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Flashcards in Histology of CNS Deck (44):
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Neuron function

transmits chemical electrical signals of the nervous system

1

Do neurons divide in adulthood

no

2

dendrites

receive input

3

Soma

neuronal cell body

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axon

sends neuronal output

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Nissl Substance

identifies neurons
Stains RER - located in dendrites and soma

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Types of Neurons (functional - 2)

Sensory
Motor

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Types of Neurons (Structural - 3)

Bipolar neuron
Pseudounipolar neuron
Multipolar neuron

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Bipolar neuron

single axon emerges from either side fo cell body
SENSORY
found only in ear and eye

9

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.

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multipolar neuron

single axon w/ many dendrites
MOTOR NEURONS AND INTERNEURONS
most abundant type of neuron in brain

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2 examples of multipolar neurons

pyramidal cell
purkinje cell

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pyramidal cell

multipolar neuron
cerebral cortex, hippocampus, amygdala
PYRAMID/triangle shaped soma
Fxn- cognition, motor control of voluntary mov't

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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

14

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)

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Cerebellar Layers (and cell types)
superficial to deep

Molecular Layer (dendritic and axonal synapses)
Purkinje Layer (purkinje cells)
Granular Layer (granular cells)

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Oligodendrocytes

myelinate axons of neurons in CNS
can myelinate multiple axons
"fried egg" histo appearance

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Dz (3) associated with oligodendrocytes

Multiple Sclerosis
progressive multifocal leukoencephalopathy
leukodystrophies

18

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

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3 components of the BBB

podocytes of astrocytes lining blood vessels
tight junctions between non-fenestrated endothelial cells
basement membrane of endothelial cells

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(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)

21

Gliosis (definition)

Astrocytes
non specific response to repair damage done to CNS after neuronal cell injury --> end result= formation of glial scar

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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"

23

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)

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Multinucleated giant cell

fusion of multiple infected microglia when HIV infects microglia

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Ependymal Cell Functions (3)

1. Make CSF
2. form blood-CSF barrier
3. form the arachnoid-CSF barrier

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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

27

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

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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)

29

Hydrocephalus

CSF blockade

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Communicating hydrocephalus - definition

decreased CSF reabsorption by arachnoid granulations OR overproduction of CSF (choroid plexus papilloma)

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Communicating hydrocephalus - caused by

scarring of meninges after meningitis, a meningioma, old blood remnants after a subarachnoid hemorrhage, choroid plexus papilloma

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communicating hydrocephalus - issues

increased ICP, papilledema, herniation of the brain

33

Non communicating hydrocephalus - defined as

structural blockage of CSF within the ventricles

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non communicating hydrocephalus - caused by

tumors, compression or stenosis of the interventricualar foramen or cerebral aqueduct

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non-communicating hydrocephalus - issues

headache, papilledema, brain herniation (uncal herniation)

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Blood CSF barrier

ependymal cells+ tight junctions

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Arachnoid-CSF barrier

arachnoid membrane prevents CSF in subarachnoid space from coming into contact with fluid of dura mater

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Dura mater

outermost, tough, durable membrane

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Arachnoid mater

between dura and pia
delicate, attached to inside of dura,
forms subarachnoid space, in which CSF flows

40

Pia mater

innermost layer
firmly adhered to surface of brain and spinal cord
thin, delicate membrane

41

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

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Hallmark Triad of Meningitis

severe headache, fever, nuchal rigidity

43

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