Transcript Protection and Injury to the Brain

Protection and Injury to the Brain
Protection of the Brain
Nervous tissue is soft and easily injured.
Several systems are in place to protect the
brain.
Meninges
The Meninges consist of three connective
tissue membranes that cover the organs of
the CNS. They have several functions:
– Cover and protect the CNS
– Protect the blood vessels and venous sinuses
– Contain cerebral spinal fluid
– Form partitions within the skull
The three layers are
– dura mater
– arachnoid mater
– pia mater
(Think DAP)
Dura Mater
The Dura Mater “tough mother” is composed
of two layers of fibrous connective tissue.
– The periosteal layer is in contact with the inner
surface of the skull
– The meningeal layer is the true external covering
– They can form venous sinuses and dural septa
Dural septa and Dural venous sinuses.
Straight
sinus
Crista galli
of the
ethmoid
bone
Pituitary
gland
Superior
sagittal sinus
Skull
Falx cerebri
Scalp
Occipital lobe
Tentorium
cerebelli
Falx
cerebelli
Cerebellum
Arachnoid
mater over
medulla
oblongata
(a) Dural septa
(b) Dural venous sinuses
Dura mater
Transverse
sinus
Temporal
bone
Superior
sagittal sinus
Skull
Falx cerebri
Scalp
Occipital lobe
Tentorium
cerebelli
Falx
cerebelli
Cerebellum
Arachnoid
mater over
medulla
oblongata
(b) Dural venous sinuses
Dura mater
Transverse
sinus
Temporal
bone
Arachnoid Mater
This is the middle layer and forms a loose
brain covering (looks like a spiders web)
It is separated from the dura mater by a
potential space known as the subdural space.
Pia Mater “gentle mother”
Has a rich supply of blood vessels. It is the
only one which clings tightly to the brain and
follows every convolution
Skull
Epidural Space
Dura Mater
Subdural Space
Arachnoid
Subarachnoid space
Pia Mater
Superior
sagittal sinus
Subdural
space
Subarachnoid
space
Skin of scalp
Periosteum
Bone of skull
Dura
Periosteal
Meningeal mater
Arachnoid mater
Pia mater
Arachnoid villus
Blood vessel
Falx cerebri
(in longitudinal
fissure only)
Conditions involving the Meninges
• Meningitis is an inflammation of the
meninges.
• It can be, most commonly, of viral or bacterial
origin
• The bacterial form is potentially fatal while the
viral form is self limited.
Signs and Symptoms
• Most common signs are:
– Headache
– Nuchal rigidity (Can’t flex neck)
– Altered mental status (acting strange)
Signs and Symptoms
Conditions involving the Meninges
Brain bleeds can be of three types, epidural,
subdural or subarachnoid.
They can wake up dead
Epidural hemorrhage typically occurs from blood
vessels bleeding into the space between the dura
mater and the skull.
– Often associated with head trauma
– Characterized by arterial blood accumulating in the
epidural space
Individuals typically are lucid and then deteriorate
rapidly due to bleeding from arteries.
They can wake up dead
Subdural hemorrhage typically occurs from blood
vessels bleeding into the space between the dura and
the arachnoid layer.
– Often associated with head trauma
– Characterized by venous blood accumulating in the
subdural space
The onset of symptoms is gradual these include
confusion and headache.
They can wake up dead
Epidural Hematoma
Subdural Hematoma
Conditions involving the Meninges
Sub arachnoid hematoma occurs in the space
between the arachnoid and pia matter.
These typically present with stroke like symptoms.
The most common sign is a “thunder clap”
headache, vomiting and changes in the level of
consciousness.
Conditions involving the Meninges
Sub arachnoid hematoma usually occurs as a
result of a ruptured blood vessel.
Cerebral Spinal Fluid (CSF)
The CSF is found in on and around the brain
and spinal column.
It forms a cushion and allows the brain to
float preventing it from crushing itself.
Cerebral Spinal Fluid (CSF)
CSF has a makeup similar to blood plasma but
has less protein.
Figure 12.26a Formation, location, and
circulation of CSF.
Superior
sagittal sinus
4
Choroid
plexus
Arachnoid villus
Interventricular
foramen
Subarachnoid space
Arachnoid mater
Meningeal dura mater
Periosteal dura mater
1
Right lateral ventricle
(deep to cut)
Choroid plexus
of fourth ventricle
3
Third ventricle
Cerebral aqueduct
Lateral aperture
Fourth ventricle
Median aperture
Central canal
of spinal cord
(a) CSF circulation
2
1 CSF is produced by the
choroid plexus of each
ventricle.
