Taste

What part of the receptor cells is the actual receptor surface for taste?

The MICROVILLI provide the receptor surface for taste

Do taste receptors adapt quickly or slowly?

They adapt quickly (1-5 min)

What are taste receptor cells? How are they arranged on the tongue?

They are modified epithelial cells with many surface folds or microvilli that protrude through the taste pore. Plasma membrane of microvilli contain receptor sites that bind selectively with chemical molecules

T/F Sour taste can be changed by pH

True More acidic the food, the stronger the sour reaction becomes

What causes sour taste?

acids (i.e. Hydrogen ion concentration)

Hypoguesia

decreased ability to taste

Ageusia

inability to taste

What is a compound frequently used to test for taste blindness?

phenylthiocarbamide

Which of the following statements about the olfactory system is true? (A) The receptor cells are neurons (B) The receptor cells are sloughed off and are not replaced (C) Axons of cranial nerve (CN) I are A-delta fibers (D) Axons from receptor cells synapse in the prepiriform cortex (E) Fractures of the cribriform plate can cause inability to detect ammonia

(A) The receptor cells are neurons

What are 3 indirect elements that influence taste perception?

1. Information from other receptors especially ODOR 2. TEMPERATURE and TEXTURE of food influence taste 3. Psychological experiences associated with PAST EXPERIENCES with food influence taste ***Note*** How cortex accomplishes perceptual processing of taste sensation is currently unknown

What is a taste-provoking chemical called?

A tastant is a taste-provoking chemical

How long is the life span of a taste receptor cell?

About 10 days The taste cells are continually replaced by the mitotic division of surrounding epithelial cells Mature cells in the center of the taste bud break up and dissolve at the end of the lifespan

What type of papillae are on the posterior 1/3 of the tongue? What type of taste does this part of the tongue detect? What is the innervation

Circumvallate and Foliate papillae It detects sour and bitter sensations innervated by CN IX (glassopharyngeal).

A lesion of the chorda tympani nerve would most likely result in A) Impaired olfactory function B) Impaired vestibular function C) Impaired auditory function D) Impaired taste function E) Nerve deafness

D) Impaired taste function The chorda tympani is part of one of three cranial nerves that are involved in taste.

T/F Disorders of taste are all or none

False taste disorders can be total (all tastes) or partial (affecting several) or specific (only one or select few tastes)

What does umami mean? What class of compounds elicits this taste?

Japanese for delicious - has a "meaty, protein rich" taste Amino acids especially L-GLUTAMATE may be related to glutamate receptors expressed in neuronal synapses of the brain

What is a taste bud? What is it made of?

Taste buds are located primarily on the edges of the papillae. They are made of about 50 receptor cells packaged with supportive cells arranged like the slices of an orange. The taste bud has a small opening called the taste pore through which fluids in the mouth come into contact with the receptor cells.

Dysgeuia

distorted ability to taste

What are the 5 taste sensations?

sweet sour salty bitter and umami

What are the three types of papillae on which taste buds are found?

1. circumvallate papillae - majority of taste buds are found here, form V line on the surface of the posterior tongue 2. fungiform papillae -over the flat anterior surface, moderate number of taste buds here 3. foliate papillae - in the folds along the lateral surfaces of the tongue, moderate number found here

Name the cranial nerves involved in taste and their pathway into the CNS (5 steps)

1.CNN VII, IX, and X enter the medulla, 2.ascend in the solitary tract 3.terminate on second order taste neurons in the solitary nucleus 4.They project, primarily ipsilaterally, to the ventral posteromedial nucleus of the thalamus 5. finally to the taste cortex.

What happens when a stimuli is at low concentration? What happens when a stimuli is at high concentration?

Each taste bud usually responds to ONE of five primary taste stimuli when the taste substance is in low concentration At high concentration, most buds are excited by TWO or MORE of the primary taste stimuli

T/F slight changes do not change the taste elicited by a certain compound

False Slight changes in the chemical structure such as adding simple radical can change a chemical from sweet to bitter

T/F Taste receptors are neurons

False Taste receptor cells are NOT neurons Note: smell receptor cells are neurons

Taste disorders are linked to

Inadequate nutritional intake Reduced social pleasure Decreased psychological wellbeing

Where are nerve fibers around taste receptor cells?

Interwoven around the body of taste cells are "taste nerve fibers" that are stimulated by taste receptor cells These fibers invaginate into the cell membranes with many vesicles formed beneath. -Vesicles contain neurotransmitters that are released through cells to excite nerve fiber endings

Taste Summary

Taste is a combination of 5 sensations Taste cells are non-neural cells with membrane channels or receptors that interact with taste ligands. This interaction creates an intracellular Ca2+ signal that finally activates the primary sensory neuron

How do taste and smell affect appetite?

They work together to stimulate digestive juices and increase appetite with good smells/tastes They also give clues as to foods/substances to avoid, bad smells and tastes are objectionable The chemical senses act as a "quality control" for ingestible substances

What class of compounds is often found in poisonous plants? What kind of taste does it elicit?

deadly toxins found in poisonous plants are ALKALOIDS Elicits a very bitter taste that leads to rejection of the food

What elicits bitter taste? What are the two classes of bitter compounds?

***Is not caused by any single class of chemicals*** Like sweet, bitter is elicited by mostly ORGANIC compounds 2 classes of bitter compounds 1) long chain organic substances that contain nitrogen 2) alkaloids (many of the drugs in medicine such as quinine, caffeine, strychnine, and nicotine)

What elicits sweet taste?

***Is not caused by any single class of chemicals*** Mostly ORGANIC chemicals elicit sweet taste some include: sugars, glycols, alcohol, aldehydes, ketones, amides, esters, some amino acids, some small proteins, sulfonic acids, halogenated acids, and inorganic salts of lead and beryllium

What are the three stops of the taste signal as it travels into the CNS?

1. Taste impulses from the anterior 2/3 of the tongue first pass into the LINGUAL NERVE 2. then through the CHORDA TYMPANI into the FACIAL NERVE 3.finally into the TRACTUS SOLITARIOUS in the brain stem

How many taste buds are present in the oral cavity and throat? Where are the greatest percentage located?

About 10,000 Most on the upper surface of the tongue in papillae

What is the back of the throat and epiglottis innervated by?

CN X, vagus

What kind of receptors are used for sense of taste?

Chemoreceptors (Note both smell and taste work with the actions of chemoreceptors)

What type of papillae are found on the anterior 2/3 of the tongue? What does this part of the tongue detect? What is the innervation?

Fungiform papillae It detects salt and sweet sensations, and is innervated by CN VII (chorda tympani).

What elicits salty taste?

Ionized salts (mainly by Na+ ion concentration) some other anions also contribute to a lesser extent

What kind of molecules stimulate different taste receptor types? -Which receptors are depolarized by ion concentration, which act via second messengers?

Ions (Na+, H+) activate salty and sour (depolarization) Sugars, amino acids and organic compounds depolarize receptors for sweet, bitter and umami (GPCRs)

How does a tastant stimulate the sense of taste?

It generates receptor potentials that initiate action potentials that travel down the facial nerve (VII) and glossopharyngeal nerve (IX) to the gustatory (taste) cortex