NEUROCYTOLOGY Flashcards
Neurons and Glial cells derived from the ___________.
Neuroectoderm
Supporting structures of the nervous system derived from the __________.
Mesoderm
The functional unit of the nervous system
Neurons
TRUE/FALSE
Signaling and Trophism are the most important function of the neurons?
TRUE
Other functions:
1. Generates and conducts electrical activity
- Transmits information throughout the N.S.
- Exerts long-term effects required for storage of information
TRUE/FALSE
Normal mature neurons do not proliferate, but they can undergo adaptive changes in response to injury?
TRUE
These supporting cells of Neuroectodermal origin comes from the greek word which means “glue”
Glial cells
This cells mainly glue together or support the neurons to make-up the nervous system
Glial cells
Consists of multiple tightly wrapped layers of plasma membrane that ensheathe large diameter axons.
Myelin
Form myelin sheaths in CNS (spinal cord and brain)
Oligodendrocytes
-In the CNS, processes from a SINGLE oligodendrocyte contribute to the myelin sheath of SEVERAL axons near the cell (1: many)
Form myelin sheaths in PNS (peripheral nerves and cranial nerves)
Schwann cells
-each Schwann cells interact w/ one axon (1:1) and contributes to the formation of a single internode.
star-like glial cells of the CNS
Astrocytes
Lie near both neurons and blood vessels
Astrocytes
maintains homeostasis and chemical microenvironment of the brain and spinal cord
Astrocytes
provide SELECTIVE BARRIER between the ventricular fluid and the brain substance
Ependymal cells
TRUE/FALSE
Ependymal cells form a single layer of ciliated cuboidal epithelial cells that lines the entire ventricular system
FALSE
Ependymal cells form a SINGLE layer of CILIATED COLUMNAR epithelial cells that lines the entire ventricular system
What are the 4 supporting cells in neuroectodermal in origin?
4 supporting cells in neuroectodermal in origin
- oligodendrocytes
- Schwann cells
- astrocytes
- ependymal cells
TRUE/FALSE
Microglia and Connective tissue cells are supporting cells of ectoderm origin?
FALSE
Microglia and Connective tissue cells are supporting cells of MESODERM origin
They are mesodermal cells of monocyte lineage that migrate into the CNS along with blood vessels from the mesoderm surrounding the neural tube.
Microglia
Remember M=M=M!
Mesoderm= Monocyte= microglia
They are mesodermal cells that are normally present in small numbers in the brain and spinal cord and only proliferate in response to injury
Microglia
They are mesodermal cells that are normally present in small numbers (physiologic state) and migrate in the CNS, proliferate to become scavenger cells/specialized macrophages, removing damaged tissues (pathologic state)
Meninges surrounding the CNS
Connective tissue cells:
Dura, pia and arachnoid
Fibrous connective tissue surrounding the PNS
Epineurium, Perineurium and Endoneurium
They are collectively known as leptomeninges
Pia and Arachnoid
also known as Pachymeninx
Dura mater
it gives rise to the choroid plexus which produces CSF
Ependymal cells
Transient neurologic disorders that may primarily affect neuronal function alone (WITHOUT changes in the physical appearance of the cell)
Transient neurological disorders:
- seizures
- TIA (transient ischemic attacks) aka mild stroke
- hypokalemic paralysis
TRUE/FALSE
Oxidative metabolism of glucose in the mitochondria is vital for cell survival in the N.S.
TRUE
Oxidative metabolism of glucose in the mitochondria is vital for cell survival in the N.S.
Both Oxygen and Glucose supply is needed
Most ATP consumptions of the nervous system is for fueling what?
NA-K ATPase pump
-to restore the ion gradient altered by excitatory neurotransmission and neuronal activity
Critical for preventing excessive accumulation of glutamate (synaptic space) and calcium ions (in the cytosol), both of which are toxic to cells
ATP
Critical for preventing excessive accumulation of glutamate (synaptic space) and calcium ions (in the cytosol), both of which are toxic to cells
NECROSIS/APOPTOSIS
abrupt ATP depletion
Necrosis
abrupt ATP depletion- hypoxia, hypoglycemia, and ischemia
NECROSIS/APOPTOSIS
slower ATP depletion
Apoptosis
The acute depletion of ATP leads to neuronal damage from excessive accumulation of _______.
L-glutamate
NECROSIS/APOPTOSIS
This process is called Excitotoxicity
Necrosis
NECROSIS/APOPTOSIS
Excessive mechanical strain
Necrosis
Excessive mechanical strain- traumatic injury
NECROSIS/APOPTOSIS
excessive neuronal energy demands
Necrosis
excessive neuronal energy demands- Status Epilepticus
A form of programmed cell death that is essential for normal development and tissue homeostasis
Apoptosis
3 Important triggers of Apoptosis.
3 Important triggers of Apoptosis:
- DNA mutations
- Inflammatory mediators
- Abnormal accumulation of intracellular proteins, and oxidative stress
Homeostatic process by which cells degrade its organelles to maintain balance between synthesis, degradation, and subsequent turnover
Autophagy
3 specific pathologic reactions of neurons
ISCHEMIC CELL CHANGE
CENTRAL CHROMATOLYSIS
NEURONAL INCLUSIONS
It is a specific pathologic reaction that is due to deprivation of oxygen and cessation of oxidative metabolism
Ischemic cell change
A change in neuronal cell bodies after severe injury to the axons.
