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


Scalp :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 MeningsThe 3 layers covering the brain :The MeningsThe 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 :Parts of the Central Nervous System 2 hemispheres Brainstem Cerebellum Spinal cord


Each hemisphere has lobes: :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 :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 :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


CSF Pathways :CSF Pathways


CSF Pathways :CSF Pathways


Arteries of the brain :Arteries of the brain


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 :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 :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


Factors Affecting the blood supply :Factors Affecting the blood supply Autoregulation Biochemical changes – O2 and CO2 Blood brain barrier - BBB


Autoregulation :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 :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 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


BLOOD BRAIN BARRIER :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 :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


Slide 47:BLOOD BRAIN BARRIER


Brainstem and Cranial Nerves :Brainstem and Cranial Nerves


Brain stem :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 :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 :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 :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 :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 :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 :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 :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 :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 :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 :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 :CN 12 – Hypoglossal N Nerve to the muscle of the tongue Motor nerve Tested with movement of the tongue