T12: Special Senses

Large group of touch receptors

Taste, smell, sight, hearing, and balance

Confined to head region; receptors aren't free endings of sensory neurons

Neuron-like epithelial cells or small peripehral neurons

-gustation
-receptors classifed as "chemoreceptros" that respond to food dissolced in saliva fluids

-stratified squamons epithelium
-filiform papillae
-fungiform papillae
-vallate papillae
-sulcus terminalis: marks border between mouth and pharynx
-Lingual tonsil: covers posterior 1/3rd of tonge that lies in oropharynx

-most numerous papillae on tongue are small and concial pointed in shape and line up in parallel rows which enable tonge to grasp and manipuate food; DON'T contain tate buds

Mushroom shapd and spread over anterior 2/3rd of tongue on surface; contain taste buds

V-shaped row bordering the posterior third of the tongue and directly anterior to the terminal sulcus (sulcus terminalis) groove; contain taste buds

-contain taste receptors
-collection of 50-100 epithelial cells
-contain two major cell types
-> Gustatory epithelial cells
-> Basal epithelial cells
-contain long microvilli (gustatory hairs): extend trhough a taste pore to the surface of the epithelim
-Cells in tastebuds replaced every 7-10 days

-Five basic qualities of taste: sweet, sour, salty, bitter, and umami; "umami" elicited by glutamate
-Taste map is a myth
-all taste modalities can be elicited from all areas of tongue containg taste buds (fungiform and vallate papillae)

-Taste information reaches the cerebral cortex primarily through the facial (CN VII), glossopharyngeal (CN IX) and vagus nerve (CN X)
-bitter taste receptors ahve been found in stomach
-Gustatory sensory neurons synapse in which solitary nuclues of medulla from which impulses are transmitted to teh thalamus and ultimately to the gustatory area of the cerebral cortex in insula

-olfaction
-Receptors: classified as "chemoreceptors" that resond to airborne chemical that dissolve in fluids of nasal mucosa

-olfactory receptors are part of the olfactory epithelium
-Olfactory epithelium is pseudostratified simple columan and contains three main cell types
->olfactory sensory neurons
->supporting epithelial cells
->basal epithelia cells