HISTOLOGY Flashcards
NEURONS
classification
FORM + NUMBER OF THEIR PROCESSES
bipolar
unipolar
multipolar
NEURONS
Nissl substance
Clumps or rough ER (endoplasmatic reticulum) with bound polysomes
sites of protein synthesis
(also are free polusomes in cytoplasm)
NEURONS
Cytoplasmic Inclusions in CNS disease
(2)
LEWY BODIES
- in degenerating neurons
- Parkinson’s - pars compact of the substantia nigra
- Dementia - cortical and brain-stem neurons
NEGRI BODIES
- eosinophilic in degenerating neurons
- Rabies - hippocampus and cerebellar cortex
NEURONS
Cytoskeleton
NEUROFILAMENTS
+
MICROFILAMENTS
+
MICROTUBULES
NEURONS
Neurofilaments
(where and why)
Most numerous in the axon and dendrites (proximal part)
+
structural support
NEURONS
Microfilaments
(where and why)
form matrix near the periphery of neuron
+
growth cones (add motility)
and
dendrites (specializations at synaptic membranes)
NEURONS
Microtubules
(where and why)
In ALL parts of the neuron
+
axonal transport
NEURONS
NEUROFIBRILLARY TANGLES
(Cytoskeleton)
DEGENERATIVE NEURONAL DISEASES
(Alzheimer’s, Amyotrophic Lateral Sclerosis, Down Syndrome)
tau protein becomes more phosphorylated and microtubules form helical filaments
(also senile plaques are formed in dendrites e in the cell body)
NEURONS
Dendrites
may contain spines
+
provide major surface for synaptic contacts
\+ highly branched (the pattern is used to define cell type)
NEURONS
Axon
(diameter, collateralls and proximal part)
uniform diameter
+
may branch at right angles into collaterals (90º)
+
proximal part is marked by axon hilllock
(lacks of Nissl substance)
+
trigger zone
(sodium ion channels)
NEURONS
Axon
(myelin sheath)
CNS
Oligodendrocyte can myelinate individual segments of many axons
PNS
Schwann cells (each one can myelinate only single internodal segment of a single axon) - also phagocyte debris after PNS injury
(node of Ranvier - saltatory conduction)
NEURONS
Axon
(cytoplasm)
Entire axon lacks
polysomes
+
Nissl substance
+
Golgi apparatus
(only contains mitochondria and smooth ER)
NEURONS
Anterograde axonal transport
(fast and slow)
cell body → synaptic terminal
- fast (100-400 mm/day) transport is dependent on kinesin (motor molecule) - deliver precursors of peptide NT
- slow transport (1-2 mm/day) is the movement of soluble cytoplasmic components (isn’t dependent of ATP or microtubules) - cytoskelon proteins, enzymes and precursos of small NT
NEURONS
Retrograde axonal transport
synaptic terminal → cell body
(material returns to recycle or be digested)
(trophic factors go to cell body)
- microtubules
- slower than anterograde (60-100 mm/day)
- dynein (ATPase) - dependent
NEUROPATHIES AND AXONAL TRANSPORT
DIABETES
hyperglicemia → alterations in proteins of microtubules → disrupt axonal transport
long axons
glove-and-stocking pattern
(altered sensation and pain)
NEUROPATHIES AND AXONAL TRANSPORT
Other causes
- Anoxia (mitochondria) and anticancer agents (depolymerize microtubules) - disrupt fast anterograde transport
- Polio, herpes, rabies and tetanus (only the toxins) - disrupt retrograde transporte of SKELETAL MUSCLE
GLIAL CELLS
general statements
(synapses, proliferation and process)
do not form chemical synapses
+
readily divide and proliferate
(glioma is the most commom type of primary tumor of the CNS)
+
have only one kind of process
GLIAL CELLS
ASTROCYTES
(most numerous glial cells)
4 functions
SRBS
- structural support - intermediate filaments (GFAP - glial fibrillary acidic protein)
- remove the NT glutamate and K+ from extracellular space
- foot processes form glial-limiting membrane- blood-brain barrier
- hypertrophy and proliferate after injury - astroglial scar
GLIAL CELLS
RADIAL GLIA
