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 CNSProtect the blood vessels and venous sinusesContain cerebral spinal fluidForm partitions within the skull

The three layers are dura materarachnoid materpia mater(Think DAP)Dura MaterThe 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 skullThe meningeal layer is the true external coveringThey can form venous sinuses and dural septa Dural septa and Dural venous sinuses.

Falx cerebriSuperiorsagittal sinusStraightsinusCrista galliof the ethmoid bonePituitarygland Falx cerebelliOccipital lobeDura materTransversesinusTemporalbone(b) Dural venous sinuses(a) Dural septaScalpSkullTentoriumcerebelliCerebellumArachnoidmater over medulla oblongata6

Falx cerebriSuperiorsagittal sinusFalxcerebelli Occipital lobeDura materTransversesinusTemporalbone(b) Dural venous sinusesScalpSkullTentoriumcerebelliCerebellumArachnoidmater over medulla oblongata7Arachnoid 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 convolutionSkullEpidural SpaceDura MaterSubdural SpaceArachnoidSubarachnoid spacePia Mater

Skin of scalpPeriosteumFalx cerebri(in longitudinalfissure only)Blood vesselArachnoid villusPia materArachnoid materDuramater MeningealPeriostealBone of skullSuperiorsagittal sinus Subduralspace Subarachnoidspace 11Conditions involving the MeningesMeningitis is an inflammation of the meninges.It can be, most commonly, of viral or bacterial originThe bacterial form is potentially fatal while the viral form is self limited.

Signs and SymptomsMost common signs are:HeadacheNuchal rigidity (Cant flex neck)Altered mental status (acting strange)Signs and Symptoms

Conditions involving the MeningesBrain bleeds can be of three types, epidural, subdural or subarachnoid.

They can wake up deadEpidural hemorrhage typically occurs from blood vessels bleeding into the space between the dura mater and the skull. Often associated with head traumaCharacterized 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 deadSubdural hemorrhage typically occurs from blood vessels bleeding into the space between the dura and the arachnoid layer. Often associated with head traumaCharacterized by venous blood accumulating in the subdural space

The onset of symptoms is gradual these include confusion and headache.

They can wake up deadEpidural 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 sinusArachnoid villusSubarachnoid spaceArachnoid materMeningeal dura materPeriosteal dura materRight lateral ventricle(deep to cut)Choroid plexusof fourth ventricle Central canalof spinal cordChoroidplexus InterventricularforamenThird ventricleCerebral 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. 4123423Cerebral Spinal FluidThe brain is made up of four ventricles.CSF is formed in these structures and flows through the CNS.Cerebral Spinal Fluid1st/2nd= paired lateral ventricles (lie in cerebral hemispheres) [separated by septum pellucidum- transparent wall]

Cerebral Spinal Fluid1st/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 Fluid1st/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 Fluid1st/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 FluidA complication seen with the ventricle system is hydrocephalus.This occurs when one of the aqueducts are blocked

32Blood 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 wallThe thick basal lamina surrounding each capillaryThe feet or processes from the astrocytes touching the capillariesBlood 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.

Injury to the BrainTraumatic brain injuries are the leading cause of death in North America.InjuriesMajor cause of death and disabilities world wide.Major population are the young

Injury to the BrainConcussion 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. ConcussionA 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 Pittsburghs Brain Trauma Research Center estimates 34 percent of college football players have had one concussion while 20 percent have endured multiple concussions.

ConcussionNeuro- 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.

StrokeThis refers to a condition of sudden onset which is due to either a blocked artery or a broken (ruptured) artery.Types of StrokesCerebral InfarctionTypes of StrokesCerebral InfarctionTransient Ischemic Attack (TIA)Types of StrokesCerebral InfarctionTransient Ischemic Attack (TIA)Hemorrhagic Cerebral InfarctionThis is due to a blocked or partially blocked artery in the brain.

Transient Ischemic AttackThis is due to a blocked or partially blocked artery in the brain but the symptoms resolve on their own in 24 hours.

Hemorrhagic StrokeThis is due to a broken blood vessel.

Symptoms

SymptomsDizzinessWeakness on one sideHeadacheVomitingSeizuresSlurred speechConfusion