makuaistin

Makuaisti, or the sense of taste, is the sensory system that detects chemical substances in the mouth and contributes to flavor perception. It works together with the sense of smell, texture, and temperature to influence food choices and safety. Most taste-sensitive cells reside in taste buds, primarily on the tongue, but also in the palate, throat, and epiglottis.

Taste buds are composed of gustatory receptor cells that respond to tastants and form synaptic contacts with afferent nerve fibers. When a tastant binds to its receptor, it triggers intracellular signaling and the release of neurotransmitters, sending information to the brain via cranial nerves VII (facial), IX (glossopharyngeal), and X (vagus).

The five basic tastes are sweet, sour, salty, bitter, and umami. Salt and sour are largely mediated by ion channels, while sweet, umami, and bitter involve G-protein-coupled receptors (GPCRs). Specific receptor combinations include T1R1+T1R3 for umami, T1R2+T1R3 for sweet, and T2Rs for bitter.

Neural pathways carry taste information from the mouth to the brain: from the tongue to the nucleus of the solitary tract in the brainstem, then to the thalamus, and finally to the gustatory cortex in the insula and frontal operculum. Flavor perception results from the integration of taste with olfactory cues and somatosensory input.

Variation and clinical aspects: Taste sensitivity generally declines with age. Several conditions can alter makuaisti, including infections, medications, zinc deficiency, smoking, and neurological diseases. Abnormal taste is described as ageusia (loss), hypogeusia (reduced), or dysgeusia (distorted). Genetic differences influence taste sensitivity, notably to bitter compounds.