Histology of CNS Flashcards
Do neurons divide in adulthood
no
Neuron function
transmits chemical electrical signals of the nervous system
dendrites
receive input
Soma
neuronal cell body
axon
sends neuronal output
Nissl Substance
identifies neurons
Stains RER - located in dendrites and soma
Types of Neurons (functional - 2)
Sensory
Motor
Types of Neurons (Structural - 3)
Bipolar neuron
Pseudounipolar neuron
Multipolar neuron
Bipolar neuron
single axon emerges from either side fo cell body
SENSORY
found only in ear and eye
Pseudounipolar neuron
single axon divides into 2 br from the cell body
one goes to the periphery the other to the cord
SENSORY
found in sensory ganglia of cranial and spinal nn.
multipolar neuron
single axon w/ many dendrites
MOTOR NEURONS AND INTERNEURONS
most abundant type of neuron in brain
2 examples of multipolar neurons
pyramidal cell
purkinje cell
pyramidal cell
multipolar neuron
cerebral cortex, hippocampus, amygdala
PYRAMID/triangle shaped soma
Fxn- cognition, motor control of voluntary mov’t
Purkinje Cell
multipolar neuron
INHIBITORY neuron in the cerebellum
100s of 1000s of signals converce on purkinje cell
It sends out ONE message of what to do
only output neuron from cerebellar cortex
6 Cell Layers of Cerebrum (and cell types)
from superficial to deep
Molecular (dendritic and axonal synapses)
External granular (small pyramidal and stellate)
External pyramidal (medium sized pyramidal cells)
Internal granular (dense stellate cells)
Internal pyramidal (large pyramidal cells)
Multiform (many cell forms)
Cerebellar Layers (and cell types) superficial to deep
Molecular Layer (dendritic and axonal synapses) Purkinje Layer (purkinje cells) Granular Layer (granular cells)
Oligodendrocytes
myelinate axons of neurons in CNS
can myelinate multiple axons
“fried egg” histo appearance
Dz (3) associated with oligodendrocytes
Multiple Sclerosis
progressive multifocal leukoencephalopathy
leukodystrophies
Astrocytes
Star-shaped glial cells
many many functions
BBB
REPAIR and SCARRING process after neuronal cell injury
physical support
maintains extracellular ion balance (K+metabolism)
removes excess NT
glycogen fuel reserve
3 components of the BBB
podocytes of astrocytes lining blood vessels
tight junctions between non-fenestrated endothelial cells
basement membrane of endothelial cells
(3) Specialized areas of the brain with no BBB
Collectively called?
Called circumventricular organs area postrema (vomitting) OVLT (osmotic sensing) Neurosecretory substances and hormones that enter circulation (ant and post pit)
Gliosis (definition)
Astrocytes
non specific response to repair damage done to CNS after neuronal cell injury –> end result= formation of glial scar
Gliosis (process)
damage–> proliferation of astrocytes–> become “reactive astrocytes”–> use their own plasma membrane to form a web to fill in the space of dead or dying neuronal cells –> glial scar
“reactive gliosis”
Microglia
Macrophages of the CNS
roll in neuro inflammation and neurodegeneration
normal response= activation, engulf foreign substances, release cytokines (IL-1, TNF-a), and then become inactivated
pathologic when they continue production of neurotoxic mediators= neuronal cell death
(alzheimers, parkinson’s aging)
Multinucleated giant cell
fusion of multiple infected microglia when HIV infects microglia
Ependymal Cell Functions (3)
- Make CSF
- form blood-CSF barrier
- form the arachnoid-CSF barrier
Ependymal Cells
line CSF-filled ventricular system of the brain and the central canal of the spinal cord
simple cuboidal epithelia cells with microvilli and cilia (apical side)
linked via tight junctions
CSF production
ependymal cells+ fenestrated capillary forms Choroid Plexus
blood comes in–>ependymal cells take up plasma and filter out specific components –>CSF–> goes into ventricles
Path of CSF through ventricle in the brain
Choroid plexus of lateral ventricles –> [ interventricular foramen of Monro] –> 3rd ventricle–>[cerebral aqueduct of sylvius]–> 4th ventricle–> formen of lushcka and magendie]–>subarachnoid space–> arachnoid granulations reabsorb CSF–> dural venous sinuses (specifically superior saggital venus sinus)
Hydrocephalus
CSF blockade
Communicating hydrocephalus - definition
decreased CSF reabsorption by arachnoid granulations OR overproduction of CSF (choroid plexus papilloma)
Communicating hydrocephalus - caused by
scarring of meninges after meningitis, a meningioma, old blood remnants after a subarachnoid hemorrhage, choroid plexus papilloma
communicating hydrocephalus - issues
increased ICP, papilledema, herniation of the brain
Non communicating hydrocephalus - defined as
structural blockage of CSF within the ventricles
non communicating hydrocephalus - caused by
tumors, compression or stenosis of the interventricualar foramen or cerebral aqueduct
non-communicating hydrocephalus - issues
headache, papilledema, brain herniation (uncal herniation)
Blood CSF barrier
ependymal cells+ tight junctions
Arachnoid-CSF barrier
arachnoid membrane prevents CSF in subarachnoid space from coming into contact with fluid of dura mater
Dura mater
outermost, tough, durable membrane
Arachnoid mater
between dura and pia
delicate, attached to inside of dura,
forms subarachnoid space, in which CSF flows
Pia mater
innermost layer
firmly adhered to surface of brain and spinal cord
thin, delicate membrane
Meningitis
inflammation of meninges
caused by bacterial viral or fungal infection
Pathophys - typically follows a URI–> invades nasal mucosa –> bloodstream–>penetrates the subarachnoid space and gets into CSF
Hallmark Triad of Meningitis
severe headache, fever, nuchal rigidity
Meningioma
tumor that arises from meninges, compresses but does not infiltrate brain tissue
presents with signs/symptoms based on location
CLASSIC WHORLED PATTERN
PSAMMOMA BODIES
