Organisation And Development, Csf Notes

Lecture 2 & 3

Organisation and Development, CSF

• Organisation of NS

  • CNS

    • Brain- within skull

    • Spinal cord- within vertebral column

  • PNS

    • Cranial nerves- 12 pairs in periphery

    • Spinal nerves- 31 pairs in periphery

• Different types of cells and their components

  • Neuron

    • Specialised cell of NS that carries messages

  • Dendrites

    • Receive information

  • Astrocytes

    • Communicate with neurons and other cells

    • Have processes surround blood capillaries

  • Oligodendrocytes

    • Produce myelin

  • Ependymal cell

    • Associated with ventricles (fluid filled spaces)

    • Move CSF through ventricles

  • Microglial cells

    • Fight infections

• What is a nerve in the PNS?

  • Named and identifiable collection of thousands of neuronal axons bundled together

  • Nerves divide to smaller nerves but axons continuous

  • Some areas, 2 or more nerves fuse then divide to allow redistribution=PLEXUS

  • Specific regions there are clumps of neuronal cell bodies=GANGLIA

• Components of PNS

  • AFFERENT NEURONES

    • Sensory

    • Enter spinal cord through DORSAL ROOTS

    • Some are SOMATOSENSORY

    • Some are VISCEROSENSORY

  • EFFERENT NEURONES

    • Motorneurones

    • Leave spinal cord through VENTRAL ROOTS

    • Some are SOMATOMOTOR

    • Some are VISCEROMOTOR (aka ANS)

• Spinal nerves

  • Each vertebral level, pair of spinal nerves emerge

  • Each nerve consists of dorsal and ventral root

  • Primary afferent neurones in dorsal root have cell bodies in dorsal root ganglia

  • 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal (31 in total)

• ANS

  • 2 divisions SYMPATHETIC and PARASYMPATHETIC

  • Both have two neurone chain and ganglia

  • Cell bodies of pre-ganglionic neurones are in CNS

  • Post ganglionic neurones are in ganglia

  • Post ganglionic neurones innervate smooth muscle

  • Sympathetic

    • Originate between ventral and dorsal horn

    • Ganglia very close to spinal column

    • Thoracolumbar

    • ACh in Preganglionic in SNS; NA in post-ganglionic

  • Parasympathetic

    • Originate from dorsal motor vagal nucleus

    • Ganglia very close to/part of target organ

    • Craniosacral

    • Ach in pre & postganglionic

• Routes of sympathetic nerves

  • Run from spinal root to spinal nerve

  • Does a turn at the white ramus and goes into the sympathetic chain

    • Sympathetic chain runs length of spinal column

  • Some nerves synapse in chain and then go to viscera

  • Some go to pre-vertebral ganglia and synapse there before going to target

• Development of nervous system

  • Embryology of NS

    • 3^rd week

    • From ectodermal layer, develops from specialised part

    • Neural groove develops in midline

    • Neural cell proliferate and form neural tube

    • Neural tube forms adult spinal cord; at cephalic end swells & flexes to form brain

    • Time line

      • Lateral folding forms a NEURAL GROOVE and NEURAL FOLDS (specialised part of ectoderm growing up and over) on either side of it

      • Neural groove cells come away from ectoderm and form separate series of cells=NEURAL TUBE

        • Will give rise to everything in CNS

      • Neural crest cells will give rise to all PNS

    • CLINICAL CORRELATIONS

      • Anterior/Cranial Neuropore

        • Closes usually at D25

        • Failure to close=hole at top of the embryo where folds failed to fuse

        • Pores have to fuse & close for proper NS development

        • No brain at all or abnormal development

        • ANENCEPHALY

      • Posterior/Caudal Neuropore

        • Cord/Part of cords do not develop properly

        • Spina bifida

  • Embryology of the brain

    • Three primary brain vesicles

      • ...

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