Central Chromatolysis
Also called as axonal reaction
Central Chromatolysis
Occurs in the distal part of axon when the parent body is destroyed or separated from the axon by disease or injury
Wallerian Degeneration
Causes of Ischemic cell change (5)
Causes of Ischemic cell change (5)
- loss of blood flow
- lack of O2 in the blood
- lack of substrates necessary for oxidative metabolism
- Poison (cyanide)
- blocking oxidative metabolism
TRUE/FALSE
After several (2-5) minutes, cells will exhibit REVERSIBLE changes
FALSE
After several (2-5) minutes, respiratory chain processes on the inner mitochondrial membrane ceases–> ATP stores depleted–> impaired ion channels –> anaerobic glycolysis–> lactate production–> further inhibition of mitochondrial function–> IRREVERSIBLE changes
TRUE/FALSE
8-12 hours: the neurons become smaller; its outline more angular
TRUE
8-12 hours: the neurons become SMALLER; its outline MORE SHARPLY BLUNT
cytoplasm: eosinophilic
nucleus: shrinks and becomes darkly stained (irreversible) complete dissolution of the neuron (red, dead neuron)
Irreversible changes that ultimately lead to cell death
- Excitotoxicity
- Accumulation of intracellular Ca++
- Generation fo free radicals
Unlike in the CNS, Wallerian degeneration occurs more rapidly in the peripheral nerves? true or false
TRUE
Impairment of axonal transport, disappearance of neurofibrils, and breaking up of axons into short fragments that will eventually disappear
Wallerian degeneration
- Impairment of axonal transport
- Disappearance of neurofibrils
- Breaking up of axons into short fragments that will eventually disappear
Central Chromatolysis is seen in small motor cells. True or false?
FALSE
Center chromatolsysis is seen in LARGE motor cells:
- spinal ventral horn cells
- motor nuclei of cranial nerves
Central chromatolysis is reversible? true or false?
TRUE
can be restored in a few months
Center chromatolysis begins how many days after injury?
2-3 DAYS; reaches maximum in 2-3 WEEKS
cell is swollen, nucleus is eccentric, and Nissl granules have disappeared except at the periphery
Center Chromatolysis
Celll: swollen
Nucleus: eccentric
Nissl granules: disappeared except at the periphery
consists of abnormal deposits of self aggregating misfolded proteins that are an important feature of several neurodegenerstive diseases
Filamentous inclusions
Neuronal inclusions of neurofibrillary tangles and neuritic plaques are typical of this disease.
Alzheimer’s disease
- Neurofibrillary tangles seen intranuclearly (tau proteins)
- neuritic plaques (amyloid beta peptide)
Cell loss and accumulation of Lewy bodies in dopaminergic neurons are characteristic of this disease
Parkinson’s disease
Lewy bodies- contains alpha-synuclein
This is possible in PNS if the parent cell body survives but this does not occur in CNS.
Axonal regeneration
Rate of remyelination in the peripheral nerves per day.
1-3 mm/day
The reason why the CNS is not capable of axonal regeneration is because there is no basement membrane or collagen sheaths (endometrium) surrounding the nerves. True or false?
TRUE
CNS is NOT capable of axonal regeneration is because there is NO:
- basement membrane OR
- collagen sheaths (endometrium) surrounding the nerves.
Oligodendroglia are capable of proliferation. True or false?
