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Brain Anatomy and Physiology Dr. Nevo Margalit – Neurosurgery Tel Aviv Sourasky Medical Center Brain Anatomy and Physiology Dr. Nevo Margalit – Neurosurgery Tel Aviv Sourasky Medical Center

Scalp • Skin • Connective tissue (superficial fascia ( • Epicranial aponeurosis (galea aponeurotica Scalp • Skin • Connective tissue (superficial fascia ( • Epicranial aponeurosis (galea aponeurotica ( • Loose areolar tissue • Pericranium • Occipitofrontalis muscle

Scalp Scalp

The Skull The Skull

The Skull The Skull

The skull The skull

The Menings The 3 layers covering the brain • Dura: covers the brain and 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 Dura

Tentorium and Falx Tentorium and Falx

Tentorium Tentorium

Arachnoid Arachnoid

Arachnoid – Basal Cisterns Arachnoid – Basal Cisterns

Parts of the Central Nervous System • • 2 hemispheres Brainstem Cerebellum Spinal cord Parts of the Central Nervous System • • 2 hemispheres Brainstem Cerebellum Spinal cord

Each hemisphere has lobes: • • Frontal lobe Parietal lobe Temporal lobe Occipital lobe Each hemisphere has lobes: • • Frontal lobe Parietal lobe Temporal lobe Occipital lobe • Insular lobe • Limbic lobe

Lateral View Lateral View

Insula Insula

Gyruses and sulci • Each lobe is composed of gyruses separated by sulci • 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 Map Brodmann

Gyruses and Sulci Gyruses and Sulci

Functional areas Functional areas

Function 2 Function 2

Function 3 Function 3

f-MRI f-MRI

The Motor Strip The Motor Strip

Fibers Fibers

Ventricles and CSF Ventricles and CSF

Ventricles and CSF • CSF is produced by the choroid plexus in the ventricles 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

CSF Pathways CSF Pathways

Arteries of the brain Arteries of the brain

Arteries of the brain • Anterior circulation – internal carotid artery, from common carotid 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 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 neck

Arteries in the subarachnoid space Arteries in the subarachnoid space

Arteries of the brain Arteries of the brain

Physiology Physiology

Blood supply to the brain • The brain gets 15% of the cardiac output 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 50 ml of blood per 100 gr 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 500600 ml per minute

Factors Affecting the blood supply • Autoregulation • Biochemical changes – O 2 and Factors Affecting the blood supply • Autoregulation • Biochemical changes – O 2 and CO 2 • Blood brain barrier - BBB

Autoregulation • Maintains a regular blood supply to the brain in changing blood pressures 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

CO 2 • The most important and powerful mechanism that controls brain blood flow CO 2 • The most important and powerful mechanism that controls brain blood flow • A change in 1 mm PCO 2 changes the flow in 4 -5% • PCO 2 of 70 gives a maximal vasodilatation. Above that the flow is pressure dependent

Hyperventilation • Hyperventilation lowers the PCO 2 • It has a strong effect but Hyperventilation • Hyperventilation lowers the PCO 2 • 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 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 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 BLOOD BRAIN BARRIER

Brainstem and Cranial Nerves Brainstem and Cranial Nerves

Brain stem • Has 3 parts: midbrain, pons and medulla • Transports all the 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 Nuclei in the brain stem

Cranial nerves • 12 pairs of nerves • All cranial nerves except I and 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 • • • The sensation of smell Pure sensory 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

CN 2 - Optic N • Visual information from the eye to the brain 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 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 • 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 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 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 • • Sensation from the pharynx Mainly sensory and CN 9 – Glossopharyngeal N • • 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 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 • 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 • CN 12 – Hypoglossal N • Nerve to the muscle of the tongue • Motor nerve • Tested with movement of the tongue