The Chemical Senses Flashcards
What tastes are innately enjoyed and why?
→ Sweet and fatty
→ They provide energy
Why is bitterness disliked?
→ Taste of bitterness is associated with poison
What are the 5 tastes?
→ Sweet → bitter → sour → salt → umami
Where are taste buds present other than the tongue?
→ Palate
→ Epiglottis
What two types of cell are inside a taste bud?
→ Basal cells
→ Taste cells
What are basal cells?
→ Juvenile taste cells
What are taste cells and what do they look like?
→ Mature taste cells which have microvilli that project towards the taste pore
What would be seen if you took a voltage recording of taste cells?
→ Different responses
How are saltiness and sourness transduced?
→ Ion channels
How are bitterness, sweetness and umami transduced?
→ GPCR via T1 and T2
What ion is the major component of salt?
→ Na+
Describe how saltiness is transduced
→ High Na+ concentration when eating salt
→ Na+ passes through Na+ selective channels down its concentration gradient
→ This depolarises the taste cell and activates voltage gated Ca2+ channels
→ Vesicular release of NT (5-HT) is elicited and gustatory afferents are activated
What is the ion component of sourness?
→ H+
Describe how sourness is transduced?
→ H+ can pass through the same Na+ channels that mediate saltiness
→ H+ blocks K+ sensitive channels
→ Increased H+ and blocking K+ depolarise the cell and activate voltage gated Ca2+ channels
→ Vescicular release of neurotransmitters is elicited and gustatory afferents are activated
Describe how bitterness is transduced
→ T2 receptors are Gq coupled
→ PLC converts PIP2 → DAG + IP3
→ IP3 activates a type of Na+ channel and releases Ca2+ from the endoplasmic reticulum
→ Depolarises the taste cell and activates voltage gated Ca2+ channels
→ Release of ATP is elicited and gustatory afferents are activated
What taste receptors is bitterness detected by?
→ T2 receptors
→ 25 types