Basic Neuroanatomy

Online Tutorial

Lars Klimaschewski MD PhD Department of Anatomy, Histology and Embryology Division of Neuroanatomy Medical University Innsbruck

www.neuroanatomy.at Resources

CNS Compendium for medical students (Division of Neuroanatomy)

Frozen brain sections (Division of Clinical Anatomy)

Histological sections (Division of Histology)

Brain Model (3B Scientific) Embryonic 3 vesicle stage  5 vesicle stage (day 25, 4 mm) (day 42, 12 mm) Telencephalon Neuroanatomy I II Lateral ventricle Prosencephalon Foramen Monroi (forebrain) III Diencephalon Mesencephalon (midbrain) Mesencephalon Rhombencephalon IV Aquaeduct (hindbrain) Rhombencephalon Met- and Myelencephalon Medulla spinalis (spinal cord) Medulla spinalis Canalis centralis

CN VII/VIII Flexura cervicalis Isthmus (CN IV)

Medulla spinalis Flexura pontina

Cerebellum CN V

CN IX-XII Telencephalic vesicle (day 60, 30 mm) Optic cup Bulbus olfactorius (CN I) Adult Gyrus precentralis Neuroanatomy Gyrus postcentralis Lobus frontalis Lobus parietalis

Sulcus lateralis Insula Lobus occipitalis

Lobus temporalis Cerebellum

Medulla spinalis 8 cervical segments 12 thoracic segments 5 lumbal segments 5 sacral segments

Diencephalon Corpus callosum Chiasma opticum Pineal gland - Pituitary gland - Epiphysis Hypophysis Cerebellum Mesencephalon (Arbor vitae)

Pons Aquaeduct

Medulla oblongata Central canal IV. ventricle Functional Neuroanatomy

Hearing Special INPUT sensory CNS Vestibular

Vision Taste Smell INPUT OUTPUT

Sensory Motor (afferent) (efferent)

Exteroception Proprioception Enteroception (surface) (musculosceletal) (viscera) Somatic Visceral

Noci- Thermo - Mechano- Chemo- ceptor ceptor ceptor ceptor Involun- Volun- Para- Sym- Enteric tary tary sympathetic pathetic

SKELETOMUSC. GLANDS

BRANCHIO- CARDIAC GENIC MUSC. MUSC.

SMOOTH MUSC.

Spinal cord

Main motor and sensory systems dorsal horn

ventral horn Cervical spinal cord

Fasciculus gracilis

Posterolateral tract Fasciculus cuneatus (from Th3) (Lissauer)

Dorsal horn Zona intermedia I II III IV Tr. corticospinalis lat. Tr. spinocerebel. post. V

Autonomic tracts VI Tr. spinocerebel. ant. VII Tr. tegmentospinalis X VIII IX Tr. spinothalamicus lat. Ventral horn IX Tr. spinoolivaris

Fasciculi proprii Tr. spinotectalis

Tr. olivospinalis Tr. spinovestibularis

Tr. reticulospinalis Tr. tectospinalis Tr. spinothalamicus ant.

Tr. vestibulospinalis Tr. corticospinalis ant. Cortical areas*

Capsula interna (Crus posterius)

Mesencephalon (Crura cerebri)

Pons (ventral) Corticospinal tract (CST)

Medulla spinalis (Tr. corticospinalis lat.) Pyramidal decussation in medulla oblongata  12% of fibers cross over at segmental level

*sources: motor cortex, pre- Ventral horn motor cortex, frontal eye field, prefrontal cortex, Broca center, cingulate motor cortex, soma- tosensory cortex (25%) Ventral horn lesion – C7/8

flaccid paralysis Corticospinal tract lesion

spastic paralysis Conscious proprioception and exteroception Gyrus postcentralis (discriminative touch): dorsal column - medial lemniscal pathway

Nucleus ventr. Lemniscus medialis posterolat. Nucleus ruber Nucleus ventr. posteromed. Substantia nigra

Ganglion trigeminale

Lemniscus med.

