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Gustation
(Taste)
Morgan, Stephanie, Lizzie, Kaitlyn.
Intro.
● Taste is a chemical sense
● Binding of molecules to receptors of the
tongue
● The tongue is a voluntary muscle structure
● Occupies floor of mouth
● Superior surface consist of stratified
squamous epithelium
● Tasting is about 80% of what you smell
I. Terms to know (Base of Tongue)
Epiglottis: Small cartilage structure keeping food from going in to
the larynx during swallowing.
Root of Tongue: The base of the tongues structure.
Palatine Tonsil: Lymphatic mass can help against respiratory
infection.
Lingual Tonsil: Lymphatic mass in the back center of the mouth.
Microscopic Anatomy
(Peripheral and Central Nervous System)
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Filiform Papillae: cone shaped & found all over the tongue (which is why tongues
look rough)
■ Fungiform Papillae: mushroom shaped & found at the tip and sides of the tongue
■ Foliate Papillae: a series of folds along the sides of the tongue
■ Circumvallate Papillae: shaped like flat mounds surrounded by a trench & found at
the back of the tongue
All papillae except Filiform contain taste buds (so the very center of your tongue which
only has Filiform Papillae is "taste-blind")
Taste buds
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Small organ located on the tongue in terrestrial vertebrates that functions in the perception of taste
Taste buds are a collection of nerve-like cells that connect to nerves running into the brain.
Each bud is flask-shaped, with a wide base and a short neck opening at the taste pore
Each taste bud contains a number of taste cells which have tips that protrude into the taste pore
Contain elongated epithelial cells and a small number of proliferative basal cells
3 types of taste bud cells
Type I cells:Type I cells (or dark cells) extend lamellate processes around other types of taste cells and express a glial
glutamate transporter (GLAst).
Type II cells:Type II cells have large, round nuclei and express all the elements of taste transduction cascade for
sweet and bitter, including T1R or T2R families of taste receptors, among others. These taste cells (type II) are
considered the transducing cells for these taste qualities.
Type III cells:Type III cells are characterized by identifiable synaptic contacts with the gustatory nerve fibers. They
express the synaptic membrane protein SNAP25 and the neural cell adhesion molecule (NCAM). The prominent
synaptic contact suggests the implication of these cells in the transmission of information to the nervous system.
Gross Anatomy(Muscles)
~Intrinsic~
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Superior Longitudinal: Retracts the tongue helping making it thin and thick
Inferior Longitudinal: Shortens tongue and turns apex under
Transverse: Makes the tongue narrow and elongated
Vertical: Flattens and broadens tongue
~Extrinsic~(attached to the bone)
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Genioglossus: Helps depress the tongue
Hyoglossus: Depresses and retracts the tongue
Styloglossus: Retracts and elevates the tongue
Palatoglossus: Raises the back portion of the tongue
We have four primary taste sensations(true/false)
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Sour: detects acidity
Salty: produced by sodium ions
Bitter: the most sensitive/ unpleasant taste
Sweet: present with sugars
Umami: savory/meaty taste
Physiology
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Involves stimulation of chemoreceptors by dissolved chemicals
The sensory receptors are stimulated by chemicals that enter the pores
dissolved in saliva
Nerve impulses are generated and conducted along the glossopharyngeal
nerve from the tongue, vagus nerves, and pharyngeal wall before
synapsing in the medulla and thalamus
Their ending point is the taste area in the parietal lobe of the cerebral
cortex.
Physiology continued...
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Chemical comes in contact with gustatory hair cells on receptor cells.
Depolarization of taste cells results in generation of action potentials in associated
sensory neurons.
In order to be tasted, a chemical:
-Must be dissolved in saliva
-Contact gustatory hairs
Binding of the food chemical:
-Depolarizes the taste cell membrane, releasing neurotransmitters
-Initiates a generator potential that triggers an action potential
The stimulus of taste is converted into a nerve impulse by:
-Na+ in salty tastes
-H+ and blockage of K+ channels in sour tastes
-Gustducin in sweet and bitter tastes
Overview
Taste receptor cells, with which incoming chemicals from food and other sources interact
Each of these groups forms a taste bud
Which is grouped together with other taste buds into taste papillae.
The taste buds are embedded in the epithelium of the tongue and make contact with the outside environment through a
taste pore.
Slender processes (microvilli) extend from the outer ends of the receptor cells through the taste pore, where the
processes are covered by the mucus that lines the oral cavity.
At their inner ends the taste receptor cells synapse, or connect, with afferent sensory neurons, nerve cells that conduct
information to the brain.
Each receptor cell synapses with several afferent sensory neurons, and each afferent neuron branches to several taste
papillae, where each branch makes contact with many receptor cells.
The afferent sensory neurons occur in three different nerves running to the brain—the facial nerve, the
glossopharyngeal nerve, and the vagus nerve.
Taste receptor cells of vertebrates are continually renewed throughout the life of the organism.
Homeostatic Imbalances
-The senses of taste and smell are very closely related. Most people go to the
doctor because they think they have lost their sense of taste are surprised to
learn that they have a smell disorder instead.
What causes these disorders?
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some people are born with them
injury/illness
poor oral hygiene
radiation therapy
types of antibiotics
ear infections
smoking cigarettes
Common Taste Disorders
Phantom Taste Perception: lingering/unpleasant taste even though you have
nothing in your mouth
Hypogeusia: A reduced ability to taste things (to taste sweet, sour, bitter, or
salty substances).
Ageusia: not being able to taste anything
Dysgeusia: is a condition in which a foul, salty, rancid, or metallic taste
sensation will persist in the mouth. Dysgeusia is sometimes accompanied by
burning mouth syndrome, a condition in which a person experiences a painful
burning sensation in the mouth