CNS Flashcards
singular meninx is composed of
specialized epithelial cells (meningothelial cells)
meninges are supported by
connective tissue
meninges have a — function
protection
the meninges are confined to
outlet layer of brain and cord in CNS
dura mater
outermost layer
thick layer of dense connective tissue, internally lined by mesothelium
dura in the cranium
fuses with the periosteum of the skull
dura in the spinal cord
dura surrounded by epidural space
subdural space
separates the dura from underlying arachnoid mater
underlying subarachnoid space is lined by
flattened mesothelial cells
subarachnoid space separates the arachnoid from the Pia mater, subarachnoid space contains
CSF
subarachnoid space is continuous with
ventricles of the brain
pia mater is highy
vascular
pia + arachnoid
leptomeninges
denticulate ligamanets
support cord, extend from pia, anchor cord to arachnoids, dura, and periosteum
neurons in the CNS are derived from
neuroectodermal cells of the neural tube
brain and cord contain
gray and white matter
peripheral gray matter contains
neuron cell bodies, dendrites, and axons
central white matter contains
mostly myelinated axons
neuroglia/neuroglial cells
large number of support cells in the CNS
neuroglia are highlight branched and provide
structural and metabolic support for neurons
aid in tissue repair following injury
oligodendrocytes
CNS equivalent of Schwann cells, elaborate myelin sheaths
astrocytes
most highly branched, largest neuroglia cells
microglia
phagocytic, fixed tissue macrophage; part of monocyte-macrophage lineage; smallest neuroglia cells; originally mesodermal, have immune function
ependymal cells
cuboidal epithelium singing ventricles and central canal of spinal cord
ependymal cells are frequently
ciliated, microvilli for reabsorption of CSF
CSF is secreted by the
choroid plexus
choroid plexus
vascular structure arising from walls fo ventricle in brain
modified — cells secrete CSF
ependymal cells of the choroid plexus
cerebrum is also known as the
cerebral cortex
in mammals, neocortex evolved to include
sensory, motor, and association areas
in humans –% of the cortex is neocortex
90%
cerebrum is grossly organized into
folds or gyri
cerebral cortex is composed of — — peripherally
gray matter
nuclei
Clusters of neuron cell bodies form small islands of gray matter in cerebrum & cerebellum
Neuroglial cells in gray matter include (2)
astrocytes and microglial cells
Deep to cortex is subcortical
white matter (medulla)
white matter contains mostly
myelinated axons surrounded by oligodendrocytes
Axons leading in & out of gray matter also grouped in bundles called
tracts
Histologically, neurons of neocortex divided into — morphological categories
five
Anatomically, divided into —layers, designated with Roman numerals I-VI, from superficial to deep
six
functionally, arranged into
vertical columns or units
cortical neurons (5)
pyramidal cells stellate cells cells of martinotti fusiform cells horizontal cells of cajal
pyramidal cells
pyramid-shaped neurons with long, slender axons, varying in size from small to large
Beta cells
largest pyramidal cells, include upper Moto neurons in the motor cortex
stellate cells
mall star-shaped neurons with short axons & dendrites
cells of martinotti
small neurons with long, horizontal axons
fusiform cells
vertically oriented, spindle-shaped neurons with vertical axons
horizontal cells of cajal
horizontally oriented, spindle-shaped neurons with horizontal axons
least common cortical neurons
horizontal cells of canal
found only in the superficial layer
first layer of the neocortex
plexiform (molecular) layer—most superficial layer; contains mostly dendrites & axons of cortical neurons
second layer of the neocortex
outer granular layer—contains large #’s of small pyramidal & stellate cells
third layer of the neocortex
pyramidal cell layer—larger cells located deeper in layer; Martinotti cells also present
fourth layer of the neocortex
inner granular layer—densely packed stellate cells
fifth layer of the neocortex
ganglionic layer—contains large pyramidal cells, stellate cells & cells of Martinotti
sixth layer of the neocortex
multiform cell layer—contains small pyramidal cells, cells of Martinotti, stellate cells & fusiform cells
cerebellum coordinates (3)
muscular activity, posture, & equilibrium
cerebellum is grossly organized into
folds, or folia, with central medullaof whitematter, contains mostly oligodendrocytes & myelinated axons
outer cerebellar cortex has - layers
2
2 layers of the outer cerebellar cortex
Outer molecularlayer
Inner granularlayer
Outer molecularlayer
contains few neurons & large #’s of unmyelinated axons
Inner granularlayer
highly cellular, very basophilicContains large # of neuroglial cells & small neurons called granulecells
Molecular & granular layers separated by single layer of large neurons called
Purkinje cells
Purkinje cells
specialized neurons, function in coordination & equilibrium
spinal cord has a similar structure throughout, with a prominent
ventral median fissure
central canal contains
CSF
central canal is lined by
ependymal cells
central canal is continuous with
ventricles of the brain
Unlike brain, gray matter of the spinal cord is located —, white matter —
centrally
peripherally
anatomy of the spinal cord
2 dorsal horns & 2 ventral horns connected by thin central commissure
what do dorsal horns of the spinal cord contain?
