What is olfaction?
Smell
What is gustation?
Taste
What do the chemoreceptors of gustation and olfaction respond to overall?
Chemicals dissolved in an aqueous solution
What do the chemoreceptors in taste specifically respond to?
Substances dissolved in saliva
What do the chemoreceptors in smell specifically respond to?
Substances dissolved in fluids of the nasal membranes
What is a specialized part of the nasal epithelium called? What is it?
The olfactory epithelium- It is found in the roof of the nasal cavity and it contains olfactory receptor cells
What is another term for olfactory neurons?
olfactory receptor cells
How are olfactory neurons unique?
They are replaced by new neurons after 4-8 weeks
These new neurons are formed from the basal cell which is a stem cell
They contain a dendrite that points downwards towards the mucus overlaying the olfactory epithelium and in mucus it branches into olfactory cilia
What does mucus capture?
Oderants-chemicals capable of detection by the receptors
About _____ unique receptors can differentiate _____ odors
1000, 1000
How many oderant receptors might need to be activated to distinguish a unique odour?
10-20
True or False: Many molecules are needed to activate an olfactory receptor?
False- Only a few molecules are needed
Where do odorants produce graded potentials?
cilia
How is smell transduced?
- Odorant binds to receptor
- Activation of G protein-coupled olfactory receptor
- G protein activates adenylate cyclase
- Adenylate cyclase converys ATP to cAMP
- cAMP opens Na+ and Ca^2+ channels
- Depolarization
- AP is triggered in neurons
True or False: Second messenger cAMP acts as an intracellular ligand to activate ligand-gated ion channels to produce and EPSP
TRUE
How is smell transmitted?
- Axons olfactory receptor -> olfactory bulbs
- Synapse of axon w/ mitral cells
- Activation of mitral cells
- Impulses flow from olfactory bulb via olfactory tracts to olfactory cortex, then limbic system
Does the input of smell pass through the thalamus?
NO- the sense of smell is the only input to the
cerebral cortex that does not pass through the
thalamus
Where do the axons of the olfactory receptor cell ascend up through?
bony roof of the nasal cavity via
tiny holes in the cribiform plate of the ethmoid
bone into the cranial cavity
What forms the olfactory nerve? What is another name for it?
Axons of the mitral cells
Olfactory tracts- as it is not a true nerve
Where are smells identified and interpreted?
Olfactory Cortex
Where is the olfactory cortex located?
Inferior frontal lobe
What location can we find memories and emotions associated with smells?
Limbic system
What are the requirements for a chemical to be tasted?
Must be dissolved in saliva
Must contact gustatory hairs
Where are taste buds located?
papillae- small protuberances on the surface of the tongue
