7. 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.
20. Gyruses and sulci
• Each lobe is composed of gyruses
separated by sulci
• The topography can be defined by
histology, anatomical relationships or
function
30. 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 spine-
absorption in sss and other sinuses
through arachnoid granulations
34. 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
35. 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
40. 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 500-
600ml per minute
41. Factors Affecting the blood
supply
• Autoregulation
• Biochemical changes – O2 and CO2
• Blood brain barrier - BBB
42. 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
43. 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
44. Hyperventilation
• Hyperventilation lowers the PCO2
• It has a strong effect but it is limited in
time
• Could be dangerous if not regulated-
ischemia
• Can be regulated with a jugular bulb
oximeter
45. 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
46. 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
49. 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
55. 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
56. CN 1- Olfactory Nerve
• The sensation of smell
• Pure sensory nerve
• From the nose to the forebrain
• Very developed in some animals
• Tested an odorous substance
57.
58.
59.
60. 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
61.
62.
63.
64. 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
65.
66.
67.
68. 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
69.
70.
71. CN 7 – Facial N
• Motor nerve of the face and taste from
the tongue
• Motor and sensory
• Tested with movement of the facial
muscles
72.
73.
74.
75.
76. 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
77.
78.
79. CN 9 – Glossopharyngeal N
• Sensation from the pharynx
• Mainly sensory and small motor part
• Problems result in aspiration
• Tested with the gag reflex
80.
81. 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“
82.
83. CN 11 – Accessory N
• Nerve to the trapezius and
sternomastoid muscles
• Motor nerve
• Tested with shoulder raise or turning
the head
84.
85. CN 12 – Hypoglossal N
• Nerve to the muscle of the tongue
• Motor nerve
• Tested with movement of the tongue
