Olfaction And Taste Flashcards
Olfactory mucosa location
. Sup. And post. Part of nasal cavity
. Consists of columnar epithelium surrounding olfactory receptors (only neurons that communicate w/ external environment)
Neuron development in olfactory mucosa
. 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
Olfactory bulbs
. 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
Olfactory tracts
. Prominent fibers from olfactory bulbs course post towards ant. Perforated substance
. At ant. Perforated substance, the tracts split into 2 striae
Medial olfactory stria
. Few fibers
. Project to septal area
. Continue to hypothalamus (MFB), thalamus (DMN) hippocampus and upper brainstem
Lateral olfactory stria
. Contains vast majority of fibers of olfactory tract
. Carries them to piriform cortex, periamygdaloid cortex, and amygdala
Olfactory cortices
. 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
Olfactory association cortex
. 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
T/F taste receptors specialized epithelial cells that come in contact w/ peripheral n. Fiber
T
Sweet taste location
Tip of tongue
Salt location
. Sides of tongue
Sour location
Sides of tongue
Bitter location
. Post. Portions of tongue
Taste receptor structure
. 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
Types of taste buds
. Fungiform and filiform (ant. 2/3)
. Foliate (lat. margins)
. Circumvallate (v sharped 2/3 back on dorsum of tongue)
Taste sensations w/ CN VII
. Chorda tympani carries taste from ant. 2/3 tongue
. Cell bodies fo these afferent fibers located in geniculate ganglion
Taste sensations from CN IX
. Branches carry taste from post. 1/3 tongue
. Cell bodies of these afferent fibers located in inf. Glossopharyngeal (petrosal) ganglion
Taste sensations from CN X
. 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
Solitary tract
. 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
Nucleus of solitary tract
. 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
Thalamic neurons involved in taste
. VPM nucleus receives inputs from ipsilat. NTS
. Third order neurons in ascending taste pathway located here
. Projects to ipsilat. Taste cortex
Taste cortex
. Insular cortex and med. aspect of the frontal operculum
. Projects to the orbital cortex and amygdala for higher integration of taste info
