Neuropathology Flashcards
What stain does Nissl use and what does it stain for?
Cressyl violet
Stains neuronal cell bodies
What can we use to stain astrocytes?
GFAP
S100beta
Glutamine synthetase
Holzer
What is isomorphic gliosis?
Gliosis refers scarring that occurs when the processes of fibrous astrocytes extend to cover and repair the damaged tissue; it is also called fibrillary gliosis.
What are microglia?
The brain’s immune cells
In a disease state microglia begin to express HDA-DR or CD68
They also change shape in disease, have fewer processes but the processes they do have become thicker and shorter
When they are very reactive they become a round blobby shape and this is called AMOEBOID MICROGLIA
What are the 4 elements of the BBB?
Endothelial cells- bound together by tight junctions which stop molecules getting out between the edges between endothelial cells
Basement membrane- lacks fenestrations (holes)
Astrocyte- fine processes which wrap around the blood vessel and use their endfeet to seal the vessel. They are another layer which prevent molecules getting out of the blood circulation
Pericytes- their activity regulates the permeability of the whole system
What does the internal carotid supply?
The carotid splits into two main branches
The external branch- supplies blood to a lot of the head and neck
The internal carotid branch- forms the middle cerebral artery which supplies blood to the side of the brain.
It also has branches coming off of it such as the anterior cerebral artery which deals with the front of the brain and the bits between the two hemispheres . The two anterior cerebral arteries are joined by the anterior communicating artery.
Together these form the anterior circulation
What do the vertebral arteries supply?
They join together to form the basilar artery which goes on to split into the two posterior cerebral arteries and these supply the back of the forebrain, the back of the medial surfaces of the forebrain and some of the inferior parts
How is the circle of Willis helpful in stroke?
It means there is a collateral circulation, a set of blood vessels that will get blood into a particular part of tissue whilst going around a blockage, it can help to minimise the damage, but you still can’t get enough blood in to prevent tissue death and damage but it does compensate a little
What are the two broad ways to compromise the blood supply to the brain?
- Block off an artery –> this will take out an entire territory of the brain depending on how far down the blockage goes
- Fail to perfuse your whole brain adequately –> e.g. when you have a heart attack you get a different pattern of brain tissue that starts to die off, the ischemic change caused by reduced blood supply
What is watershed infarcts/stroke?
Defined as brain ischemia that is localised to vulnerable border zones between tissues which are supplied by all 3 arteries (anterior, posterior and middle arteries)
When looking at a brain slice you lose the interface between grey/white matter which shows hypoxic ischemic changes to the brain, it appears dusky and squishy
What is a sinus?
A large venous structure that has blood coming away from the brain heading back towards the heart
What will you see if you lay someone with heart disease back by 45 degrees?
You will see the pulse from the jugular vein in the neck
What is the blood supply to the spinal cord?
Running up the front of the spinal cord is the anterior spinal artery
Up the back of the spinal cord is a complex plexus of different arteries
What is in a spinal cord cross section picture? (H)
The white matter is around the outside and the grey matter which is the information processing is on the inside
Inside it are two horns- the ventral horns which is where motor neurons live and the dorsal horns which deal with sensory information
In general stuff in the spinal cord goes in through the back and out through the front. What type of information goes in and what type of information goes out of the spinal cord?
Sensory information comes in through the back
Motor information comes out through the front
What neurons are in the anterior horn?
Motor neurons which have really big axons and big cell bodies
They are completely decimated in MND- when you lose motor neurons, the spinal nerve rootlets begin to atrophy and shrink
How does the spinal cord white and grey matter change depending on the level?
Higher up there is more white matter- you’ve got white matter up here that us sending axons to and from the whole of the cord
Down at the bottom there is less white matter- only sending axons to and from that little bit of the cord at the bottom
Grey matter is different- it varies depending on the amount of motor neurons there are, its more a reflexion of the complexity of movement in that area- areas controlling arms and legs will have more neurons in these areas
What is anterolateral cordotomy?
It is done for the treatment of intractable pain
It is a surgical procedure that disables selected pain-conducting tracts in the spinal cord, in order to achieve loss of pain and temperature perception
side effects:
sleep apnoea
What is the spinothalamic tract?
Carries pain and temperature sensation
Ascending pathway (up)
Pathway is across then straight up
It synapses at the thalamus and this then projects up to the cortex to the postcentral gyrus
What is the dorsal column-medial lemniscus pathway
a.k.a. Posterior column–medial lemniscus pathway
About joint position sense and vibration
Ascending pathway (up)
The sensation comes in and goes straight up the medulla where it decussates to the medial lemniscus (white matter at the bottom of the medulla). Then it goes up through the pons and the midbrain, synapsing into the thalamus and then it projects to the postcentral gyrus
What is the corticospinal (pyramidal) tract?