(function)
precursors of astrocytes
+
guide neuroblast migration during CNS development
GLIAL CELLS
MICROGLIA
(smallest glial cells)
link between cells of CNS and immune system
- derived from bone marrow monocytes (enter the CNS after birth)
- phagocytose neuronal debris (during CNS injury) - secrate toxic free radicals (eg. superoxide)
- diferenciated in pericytes - blood-brain barrier
- determine the chances of survival of a CNS tissue graft
(also are the cells targeted by HIV-1 virus)
GLIAL CELLS
EPENDYMAL CELLS
line the ventricles in the adult brain
(some cells differentiate into choroid epithelial cells)
+
produce cerebrospinal fluid (CSF)
+
ciliary action helps circulate CSF
GLIAL CELLS
TANYCYTES
specialized ependymal cells
+
basal cytoplasmic processes in contact with blood vessels
+
transport substances
(blood - ventricle)
DISORDERS OF MYELINATION
(leukodystrophies)
MULTIPLE SCLEROSIS (MS)
(SCRIPTS)
- S: vision loss (optic neuritis) + internuclear ophthalmoplegia (MLF) + motor and sensory deficits + vertigo + neuropsychiatric
- C: symptoms separated in space and time + relapsing-remitting course
- R: 2:1 woman + 30-40 aged + temperate zones (high prevalence)
- I: demyelinated plaques (often in periventricular areas), IgG (oligoclonal bands) in CSF, chronic inflamatory-axons initially preserved
- T: high-dose steroids, interferon-beta, glatiramer
DISORDERS OF MYELINATION
(leukodystrophies)
METACHROMATIC LEUKODYSTROPHY
(MLD)
SCRIPT
- S: motor and cognitive issues with seizures - four types
- I: arylsulfatase A deficiency in lisosomes
(both CNS and PNS)
DISORDERS OF MYELINATION
(leukodystrophies)
PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY
(PML)
SCRIPTS
- S: limb weakness, speech problems
- R: JC virus (John Cunningham), affect immunocompromised (AIDS)
- I: cortical myelin affected - demyelination, astrogliosis, lymphohistiocytosis
DISORDERS OF MYELINATION
(leukodystrophies)
CENTRAL PONTINE MYELINOLYSIS
(CPM)
SCRIPTS
- S: pseudobulbar palsy + spastic quadriparesis + mental changes + locked-in syndrome
- R: severely malnourished + alcoholics + liver disease
- I: focal demyelination of central area of basis pontis (corticospinal and corticobulbar tracts) + probably caused by overly aggresive correction of hyponatremia
DISORDERS OF MYELINATION
(leukodystrophies)
GUILLAIN-BARRÉ
SCRIPTS
- S: weakness first in lower limbs and ascends, respiratory failure can occur, autonomic dysfunction, cranial nerve involviment and decrease reflexes
(sensory loss, pain and paresthesias rarely occur)
- C: 2/3 of patients have history of respirtatory or GI illness 1-3 weaks prior
- I: CSF protein elevate + normal cell count
BLOOD-BRAIN BARRIER
functions
restricts access of
- micro-organisms
- proteins
- cell
- drugs
BLOOD-BRAIN BARRIER
structures
- capillary endothelial cells (intercellular tight junctions)
- underlying basal lamina
- astrocytes - “end feet” cover > 95% of the basal lamina
- pericytes
BLOOD-BRAIN BARRIER
transport
diffusion (O2, CO2, heroin, ethanol and nicotine)
seletive transport (glucose, aminoacids, vit K and vit D)
ion channels (Na+ and K+)
LESIONS
response of axons to a destructive or irritative lesions
TUMORS
half of brain and spinal cord tumors are metastatic
TRUE or FALSE?
TRUE
TUMORS
GLIOBLASTOMA MULTIFORME
(astrocytoma grade IV)
features + pathology
TUMORS
ASTROCYTOMA
(pilocytic)
features + pathology
TUMORS
OLIGODENDROGLIOMA
features + pathology
TUMORS
EPENDYMOMA
features + pathology
TUMORS
MEDULLOBLASTOMA
features + pathology
TUMORS
MENINGIOMA
features + pathology
TUMORS
SCHWANNOMA
features + pathology
TUMORS
RETINOBLASTOMA
features + pathology
TUMORS
CRANIOPHARYNGIOMA
features + pathology