False
Oligodendroglia are INCAPABLE of proliferation
Most common immune-related demyelinating disease
Multiple sclerosis
Cytoplasmic inclusions consist of accumulations of alpha synuclein
Lewy bodies
-Identified as pale ‘halo’
intranuclear inclusions of subacute sclerosing panencephalitis
Cowdry type A
Lewy body @cytoplasm
Parkison disease
pick body @cytoplasm
Pick disease
Lafora body @cytoplasm
Myoclonus epilepsy
Negri body @cytoplasm
Rabies
cowdry type A inclusion @ nucleus
Viral infections
accumulation of metabolic products within the nerve cell
Storage cells
Neuron in this lipid-storage disease: ballooning of cytoplasm with stored material, forcing the nucleus and Nissl granules to one corner of the cell
Tay-Sach disease
2 pathologic reactions of oligodendroglia
2 pathologic reactions of oligodendroglia
- Demyelinating or Myelonoclastic diseases
- Leukodystrophies or dysmyelinating disease
Pathologic reaction of oligodendroglia: NORMAL myelin is attacked by some exogenous agent, usually unknown, and broken down into its component lipids and absorbed
Demyelinating or Myelonoclastic diseases
ex. multiple sclerosis
Pathologic reaction of oligodendroglia: myelin is ABNORMALLY formed owing to a genetically determined error in metabolism
Leukodystrophies or dysmyelinating disease
2 pathologic reactions of Schwann Cells
2 pathologic reactions of Schwann Cells
- Segmental demyelination
- repeated demyelination and remyelination
Pathologic reaction of Schwann cells:
immune-mediated disorders such as acute and chronic inflammatory neuropathies may produce segmental loss of myelin
Segmental Demyelination
ex. Guillain-Barre syndrome- Acute
Pathologic reaction of Schwann cells:
- Hereditary demyelinating neuropathies
- Genetic disorders affecting peripheral nerves (mutations of genes encoding for peripheral myelin proteins)
repeated demyelination and remyelination
ex. Charcot Marie-Tooth disease or HSMN 1
reflecting cycles of degeneration and regeneration of the myelin sheath in patient w/ hereditary sensory and motor peripheral neuropathy
Onion bulb formation
2 types of astrocytes
Protoplasmic and Fibrillary
Astrocytes predominantly in the gray and subcortical white matter
Protoplasmic astrocytes
shorter processes, less fibrils
Protoplasmic astrocytes
Astrocytes predominantly in the white matter
Fibrillary astrocytes
longer processes, abundant fibrils
Fibrillary astrocytes
TRUE/FALSE
In diseases, protoplasmic astrocytes may convert to fibrillary
TRUE
In diseases, protoplasmic astrocytes may convert to fibrillary
Swollen astrocyte inside the brain such as in stroke.
Gemistocytic or hypertrophied astrocyte (“PLUMP”)
Major function is the surveillance of and participation in immunologic processes
Microglial cells
Rod cells, prominent in viral disease and parenchymal neurosyphilis, are distinguished by conspicuously hypertrophied rod-shaped nuclei
Activated microglia
ex. chronic encephalitis with neurosyphilis
TRUE/FALSE
reactive microglial cells are prominent in chronic infections
TRUE
reactive microglial cells are prominent in chronic infections
more likely to affect gray matter failure of Na-K pump
Cytotoxic Edema
- occurs with HYPOXIA and metabolic disorders (ex.stroke)
- primarily affects the GRAY and WHITE matter (CT scan: hypodensity areas
loss of integrity of the blood-brain barrier.
Vasogenic Edema
- occurs with MASS or inflammatory disease
- primarily affects the WHITE matter
Vasogenic edema is predominantly in the gray matter. true or false?
false
Vasogenic edema is predominantly in the white matter
Involving a single, circumscribed area or group of contiguous structures
Focal
more than one circumscribed area or several noncontiguous structures
multifocal
portions of the nervous system, in bilateral, symmetrical fashion
Diffuse
development of symptoms in minutes
Acute
development of symptoms within days
Subacute
development of symptoms within weeks/months
Chronic
symptoms have resolved completed after onset
Transient
symptoms have decreased from their maximum but not have completely resolved
improving
symptoms continue to increase in severity
progressive
symptoms remain unchanged after reaching maximum severity
stationary
Suggest progression of a focal lesion
mass lesion
ex. hematoma, neoplasm
suggest when lesion is diffuse in location or when there is non-progressive focal abnormality
Non-mass lesion
ex. meningitis, encephalitis
Acute and focal
vascular
infarct or intraparenchymal hgg.
acute and diffuse
vascular
subarachnoid hgg., anoxia
subacute and focal
inflammatory
abscess, myelitis
subacute and diffuse
inflammatory
meningitis, encephalitis
chronic and focal
neoplasm
chronic and diffuse
degenerative
chronic, progressive and diffuse
degenerative diseases
gradual decrease in neuronal function
degenerative disease
neurons shows specific changes
degenerative disease
chronic, progressive, and focal
neoplastic changes
Most common primary CNS tumors
Astrocytomas
What is the most common infratentorial tumors in children?
cerebellar medulloblastoma
TRUE/FALSE
in children, infratentorial tumors are common
TRUE
in children, infratentorial tumors are common
TRUE/FALSE
in adults, infratentorial tumors are common
FALSE
in adults, supratentorial tumors are common
two types of vascular disease
infarct and hemorrhagic
various chemical agents, vitamin deficiencies, genetic biochemical disorders and encephalopathies of kidney and liver diseases
toxic-metabolic disease
POST QUIZ QUESTION:
which cells proliferate in response to injury?
astrocytes
POST QUIZ QUESTION:
which cells myelinate the CNS?
oligodendrocytes
POST QUIZ QUESTION:
which does NOT produce physical changes in the cells?
a. demyelinating disease
b. infarction
c. neoplasm
d. TIA
d. TIA
POST QUIZ QUESTION:
chronic progressive disease
degenerative disease
POST QUIZ QUESTION:
capable of axonal regeneration?
a. brainstem
b. cerebrum
c. peripheral nerve
d. spinal cord
c. peripheral nerve
POST QUIZ QUESTION:
which cells dissolve in response to injury/?
a. astrocytes
b. fibroblasts
c. oligodendrocytes
d. microglia
c. oligodendrocytes
POST QUIZ QUESTION:
forms gliotic scars in the CNS?
Astrocytes
