Central Nervous System: Structure

General Structure

• The central nervous system has several main structures
• These include the cerebrum, cerebellum, brain stem, and spinal cord

Cerebrum

• The cerebrum, or large brain, divides into right and left hemispheres
• The left hemisphere is usually dominant, controlling language and speech (90% of right-handed and 60-70% of left-handed people)
• The right hemisphere relates to spatial vision, musical talent and drawing
• The corpus callosum, a network of fibers, connects the hemispheres
• The brain has two tones, reflecting white versus gray matter
• Gray matter contains neuron bodies
• White matter contains long, myelinated extensions

Cerebellum

• The cerebellum, or small brain, sits behind and below the cerebrum and is related to coordination and balance

Brain Stem

• The brain stem connects the brain to the spinal cord
• It consists of three parts to be discussed

Spinal Cord

• The spinal cord extends through the segments of the spinal column to vertebra L2

Gyri and Sulci

• The brain has ridges (gyri) and grooves (sulci)

Directions in the Brain

• All standard directional terms apply, but there are also specific terms
• Rostral: toward the “beak," or nose or forehead; superiorly and anteriorly
• Caudal: toward the tail; inferiorly and posteriorly
• Ventral: toward the belly; usually anteriorly; inferiorly in the brain
• Dorsal: toward the back; usually posteriorly; superiorly in the brain

Sections

• Coronal or frontal, horizontal or transverse and midsagittal

Embryology

• Brain and spinal cord develop from a hollow tube sealed at both ends and fluid-filled
• The caudal part becomes the spinal cord
• Its walls thicken, shrinking the tube, which becomes the central canal of spinal cord
• The rostral part of the tube develops differently
• Walls thicken, interior expands and then divides into three parts

Prosencephalon

• Further divides into two parts
• The upper part is called the telencephalon
• The lower part is called the diencephalon
• Two sides of the telencephalon sprout two bulges that grow and extend down almost covering the diencephalon from two sides
• These create the cerebral hemispheres, or right and left hemispheres
• Ventricles of the brain then form

Diencephalon

• As the diencephalon differentiates, its walls thicken and form two crucial nuclei or right and left thalami
• A third ventricle is formed between these nuclei

Midbrain

• The midbrain stays in its original form with a cerebral aqueduct

Rhombencephalon

• The rhombencephalon develops into two parts
• The upper part or metencephalon becomes the pons
• Also becomes cerebellum
• It closely resembles pons in structure but smaller without any cavity
• The lower part or myelencephalon forms the medulla oblongata, which is contiguous with the spinal cord
• This makes up the fourth ventricle

Meninges

• The brain is wrapped in three membranes, from outer to inner: dura mater, arachnoid mater, and pia mater
• Dura mater usually remains attached to the skull and creates folds
• Falx cerebri: between the cerebral hemispheres within the longitudinal fissure
• Tentotium cerebelli: Separates the cerebellum and the cerebrum
• The two layers separate, and sinuses are formed, draining veins of the brain, and CSF
• Super sagittal sinus: Along the superior boarder
• Interior sagittal sinus: Boarding the bottom
• Straight sinus: At bottom and Falx cerebri
• Transverse sinus : Side

Layers of Membranes

• Arachnoid mater is a delicate, thin and transparent layer detached
• Separates dura mater with Subdural space and Pia Mater
• Trabeculae connect the two named after spider webs and are the Arachnoid
• In addition Subarachnoid space flows CSF then drains to structures,
• Meningeal structure is age Arachnoid villi at a more advanced
• Blood vessels can be seen in the pia mater Subarachnoid

Key cistern

• cisterna magna is main point in the inferior view and is a Cerebellomedullary cistern

Vessels In The Brain

• Review the map and follow the time through the various tools
• Pay special attention in particular the lobe where the lateral structure
• All temporal and general brain topography will be covered

Veins in brain

• Superficial Middle cerebral Vein flows along the lateral structure, and links to Superior structure, with Superior anastomosis vein-
• Innumerable veins that are connected in all veins with Cerebelar and Superficial veins make for Inferior structure
• Deep Cerebral cord flows through deep veins for Inferior views to get the deep Middle Cerebelar Vein and the Anterior structure connected to Basal Vein to get to Galen

Brain arteries

• In the chest, one to three from the aorta
• From the Internal Catorid arteries -Subclavian

Internal -Arteries

• Right,Left Arterial - Circle allows blood despite blockage Internal Middle Posterior
• 4 splitings

Basilar

• Artery smaller and connects through Pons laterally to the structure cerebalus where it is part of the PICA- smaller areries that connect on Cerebal cord
• Pontine Arteries then Superior connecting all Cerebal Artery

Internal carotid arteries

• Posterior connecting cord the internal -Arteries Small then all parts- connecting with the Pericallosal/Callosonmarging vessel which then creates the cycle

Overview

• Review the previous map and get a better understanding

Cranial Nerves

• Exit cranium and Lead motor nerves from the brain, to muscles and carry sense information to all parts are associated to cranium
• Nerves lead to different areas -Sensory -Motor

CN1- Olfactory Nerve

• Related to smell from bulbs with fibers leading into tract
• Then is when Lateral

CN2- Optic Nerve

• Associated with sight From nerves that reach with Optic Chiasma and tract leading to area of Central nervous system

CN3- CN5

• Oculomotor is cranial Motor, Trochlear related to muscles
• Tigeminal is Large connected to pons to interior area

CN6 and CN7

• Abducens to muscle from side of border to pons

CN8

• Vestibulocochlear tied to all other facial areas. that are connected to the hearing system

CN9-CN11

• Glossopharynygeal to oral area
• CN9 connected from head
• Nerve accesory

CN12: Hypoglossal

• Connected to language all are all linked in area