GROSS ANATOMY OF THE NERVOUS SYSTEM
Set stage:
CNS vs PNS
Intricate anatomy (most complex organ) as key to powerful function
TERMINOLOGY
Orientation
Medial vs. Lateral (relative terms)
Rostral (toward forward end of neuraxis) vs. Caudal (toward tail
end of neuraxis)
Dorsal (toward back) vs. Ventral (toward "belly" of neuraxis)
Relation to Anterior/Posterior; Superior/Inferior
Rat (anterior = rostral; dorsal = superior)
Humans
Bending of neuraxis so...
In forebrain resembles relationships in rat but...
In spinal cord anterior = ventral
Contralateral (opposite side) vs. ipsilateral (same side)
Planes of section
Horizontal
Sagittal
Frontal (=coronal)
Transverse (perpendicular to neuraxis)
Naming of structures
Cell-rich areas
Gray Matter
"Nuclei" (not same as nucleus of a cell!)
Fiber-rich areas
White Matter
Nerves (PNS) vs. tracts (CNS)
Special terms for white-matter zones
Lemniscus (ascending sensory tract)
Funiculus (spinal-cord fiber bundle)
Fasciculus (small bundle of axons)
Commissure (fiber tract crossing midline)
Decussation (crossover point in a tract)
Pathway naming (origin = prefix, target = suffix)
Examples: Corticospinal, spinocerebellar
Contralateral vs. ipsilateral
MAJOR CNS DIVISIONS
Spinal cord
Brainstem (medulla, pons, midbrain)
Cerebellum
Diencephalon (includes thalamus, hypothalamus)
Cerebral hemisphere (includes cortex, basal ganglia)
LATERAL VIEW
Cortex, cerebellum
Gyri, sulci
Fissures
Sylvian (=lateral)
Central sulcus (--> pre- and postcentral gyri)
Lobes of the cerebrum
Sagittal fissure ( splits the 2 hemispheres )
MEDIAN VIEW (MIDSAGITTAL SECTION)
Summary of divisions
Cortex
Corpus callosum
Septum pellucidum
Brainstem
Medulla (abuts spinal cord)
Pons (pontine protuberance)
Midbrain (upper most brainstem division)
Diencephalon (thalamus, hypothalamus)
VENTRICULAR SYSTEM
Appearance in median view of brain
Complex adult geometry, but simple roots
Neural tube
Telencephalic vesicles (lateral ventricles)
"Ram's horn" movement into temporal lobe
Adult form
Lateral (one in each hemisphere)
Third (at level of diencephalon)
Interventricular foramen (connects lateral and 3rd)
Aqueduct (midbrain)
Fourth (medulla, pons)
Appearance in midsagittal
Where are lateral ventricles? Off midline, not visible.
Cerebrospinal fluid
Choroid plexus as source
Outflow (lateral, median apertures of 4th ventricle)
Hydrocephalus when outflow blocked
VENTRAL VIEW OF BRAINSTEM
Brainstem divisions
Hypothalamus (diencephalon)
Cranial nerves
Can be sensory, motor, or mixed. Examples:
8th (auditory - SENSORY)
5th (trigeminal - MIXED)
3rd (oculomotor - MOTOR)
Optic nerves, chiasm (really tracts of CNS)
Pyramids of medulla
Cerebral peduncles of midbrain
DORSAL VIEW
Cerebellar peduncles (not same as cerebral peduncles)
4th ventricle
Superior and inferior colliculi of midbrain
INTERNAL ORGANIZATION OF FOREBRAIN
Cerebral cortex (gray matter) [Nissl stain]
Cortical white matter. Contains the following classes of fibers:
Association (cortico-cortical)
Callosal (interhemispheric)
Descending/Ascending
Corona radiata (show in median view after peeling away
thalamus)
Internal capsule
Important landmark
View in horizontal section
Also visible in same section...
Basal Ganglia
Subcortical components of cerebral hemisphere
Striatum (caudate plus putamen)
Globus pallidus
Keys to Localization:
Lateral ventricle (caudate just lateral to it)
Internal capsule (splits caudate from putamen+globus
pallidus)
3-D shape - complex
Caudate shape from lateral ventricle
Putamen split off from caudate by internal capsule
Transverse sections (rostrocaudal series)
Caudate shrinks. Note relationship to ventricle, capsule
Note third ventricle at midline. Its walls are
diencephalon.
Diencephalon
Thalamus: gateway to cortex
Lateral to third ventricle
Medial to internal capsule (like caudate)
Just rostral to brainstem
Hypothalamus (head ganglion of autonomic, neuroendocrine
systems)
Limbic system
Emotion, memory, autonomic
"Border" of hemisphere
Median view
Hippocampus
Septum
Fornix (interconnects hippocampus and septum)
Amygdala
Pop out view of hippocampus - fornix: complex shape follows
lateral ventricle
MENINGES
Dura
Falx (between hemispheres)
Tentorium (between occipital lobe and cerebellum)
Arachnoid
Stays outside sulci
Pia
Follows brain surface into sulci
Subarachnoid space (contains cerebrospinal fluid)
BLOOD SUPPLY
Vertebral vs. carotid:
Clinically important:
Supply different structures so...
Occlusion  different symptoms
Carotid (anterior) circulation
Middle cerebral (supplies most of lateral surface of hemisphere)
Anterior cerebral (supplies medial surface except
occipitotemporal)
Vertebral (posterior or vertebrobasilar supply)
Basilar artery (fused midline vessel; coextensive with pons)
Posterior cerebral (supplies inferior, medial surfaces of occipital,
temporal lobes)
Other branches of vertebrobasilar system supply brainstem and
cerebellum
Superior cerebellar
Anterior inferior cerebellar
Posterior inferior cerebellar
Circle of Willis; completed by…
Posterior communicating
Anterior communicating