Nervous System Review Flashcards
Encased in the bones of the skull and vertebral column
CNS
Grossly consists of the brain (cerebrum, cerebellum, brainstem and subcortical structures) and spinal cord
CNS
Control center, integration, processing
CNS
Spinal nerves –31 pairs
Cranial nerves—12 pairs
PNS
Carrying information to and from the central nervous system
And the autonomic nervous system (ANS)
Involuntary, automatic
PNS
Sensation from skin, organs, joints, etc.
somatic division of PNS
motor neurons and impulses from CNS to skeletal muscles
somatic division of PNS
sensory info from visceral organs to CNS
autonomic division of PNS
motor info from cns to smooth muscles, cardiac and glands
autonomic division of PNSf
frontal lobe
Higher mental processes
parietal lobe
processes sensory information
occipital lobe
Processes visual information
temporal lobe
Processes auditory information
insula
Involved in consciousness
May be implicated in expressive aphasia
limbic lobe
Processes memory and emotion
covering over insula
opercula
Emerges from between two adjacent vertebrae
spinal nerve PNS
Well protected
Vertebrae
Meninges
spinal cord (CNS)
What do spinal nerves do?
convey sensory and motor information
limbic lobe is mostly composed of
the cingulate and parahippocampal gyri
limbic lobe, aka
cingulate gyrus
spinal nerve carrying motor information
To muscle or gland
Efferent/descending
spinal nerve carrying sensory information
From receptor organ
Afferent/ascending
The cauda equina lies below
the lumbar 2 vertebra
gives rise to the spinal cord
medulla
Do the spinal nerve roots and numbered vertebrae correspond to one another
yes
cervical
7 vertebrae, 8 spinal nerves
thoracic
12 vertebrae and 12 spinal nerves
lumbar
5 vertebrae and 5 spinal nerves
sacral
1 vertebrae (5 fused) and 5 spinal nerves
anterior =
ventral
posterior =
dorsal
motor roots
anterior
sensory roots
posterior
Coccygeal
1 fused vertebrae (3-4) and 1 spinal nerve
what causes massive bleeding if a meningeal artery is torn?
High arterial blood pressure
3 layers of meninges
dura, arachnoid, pia
2 layers of dura
meningeal and endosteal
which dura is closest to the skull?
endosteal
what protects CNS
scalp and skin
skull and vertebral column
meninges
what is the falx cerebri
dura that dips in and separates l and r hemisphere and doesn’t go all the way in because of the cc (connection bw two hemispheres
which layer adheres to the skull?
endosteal
this outer layer serves as the periosteum
endosteal
Spaces where the endosteal and meningeal layers of the dura separate
Cavities
venous sinus
largest of venous drainage system
superior sagittal sinus
part of venous drainage system that drains blood
inferior sagittal sinus
end in jugular vein to drain used blood and fluids from the brain (cranial vault)
transverse, straight and sigmoid sinus and others
two layers of dura folded together and separates down into long fissure and provides separation of structures
falx cerebri
explain the tentorium cerebelli
separates the cerebellum from the cerebral hemispheres
near cerebellum (tent over it)
helps keep parietal and occipital from squishing down on the cerebellum
holds these up to avoid this
below tectorium (cerebellum and bs)
infratentorial
above tent (cerebral hemispheres)
supratentorial
are lesions in supratentorial or infratentorial better
lesions in supratentorial because infratentorial in the BS because all life sustaining things happens here and having a lesion can be fatal
the opening where the brainstem passes into the cerebrum
tentorial notch
why is the area of tentorial notch dangerous for concussions or head trauma ?
because soft tissues are sheared at this notch against hard leather and can cause damage
provides lift and support and keeps things from squishing other things
dura mater
what sits above the tentorial cerebelli
occipital lobe
what sits below TC?
cerebellum
another name for tentorial notch
tentorial incisure
lies on the inner surface of the dura
Web-like
arachnoid
the space below the arachnoid but above the pia
subarachnoid space
what is in the subarachnoid space
CSF
cisterns (large pockets) - enlargement of sub space
what are Arachnoid trabeculae?
collagenous (collagen fibers) strands connect the arachnoid and the pia for suspension
closely adheres to the CNS tissue, following the gyri and fissures
pia
do all of the meninges cover the spinal cord too?
