lecture 7: CN I-CN VI Flashcards
where do axons of olfactory receptor neurons locate?
- how many bipolar neurons are located here?
sphenoethmoid recess of nasal cavity
- ~ 3 million
Can olfactory receptor neurons renew? if so, how long does it take & how?
yes
every 30-60 days by stem cells
odorant receptors are located on the _______ which detect and bind to other molecules to activate.
once activated, chemical information gets converted into _____ ____ to help _____ and ______ odor
dendrites
electrical signals
process and identify
mainly _____ receptors but also less likely ______ receptors make up odorant receptors
G-protein coupled receptors (GPCR)
ionotropic receptors
CN ____ fibers also spread in the olfactory epithelia. It can detect _____
V
pungency
CN I:
- myelinated or non-myelinated?
- thick or thin?
- fast or slow transmission?
- what makes up the olfactory filaments?
—> where is the crossing point? synapses with?
- nonmyelinated
- thinnest axons (.2 micrometers)
- slowest transmission speed (0.1 m/sec)
- 20-30 axon bundles
—> cribriform plate; olfactory bulb
are mitral cells similar to pyramidal cells in the neocortex? why or why not?
yes
both are excitatory neurons that release glutamate.
the axons are stimulated to promote firing of an action potential
what are centrifugal fibers?
negative circuit regulating odorant detection
Takes signals from CNS to peripheral structures
* allows us to have adaptation to certain odors
the olfactory projection pathway is a _____ neuron pathway
- list them
3
1st order: olfactory receptor neuron
2nd order: mitral cell
3rd order: olfactory cortex & limbic system
what is the only sensation that doesn’t need the thalamus for relay of conscious perception?
smell (olfaction)
what makes up the primary olfactory cortex?
piriform cortex and periamygdaloid cortex
what structures do the primary olfactory cortex project to & what do each do?
- hypothalamus: drive. (you smell food, now you want it too)
- amygdala: emotional learning. (smell gas & know it’s bad)
- hippocampus: memory. (smell something familiar)
- thalamus: relay station and coordination center
although the thalamus isn’t directly correlated to olfaction, how does it indirectly play a role in olfaction?
feedback projections from olfactory cortex go to olfactory association cortex in insula near gustatory cortex (involved in perception of flavor/taste).
because it has multisensory integration, perceptions of smell and taste can overlap.
which stage of eye development is this:
protrusion of optic vesicle from diencephalon
4th week
which stage of eye development is this:
- optic vesicle folds in to form double layered optic cup
- invasion of ectoderm forms lens vesicle
5th week
which stage of eye development is this:
- optic cup inner layer: retina
- optic cup external layer: retinal pigment epithelia
- both layers: continue to grow anteriorly to form ciliary body and iris
- lens vesicle: pinch off to form lens
- leftover ectoderm to form cornea
6th week
landmarks around the eye:
- anterior end of photosensitive retina:
- circular transition zone, junction of cornea and sclera
- ora serrata
- limbus
structures in external and internal layers:
- limbus –>
- blood supply, absorb stray light –>
- ora serrata –>
- sclera and cornea
- choroid capillaries
- retina and ciliary bodies
what does the ciliary body do?
lens accommodation and aqueous humor secretion
what does the iris do?
controls the amount of light that enters the eye
_____ and ______ increase inner pressure to maintain eyeball shape
aqueous humor and vitreous humor
what is aqueous humor?
- location:
- secreted by:
- drains into:
clear, watery fluid that fills ant. and post. chambers of eye. provides nutrients
- anterior to lens
- epithelia in ciliary body
- scleral venous sinus then to venous drainage of eye
what is vitreous humor?
- location:
clear, jelly like humor in eyeball
- posterior to lens
what is glaucoma?
what other condition is it like?
increased production or blocked circulation of aqueous humor
- like hydrocephalus in the brain