Exam 1 Review Flashcards
Describe the CNS
Encased in the bones of the skull and vertebral column
Grossly consists of the brain (cerebrum, cerebellum, brainstem and subcortical structures) and spinal cord
Control center, integration, processing
Describe the PNS
Spinal nerves –31 pairs
Cranial nerves—12 pairs
Carrying information to and from the central nervous system
And the autonomic nervous system (ANS)
Involuntary, automatic
Higher mental processes
FRONTAL
Processes sensory information
Parietal
Processes visual information
occipital
Processes auditory information
temporal
Involved in consciousness
May be implicated in expressive aphasia
insula
Processes memory and emotion
limbic lobe
motor info going to muscles or glands
efferent/descending
sensory info going to receptor organs
afferent/ascending
cervical vertebrae and nerves
7 v 8 nerves
thoracic vertebrae and nerves
12
lumbar vertebrae and nervesf
5
sacral vertebrae and nerves
1 fused, 5 nerves
coccyx vertebrae and nerves
1
what are the 3 layers of meninges
dura, arachnoid, pia
what are the layers of the dura
Meningeal layer (attaches to arachnoid) and endosteal layer (this outer layer serves as the periosteum)
Dural layers are tightly attached to one another
Endosteal layer adheres to inside of the skull
what causes massive bleeding if a meningeal artery is torn.
high arterial blood pressure
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
what is the protection of the CNS?
skin and scalp
vertebral colum and skull
meninges
describe 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) supratentorial
infratentorial
above tent (cerebral hemispheres)
supratentorial
the opening where the brainstem passes into the cerebrum
tent needs opening
BS passes up into cerebral hemispheres
tentorial notch
what type of lesions are better? supra or infra?
supratentorial lesions are better than infratentorial in the BS because all life sustaining things happens here and having a lesion can be fatal
why is the area of tentorial notch dangerous for concussions or head trauma?
area where concussion or head trauma - soft tissues are sheared at this notch against hard leather and can cause damage
Lies on the inner surface of the dura
Web-like
arachnoid
what is in the subarachnoid space
csf
what is the arachnoid trabiculae
collagenous (collagen fibers) strands connect the arachnoid and the pia for suspension
what is the arachnoid villa
pressure sensitive straws or one way valves; one way valve taking high pressure CSF into villi to go to the sinuses and then dumped into other sinuses and out through the jugular vein
closely adheres to the CNS tissue, following the gyri and fissures
pia
ARe there meninges in the sc?
All of the meninges cover the spinal cord too
Slight differences in how the dura and pia connect to the spinal cord, vertebrae and nerve roots
Spinal dura is a single layer
There is an epidural space in the spinal cord (the dura is not attached tightly to bone as in the skull)
don’t want something tightly attached to something that has movement if it was attached to bone in spinal cord, we were tear it every time we moved
Arachnoid layer and subarachnoid space are similar to those in the brain
what anchors the spinal cord
Lumbar cistern exists (pocket), denticulate ligament and filum terminale of pia and dural sheat
where can we do epidural injections without causing damage?
go into subarachnoid space in cauda equina and pull out CSF without damaging tissue in areas of lumbar cistern or filum terminale??
Spaces where the endosteal and meningeal layers of the dura separate
Cavities
venous sinuses
end in jugular vein to drain used blood and fluids from the brain (cranial vault)
Transverse sinus, straight sinus, sigmoid sinus and a few more
collects used blood
inferior saggital sinus
largest of venous system
superior sagittal sinus
what is the drainage system to carry blood and CSF away from the brain and to be recycled in the systemic blood flow.
venous system
what tissue makes side of sinuses?
dura
describe an epidural hematoma
also called extradural and has “lemon”shape)
occurs if the meningeal arteries are torn
Most frequently after skull fractures (traumatic skull injury)
Bleeding between the periosteum (endosteal layer of the dura) and the skull bones
Death can occur within minutes if meningeal arteries are torn
above dura
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
describe subdural hematomas
“banana” shape)
from dural venous sinus or vein attachment at the sinus (blood is beneath the dura)
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
underneath dura
head injury from motorcycle accident
can still cause problems like epidural but not as likely
describe subarachnoid hematomas
sometimes called subarachnoid hematoma
More common
Bleeding between the brain and the arachnoid (under the arachnoid)
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)
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
lemon shape bc the dura is adhering to bone and make a pocket
epidural hematoma
banana shape, following the contour of the subarachnoid space and cerebrum
subdural hematoma
List all the things that protect the CNS
Hard bony skull and vertebrae
Meninges
CSF for buoyancy and cushioning
weighs less when it is sitting in fluid, provides cushion, protects because it is cushioning and protect from chemical homeostasis
Protection from vibration, pressure, temperature
Chemical barrier—blood brain barrier
Regulation of temperature and function by the brain itself
what are the 3 major functions of the CSF
to keep the tissue buoyant, acting as a cushion
acts as a vehicle for delivering nutrients to the brain and removing waste
to flow between the cranium and spine and compensate for changes in intracranial blood volume
List the ventricles and the foramina and how the CSF is produced; and how it flows
CSF is produced by choroid plexus and flows from the 2 lateral ventricles through the interventricular foramina to the third ventricle and then through the cerebral aqueduct to the fourth ventricle and then out into the subarachnoid space
The CSF 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 (thalamus). 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
The CSF 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)
CSF 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.