2 CSF flows through the
ventricles and into the
subarachnoid space via the
median and lateral apertures.
Some CSF flows through the
central canal of the spinal cord.
3 CSF flows through the
subarachnoid space.
4 CSF is absorbed into the dural venous
sinuses via the arachnoid villi.
Cerebral Spinal Fluid
The brain is made up of four ventricles.
CSF is formed in these structures and flows
through the CNS.
Cerebral Spinal Fluid
• 1st/2nd= paired lateral ventricles (lie in cerebral
hemispheres) [separated by septum
pellucidum- transparent wall]
Cerebral Spinal Fluid
• 1st/2nd= paired lateral ventricles (lie in cerebral
hemispheres) [separated by septum
pellucidum- transparent wall]
• 3rd ventricle lies within diencephalon
[connected to each lateral ventricles by
interventricular foreamen]
Cerebral Spinal Fluid
• 1st/2nd= paired lateral ventricles (lie in cerebral
hemispheres) [separated by septum
pellucidum- transparent wall]
• 3rd ventricle lies within diencephalon
[connected to each lateral ventricles by
interventricular foreamen]
• In midbrain is central cavity => cerebral
aqueduct [connects 3rd/4th ventricle]
Cerebral Spinal Fluid
• 1st/2nd= paired lateral ventricles (lie in cerebral
hemispheres) [separated by septum pellucidumtransparent wall]
• 3rd ventricle lies within diencephalon [connected
to each lateral ventricles by interventricular
foreamen]
• In midbrain is central cavity => cerebral aqueduct
[connects 3rd/4th ventricle]
• 4th ventricle lies in the brain steam, dorsal to the
pons
Cerebral Spinal Fluid
Cerebral Spinal Fluid
CSF is formed in the
choroid plexuses that
hang is each ventricle.
Cerebral Spinal Fluid
• A complication seen with the ventricle system
is hydrocephalus.
• This occurs when one of the aqueducts are
blocked
Blood Brain Barrier
This is a protective mechanism that helps to
maintain a stable internal environment.
This is to keep the neurons from firing
uncontrollably when there is a slight shift in
ion or water concentrations.
Blood Brain Barrier
To reach the neurons, 3 layers must be passed.
These are:
– The endothelium of the capillary wall
– The thick basal lamina surrounding each capillary
– The “feet” or processes from the astrocytes
touching the capillaries
Blood Brain Barrier
The barrier is NOT effective against nonpolar
compounds such as fats or gases, this why
anesthetics, alcohol and nicotine can affect
the brain.
Injuries
• Major cause of
death and
disabilities world
wide.
• Major population
are the young
Injury to the Brain
Concussion which is a temporary alteration in
brain function. This is typically caused by a
blow to the head. Signs and symptoms usually
include dizziness and mild headache.
Concussion
• A study from McGill University in Montreal
found 60 percent of college soccer players
reported concussion symptoms at least once
during a season.
• The University of Pittsburgh’s Brain Trauma
Research Center estimates 34 percent of
college football players have had one
concussion while 20 percent have endured
multiple concussions.
Concussion
• Neuro- Psychological testing is designed to
test brain function and identify elements of
cognitive damage and recovery that may not
be discernible through self-reporting.
Stroke or CVA
Cerebral vascular accidents or strokes are the
single most common type of brain injury. This
is brought about by a blockage of the arteries
to the brain. Depending on where the
blockage occurs, the CVA can go be mild or
devastating.
Stroke
This refers to a condition of sudden onset
which is due to either a blocked artery or a
broken (ruptured) artery.
Types of Strokes
• Cerebral Infarction
Types of Strokes
• Cerebral Infarction
• Transient Ischemic Attack (TIA)
Types of Strokes
• Cerebral Infarction
• Transient Ischemic Attack (TIA)
• Hemorrhagic
Cerebral Infarction
• This is due to a
blocked or partially
blocked artery in
the brain.
Transient Ischemic Attack
• This is due to a
blocked or partially
blocked artery in
the brain but the
symptoms resolve
on their own in 24
hours.
Hemorrhagic Stroke
• This is due to a
broken blood
vessel.
Symptoms
Symptoms
•
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Dizziness
Weakness on one side
Headache
Vomiting
Seizures
Slurred speech
Confusion