The nervous system

The nervous system

1. Central Nervous system

   • The brain
     • Function
       • Speech
       • Movement
       • Balance
       • Memory
     • Anatomy
       • 4 paired lobes, the cerebellum & brain stem
       • Areas of socialisation with many interconnections
       • 6 layered estruture which is created by waves of migrating cells in the embreyo
   • Spinal cord
     • Relayes information
     • Cerebral spinal fluid
       • Is within brain ventricles and surrounds exterior of brain and spinal cord
       • Cushions the brain and provides a controlled fluid environment

2. Peripheral nervous system

   • Cranial nerves pass impulses to/ from the brain
     • MOTOR NEURONES convey impulses from the CNS to the body to initiate a response from the muscles or glands
   • Spinal Nerves pass impulses to/ from the spine
     • SENSORY NEURONES convey impulses to the central nervous system from sensory receptors
   • Myelination
     • Process of coating the axon of neutrons with fatty coating MYELIN; Associated with development of new skills
       • Myelin sheath has fat containing cells that increase speed of signals
     • Begins in brain stem & cerebellum before birth & completed in frontal cortex in late adolescence

3. Formation of the CNS

   • Neural tube cells differentiate into
     • The brain
     • Spinal Cord
   • Neural crest cells differentiate into
     • Neurons and glia of the peripheral sensory
     • Autonomic nervous system
     • Neuroendocrine cells
   • 1. Ectoderm cells rise up in two ridges with neural crest cells on either side
   • 2. Folding process and the two sides fuse and close like a zip producing fluid filled neural tube
   • 3. When completed the neural tube & neural crest cells are covered by epidermis

4. Brain Development

   • 3 primary sections of the brain
     • Forebrain
     • Midbrain
     • Hindbrain
   • Week 4&5: Three primary vesicles divide into 5 secondary vesicles
   • DAY22- Neural tube forms
   • DAY 28- Closure of Neuropores
   • Week 4- Early development of brain vesicles
   • WEEK 6- Major subdivisions of the brain present
   • WEEK 10& 18- Number of neutrons increase and don't divide

5. Postnatal CNS growth

   • Brain weight triples in first 4-5 years
   • Neurons continue to form synopsis & stabilise
   • Pathways Mature: emotions, speech, language & cognitive functions

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