14 - Chemical Senses Flashcards
What are the peripheral receptors of the olfactory system?
Olfactory epithelium: olfactory neurons, basal stem cells, supporting, Bowman’s glands. Odorant receptors.
What are the components of the central pathway of the olfactory system?
Olfactory bulbs, olfactory cortex.
What is the area of space in which peripheral receptors are in the olfactory epithelium? What type of cells are these?
5 cm^2 Pseudostratified epithelium
What is the path of peripheral receptors in the olfactory system?
Bipolar receptor neurons located in the mucosa of the nasal cavity and project axons in bundles through the olfactory foramina of the cribiform plate.
How are olfactory neurons unique? What helps them?
They have a lifespan of 30-60 days and are regularly replaced by basal stem cells that give rise to new neurons. They are bipolar and have cilia within the mucosa.
What happens to the ability to regenerate new olfactory neurons?
It decreases with age. That’s why old people don’t have as good of a sense of smell.
What other cell types are located in the olfactory epithelium?
Supporting cells that secrete mucus. Bowman’s glands that decrete mucus. Mucus acts as a solvent for odorants so they can be dissolved.
What is the structure of odorant receptors? How does an odorant bind?
GPCRs (1000 different types) located on olfactory neuron cilia. Each neuron expresses only 1 type of odorant receptor. Odorant binds to receptor in pocket. Highly variable amino acid sequence in transmembrane regions provides a possible mechanism for recognition of many different odorants. Odorant binding results in depolarization.
Olfactory neurons project through the cribiform plate to the _______ where they synapse onto neurons located in clusters called _____.
Olfactory bulb. Neurons located in clusters called glomeruli. Within each glomerulus are mitral cells and tufted cells.
What is the organization of the information given to the glomeruli in the olfactory bulb?
Olfactory neurons with the same preceptor type project to the same glomeruli such that each glomeruli gets signals from a single receptor type. Receptors recognize different structural features on an odorant. This results in a spatial map in the olfactory bulb.
What is population coding?
The identity of an odorant is encoded by the combination of receptors that it activates.
What is the structure of the olfactory tract?
Consists of axons of mitral and tufted cells from the olfactory bulb.
What does the olfactory tract project to?
- Anterior olfactory nucleus: -provides feedback to the ipsilateral olfactory bulb -projects via the anterior commissure to contralateral olfactory bulb 2. Primary olfactory cortex (ipsilateral)
Where in the primary olfactory cortex does the olfactory track project to?
Piriform - adjacent to the olfactory tract Periamygdaloid - overing the amygdala, just deep to the uncus Entorhinal - by the uncus These are all medial parts of the anterior portion of the temporal lobe.
The primary olfactory cortex projects where?
Hypothalamus: physiological aspects of smell like salivation Limbic structures: amygdala and hippocampus, emotional and motivational parts of smell Thalamus: attention to stimulus Orbital cortex/orbital gyri
What is the difference between taste and flavor?
Taste: gustatory sensation Flavor: gustatory sense + olfactory sense + general sensation
What nerve transmits taste from the anterior 2/3 of the tongue? Where is the cell body? Where is the central process of the sensory neuron located? What about the posterior 1/3?
Anterior 2/3: Facial n. via chorda tympani, geniculate ganglion rostral nucleus solitarius (gustatory nucleus). Posterior 1/3: Glossopharyngeal, petrosal ganglion, rostral nucleus solitarius.
What nerve transmits taste from the palate? Where is the cell body? Where is the central process of the sensory neuron located? What about from the epiglottis and esophagus?
Palate: Facial nerve via the greater petrosal n., geniculate ganglion, rostral nucleus solitarius. Epiglottis and esophagus: vagus n. via the internal laryngeal branch of the superior laryngeal n., nodose ganglion, rostral nucleus solitarius.
What are taste recetors?
Epithelial cells with microvilli receptors that extend into the taste pores to sample.
What are the five taste qualities?
Bitter, salty, sour, sweet, umami.
In the central taste pathway, where do the 1st order sensory neurons project? What about second and 3rd order neurons?
1st order: To the rostral part of the solitary nucleus in the medulla (gustatory nucleus) 2nd order: project to the CN motor nuclei or VPM of thalamus 3rd order: project to the amygdala (then hypothalamus( and taste cortex (insula)
Taste buds = ______
peripheral receptors.
What are the primary afferent neurons in the taste system? Where do the secondary neurons they project? What about the third order neurons
primary: CN VII, IX, and X secondary: rostral nucleus solitarius tertiary: VPM
What can cause disorders in taste?
Dry mouth, inflammation of oral cavity, radiation therapy, neoplasms, agin, drugs that affect cell turnover.
What is this a cross section of?
The midbrain
What is this a cross-section of?
The caudal medulla.
What is this a cross-section of?
The rostral medulla
What is this a cross-section of?
The pons.
What structure is each line pointing to?
What systems are associated with the blue and the green colors?
The blue is the DCML system.
Green is the spinothalamic system.
What is each line pointing to?
What structure does each line point to?