YES
areas where we can do epidural injection or go into
subarachnoid space in cauda eqina and pull out CSF without damaging tissue in areas of lumbar cistern or filum terminale??
does the dura in the SC have two layers?
no, just one
do the meninges in the SC attach the same as in the cerebral cortex?
no, slight differences in how the dura and pia connect to the spinal cord, vertebrae and nerve roots
is there an epidural space in the sc?
yes
are the Arachnoid layer and subarachnoid space are similar to those in the brain?
yes
what anchors the spinal cord
Lumbar cistern exists (pocket), denticulate ligament and filum terminale of pia and dural sheat
what occurs if the meningeal arteries are torn
epidural hematoma
Explain what happens with an epidural hematoma
Most frequently after skull fracture
above dura
Bleeding between the periosteum (endosteal layer of the dura) and the skull bones
Death can occur within minutes if meningeal arteries are torn
bleeding bw dura and bone and pushes dura down to create pocket of blood here
happens with meningeal artery tears
this is the biggest concern with head trauma
are arteries or veins under more pressure?
arteries needs pressure to pump up but veins drain more so with gravity down
torn artery creates squirting artery
from dural venous sinus or vein attachment at the sinus (blood is beneath the dura)
subdural hematoma
Explain what happens with a subdural hematoma
underneath dura
head injury from motorcycle accident
can still cause problems like epidural but not as likely
Rapid accelerations or decelerations of the head can cause the tearing of cerebral veins
May be acute with fast symptoms like an epidural hematoma or very slow in producing symptoms
Bleeding between the brain and the arachnoid (under the arachnoid)
Subarachnoid hemorrhage (sometimes called subarachnoid hematoma
explain what happens with a subarachnoid hematoma
Bleeding is generally from veins—less pressure
Can be from an artery
From severe blow to the head or from a rupturing blood vessel in the brain (i.e. a ruptured aneurysm)
Epidural (extra-dural) CT results
lemon shape bc the dura is adhering to bone and make a pocket
Subdural CT results
banana shape, following the contour of the subarachnoid space and cerebrum
what are the protections of the CNS?
Hard bony skull and vertebrae
Meninges
CSF for buoyancy and cushioning
Protection from vibration, pressure, temperature
Chemical barrier—blood brain barrier
Regulation of temperature and function by the brain itself
what is the role of CSF
Clear and colorless
Buoyancy and chemical homeostasis
How does CSF contribute to chemical homeostasis
Draining unwanted water-soluble substance away from the CNS, out of the skull
Supplying some nutrients
Excretion of waste products as CSF leaves the CNS
Transporting hormones
Adult brain contains approx ____ ml of CSF
150
most of the CSF is in ventricles and smaller amount is in the subarachnoid space
false, most is in the subarachnoid space and less in the ventricles
where is CSF produced
by choroid plexus (in all ventricles and granular tissue)
How often is CSF replaced?
replaced multiple times per day
Explain the flow of CSF
lateral is in arching c shape
fluid flows down in where two thalami make a pocket (3rd)
flows down cerebral aqueduct into 4 ventricle
leave out of openings and flows up and around brain and down and around spinal cord
flows from the two lateral ventricles (one in each hemisphere) through the paired interventricular foramina of Monro (holes) to the single midline third ventricle of the diencephalon. From the third ventricle, CSF flows through the tube-like cerebral aqueduct of Sylvius in the midbrain to the fourth ventricle of the pons and medulla
Explain process of CSF (think of choroid plexus)
made by the choroid plexus and circulates throughout the brain, through the ventricles, through the cerebral aqueduct, and out of the brain through the foramen of Magendie. From there, it circulates around the brain and is absorbed by way of the arachnoid granulations into the venous sinuses (sagittal sinus along the convexity and epidural sinuses in the root sleeves)
one way valve taking high pressure CSF to go to the sinuses and then dumped into other sinuses and out through the jugular vein
arachnoid villi or granulations (pressure sensitive straws or one way valves)\
what happens to csf after the 4th ventricle?