The output pathway- responsible for voluntary movement of the limbs and trunk and also for fine movement
Descending (down)
From the precentral gyrus upper motor neurons project down though a big white matter pathway, through the peduncles, down the pyramids, down through the right front end of the medulla where 80% of fibres decussate and project down the lateral corticospinal tract and then communicate with lower motor neurons in the spinal cord
the other % do not decussate at the medulla but continue down via the anterior corticospinal tract to the skeletal muscle
What is the superior colliculus?
Talks to the lateral geniculate of the thalamus, its the visual part of the brainstem
(superior colliculus is higher than the inferior colliculus so superior is sight and inferior is hearing- eyes are higher than ears)
What is the inferior colliculus?
Projects to the muddle geniculate of the thalamus, its the auditory part of the brainstem
What is the rhomboid fossa?
Floor of the 4th ventricle, its the space between the cerebellum and the brainstem
What are the two fibre pathways coming back up the back of the medulla?
Fasciculus cuneatus
Fasciculus gracilis
Together these two form the dorsal columns
What is the locus coeruleus?
The locus coeruleus is a nucleus in the pons of the brainstem involved with physiological responses to stress and panic.
It is badly affect in PD
What attaches the cerebellum to the brainstem?
Middle cerebellar peduncle
How does the wiring in the cerebellum work via granule cells and purkinje cells etc?
Across folia are large dendritic trees of purkinje cells, in between them the cerebellar granule cells send a process up that forms an axon that runs along the length of the folia and this axon synapses onto multiple different purkinje cell dendritic trees.
1 granule cell can synapse onto multiple purkinje cells.
Purkinje cells are the main output pathway of the cerebellum, they project down to the deep cerebellar nuclei and then on from there, the input comes from these mossy fibres that connect onto these cerebellar granule cells from the vestibular nucleus, the spinal cord etc to coordinate movement, then there is also some interaction there regulating the interplay between these climbing fibres from the inferior olivary nucleus
What does the cerebellum look like after alcoholism?
Somewhat healthy at the bottom but completely shrivelled away and wasting at the top
What is the brown pigmentation in the substantia nigra?
It is neuromelanin, the by product of natural dopamine
What happens to dopaminergic neurons in PD?
They die
What does cutting the corpus callosum do in epileptic patients?
It reduces the number of excitatory processes occurring and thus reduces seizures
What is the intraventricular foramen also referred ti as?
The foramen of monroe
What is on either side of the 3rd ventricle?
The basal ganglia and the thalamus
How does CSF drain out of the 4th ventricle?
Through the foramen of magendie and the foramen of luschka
What cells line the ventricles?
Ependymal cells- they have wavey things on top of them called cilia which beat and are motile, and help move CSF through the system.
What is CSF produced by?
choroid plexus
What is the striatum made up of?
caudate, putamen and globus pallidus
What is the lentiform nucleus made up of?
Putamen and Globus Pallidus
What is the massa intermediate?
A connection between the two halves of the thalamus across the third ventricle
It does not provide any useful functional connectivity - some people don’t even have one
What does damage to the thalamus cause?
Loss of sensation, pain or movement disorders, plus some potential memory problems
What structures are in the basal ganglia?
The basal ganglia consist of five pairs of nuclei: caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra
What are striatum inputs?
Inputs from cortex, input from thalamus and input from substantia nigra
In PD what happens to the dopaminergic neurons?
They shed their neuromelanin (brown pigment) into the surrounding tissue. You lose the pigment and the substantia nigra becomes pale
What happens to the head of caudate in Huntington’s Disease?
It withers away, its concaved
What is the genetic mutation in Huntington’s Disease?
An expanded polyglutamine repeat
What is the main source of Acetylcholine input to the whole brain?
Nucleus Basalis of Meynert
What disease has huge reductions in acetylcholine?
Alzheimer’s Disease
What does the drug Aricept do?
Boosts acetylcholine in the brain - although its not particulalry effective
What is the main input to the limbic system?
The olfactory system
What are Betz cells?
Classic archetype of pyramidal cells, they’re really big
What are the 3 broad systems of fibres?
Association fibres- within a hemisphere, take impulses from one part of cortex to another
Commisure fibres- allow cortical regions to communicate between different hemisphere
Projection fibres- go from cortex down to deeper structures, mostly the brain stem and spinal cords
