Pt8 Olfaction & Gustation

Question 1

Describe olfactory & taste systems.

Answer 1

-taste & smell = complementary
>choose right food
>physiological response in digestion
>recognition of other animals
-primitive emotional & behavioral functions of NS

Question 2

What does the olfactory system consist of?

Answer 2

-olfactory bulb
-olfactory tract
-lateral olfactory gyrus
-piriform lobe

Question 3

What is the olfactory system essential for?

Answer 3

-localization of food
-reflex stimulated secretion of digestive enzymes
-detect danger

Question 4

Describe the olfactory system.

Answer 4

-olfactory cells = specialized epithelium found on ethmo-turbinate bones of nasal cavity
-olfactory mucosa = 220 mil receptors in dogs & 5 mil in humans
-olfactory cells give rise to olfactory nerve fibers that terminate in olfactory bulb

Question 5

Describe olfactory cells.

Answer 5

-receptor cells for smell
-bipolar neurons derived from CNS
-located in olfactory epithelium among supporting cells
>cilia projecting into mucus that coats inner surface of nasal cavity
>cilia reacts to odors in air & stimulate olfactory cells
-spaced in olfactory cells = olfactory glands
>secrete mucus onto surface of nasal cavity

Question 6

What are the steps to stimulate olfactory cells?

Answer 6

olfactory cilia responds to olfactory chemical stimuli
1. Odor molecules enter nasal cavity & diffuse in mucus
2. Bind to GCPR in membrane of cilium
3. Alpha subunits activates adenylyl Cyclase = cAMP
4. CAMP activates gated Na/Ca ion channel = influx of cations (mostly Ca)
5. Influx of Ca = Cl channels open & Cl leaves cell
6. Depol = gen of excitatory post synaptic potential in cilia
7. EPSP travels from cilia to trigger zone of olfactory cell = gen AP

Question 7

What is the central pathway for olfaction?

Answer 7

-olfactory nerve fibers terminate & synapse in olfactory bulb = olfactory tract (CN I)
-olfactory tract reaches piriform lobe & nonolfactory portions of brain = limbic system
-amydgala entorhinal cortex, hippocampal formation, septal nuclei
>areas that send olfactory signals to the hippocampus & frontal cortex
>olfactory signals dont directly project to thalamus
-limbic system responsible for forming olfactory memories
>emotional & autonomic responses
connection between olfactory & gustatory system

Question 8

Describe the gustation system.

Answer 8

-chemicals that trigger sense of taste are dissolved by saliva
-enter thru taste bud pore
-bind to receptor located in microvilli
-binding = depol membrane of taste cells
each flavor has its own mechanism

Question 9

Describe the central pathway for gustation.

Answer 9

-taste cells innervated by bipolar neurons = contribute axons to 2 cranial nerves
>CN VII facial
>CN IX (9) glossopharyngeal
-afferent fibers send message to CC
>projects to amygdala of limbic system = memory