afferent, sensory nerve tracts
what do dorsal nerve roots form
lateral extensions of dorsal horns of gray matter
central bodies of somatic sensory neurons lie in the
dorsal root ganglia of spinal nerves
ventral horns contain
efferent (motor) n cell bodies to innervate skeletal muscle
surrounding white matter of spinal cord contains (2)
ascending and descending fiber tracts
columns
ascending and descending fiber tracts
spinal cord contains mostly — axons
myelinated
spinal cord contains mostly myelinated axons which carry
sensory and motor data
in the PNS, connective tissue scar and Schwann cells form bridge between
ends of nerve
if the gap is not too big, what is possible?
regeneration of the axon
3 steps to regeneration of axons
1: Schwann cells multiply to physically bridge the gap
2: nerve axon sprouts neurites from proximal stump
3: neurites grow into distal stump; contact reestablishes function
if damage is too old or severe, the axon may need to
regrow its entire length
how long can response to injury take?
weeks to months
anterograde (wallerian) degeneration
if portion of axon distal to point of injury degenerates
due to interruption of
axonal transport (nutrient synthesis occurs in cell body, transport down axon)
cell body of an injured neuron also swells, becomes
brightly eosinophilic, loses nissl substance
chromatolysis
loss of nissl substance
what happens if injury is severe?
results in retrograde degeneration and death of cell body
in the CNS, oligodendrocytes are less efficient than Schwann cells; instead,
neuroglia cells multiply
scar tissue proliferation from glial cells prevents
regeneration
how does scar tissue prevent regeneration?
physically blocks contract between body and axon
neurons terminally differentiated (Go) o they are unable to be
replaced
ALS
amyotrophic lateral sclerosis
ALS is also known as
lou gehrigs disease
ALS
due to death of motor neurons controlling voluntary mm
meningitis
inflammation of the meninges
meningitis may be
bacterial or viral
encephalitis
inflammation of the brain
myelitis
inflammation of the spinal cord
encephalomyelitis
brain and cord
meningoencephalitis
meninges and brain
symptoms/severity vary from
mild (headaches) to paralysis, debilitation and death
viral meningitis generally
transient lymphocytic inflitrate
bacterial meningitis ex (2)
meningococcus, streotococcus
bacterial meningitis can result in
neutrophilic infiltrate and may be life threatening
polo
poliovirus affects alpha-motor neurons of the ventral horn of spinal cord
poliomyelitis
lower motor neuron paralysis and subsequent mm atrophy
how was poliomyelitis eradicated?
invention of Salk vaccine
Parkinson’s disease
neurodegenerative disease characterized by muscular tremor due to death of neurons in substantial nigra
Parkinson’s disease decrease production of
dopamine in the brain
treatment of Parkinson’s involves administration of
l dopa
l dopa
dopamine precursor
Alzheimers disease
form of dementia characterized by neural plaques and fibrillary tangles within the cortex
multiple sclerosis (MS)
an autoimmune, inflammatory, demyelinating disease of the CNS
in MS, antibodies destory
myelin sheaths around axons
destruction of myelin sheaths results in
plaque formation
who does MS usually affect?
women between 20-40 years of age
symptoms of MS vary with (2)
location of affected neurons and degree of degeneration
MS is often multiple episodes with
partial resolution in between
Guillain barre syndrome
immune mediated demyelination in PNS
Gillian barre is often imitated by infection, leading to
progressive weakness in peripheral mm