Bio Basis: TASTE
Where are taste buds located?
(Taste buds are located in papillae except for filiform, and the taste buds in throat, roof of mouth, and cheeks) ~tongue contains 10,000 taste buds (density changes over lifespan 10days) -each taste bud has 50-100 taste cells with tips (cilia) that extend into the taste pore • Shaped like garlic bulb
¨These pathways make connections in the nucleus of the solitary tract (NST) in the medulla ¨From here signals travel along two different pathways:
1. Travels to Ventral Posteromedial nucleus of thalamus • Followed by areas in the cortex *insula- primary gustatory cortex *orbital frontal cortex(OFC)- secondary gustatory cortex *frontal operculum 2. Travels from NST in brainstem to: • Amygdala • Hypothalamus *these regions influence emotional responses to sensation from mouth to help control appetite -Reinforcement- fibers serving taste system also reach OFC, which receives olfactory signals
Animals
Animals: -Phenylthiocarbamide (PTC) - substance ass. with bitter taste in humans • Mice do not have or respond to this CATS can not taste SWEET
Chemical Detection
Chemical detection •Transduction occurs when chemicals contact the receptor sites on the cilia •Taste receptors form synapses with bipolar neurons (dendrites) ¨Release adenosine triphosphate (ATP) onto bipolar cells •Bipolar cells (axons) transmit information to brain via cranial nerves (7th, 9th, & 10th) • Chemical senses require molecules to be taken into body to experience/ analyze substance Taste - substance physically put in mouth → molecules stimulate receptors on tongue Smell - involves taking molecules into nose to experience substance •As receptors are exposed to chemicals that are both good & harmful, life cycle takes 5 - 7 weeks •Substances that are harmful are typically unpleasant whereas substances that are good for us generally smell (or taste) good.
Gus Pathway- Which 3 cranial nerves carry info
Gus Pathway which 3 cranial nerves carry info through #7.Facial #9 Glossppharyngeal #10 .Vagus
Who determined 4 categories of taste in 19th Century? In 20th Century?
Hans Henning (19th) Ikeda (20th added Umami)
TASTE Sensations Sour
Hydrogen (H) ions sensation results when sourness receptors bind hydrogen (H) ions
TASTE Sensations Salty
Na+ channel associated with the presence of sodium substances bind with Na+ channel
Taste Buds
Neurotransmitter utilized in gustatory system: Taste buds are sensory taste receptors found on the tongue, throat, and palate that help form the perception of taste. Taste buds detect chemicals dissolved in saliva from food in the mouth and throat. Then, these taste buds send their sensory information through neurons to the gustatory center
Taste Receptors: What are the basic taste qualities?
Salty Sour Sweet Bitter Umami - described as meaty, brothy, or savory and associated with MSG Fat - preferred by most species Molecules broken down into fatty acids on tongue by lingual lipase located near taste buds
TASTE Receptor chemical detection Substances bind with specific taste receptors to produce various taste sensations. What are they?
Salty Associated with presence of Sodium - substances bind with Na+ channel Substance must ionize Influx of Na+ → depolarization/ AP → release of ATP which acts as NT in gustatory system Amiloride blocks Na+ channels → ↓ saltiness sensation, but doesn't block completely Decreases response of neurons in nucleus of solitary tract that respond best to salt Sour sensation results when sourness receptors bind hydrogen (H) ions Sourness receptor responds to acids but also anions Polycystic-kidney-disease-like ion channel (PKD2L1) responds to acids Bitterness (TR2) usually perceived from alkaloid Sweetness (T1R1 and TR3) perceived from glucose & fructose Umami: (T1R1 and T1R3) Glutame Receptors for bitterness, sweetness, & umami associated with G-protein called gustducin Receptors T1R2 & T1R3 - sweetness Also found in nose
Where are taste buds located?
Taste buds are located in papillae except for filiform Tongue contains ~ 10,000 taste buds (individual differences exist) Taste bud density changes over lifespan Each taste bud has 50 - 100 taste cells (receptors) with tips (cilia) that extend into the taste pore Shaped like garlic bulb Lifespan ~ 10 days Taste buds located in throat, roof of mouth, and cheeks are not housed in papillae
TASTE Sensations Bitterness (TR2)
alkaloid
TASTE Sensations Sweetness (TR1 and TR3)
glucose & fructose
Structures: →Tongue contains papillae
• Filiform- shaped like cones and located centrally -no taste buds (blind spot) -not in papillae • Fungiform-shaped like mushrooms and found on sides and tip (anterior 2/3) • Foliate- series of folds on back and sides -contain 1300 taste buds • Circumvallate- shaped like flat mounds in an inverted V-shaped trench located at back (posterior 1/3) -250 taste buds
Gustatory Pathway: Tongue Gus Pathway which 3 cranial nerves carry info through #7.Facial #9 Glossppharyngeal #10 .Vagus PATHWAY in BRAIN to the: Ventral Posterior Medial Nucleus of Thalamus >Gustory cortex (anteir Insula frontal operculum) >Orbial frontal cortex what makes it special is that it is the first place in brain where our sensation of flavor occurs. Taste and smell. TASTE: Orbital Frontal Cortex OFC may be cortical center for detecting flavor and perceptual representation of food
⇒ Transduction= chemicals contact the receptor sites on cilia ⇒ Taste receptors form synapses with bipolar neurons (dendrites) ⇒ Release of ATP onto bipolar cells ⇒ Bipolar cells (axons) transmit info to brain via cranial nerves 7, 9, 10 (facial, glosso, vagus) *Signals from taste cells travel along a set of pathways • Facial nerve (V)- -chorda tympani nerve: branch of facial nerve that transmits signals from front and sides of tongue -anterior 2/3 • Glossopharyngeal nerve (IX)- -lingual branch carries info back of tongue -posterior 2/3 • Vagus nerve (X) -transmits info from palate, pharynx, larynx and throat (epiglottis) *These pathways make connections in the nucleus of the solitary tract (NST) in the medulla -from here signals travel along two diff pathways
