Olfaction And Taste

Question 1

Olfactory mucosa location

Answer 1

. Sup. And post. Part of nasal cavity
. Consists of columnar epithelium surrounding olfactory receptors (only neurons that communicate w/ external environment)

Question 2

Neuron development in olfactory mucosa

Answer 2

. Basal cells near lamina propria develop into olfactory receptors every 5-8 weeks
. Bipolar olfactory neurons has a dendrite to apical mucosa and terminal ending w/ 5-25 cilia in mucosa on surface
. Each cilia has 40 receptors membrane proteins for interactions w/ odors
. Unmyelinated axons of bipolar neurons make up CN I
. CN I passes from nasal cavity to interior of braincase via foramina in cribiform plate of ethmoid bone to terminate in olfactory bulbs

Question 3

Olfactory bulbs

Answer 3

. Flattened ovoid bodies resting on cribiform plate of ethmoid bone
. 1st processing station for olfactory info
. Receives input from olfactory n. And contains second order neurons (mitral cells)
. Axons of mitral cells form olfactory tract

Question 4

Olfactory tracts

Answer 4

. Prominent fibers from olfactory bulbs course post towards ant. Perforated substance
. At ant. Perforated substance, the tracts split into 2 striae

Question 5

Medial olfactory stria

Answer 5

. Few fibers
. Project to septal area
. Continue to hypothalamus (MFB), thalamus (DMN) hippocampus and upper brainstem

Question 6

Lateral olfactory stria

Answer 6

. Contains vast majority of fibers of olfactory tract

. Carries them to piriform cortex, periamygdaloid cortex, and amygdala

Question 7

Olfactory cortices

Answer 7

. Lat. olfactory: thin layer of gray matter overlying the lat. olfactory stria
. Small portion of the incus: prepiriform cortex, periamygdaloid cortex
. Primary olfactory cortex projects to the amygdala and the olfactory assoc. cortex

Question 8

Olfactory association cortex

Answer 8

. Ant. Part of parahippocampal gyrus
. Called entorhinal cortex
. Has heavy projections to hippocampal formation allowing olfactory info into limbic system
. Primary + assoc. cortices = piriform cortex

Question 9

T/F taste receptors specialized epithelial cells that come in contact w/ peripheral n. Fiber

Answer 9

T

Question 10

Sweet taste location

Answer 10

Tip of tongue

Question 11

Salt location

Answer 11

. Sides of tongue

Question 12

Sour location

Answer 12

Sides of tongue

Question 13

Bitter location

Answer 13

. Post. Portions of tongue

Question 14

Taste receptor structure

Answer 14

. Receptors located in buds on surface (1 bud = 40-60 receptor)
. Apical ends of recepto cells extend into taste pore
. Sensory fibers attach to basal surface of receptor cells
. Each receptor has life of 1-2 weeks then is replaced y basal cell differentiation in taste buds
. Distributed on dorsal tongue, palate, and pharynx

Question 15

Types of taste buds

Answer 15

. Fungiform and filiform (ant. 2/3)
. Foliate (lat. margins)
. Circumvallate (v sharped 2/3 back on dorsum of tongue)

Question 16

Taste sensations w/ CN VII

Answer 16

. Chorda tympani carries taste from ant. 2/3 tongue

. Cell bodies fo these afferent fibers located in geniculate ganglion

Question 17

Taste sensations from CN IX

Answer 17

. Branches carry taste from post. 1/3 tongue

. Cell bodies of these afferent fibers located in inf. Glossopharyngeal (petrosal) ganglion

Question 18

Taste sensations from CN X

Answer 18

. Sup. Laryngeal n. Carries taste from area around epiglottis
. Cell bodies of afferents in inf. Vagal ganglion
. Peripheral fibers all enter brainstem and then enter solitary tract

Question 19

Solitary tract

Answer 19

. Carries aste fibers of CN VII, IX, and X to nucleus of solitary tract
. In medulla, fibers surrounded by nucleus of solitary tract and they enter and terminate in nucleus

Question 20

Nucleus of solitary tract

Answer 20

. Principal visceral afferent nucleus in brainstem
. Receives taste (special visceral afferent) inputs and also receives general visceral afferent inputs from CNs IX and X
. Divided into rostral and caudal subdivisions (caudal = GVA input, rostral = SVA inputs)
. Contains 2nd order neurons in the ascending taste pathways
. Axons of NTS neurons will ascend to the VPM thalamic nucleus, ipsilaterally in central tegmental tract

Question 21

Thalamic neurons involved in taste

Answer 21

. VPM nucleus receives inputs from ipsilat. NTS
. Third order neurons in ascending taste pathway located here
. Projects to ipsilat. Taste cortex

Question 22

Taste cortex

Answer 22

. Insular cortex and med. aspect of the frontal operculum

. Projects to the orbital cortex and amygdala for higher integration of taste info