GUSTATION: SENSE OF TASTE - Human Anatomy and Physiology B. Pharma 1st Semester



At the end of this lecture, student will be able to

• Describe the anatomy of taste bud and papillae

• Explain the physiology of gustation and gustatory pathway


• Anatomy of taste bud and papillae

• Physiology of gustation and gustatory pathway


• Taste or gustation like olfaction, is a chemical sense

Five primary tastes can be distinguished:

• Sour, sweet, bitter, salty, and umami

• Umami taste, recently reported by japanese scientists, is described as “meaty” or “savory”

Anatomy of Taste Buds and Papillae

• Receptors for sensations of taste, located in the taste buds

• Taste bud - an oval body consisting of three kinds of epithelial cells

a) Supporting cells

b) Gustatory receptor cells

c) Basal cells

• Supporting cells surround about 50 gustatory receptor cells

• A single, long microvillus, called a gustatory hair

Projects from each gustatory receptor cell to the external surface

• Through the taste pore (opening in the taste bud)

• Basal cells, stem cells found at the periphery of the taste bud

• Produce supporting cells, develop into gustatory receptor cells

• Gustatory receptor cells synapse with dendrites of the first-order neurons

• Form the first part of the gustatory pathway


• Taste buds are found in elevation on the tongue, Papillae

• Provide a rough texture to the upper surface of the tongue

• Three types of papillae contain taste buds

a) Vallate (circumvallate) papillae

b) Fungiform papillae

c) Foliate papillae

Circular vallate (circumvallate) papillae

• About 10-12, form an inverted V-shaped row at the back of the tongue

• Each of these papillae houses 100–300 taste buds

Fungiform papillae

• Mushroom-shaped elevations scattered over the entire surface of the tongue

• Contain about five taste buds each

Foliate papillae

• Located in small trenches on the lateral margins of the tongue

• Most of their taste buds degenerate in early childhood

Physiology of Gustation

Chemicals that stimulate gustatory receptor cells are known as tastants, Tastant is dissolved in saliva


Contact with the plasma membrane of the gustatory hairs (sites of taste transduction)

                                 â Receptor potential

Exocytosis of synaptic vesicles from the gustatory receptor cell


Neurotransmitter release


Nerve impulses in the first-order sensory neurons

The receptor potential arises differently for different tastants

• Sodium ions (Na+) in a salty food enter gustatory receptor cells

• Via Na+ channels in the plasma membrane

• Accumulation of Na+ inside cause depolarization

• Leads to release of Neurotransmitter

Tastants, responsible for stimulating sweet, bitter, and umami tastes

• Bind to receptors on the plasma membrane that are linked to G proteins

• Activate second messengers

• Depolarization; release of neurotransmitter

The Gustatory Pathway

• Gustatory receptor cells trigger nerve impulses in cranial nerves VII (facial), IX (glossopharyngeal) and X (Vagus)

• Taste signals then pass to the medulla oblongata, thalamus, and cerebral cortex (parietal lobe)


• Gustation is a chemical sense

• Five primary tastes - Sour, sweet, bitter, salty, and umami

• Receptors for sensations of taste are located in the taste buds

• Tastants binds to receptors; generates potential; release of neurotransmitter; initiates nerve impulse

• Taste signals pass to the medulla oblongata, thalamus, and cerebral cortex (parietal lobe)

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