Nucl. n. trigemini

Nucleus gracilis

Dorsal root ganglion Nucleus cuneatus Dorsal column syndrome (Th10)

hypesthesia sensory ataxia Exteroception (pain, temperature): Gyrus postcentralis spinothalamic pathway

Thalamus (VPLN)

Formatio reticularis

Spinal lemniscus

Tractus spinothalamicus lateralis (LSTT) Dorsal horn syndrome (C5-C8)

analgesia thermanaesthesia Unconscious proprioception: spinocerebellar and cuneocerebellar tracts

Vermis, Zona intermedia Pedunculus cerebellaris superior

Tractus spinocerebellaris anterior Tractus spinocerebellaris posterior Tractus cuneocerebellaris Brain Model White matter Granule cell layer

Fissura cerebelli Arbor vitae

Nucl. globosus

Nucl. fastigii

Nucl. emboliformis

Nucl. dentatus

Folia cerebelli

Molecular layer

Caput nucl. caudati Pedunculi cerebri

Capsula interna Nucl. ruber crus anterius

Putamen

Pars sublentiformis

Pars retrolentiformis Nucl. n. III

Aquaeduct Substantia nigra pars compacta Dopamine

Striatum Frontal lobe

Substantia nigra

VTA (Ventral Tegmental Area) week 8 Lateral ventricle Epithalamus Epiphysis and Commissura posterior Plexus of lateral ventricle Thalamus dorsalis Specific and unspecific nuclei, Plexus of III. ventricle Metathalamus (Corpora geniculata)

Ganglionic eminence Subthalamus Globus pallidus Nucl. subthalamicus Hypothalamus Hypophysis Corpora mamillaria

Nucleus caudatus adult Corpus callosum

Thalamus dorsalis Fornix

Putamen Capsula interna

Globus pallidus III. ventricle

Tractus opticus Hypothalamus Hippocampus Lateral ventricle

Fornix

C.c.

Thalamus

Caudate nucleus Hippocampus

Claustrum Caudate nucleus * * * * * * Internal capsule * *

III. V. * Fornix Archi- and Paleocortex - 'Limbic System' Limbic structures

Commissura fornicis

Genu corporis callosi Splenium corp. callosi

Nucl. anterior thalami Corpus fornicis

Columna fornicis

Corpora mammillaria Crus fornicis

Fimbria hippocampi Chiasma opticum

Gyrus dentatus Infundibulum

Hypophysis Pes hippocampi Cornu ammonis Pons C.c.

* * * Cajal Acetylcholine

Neocortex Thalamus

Medial septal nuclei Basal nucleus of Meynert

Ponto-mesencephalo- tegmental complex Neocortex cerebri I

II

III

IV

V

VI

white matter Brodmann Areas

Quantitative neuroanatomy of the neocortex - comparative aspects

• 50,000–100,000 neurons under 1 mm2 cortical surface (primates have higher numbers in the visual cortex) • Cortical thickness varies (2–4 mm) and is highest in humans • 100,000,000 cortical minicolumns with up to 110 neurons each • Cortical neurons packed at high density: ~100,000/mm3 (mouse), humans (24,000/mm3), rats (55,000/mm3), and only 6,000/mm3 in elephants

Terrestrial brain Elephant Human Rat Brain weight (g) 4800 1300 2 Neocortex (mm2) 630,000 250,000 600 Neuron density (/mm3) 6000 24,000 55,000 Neuron number 11 billion 20 billion 0.02 billion

• Each neuron contacts 500 other neurons on average; synaptic density remarkably similar at around 1 billion synapses per mm3; 80% of cortical neurons are excitatory and 20% are inhibitory; average number of synapses per neuron = 8000 • Dependent on cortical thickness axonal length is appr. 4 km/mm3 and dendritic length is appr. 0.4 km/mm3

Thank you for your attention!