Smell

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the three types of cell in the olfactory epithelium
receptor cell, supporting cell (produce mucus) and basal cells (precursors of new receptor cells)
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Mucus constituents and role
polysaccharides, water and some protiens including antibodies that stop viruses entering the brain. The mucus dissolves odorants
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What can a bang to the head cause? Why?
Anosmia - lack of ability to smell because theaxons held in the cribiform plate get sheared
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Describe the process of olfactory transduction
Odorants bind to gpcr receptors which activate G protien Golf. Golf activates adenyl cyclase, forming cAMP. cAMP binds to ion channels and opens them, allowing Na+ and ca2+ to enter. Ca2+ opens ca2+ activated cl- channels -> DEPOLARISATION
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What terminates the olfactory response
odorants diffuse away, scavenger enzymes in the mucus break them down, cAMP may activate other signalling pathways that end the transduction process.
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Human olfactory receptor genes
350 scattered about on the genome, every chromasome has at least a few. Each receptor cell expresses a few types of receptor, and they are organised in large zones on the epithelium
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What happens in the first layer of the olfactory bulb
within large spherical glomeruli, 25,000 primary axons synapse on 100 second order olfactory neurons
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Presicision of mapping in the glomeruli
each type of receptor maps to one or two glomeruli - very precisely placed. same in both bulbs.
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the next 4 layers in the bulb
external plexiform layer, mitral cell layers, internal plexiform layer, granule cell layer.
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Where is a particuarly important output of the olfactory tract
the olfactory cortex in the temporal lobe. no thalamus so it has a widespread effect on areas that influence odour discrimination like emotion, memory
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Pathway for concious perceptions of smell
from the olfactory tubercule, to the medial dorsal nucleus of thalamus, to the orbitofrontal cortex.
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The three features that help the brain recognise smells
population maps, spatial mapping and action potential timing
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How does population coding work
combining responses of different intensity to get a unique response for a specific odorant
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Card 2

Front

Mucus constituents and role

Back

polysaccharides, water and some protiens including antibodies that stop viruses entering the brain. The mucus dissolves odorants

Card 3

Front

What can a bang to the head cause? Why?

Back

Preview of the front of card 3

Card 4

Front

Describe the process of olfactory transduction

Back

Preview of the front of card 4

Card 5

Front

What terminates the olfactory response

Back

Preview of the front of card 5
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