Anatomy of the Central Nervous System: Part 1

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Anatomy of the Central Nervous SystemPart 1

• Lecture 10

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The Central Nervous System

• CNS
• Brain
• Spinal cord

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Peripheral Nervous System

• Somatic Nervous System - SNS
• Sensory Motor
• Autonomic Nervous System - ANS
• Sympathetic Division
• Parasympathetic Division
• Cranial Nerves - 12 Pair
• Spinal Nerves - 31 Pair

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Terminology

• Afferent - toward
• Sensory
• Efferent - away from
• Motor

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Terminology

• Dorsal - toward the back
• Ventral - toward the stomach
• Anterior Posterior
• Rostral Caudal

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In reference to the BRAIN
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Brainstem spinal cord
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Neural Axis
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Neural Axis
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Terminology

• Medial - toward the midline
• Lateral - away from the midline
• Ipsilateral - same side
• Contralateral - opposite side
• Decussate - crossover

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Planes

• Coronal - frontal
• cross-section - salami - front view
• Sagittal - side view
• hot-dog bun
• Horizontal - top view

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Coronal Section
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Horizontal Section
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Mid-sagittal Section
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Development of the Nervous System
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Embryological Origin

• Embryo has 3 layers
• endoderm ---gt internal organs
• mesoderm ---gt muscles skeleton
• ectoderm ---gt nervous system skin
• Neural plate (3 weeks)
• sheet of cells
• neural groove
• folds rostral to caudal ---gt tube

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Development of N.S.

• Neural tube
• CNS develops from walls
• as tube develops dorsal portion pinches off
  forms...
• Neural crest
• develops into all neurons of PNS
• Mesoderm
• somites ---gt vertebrae muscles

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Neural Tube Defects

• Neural tube fails to close
• Rostral failure
• anencephaly
• skull brain partially or totally absent
• perinatal mortality
• Encephalocele
• parts of brain protrude outside skull
• mental disability depends on extent

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Neural Tube Defects Spina Bifida

• Cleft spine
• Caudal neural tube fails to close
• Incidence
• Spina bifida occulta
• 40 of Americans
• Spina Bifida Manifesta
• 1 in a 1000 births
• myelomeningocele 96
• meningocele 4

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Neural Tube Defects Spina Bifida

• Myelomeningocele
• protruding cyst as with meningocele
• spinal cord / nerves in protruding sac
• Effects
• paralysis, incontinence, learning disabilities
• 70-90 also hydrocephalus
• can cause severe brain damage
• Repaired surgically

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Neural Tube Defects Spina Bifida

• Meningocele
• fluid-filled meningeal cyst
• protrudes through unfused vertebral arches
• SC/nerves not in sac
• repaired surgically
• less severe disability than myelomeningocele

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Neural Tube Defects Prevention

• Possible genetic component
• reoccurrence in families
• ethnic/racial relationship
• Folic Acid (Folate) Deficiency
• 50-70 of cases preventable
• CDC guidelines
• not planning pregnancy 400 mg/day
• planned pregnancy 4000 mg/day
• under direction of health care provider

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Stages of Cellular Activity

• 6 distinct stages
• 1. Neurogenesis
• mitosis
• nonneural cells
• neurons do not divide
• develop into neurons or glia
• glia produced throughout life

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Stages of Cellular Activity

• 2. Cell migration
• to specific brain locations
• along radial glia
• later along other neurons
• 3. Differentiation
• into specific neuron types
• by induction
• influenced by surrounding cells
• or cell-autonomous

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Stages of Cellular Activity

• 4. Synaptogenesis
• formation of synapses
• growth of axons dendrites
• growth cones
• 5. Neuronal cell death
• apoptosis programmed cell death
• 20-80 of neurons in a region
• genetically programmed
• lack of neurotrophic factors

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Stages of Cellular Activity

• 6. synaptic rearrangement
• elimination of synapse
• formation of new synapses
• dependent on neural activity

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Differentiation

• Specialization of structures
• 3 primary vesicles
• rostral end of tube
• develops into brain
• Prosencephalon ---gt forebrain
• Mesencephalon ---gt midbrain
• Rhombencephalon ---gt hindbrain

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Prosencephalon

• Secondary vesicles form separate
• optic ---gt retinas
• retina optic nerve part of brain
• not PNS
• telencephalic ---gt telencephalon
• remainder ---gt diencephalon

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Other Primary Vesicles

• Mesencephalic ---gt mesencephalon
• dorsal - tectum
• ventral - tegmentum
• tube - cerebral aqueduct
• Rhombencephalic
• rostral - metencephalon
• caudal - myelencephalon
• tube - 4th ventricle

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Telencephalon

• Cortical areas
• Fiber systems
• Landmarks
• Fissures /Sulci
• Lobes
• Gyri

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Superior surface
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Parietal
Frontal
Occipital
Temporal
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M1
S1
A1
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The Meninges

• Tough connective tissue
• Dura mater - tough outer layer
• Arachnoid membrane - soft middle layer
• Pia mater - soft inner layer, next to brain

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Subarachnoid space

• Gap between arachnoid membrane and pia mater
• Filled with CSF
• Brain floats in CSF

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The Meninges

• Dura mater
• Arachnoid membrane
• Subarachnoid space CSF
• Pia mater

Brain
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Ventricular System

• Another circulatory system for the brain
• 4 interconnected ventricles
• chambers
• Cerebral Spinal Fluid (CSF)
• manufactured in choroid plexus
• Hydrocephalus - blockage of CSF flow

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Ventricular System
Lateral Ventricles
L V
L V
Third Ventricle
3rd
Fourth Ventricle
4th