09 Control and Coordination - part 10 - Autonomic Nervous System (ANS)

 

09 Control and Coordination - part 10 - Autonomic Nervous System (ANS)

Autonomic Nervous System (ANS) :

  • Transmits impulses from CNS to the involuntary organs and smooth muscles of the body.
  • Consists of a special set of peripheral nerves that regulate the activities of involuntary organs like cardiac muscles, smooth muscles, glands etc. 
  • Impulses are conducted from the CNS by an axon that synapses with an autonomous ganglion. It is preganglionic neuron. 
  • The second neuron in this ganglionic pathway has an axon that extends from the autonomic ganglion to an effector organ and is known as postganglionic neuron.
  • Autonomic nervous system consists of - 
  1. Sympathetic nervous system and 
  2. Parasympathetic nervous system.

1.Sympathetic Nervous System (SNS):
  • Also called thoraco-lumbar outflow. 
  • Originates in the thoracic and lumbar region of spinal cord (T1 to L3).
  • Consists of 22 pairs of sympathetic ganglia which lie on a pair of sympathetic cords on lateral sides of the spinal cord.
  • Pre-ganglionic nerve fibres are short and post ganglionic nerve fibres are long.
  • Adrenaline and Noradrenaline is produced at the terminal ends of postganglionic nerve fibres at the effector organ, hence it is also called Adrenergic fibres. 
  • Controls body activities during emergencies (fight or flight response). 
  • Has excitatory and stimulating effect on most organs of the body except in the digestive and the excretory organ.
2. Parasympathetic Nervous System :
  • Also called cranio-sacral outflow. 
  • Consists of the branches from -  
  1. Cranial (III, VII, IX, X) nerves
  2. Sacral (II, III) and 
  3. Spinal (IV) nerves. I
  • Consists of ganglia which are very close or within the wall of the effector organs. 
  • Pre-ganglionic nerves are long and post-ganglionic nerves are short. 
  • Acetylcholine is produced at the terminal end of postganglionic nerve at the effector organ, hence these are also called cholinergic fibres.
  • Antagonistic to sympathetic nervous system. 
  • It brings back to normal, all activities which are stimulated by the sympathetic system. Hence it is also called housekeeping system. 
  • Has an inhibitory effect on most organs. 
  • However, the activities like those associated with digestion, peristalsis and micturition, which are inhibited by sympathetic system are thus accelerated by the parasympathetic system.
  • The answers to all these questions are the presence of a sensory system in our body. 
  • Itconsists of simple to complex structures called sensory receptors.

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