Intro to Neuro - Taste

What are the 5 tastes?

Salty, sweet, sour, bitter, umami

What is an advantage for being able to tell different tasts?

Advantage for survival is that you can differentiate between normal and poisonous substances bc those are often bitter

Can multiple taste receptors be activated when eating?

Yes, different foods have different activation combinations

Sweetness is found at the _______________.

tip of the tongue

Bitterness is found at the ______________.

back of the tongue

Saltiness and sourness are found at the ________________.

sides of the tongue

Papillae

small tissue lumps found on the upper surface of the tongue; function is to INCREASE SURFACE AREA → 3 different types (foliate, vallate, fungiform)

Taste buds

taste receptors found on sides of papillae and lining mouth; there are over 10,000 taste buds on the tongue; new taste buds every 10-14 days

Taste bud structure

taste pore (w/ microvilli) → support cells cluster → nerve fiber

What are the different ways that taste stimuli can be processed?

1. Pass through ion channels

2. Bind and block ion channels

3. Bind to G-protein-coupled receptors w/ 2nd messengers

Salty Transduction

1. Na+ ions enter taste cells through ion channels

2. Depolarization event occurs and neurotransmitter is released

3. TRPV1 = salt sensor that increases sensitivity to Na+ and detects other salty cations

Sour Transduction

1. Acids release H+ causing sour taste

2. Ion channel allows influx of protons

3. Depolarization occurs

Sweet Transduction

1. Sweet tastants bind to heterodimer T1R2/T1R3

2. Second messenger is activated

Bitter Transduction

1. Bitter tastants bind to T2R receptor

2. Second messenger is activated

   • EACH BITTER SENSING CELL HAS ALL THE BITTER RECEPTORS

Umami Transduction

1. Umami tastants bind to either metabotropic glutamate receptor (stimulated by MSG) OR T1R1/T1R3 heterodimer

2. Second messenger is activated

Gustatory System

Tongue → brainstem nuclei → thalamus → somatosensory cortex

• brain monitors which axons are active to determine taste

Which sensations use ion channels?

Salty and sour

Which taste sensations use GPCRs?

Sweet, bitter, umami

Which taste receptor also detects carbonation in drinks?

Sour!

Which taste is associated with poison if strong taste detected?

Bitter?