Cells of the nervous system, neurotransmitters (3.4)

• Nerve cells


  Also called neurons, they carry an electrical message or impulse when stimulated
• Nerve cells


  • They are adapted to carry electrical impulses from one place to another
  • They feature an axon - a single nerve fibre that carries nerve impulses away from a cell body which is insulated by a myelin sheath
  • They feature dendrites - branched nerve fibres which receive nerve impulses and pass them towards a cell body
• Axon


  The long part of a nerve cell along which the electrical signal quickly moves
• Dendrites


  Small extensions found on the end of dendrons that connect one neuron to another
• Myelin


  A substance made from protein and lipids (fat) that surrounds the axon of a nerve cell, insulating it and increasing the rate at which electrical signals travel through the nerve
• Myelination


  The process of myelin developing around the axon fibres, continuing from birth to adolescence
• Certain diseases (multiple sclerosis, poliomyelitis)


  Cause the myelin sheath to be destroyed, damaging motor neurons and resulting in loss of strength and co-ordination in the limbs
• Glial cells


  They maintain homeostasis, form myelin, and provide support and protection for neurons. They also remove debris by phagocytosis.
• Glial cells do not transmit nerve impulses