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 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?