exits the fourth ventricle via the two lateral foramina of Luschka and the single median foramen of Magendie to enter the cisterna magna of the subarachnoid space
in the fourth ventricle can flow into the central canal which runs down the length of the spinal cord (This is usually closed in adults)
circulates rostrally through the subarachnoid space to reach the superior sagittal sinus
if the CSF pressure is less than the venous pressure, what happens?
the blood in the sinuses does not get to back flow through the arachnoid villi into the ventricular system.
When the CSF pressure is higher than the venous pressure
CSF will flow into superior sagittal sinues. Arachnoid villi are”one way valves”
in the skull, are the drainage system to carry blood and CSF away from the brain and to be recycled in the systemic blood flow.
Veins and the venous sinuses
Streptococcus pneumoniae is the major responsible bacterial organism
meningitis
How is meningitis acquired
infection spreads from meninges to the cochlea via the cochlear aqueduct
Cochlear damage to hair cells, supporting cells, stria vascularis and spiral ganglion (CNVIII cell bodies)
Most common cause of acquired postlingual profound SNHL
Also ossification of the labyrinth
meningitis
What is hydrocephalus
Disruption of CSF circulation
How is hydrocephalus acquired
CSF pressure rises and ventricles expand
Can be from excess CSF production, blockage of circulation or deficiency in reabsorption
Blockage of circulation is most common (maybe from tumors occluding an area, usually a bottleneck area)
what is communicating hydrocephalus
when lateral ventricles are still “communicating”/connected with the subarachnoid space and the problem is with the reabsorption through the arachnoid villa or tentorial notch
what is noncommunicating hydrocephalus
Blockage could be due stenosis of the cerebral aqueduct or occlusion of the openings out of the 4th ventricle
How is hydrocephalus treated
Shunt from the area of the problem in the ventricles to a remote areas such as the peritoneal cavity or other surgeries
Pressure from CSF of a growing mass (tumor) or a hematoma can cause parts of the CNS to herniate from one compartment to another in the CNS
If the brainstem is compressed the consequences are generally severe
what is NPH
Normal pressure hydrocephalus
Generally in patients over 60
Usually idiopathic NPH
Slowly developing from gradual blockage of CSF
CSF builds up and ventricles enlarge, compressing brain tissue—can be difficult to measure the increased pressur
what are symptoms of NPH
abnormal gait, incontinence, memory problems, dementia
treatment for NPH
ventriculoperitoneal shunt
can NPH symptoms resolve?
yes if correctly diagnosed and treated
what is NPH commonly mistaken for?
Can be mistaken for Alzheimer disease or Parkinson disease
does CSF flow through central canal?
not in adults, this is usually closed
why are CI’s rushed for individuals with meningites
profound snhl is cause of meningitis and our cure is CI’s- ossification is right where CI electrode goes so they want it in quickly before it ossifies completely
water on the brain
excess CSF around the brain
hydrocephalus
what are the 3 causes of hydrocephalus
excess CSF production, blockage of circulation or deficiency in reabsorption
where is there a bottleneck ?
from lateral to interventricular = tiny tube
out of 4th ventricle at medial and lateral
third to central aqueduct
disruption of CSF circulation
hydrocephalus
where can hydrocephalus occur
inside ventricles - expand inside out
push on walls of brain
subarachnoid space - pushing down from outside on brain
pressure from outside - sas is pressing down on the tissues
communicating hydrocephalus
balloons from inside - CSF stuck in ventricles
noncommunicating hydrocephalus
unknown cause
idiopathic
caused by drug or substance that interferes with development of the embryo or fetus
teratogenic
caused by dx, manner or tx of a physician
Iatrogenic
characterized by ventriculomegaly, impaired gait, cognitive impairment and urinary incontinence
NPH
