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.

Falx cerebri

Superiorsagittal sinus

Straightsinus

Crista galliof the ethmoid bone

Pituitarygland

Falx cerebelli

Occipital lobe

Dura mater

Transversesinus

Temporalbone

(b) Dural venous sinuses(a) Dural septa

Scalp

Skull

Tentoriumcerebelli

Cerebellum

Arachnoidmater over medulla oblongata

Falx cerebri

Superiorsagittal sinus

Falxcerebelli

Occipital lobe

Dura mater

Transversesinus

Temporalbone

(b) Dural venous sinuses

Scalp

Skull

Tentoriumcerebelli

Cerebellum

Arachnoidmater over medulla oblongata

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

SkullEpidural SpaceDura Mater

Subdural SpaceArachnoid

Subarachnoid spacePia Mater

Skin of scalpPeriosteum

Falx cerebri(in longitudinalfissure only)

Blood vesselArachnoid villus

Pia materArachnoid mater

Duramater Meningeal

PeriostealBone of skull

Superiorsagittal sinus

Subduralspace

Subarachnoidspace

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.

Superiorsagittal sinus

Arachnoid villus

Subarachnoid spaceArachnoid materMeningeal dura materPeriosteal dura mater

Right lateral ventricle(deep to cut)

Choroid plexusof fourth ventricle

Central canalof spinal cord

Choroidplexus

Interventricularforamen

Third ventricle

Cerebral aqueductLateral apertureFourth ventricleMedian aperture

(a) CSF circulation

CSF is produced by thechoroid plexus of eachventricle.

1

CSF flows through theventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord.

2

CSF flows through thesubarachnoid space.

3

CSF is absorbed into the dural venoussinuses via the arachnoid villi.

4

1

2

3

4

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 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]

• 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

• Dizziness• Weakness on one side• Headache• Vomiting• Seizures• Slurred speech• Confusion