Neuroanatomy - Chapter 1

Neuroanatomy - Chapter 1

1. DEFINITIONS

   • Rostral
     • Towards the head end
   • Caudal
     • Tail end
   • Dorsal
     • back
   • Ventral
     • Belly
   • CNS
     • brain and spinal cord
   • PNS
     • cranial and spinal nerves and their ramifications
   • Somatic NS
     • neurons concerned with detecting changes in external environment or with control of movement
   • Autonomic NS
     • Neurons that detect change in and control activity of viscera
       • sympathetic
       • Parasympathetic
   • Afferent neurons
     • nerve cells carrying info from peripheral receptors to CNS
       • If info reaches consciousness, they are also called SENSORY NEURONS
   • Efferent neurons
     • carry impulses away from CNS
       • if they innervate skeletal mUscles to cause movement they are also called MOTOR NEURONS
   • Grey matter
     • contains nerve cell bodies
   • White matter
     • contains mostly nerve processes (axons)
   • Nuclei
     • Clusters of cell bodies with similar functions
   • Tracts/ Pathways
     • Nerve processes sharing common connections and functions following the same course
   • Neurulation
     • process of formation of embryonic NS
   • Brain Stem
     • medulla, pons and midbrain

2. Development of CNS

   • 2nd week 3 germ cells become established
     • 1) Ectoderm
       • gives rise to skin and NS
     • 2) Mesoderm
       • forms skeletal, muscular and connective tissue
     • 3) Endoderm
       • forms alimentary, respiratory and genitourinary tracts
   • 3rd week - dorsal midline ECTODERM undergoes thickening
     • forms neural plate
       • lateral margins of neural plate elevate =
         • neural folds
           • on either side of a longitudinal midline depression =
             • neural groove
           • become apposed and fuse together, sealing neural groove
             • neural tube
               • completed by middle of 4th week of development
           • some cells from neural folds become separated = form groups =
             • neural crests
   • 5th week, 3 primary brain vesicles can be identidied
     • 1) PROSCENCEPHALON
       • forebrain/ cerebrum
     • 2) MESENCEPHALON
       • Midbrain
     • 3) RHOMBENCEPHALON
       • hindbrain
       • Medulla oblongata
     • 7th week further differentiation distinguishes 5 secondary brain vesicles
       • 1) PROSENCEPHALON
         • divides into
           • TELENCEPHALON
             • divides into
               • 2 cerebral hemispheres
                 • Outer layer of grey matter
                   • cerebral cortex
                 • inner mass of white matter
                   • within which various groups of nuclei lie
                     • e.g. CORPUS STRIATUM
           • DIENCEPHALON
             • consists largely of
               • thalamus
         • (CEREBRUM)
       • 2) MESENCEPHALON
       • 3) RHOMBENCEPHALON
         • divides into
           • METENCEPHALON
             • Develops into
               • PONS and overlying CEREBELLUM
           • MYELENCEPHALON
             • Forms
               • MEDULLA OBLONGATA

3. Overview of Anatomy of CNS

   • Coverings and Blood Supply
     • MENINGES
       • 1) Dura Matter
         • outermost
           • surrounds brain and spinal cord like a loose-fitting bag
         • 2 sheets
           • FALX CEREBRI
             • between 2 cerebral hemispheres
           • TENTORIUM CEREBELLI
             • beneath occipital lobes of cerebral hemispheres and above cerebellum
           • fused together except in certain locations where they become separated to form spaces
             • DURAL VENOUS SINUSES
               • channels for venous drainage of brain
         • SUBDURAL SPACE in between
       • 3 layers of membrane ensheating CNS
       • 2) Arachnoid Matter
         • between both is SUBARACHNOID SPACE
           • CSF circulates through it
       • 3) Pia Matter
         • firmly adherent to surface of brain and spinal cord, following their contours
       • Supplied by no. of vessels
         • MIDDLE MENINGEAL ARTERY
           • Most significant, between skull and dura
     • brain's arterial supply is via
       • Internal Carotid
         • Anastomose to form
           • CIRCLE OF WILLIS
             • (Circulus arteriosus)
             • on base of brain
       • Vertebral arteries
     • spinal cord is supplied by vessels arising from
       • vertebral arteries reinforced by RADICULAR ARTERIES

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