Download Brain Anatomy

Brain Anatomy and
Physiology
Dr. Nevo Margalit – Neurosurgery
Tel Aviv Sourasky Medical Center
Scalp
• Skin
• Connective tissue (superficial fascia)
• Epicranial aponeurosis (galea
aponeurotica)
• Loose areolar tissue
• Pericranium
• Occipitofrontalis muscle
Scalp
The Skull
The Skull
The skull
The Menings
The 3 layers covering the brain
• Dura: covers the brain and spinal cord. The
venous sinuses run through the dura. 2
additional Parts of the dura are the Tentorium
and the Falx Cerebri.
• Arachnoid: Transparent, thin web structure.
Creates a space around the brain called the
sub arachnoid space where the CSF and the
main blood vessels pass.
• Pia: a very thin layer. Coats the brain and
spinal cord and is inseparable from them.
Dura
Tentorium and Falx
Tentorium
Arachnoid
Arachnoid – Basal Cisterns
Parts of the Central Nervous
System
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2 hemispheres
Brainstem
Cerebellum
Spinal cord
Each hemisphere has lobes:
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Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
• Insular lobe
• Limbic lobe
Lateral View
Insula
Gyruses and sulci
• Each lobe is composed of gyruses
separated by sulci
• The topography can be defined by
histology, anatomical relationships or
function
Map Brodmann
Gyruses and Sulci
Functional areas
Function 2
Function 3
f-MRI
The Motor Strip
Fibers
Ventricles and CSF
Ventricles and CSF
• CSF is produced by the choroid plexus
in the ventricles
• The circulation is from the lateral
ventricles to the third through the
Monroe- aqueduct- IV ventricle- sub
arachnoid space in skull and spineabsorption in sss and other sinuses
through arachnoid granulations
CSF Pathways
CSF Pathways
Arteries of the brain
Arteries of the brain
• Anterior circulation – internal
carotid artery, from common
carotid in the neck. Bifurcates to
MCA and ACA
• Posterior circulation – vertebral
arteries that join to form the basilar
artery that will then bifurcate to 2
PCA
Circle of Willis
• Communication between 2 sides –
anterior communicating (a-com)
• Communication between anterior
and posterior circulation – posterior
communicating (p-com)
• Many anomalies may exist
Arteries in the neck
Arteries in the subarachnoid
space
Arteries of the brain
Physiology
Blood supply to the brain
• The brain gets 15% of the cardiac output
and 20% of the oxygen consumption
• The brain tissue gets in average 50ml of
blood per 100gr of tissue per minute. The
gray matter receives about 3 to 4 times
more then the white matter
• Total blood supply to the brain is about 500600ml per minute
Factors Affecting the blood
supply
• Autoregulation
• Biochemical changes – O2 and CO2
• Blood brain barrier - BBB
Autoregulation
• Maintains a regular blood supply to the
brain in changing blood pressures
• The range is 50-130 mm mercury
• Possible mechanisms are the
myogenic control, neurogenic and
biochemichal control
CO2
• The most important and powerful
mechanism that controls brain blood
flow
• A change in 1mm PCO2 changes the
flow in 4-5%
• PCO2 of 70 gives a maximal
vasodilatation. Above that the flow is
pressure dependent
Hyperventilation
• Hyperventilation lowers the PCO2
• It has a strong effect but it is limited in
time
• Could be dangerous if not regulatedischemia
• Can be regulated with a jugular bulb
oximeter
BLOOD BRAIN BARRIER
• The BBB is composed of the tight
junctions in the endothelium cells of
the blood vessels
• Prevents passage of large molecules
and even small ions like Na and Cl
• Specific substances pass the BBB like
glucose and amino acids
BLOOD BRAIN BARRIER
• Because of the BBB, in the brain
hydrostatic and oncotic pressures are
not significant. The important
parameter is the osmotic pressure
• The BBB is damages in trauma, tumor,
infarct, SAH and infection
BLOOD BRAIN BARRIER
Brainstem and Cranial Nerves
Brain stem
• Has 3 parts: midbrain, pons and medulla
• Transports all the information to and from
the brain
• Centers for breathing and blood pressure
• The origin or endpoint for cranial nerves
• Contains the center of consciousness
• Creates connections to the cerebellum
Nuclei in the brain stem
Cranial nerves
• 12 pairs of nerves
• All cranial nerves except I and II
originate from the brainstem
• The nerves are sensory, motor or
mixed
• There are nuclei in the brainstem that
are the origin or the endpoint of the
cranial nerves
CN 1- Olfactory Nerve
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The sensation of smell
Pure sensory nerve
From the nose to the forebrain
Very developed in some animals
Tested an odorous substance
CN 2 - Optic N
• Visual information from the eye to the
brain
• Pure sensory nerve
• Belongs to the CNS and is not part of
the PNS
• Problems could result in field problem,
acuity problem and more
• Tested with a vision chart and field
exam on confrontation
CN 3, 4, 6- occulomotor, trochlear
and abbducence
• Nerves that control the movement of the
eyes and the constriction of the pupil
• Pure motor nerves
• Problems result in unsynchronized eye
movements and/ or dilated pupil
• Tested with the patient following a finger
and with light
CN 5 – Trigeminal N
• The largest CN
• Sensory and motor
• Sensation from the face eyes, mouth,
and motor for mastication muscles
• Tested with touch and pin on face
CN 7 – Facial N
• Motor nerve of the face and taste from
the tongue
• Motor and sensory
• Tested with movement of the facial
muscles
CN 8 – Vestibulocochlear N
• The nerves for hearing and balance
• Sensory nerves
• The most common origin of a
schwanoma
• Tested by hearing test and balance
function
CN 9 – Glossopharyngeal N
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Sensation from the pharynx
Mainly sensory and small motor part
Problems result in aspiration
Tested with the gag reflex
CN 10 – Vagus N
• Motor to the muscles larynx and
pharynx and the parasympathetic of
the body
• Motor nerve
• Problems result in hoarseness
• Tested by opening mouth wide and
saying “AH“
CN 11 – Accessory N
• Nerve to the trapezius and
sternomastoid muscles
• Motor nerve
• Tested with shoulder raise or turning
the head
CN 12 – Hypoglossal N
• Nerve to the muscle of the tongue
• Motor nerve
• Tested with movement of the tongue