4/11 stuff? Flashcards
Will white or gray matter be lighter on T2 MRI images? why?
gray matter will be lighter
cuz it has 10% more water then white
How will CSF show up on T2 MRI
hyperechoic
How will csf/fluid show up on flair T2 images? what about bone & fat?
fluid = black
bone vs fat is harder to distinguish
what is ct air value? how about wters?
air= -1000
water = 0
How does an MRI make different structures more weighted etc?
weight is from proton organization and disruption
the difference is the speed and when energy goes in and when we listen
I show you a CT or MRI that has a bleed (skull = pacman, then it would be contained in the mouth area of a pacman)
What type f bleed is this and what was likely the cause?
Epidural hematoma (membrane contains it)
-wont cross suture lines
Usually from skull fracture that causes arterial bleed
Now you have a CT/MRI that looks like a cookie that someone nibbled around half the edge (this area where cookie is missing is the bleed).
What kind of bleed and what caused it)
Subdural hematoma
Shearing of bridging veins
If a hemorrhage occurs in the basal ganglia or cerebellum? What is the usual cause of it?
Hypertension!
What type of image is IV contrast used in?
what type of contrast is used?
T1 MRI images
gadolinium is the contrast
What CN’s are involved in smell and taste (be specific for each)?
smell: CN I
Trigeminal (chemosense) CNV (menthol, capsaicin, alcohol)
taste: CN VII, IX, X
Describe the pathway of olfaction/olfactory nerve?
Include 2nd order as well
ON axons–> through cribiform plate –>synapse in olfactory bulb glomeruli
2nd order neurons move down olfactory tract to primary olfactory center near the uncus OR some go to olfactory value site
What is olfactory epithelium (histo) like?
ciliated psuedostratified columnar –> non motile
what is special about olfactory cilia?
they are dendrites (with GPCR on them or interact with the R)
What type of receptors are odorant receptors?
GPCRs
Describe pathway for odorant to smell detection?
odorant–> attach to GPCR –> G protein activates odor specific Adenylate cyclase III –> binds CAMP gated ion channel –>triggers Ca+ gated Cl- channel
note this only happens in dendrite, but AP is transmitted regularly other then this/above
HOw many different odorant receptors and transmembrane domains are there? why are they important
400 diff receptors
7 transmembrane domains
These are important because they allow for multiodorant reception
What is special about an odorant on the body?
will not = [trigger] a scent AP?
What are the 2 most important (or noted by your professor) 2nd order neurons of olfaction pathway?
Mitral and tufted cells
What are mitral and tufted cells?
mitral = primary output to POC & AON
tufted cells are 2nd output (to POC & AON)
what are granule cells (related to olfaction)?
they are inhibitory (decide what signals move on)
also most common & the deepest
where are the tufted cells located?
external plexiform layer
Review layers of… olfactory organ/system?
- outer = ON layer
- glomerular (means what it sounds like)
- external plexiform layer (tufted cells here)
- mitral cell layer
- internal plexiform layer
- granule cell layer
What is the enterorhinal complex?
-what is it most important for? (2 things)
enterorhinal complex deals with memory smell relations
-most important for triggering memories from pre-adolescent age
-used for alzheimers memory regain
What is the overall function/role of the orbitofrontal olfactory area?
it integrates all sensory input
What is UPSIT?
-what sex is better at smelling?
-how is smell correlated with age?
UPSIT is a test to measure smell loss/ability
Females are always better at smelling
ABility to smell decreases with advancing age
What is one of alzheimers major affects on the olfactory system?
diminishes piriform cortex function (early on in the dz)
What are the major CN involved in taste (from front to back in oropharynx)?
7, 9 , 10
What are the taste buds on the side of papillae called?
circumvallate papillae
What is the histo of taste buds?
What is the physiologic reason for having tastebuds?
psuedostratified columnar epithelium embedded in squamous
Taste buds help us get good nutrients & avoid toxins (bitter)
briefly tell me what each type of taste bud cells do? (think overall function in the system and types of cells in each category)
I - glial cells who maintain the environment (aka sustentacular cells)
II - DO NOT form true synapses w/ 1st order neurons
-responsible for tasting sweet, umami, bitter OR ENaC (salt)
III- form true synapses w/ 1st order neurons
-taste sour stuff only
IV - basal cells (lil’ puramid @ lower end of these) and stem cells are here
Lets do the Type II cell signal cascade, oh boy!
(the first half is the same as odorant detection but major points have a # next to them))
odorant–> (1) attach to GPCR –> G protein activates odor specific Adenylate cyclase III –> binds CAMP gated ion channel –>triggers Ca+ gated Cl- channel –>starts intracellular Ca+ release –>
(2) Ca+ activates TRPM channel –> allows sodium to enter and depolarize the cell –> (3) activates the VGSC and spreads AP–> (4) VGSCs allow ATP release which realeases NTs!!
What are Type 2 taste bud cells responsible for telling us? via what receptors and what is their structure?
Tells us things to crave vs avoid
CRAVE:
- umami = T1R1 & R2
-sweet = T1R2 & R3
both are heterodimers
AVOID:
-bitter = T2 R1 - 5)
this is a monomer
What are the 3 things that activate TRPM?
