Sensory system - Smell

what are chemoreceptors

• they are receptors taste and smell

• they are detect certain chemical through sense of smell are odors

what is a olfactory bulb

The olfactory bulb is a neural structure located in the forebrain

• the olfactory receptors cells directly detect chemicals we breathe into the nasal cavity

what are basal cells

Basal cells are stem cells located in the olfactory epithelium that continuously regenerate olfactory receptor neurons throughout a person's life

what are the bi-polar 2 projections

1. goes down to the epithelium surface where the cilia extends to the mucus layer

2. goes opposite direction into the plate of the olfcatory

why are odorants volatile & soluble in the mucous layer

Odorants must be volatile to evaporate and enter the nasal cavity, and they must be soluble in the mucous layer to interact with olfactory receptors effectively.

where does olfactory transduction occurs

t the olfactory mucosa located in the nasal cavity

how many olfactory receptors in humans

• it has 400

• each neurons expresses a single type of odorant receptor

what type of receptor is a odorant

a GPCR(G protein-coupled receptor).

How many odorant does a mice have

approx 1000

what are trace-amine associated receptor (TAARs)

• they recognise volatile amines that play a role in detecting odors related to pheromones and environmental cues.

what is a formyl peptide receptor (FPRs)

It is involved in chemo taxis and immune response by recognizing formylated peptides.

what Vomeronasal Receptor (V1R, V2R)

are part of the vomeronasal organ and are responsible for detecting pheromones and other social cues.

what is a sensitive smell

• methyl mercaptan ( the smell of gas)

• it can be detected at 1 molecule in 50 billion

describe the olfactory signal transduction

1. chemoreceptors are GPCRs

2. activation of this causes an increase in cAMP through a small G protein - G_αolf which is related to G_αs

3. the increase in the cAMP causes the activation of a cation channel, a cyclic-nucleotide gated (CNG)

4. Channel opening allows Na+ & Ca2+ influx causing a depolarisation - the receptor potential

what is higher processing in the olfactory cortex

when signal is passed from the olfactory bulb to the primary olfactory cortex

• the axon converge on secondary neurons sending information to the CNS in different combination

what is the term for loss of smell

• anosmia

• some people cannot smell certain odorants - this is due to genetic variation e.g 1% of people cannot detects the smell of vanilla