82 - Special Senses III (Vision, Taste and Olfaction) Flashcards
What are the five primary taste sensations?
1 - Sour 2 - Salty 3 - Sweet 4 - Bitter 5 - Umami
What can elicit the sour sensation?
intensity of sensation Depends on amount of hydrogen ion, caused by acids, e.g. HCl
What can elicit the salty sensation?
Caused by ionized salts e.g. - NaCl
What can elicit the sweet sensation?
Not caused by any one class of chemicals – e.g. some members of classes: sugars, glycols, alcohols, amino acids, inorganic salts of lead
What can elicit the bitter sensation?
Not caused by any one class of chemicals - almost all though organic substances e.g. alkaloids - quinine, caffeine, strychnine, nicotine
What can elicit the umami sensation?
This taste is elicited by monosodium glutamate, glutamate, and other amino acids. Taste common to protein rich foods like meat and cheese.
Which cranial nerves are involved in taste innervation in the tongue and mouth?
CN VII (facial) CN IX (glossopharyngeal) CN X (vagus)
Which cranial nerve innervates the anterior 2/3 of the tongue?
CN VII (facial) chorda tympani branch
Which cranial nerve innervates the posterior 2/3 of the tongue?
CN IX (glossopharyngeal)
Which cranial nerve innervates the soft palate?
CN VII (facial) greater superficial petrosal branch
Which cranial nerve innervates the epiglottis and esophagus?
CN X (vagus)
What are the receptor cells for taste?
Taste buds
What is the typical life span of a taste cell?
10 days to 2 weeks
What is the difference between a taste cell and a taste bud?
The taste bud is on the papillae and the taste cells is the only cells that is specialized for sensory transduction of taste sensation
Are taste receptor cells neurons?
NO - they are not neurons, they release neurotransmitters onto different afferent (sensory) fibers which then carry that information to the brain
How are olfactory receptor cells different from taste receptor cells?
They ARE neurons
Olfactory receptor cells are bipolar nerve cells that generate action potentials (via G protein and cell depolarization) in response to odorant molecule binding
Further describe olfactory receptor cells
- Turnover rate is 60 days
- There are 400 odorant receptor proteins in humans
- Olfactory neurons expressing the same type of olfactory receptor project to the same glomeruli
- An odorant might interact with several different types of olfactory receptors.
- Different odorants cause different patterns of electrical activity in the olfactory bulb.
Describe the interaction of an odorant and receptors
When an odorant molecule binds to receptor protein the associated G-protein is activated. This eventually (several steps you do not need to know) causes depolarization of the olfactory cell and the generation of an action potential.
Can you generate new olfactory receptors?
Yes - New olfactory receptor neurons (ORN) are generated continuously from dividing stem cells which are maintained among the population of basal cells
What are the probable biological roles of taste and olfaction?
- Edibility
- Diet selection
- Taste aversion (poisonous)
What is bait-shyness?
If an animal feels sick after eating, assumption by the brain is that (most) novel food is responsible. Animal “loses its taste” for that food.
Why is bait-shyness beneficial?
b. The ability to develop a taste aversion is considered an adaptive trait or survival mechanism that trains the body to avoid poisonous substances (e.g., poisonous berries) before they can cause harm.
Describe the role of the limbic system in bait-shyness
Several routes for olfactory information to get to various parts of the limbic system
- Limbic pathways probably mediate affective component of odors - whether odor pleasant or unpleasant, etc.
- Bait-shyness or the clinical equivalent results from pairing taste and/or odor of a food with nausea and vomiting. This phenomenon is probably dependent on olfactory - limbic interconnections.
Hyposmia
Impaired sense of smell
