Taste (Gustation) System
Pathway from the taste buds to the brain.
1. Taste Receptors (Taste Buds)
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Located mainly on the tongue (fungiform, circumvallate, foliate papillae), and to a lesser extent on the soft palate, pharynx, and epiglottis.
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Contain gustatory receptor cells, which detect chemicals dissolved in saliva corresponding to the five primary taste qualities: sweet, sour, salty, bitter, umami.
2. Cranial Nerve Pathways
Taste information is carried by three cranial nerves, depending on the region of the tongue/mouth:
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Facial nerve (CN VII, chorda tympani branch) → anterior two-thirds of the tongue.
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Glossopharyngeal nerve (CN IX) → posterior one-third of the tongue.
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Vagus nerve (CN X, superior laryngeal branch) → epiglottis and pharynx.
3. First Synapse – Nucleus of the Solitary Tract (NST)
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Afferent fibers project to the rostral part of the nucleus tractus solitarius (NST) in the medulla (also called the gustatory nucleus).
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This is the first central relay station.
4. Second Synapse – Thalamus
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From the NST, taste fibers ascend (via the central tegmental tract) to the ventral posteromedial nucleus (VPM) of the thalamus.
5. Cortical Representation
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Thalamic neurons project to the primary gustatory cortex, located in:
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The insula and
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The frontal operculum (adjacent to the insula).
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Here, conscious perception of taste occurs.
6. Higher-Order Processing
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The gustatory cortex projects to:
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Orbitofrontal cortex (integration with smell, texture, and reward value of food).
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Hypothalamus and amygdala (emotional and autonomic responses to taste, e.g., appetite, salivation, nausea).
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✅ Summary Pathway:
Taste buds → CN VII/IX/X → nucleus of the solitary tract (medulla) → VPM of thalamus → primary gustatory cortex (insula, frontal operculum) → orbitofrontal cortex, hypothalamus, amygdala.
Do you want me to also make you a diagram-style flowchart of this pathway for easier memorization?