Sensory Systems part 2 Flashcards
Most cells can sense chemical stimuli, what is this called?
Chemoreception
Animals have many types of chemoreceptors, give examples of two
Olfaction and gustation
What is olfaction?
Smell - the detection of chemicals in the air
What is gustation?
Taste - detection of chemicals emitted from food
What three structural criteria distinguish olfaction and gustation?
- performed by different sense organs
- different signal transduction mechanisms
- processed in different integrating centres
What type of receptors does the olfactory system contain?
Odorant receptors
Binding of an odorant to an odorant receptor causes what?
A conformational change
What happens once a odorant binds to an odorant receptor causing a conformational change?
A G protein is activated, G-olf. It then moves through the membrane and activates the enzyme adenylate cyclase
What does the enzyme adenyl cyclase convert into what?
It converts ATP into cAMP
What is the purpose of cAMP in the olfactory system response?
cAMP opens cAMP gated ion channels
Once cAMP gated channels are opened, what two ions can enter the cell causing a generator potential?
Ca2+ and Na+
How do Cl- ions leave the cell and cause depolarisation?
The Ca2+ ions that enter the cell opens ca2+ activated cl- channels, causing cl- to leave the cell, increasing the depolarisation
How are action potentials finally triggered by the olfactory system?
The generator potential opens the voltage gated na+ channels, triggering action potentials
The gustatory system consists of five classes of tastants, what are these?
Salty, sweet, bitter, sour and umami
What do sweet, umami and salty tastes indicate?
Carbohydrates, proteins and ions
What do bitter and sour tastes indicate?
Potentially toxic substances
*Label this vertebrate taste bud
There
Taste receptor transduction pathways vary for
The different tastes, salty, sour, sweet, bitter
In the salty taste receptor transduction pathway what happens?
The Na+ from salty food enters through a Na+ channel
The resulting depolarisation opens voltage gated Ca2+ channels
The influx of Ca2+ causes neurotransmitter release
What happens in the sour taste receptor pathway?
H+ ions from sour foods block the K+ channel
This blockage prevents K+ from leaving the cell
The resulting depolarisation opens voltage gated ca2+ channels
The influx of Ca2+ causes neurotransmitter release
What happens in the sweet taste receptor transduction pathway?
A sweet substance binds to its receptor causing a conformational change
The activated G protein, gustducin activates adenylate cyclase
Adenylate cyclase catalyses the conversion of ATP to cAMP
The cAMP activates a protein kinase that phosphorylates and closes a K+ channel
The resulting depolarisation opens voltage gated ca2+ channels
The influx of Ca2+ causes neurotransmitter release
What happens in the bitter taste receptor transduction pathway?
A bitter substance binds to its receptor, causing a conformational change
The activated g protein, transducin activates phospholipase c
PLC catalyses the conversion of PIP2 into the second messenger IP3
IP3 causes the release of Ca2+ from intracellular stores
The influx of Ca2+ causes neurotransmitter release
