NEURON/ NERVE   PARTS OF NERVOUS SYSTEM: Brain Spinal cord Peripheral nerves NERVOUS SYSTEM The system that c...

NEURON AND ITS PART |FINDYOURSELF

July 25, 2019 4 Comments


NEURON/ NERVE




 PARTS OF NERVOUS SYSTEM:

  • Brain
  • Spinal cord
  • Peripheral nerves

NERVOUS SYSTEM

The system that control all of the activities of the body
It is made of:
  • The brain       
  • The spinal cord
  • The nerve
  • The senses

NERVOUS SYSTEM
1.          CENTRAL NERVOUS SYSTEM
·    Brain
·    Spinal cord
         
2.          Peripheral nervous system
·    Sensory output
·    Motor output

NEURON
It is a basic structural and functional unit of the nervous system.
It is a highly differentiated and specialized excitable tissue.
•      The Human NS contains 100 billion neurons.
•      The nerves allow you to react to a stimulus.
Functions
•      Reception of the stimulus
•      Generation of the nerve Impulse
•      Transmission of the nerve Impulse
Structure of the A Typical Neuron
•      A typical neuron thus has the following parts:
1.                      Soma or Nerve Cell body
2.                      Axon with the axon terminals
3.                      Dendrites
Nerve Cell Body
•      Nissl bodies
–   Are rough endoplasmic reticulum with ribosomes
–   Stained with basic dyes
–   Composed of RNA & polysomes.
–   Tigroid substance (due to striped appearance)
–   Not present in the axon
–   Synthesis of proteins
–   Dissolve & disappear if cell injured (nerve cut, injured, fatigued, poisoned)
•      Neurofibrils
–   Formed by clumping of neurotubules & neurofilaments
–   Delicate threads running from cytoplasm of the nerve cell body into the axon and the dendrite
–   Functions:
–   Neuronal microtubules transport substances from the cell body to the distal cell processes.
–   Neurofibrils give support and shape to the neuron.
Axon
•      Also called axis cylinder or nerve fiber.
•      Longest process
•      A single axon arises  from a cone-shaped area of the neuronal cell body called the axon hillock
•      Axon hillock & first 100 µm of axon (no myelin sheath) is called Initial segment.
•      Trigger zone: is the name given to the axon hillock & the initial segment. It is an area that shows high excitability and a nerve impulse is generated here.
AXON IS MADE UP OF:
•      Jelly-like semi fluid substance called Axoplasm
•      Plasma membrane called Axolemma
•      Mitochondria and ER
•      No Nissl granules so Does NOT synthesize proteins.
AXON ENDS IN:
Terminal Buttons (Synaptic knob or Bouton Terminaux)
–   Axon break up into no. of terminal branches called Telodendria or Terminal filaments
–   At their end is a small swelling called Terminal knob.
–   These knobs contain granules or vesicles with neurotransmitter substance
Dendrites
•      Short, tree-like, highly branched tapering processes of the nerve cell
•      Receive and then carry impulses to the cell body
•      Small knob-like projections called dendritic spines
•      Have all the components of the cell body 





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