are constantly exposed not only to the chemicals that they are designed to sense but also to harmful materials such as bacteria and dirt, they undergo a cycle of birth, development, and death over 5–7 weeks for olfactory receptors and 1–2 weeks for taste receptors. This constant renewal of the receptors, which is called neurogenesis, is unique to these senses. In vision, hearing, and…

2. What does 2AFC stand for?

   2-Alternative Forced Choice

3. How is the smell threshold measured?

   By the 2-alternative forced choice (2AFC): we present the participant with a weak odorant and no odorant. The participant’s task is to indicate which trial has a stronger smell. This eliminates having to decide whether a smell is present, because the participant knows it is present on one of the trials. Threshold can be measured by determining the concentration that results in a correct response on 75 percent of the trials (50 percent would be chance performance).

4. Why do dogs have a stronger smell than humans?

   Human olfactory receptors are as sensitive as dogs, however dogs have a lot more receptors. Humans: 10 million receptors.Dogs: 1 billion receptors. But even though humans are unaware of odors that other animals can detect, humans’ individual olfactory receptors are as sensitive as any animal’s. H. deVries and M. Stuiver (1961) demonstrated this by showing that human olfactory receptors can be excited by the action of just 1 molecule of odorant.This is similar to the situation in vision, in whic…

5. Detection threshold VS recognition threshold?

   Detection threshold - when we can detect presence of an odor. Recognition threshold - when we can detect what the odor is. When odorant concentrations are near threshold, so a person can just detect the presence of an odor, the person usually cannot sense the quality of the odor—whether it is “floral” or “pepperminty” or “rancid.” The concentration of an odorant has to be increased by as much as a factor of 3 above the threshold concentration before the person can recognize an odor’s quality. T…

6. What are 2 organs shown here?

   Olfactory bulb is a part of the brain The mucosa is a dime-sized region located high in the nasal cavity that contains the receptors for olfaction. Olfactory mucosa is on the roof of the nasal cavity and just below the olfactory bulb. Odorant molecules are carried into the nose in an air stream (blue arrows), which brings these molecules into contact with the mucosa.

7. There are 4 types of photoreceptors (rods, 3 cones). How many types of olfactory receptors are there?

   The olfactory mucosa contains 350 types of olfactory receptor neurons, and about 10,000 of each type. An important difference between the visual system and the olfactory system is that while there are only four different types of visual pigments (one rod pigment and three cone pigments), there are 350 different types of olfactory receptors, each sensitive to a particular group of odorants.

8. What are chemical senses?

   Senses that detect chemical molecules in the environment. Smell and taste.

9. What's the relationship between olfactory sense and thalamus?

   There is no thalamic relay between olfactory bulb and cortex! There is a connection to the thalamus, but it happens after it's been to the olfactory cortex.