PHYSIOLOGY OF TASTE

Taste

A chemical sensation in which various tastants contained in food or beverages interact with taste receptors.

Gustation

The sense of taste detected by the gustatory system.

Gustatory system

The sensory system responsible for detecting and processing taste.

FUNCTIONS OF TASTE

• To analyze the chemical components of food that come in contact with receptor cells

• ACT as a screening mechanism for potentially harmful compounds.

Tongue

The main organ for tasting.

Taste papillae

The peripheral organ in the gustatory system located on the tongue.

Lingual papillae

The irregularities and elevations in the dorsal surface of the tongue forming clusters of small mucous membrane projections.

Circumvallate papillae

Dome-shaped papillae located on the dorsal surface of the tongue between the anterior two-thirds and posterior one-third along the V-shaped line.

Vallate papillae

Another name for circumvallate papillae.

Foliate papillae

Pocket-shaped invaginations on the posterolateral border of the tongue lined with taste buds and associated with sour taste.

Fungiform papillae

Mushroom-shaped papillae located on the anterodorsal surface of the tongue mostly at the tip and sides.

Filiform papillae

The most abundant papillae with hair-like or thread-like appearance that do not contain taste buds.

Taste buds

The functional unit of the taste organ that are onion-shaped and contain 50–100 taste receptor and supporting cells.

Taste pore

A 3–5 micron opening in the buds where the apical tip containing the taste receptor proteins is exposed to the oral cavity.

Taste sensory cell

A cell where flavor molecules bind to receptors on the microvilli causing electrical changes that release neurotransmitters to nerve endings.

Microvilli

Tiny hair-like folds in the plasma membrane that extend from sensory cells and increase surface area.

Taste receptor proteins

Proteins on taste sensory cells that detect flavor molecules.

Sensory cell

A specialized cell that receives taste stimuli and transmits signals to nerve fibers.

Nerve fibers

Structures that transmit taste signals from taste receptor cells to the brain.

Flavor molecules

Chemical substances from food that interact with taste receptors.

How we taste

The tongue detects flavor and the grooves on its surface contain taste buds that function as taste receptors.

Process to taste food

Flavoring chemicals in food dissolve in saliva, stimulate taste buds to send messages, and these messages are transmitted to the brain to produce taste perception.

Transmission of taste signals

Taste signals begin when receptor proteins detect food particles and trigger electrical impulses that travel through the nervous system to the brain.

Facial nerve (cranial nerve VII)

Provides taste fibers to the anterior two-thirds of the tongue.

Glossopharyngeal nerve (cranial nerve IX)

Provides taste fibers to the posterior third of the tongue.

Vagus nerve (cranial nerve X)

Provides taste fibers to the epiglottis region.

Primary taste sensation

The main taste qualities detected by humans.

Sweet taste

A taste elicited by sugars, sugar derivatives, and artificial sweeteners and associated with high-caloric foods.

Sour taste

A taste produced by hydrogen ions (H+) and often serves as a protective or warning signal and strong stimulus for salivary secretion.

Salty taste

A taste caused by ionized salts mainly sodium ions interacting with ion channels.

Bitter taste

A taste that detects toxic or harmful compounds and has the lowest threshold and the greatest number of receptors.

Umami

A savory taste sensation caused by amino acids such as monosodium glutamate and associated with L-glutamate.

Spicy sensation

A sensation of pain in the tongue caused by hot foods such as chili rather than a true taste.

Taste signals in the limbic system and cerebral cortex

The brain areas responsible for processing and interpreting taste signals.

Factors affecting taste perception

Aging, color or vision impairments, hormonal influences, genetic variations, oral temperature, drugs and chemicals, and plugged or clogged noses.

Taste disorder

A condition that alters or affects the ability to perceive taste normally.

Phantom taste perception

A persistent unpleasant taste in the mouth even when no food is present.

Ageusia

A complete loss of the sense of taste.

Hypogeusia

A reduced ability to taste sweet, sour, bitter, salty, and umami.

Dysgeusia

An altered or distorted taste sensation where foods may taste metallic, bitter, or different.

Parageusia

An unpleasant abnormal taste sensation.

Causes of taste disorders

Upper respiratory infections, COVID-19, sinus infections, middle ear infections, poor oral hygiene, dental problems such as gingivitis, exposure to chemicals such as insecticides, certain medications including antibiotics and antihistamines, surgeries of the mouth throat nose or ear, head injuries, and radiation therapy.

Diagnosis of taste disorders

Evaluation by an otolaryngologist including examination of mouth and nose, breathing, signs of infection, medical history, drug use, exposure to chemicals, and sip spit rinse testing.

Sip spit rinse test

A diagnostic test where chemicals are applied to specific areas of the tongue and the patient’s response is used to evaluate taste function.

Treatment of taste disorders

Management may include antibiotics for infections, changing medications causing the problem, treating respiratory infections or allergies, or individualized treatment for nervous system disorders or head injuries.

Circumvallate papillae taste buds

100-250 taste buds.

Foliate papillae taste buds

About 1000-1280 taste buds.

Fungiform papillae taste buds

171-253 taste buds.

Filiform papillae taste buds

0 taste buds because they are non-gustatory.

Taste buds per taste bud structure

50-100 taste receptor and supporting cells.

Taste pore size

3-5 micron opening.

Types of lingual papillae

4 types.

Papillae that contain taste buds

3 types.

Papilla without taste buds

Filiform papilla.

Basic taste qualities

5 tastes.

Primary tastes

Sweet, sour, salty, bitter, umami.

Taste from smell

About 80% of taste perception comes from smell.