CSF circulates rostrally through the subarachnoid space to reach the superior sagittal sinus
It then enters the venous blood flow via giant vacuole transport (sucked up) through the specialized arachnoid villi. The CSF mixes with the blood in the sinuses and is carried to the jugular vein to be recycled and be removed from the brain
when will CSF flow into the superior sagittal sinus?
When the CSF pressure is higher than the venous pressure
one way valves
arachnoid villa
what is the cisterna magna
space under cerebellum; widest part of subarachnoid space under cerebellum
the major responsible bacterial organism (formerly Haemophilus influenzae but H. influenzae vaccines lowered this rate) for bacterial meningitis
Streptococcus pneumoniae
Most common cause of acquired postlingual profound SNHL and ossification of the labyrinth
bacterial meningitis
how does infection reach the inner ear?
through cochlear aqueduct (links subarachnoid space to basal turn of scala tympani
this explains why we see more high frequency hearing loss associated with it
HL associated with this occurs as early as 48 hours after infection
Disruption of CSF circulation
CSF pressure rises and ventricles expand
hydrocephalus
What can cause CSF?
Can be from excess CSF production, blockage of circulation or deficiency in reabsorption
what is the most common cause of hydrocephalus?
aqueductal stenosis - results from narrowing of cerebral aqueduct between the third and fourth ventricles in middle of the brain
what is communicating hydrocephalus?
This is when the lateral ventricles are still “communicating”/connected with the subarachnoid space and the problem is with reabsorption through the arachnoid villi or tentorial notch
pressure from outside - sas is pressing down on the tissues
occurs when flow is disrupted after it leaves the ventricles
what is noncommunicating hydrocephalus?
aka obstructive hydrocephalus
occurs when the flow of csf is blocked among one or more of the narrow passages connecting the ventricles
blockage could be due stenosis of the cerebral aqueduct or occlusion of the openings out of the 4th ventricle
balloons from inside - CSF stuck in ventricles
what are the symptoms of NPH?
abnormal gait, incontinence, memory problems, dementia
gait of individuals with NPH is distinct and appears as though their feet are glued to the floor as they try to ambulate; the gait has also been described as magnetic (Weiner, Constantini, Cohen, & Wisoff, 1995). NPH is one of the few reversible causes of dementia in older adults
describe NPH
usually a result from subarachnoid hemorrhage, head trauma, infection, tumor, or surgery complications
Generally in patients over 60
Usually idiopathic NPH
Slowly developing from gradual blockage of CSF
idiopathic
unknown cause
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
what can nph be mistaken for?
Can be mistaken for Alzheimer disease or Parkinson disease
Can we treat NPH? if so, with what?
If NPH is correctly diagnosed and treated, the symptoms can resolve
Tx may be ventriculoperitoneal shunt
what are the two main divisions of the neurovasculature?
carotid circulation
vertebrobasilar circulation
ascends from left ventricle of heart
aorta
arise from aorta and subclavian arteries
common carotid and vertebral arteries
anterior supply
carotid
posterior supply
vertebral
arise from aorta
subclavian arteries
branch from subclavian and provide 20% of blood supply to CNS
vertebral arteries
branch off of subclavian on the right and aorta on the left
common carotid
begins at upper border of thyroid cartilage and ascends to reach base of the skull
internal carotid
enters at carotid canal (lacerum)
internal carotid
ophthalmic artery branches off from here and divides into many branches
internal carotid
also gives rise to middle cerebral arteries and anterior cerebral arteres and posterior communicating arteries
internal carotid
blood to brain eyes, etc
internal carotid
provide about 80% blood supply to telencephalon (hemispheres) and diencephalon (thalamus?)
internal carotid
arises opposite the upper border of thyroid cartilage, inclines backwards to space between neck and condyle of lower jaw and external auditory meatus
external carotid