10.2 Neurones

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10.2 Neurones

  • A Cell body – contains a nucleus, large amounts of rough endoplasmic reticulum. Associated with the production of proteins and neurotransmitters.  
  • Dendron’s –small extensions of the cell body, subdivide into smaller branched fibres called dendrites. Carry nerve impulses towards the cell body.
  • - Axon – a single long fibre that carries nerve impulses away from the cell body. 
  • Schwann cells – Surround the axon, protect it, provide electrical information. They carry out phagocytosis (the removal of cell debris) and play a part in nerve regeneration. Wrap themselves around the axon many times, so layers of membranes build up around it. 
  • Myelin sheath – which forms a covering to the axon and is made up of the membranes of the Schwann cells. These membranes are rich in a lipid known as myelin. Myelinated neurones transmit nerve impulses faster than unmyelinated.
  • nodes of ranvier – gaps between adjacent schwann cells where there is no myelin sheath
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Picture

(http://www.jtaqld.com/neuron.jpg)

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Neurones can be classified according to their func

  • Sensory neurones transmit nerve impulses from a receptor to an intermediate or motor neurone. They have one dendron that carries the impulse towards the cell body and one axon that carries the impulse towards the cell body and one axon that carries it away from the cell body. 
  • Motor Neurones transmit nerve impulses from an intermediate or sensory neurone to an effector , such as a gland or muscle. They have a long axon and many short dendrites. 
  • Intermediate neurones transmit impulses between neurone, for exmaple, from sensory to motor neurones. They have numerous short processes. 
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Motor Neurone

(http://www.dmacc.edu/instructors/rbwollaston/Nervous_system/motor_neuron.gif)

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Sensory Neurone

(http://image.wistatutor.com/content/feed/u504/Sensory%20neuron.jpg)

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intermediate neurone

(http://pespmc1.vub.ac.be/POS/turchFigs/IMG.FIG1.6.GIF)

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