(one electrolyte & 2 outside sources)
Ca+
stevia
temperature (warm = depolarization and thus same pathway as in type 2 cascade)
What is Type 3 taste bud cells responsible for tasting
sour
What is the signal cascade in Type 3 taste bud cells?
1) protons go through “novel channel) –> local depol
2)depol activates VGSCs –> make an AP
3) AP activates VGCCs –> Ca+ influx
4)Ca influx –> triggers synaptic vesicle fusion and NT release
How many tastes can a cell type taste at one time?
Just one!
Its the AP frequency from the cell inputs that differentiates
Where do the taste signals go after AP generated?
signals go to:
1) Nucleus Solitarius –>
2) 2nd order N go through ipsilateral Central Tegmental Tract–>
3) arrive at VPM nuc in the thalmus –>
4) go to gustatory cortex (in insula)–>
5) Orbitofrontal cortex!!!
What 2 senses combine so we can get better flavor detection?
Where does this final detection/determination [if good or not] take place?
smell & taste together!
assessment/detection is done by OFC
What is the noly sense that doesn’t relay through the thalamus?
olfaction
What are the two parts of the thalamus?
Epithalamus & subthalamus
What are the 2 parts of the epithalamus and what are their functions?
1)Habenula = limbic path for lack of reward that affects reticular system
2) Pineal gland = produces melatonin
-pineal gland can be inhibited by light
are there a shit ton of nuclei in the thalamus?
yes (31 to be exact)
what does the subthalamic nucleus do?
Subthalamic nuc
-it does indirect modulation of basal ganglia
where is the zona incerta? whats it do?
Its in the subthalamus and is a rostral midbrain continuation
what is the internal medullary lamina (of the thalamus)?
curved sheet of myelinated fibers that divide most of the nuclei in the thalamus
What are the 3 divisions of the thalamus?
anterior, medial and lateral
**lateral is broken into dorsal and ventral
what are the two main arteries that provide blood supply to the thalamus?
Posterior communicating artery (the tuberothalamic branch)
And a bunch of branches from the posterior cerebral artery
What are the afferent input and efferent output of the anterior nucleus (which is actually a group of nuclei in ant division)?
afferent input from mammillothalamic tract–>
ant nuclei–>
sends efferent info to cingulate gyrus
Dorsomedial nucleus:
1) whats it do/role?
2) afferents
3) efferents
aka association nucleus
1)gate info b/w cortical areas
2) afferents come from prefrontal cortex, olfactory and limbic structures
3)efferents sent to prefrontal cortex
Laterodorsal nucleus (LD)
1) whats it do/role?
2) afferents
3) efferents
1) also association and similar to ant nucleus
2) afferent from hippocampus
3) efferent to cingulate gyrus
What 3 nuclei of thalamus are involved in vision?
lateral posterior (LP)
pulvinar
lateral geniculate (LGN)
Which is the largest nucleus in the thalamus?
What does it do?
Largest is Pulvinar-LP nuclei complex
Involved in vision & do the parieto-occipital-temporal association cortex
aka crosstalk?
which nuclei of thalamus are primarily for motor control?
ventral anterior and ventral lateral nuclei
these 2 are relay nuclei for the striato cortical circuit (aka basal ganglia)
What 2 nuclei of the thalamus are involved in touch, pain, consciousness, and proprioception?
Ventral posterolateral VPL & VPM (medial)
what are the afferents and efferents for the VPL?
aff: medial lemniscus and spinothalamic (trunk/extremities)
eff: somatosensory cortex
what are the afferents and efferents of the VPM?
aff: trigeminothalamic (head region)
eff: somatosensory cortex
VPL & VPM segregate modalities of touch/sensation; which areas (ant, middle, and posterior) do which form of tactileness?
ant = proprioceptive
middle = tactile
post = nociceptive/pain
What happens if you have a vascular event/accident in thalamogeniculate artery? (what structures are affected and what symptoms would a person have)
Major vpl/vpm damage =
-central pain from peripheral stim
-ataxia
-tactile insense
-thalamic pain
What is thalamic syndrome?
what side do symptoms occur on?
damage to vpl/vpm
-get ataxia, tactile insense, thalamic pain
these will be on the contralateral side of the lesion
what nuclei of the thalamus is responsible for auditory relay?
Medial geniculate nuclei
what are the aff and eff for LGN?
input from optic N sends to 1’ visual cortex
What 2 nuclei of the thalamus are non-specific?
centromedian CM
parafascicular PF
What thalamic nuclei is considered the gatekeeper?
what is its special/specific function?
Thalamic reticular nucleus (TRN)
Binds gaba to itself to prevent ascending (unwanted) signals
what are the tonic states of thalamic neurons?
when does this occur?
normal depolarization of thalamic neuron –> AP chain
wake or REM
what are burst states of thalamic neurons?
neuron is hyperpolarized, and sensory info then blocked
This is when your sleeping
What is the ascending reticular activating system (RAS)
helps with consciousness
when preoptic system inhibits RAS, you get SLEEP
