OS III, Ex II, smell Flashcards
What is the olfactory nerve?
Cranial nerve 1
what type of receptor cells form the nerves that project into CN !
Bipolar receptor cells
what type of materials can activate receptors?
Mucous soluble materials
what has odarent receptors?
cilia that project into nasal mucous
life span of olfactory receptors?
1 - 2 months
How are olfactory receptors replaced?
basal stem cells.
Why can elderly people not smell well?
overall number of receptor cells decrease with age
what do mucous soluble odarants activate?
Na/Ca and Cl ion channels on receptor microvilli
Activation of the ion channels, Na/Ca, Cl does what
depolarization and AP generation
what is sensory adaptation?
cant smell something after prolonged exposure
what causes sensory adaptation?
Ca+ independent and dependent paths that inhibit receptors, close ion channels and remove ions that have got in
How many types of odarant receptors does human have?
300 types of odarante receptor, but only one per receptor
What cell type does the bipolar receptor cells innervate in olfactory bulb?
mitral cells, this is on the top side of cribiform plate
What converge onto individual mitral cells?
axons with similar inputs(smells/receptor type) in groups of 10-100
what is a mitral cell?
what the odarant cells innervate with in the olfactory bulb
where does olfactory bulb project to?
piriform cortex on the medial surface of the temporal lobe
Where does the piriform cortex project olfactory info to?
amygdala, hippocampus and prefrontal cortex
What are the characteristics of the primitive piriform cortex? 3
Conciousness of odors, singularity, habituation
What does piriform cortex neurons respond to?
odarent mixtures not components
what makes olfactory conscious experient different from vision and audition?
the experience is usually singular with one odar event at a time
what is it rare for someone to be able to do?
recal mental images of odars, or to detect more than one component at a time
What is habituation?
reduced cortical restponse to continuted chemical stimulation
What are the two reasons we can smell the same odor for a prolonged time?
Habituation - reduced cortical response and, receptor ataptiation - Ca dep/indep responses at olfactory epithelium
what is the point of habituation?
to detect new odarants against background of current odars.
What does amygdala have to do with olfaction
Amygdala is for generating emotion and associatave learining, smell goes through here, that is why a certain scent can bring back such strong memories.
what sensations can bring back the strongest emotions
smell is greater than both vision and autitory cues
what does the following scents do?
citrus - improve psychological states and immune function of those with depression, rose - inhibit stress induced skin barrier distruption, orange and laventer - reduce anxiety of patients.
where does the piriform cortex and amygdala project to?
orbitofrontal cortex OFC, a part of the prefrontal cortex
what does the orbitofrontal cortex act with?
amygdala in emotion and associative learning
what gives us the subjective idea of an odar smelling good or bad?
orbitofrontal cortex, OFC
what does the OFC, orbitofrontal cortex associate olfactory with?
Associates smell with taste, oral texture, visual inputs, to give us food reward value
What is retronasal olfaction
how taste interacts with smell
what is valuation of smell from OFC inportaint for?
emotion, and in autonomic responses such as heart rate, skin conductances responses mediated by amygdala
what is one draw back to olfacton?
the receptors come in direct close contact with brain allowing spread of pathogens
how do viruses get to olfactory bulb?
they travel along axons, then across synaps to limbic system
How do bacteria get to olfactory bulb?
penetrate olfactory mucosa cells, then transported into the subarachnoid space leading to meningitus
what is intranasal infusion?
a way for medications to be delivered to CNS through the nasal mucosa, bypassing the BBB. Insulin can do this.
What is another pathway to get from nasal mucosa to CNS
through the trigenimal nerve pathway.
