Nervous systems

• The ANS is divided into the sympathetic nervous system and the parasympathetic nervous system
• Sympathetic nervous system:

  • generally has an excitatory effects on the body e.g. increasing heart rate and ventilation rate.
  • Most sympathetic neurones release noradrenaline as a neurotransmitter which has similar effects on target cells as the hormone adrenaline. It is released into the tissues from the sympathetic motor neurone endings.
  • All nerve pathways begin in the middle of the spinal cord from motor neurones
• Parasympathetic nervous system:

  • generally inhibitory effects on the body e.g. decreasing heart rate and ventilation rate.
  • Most parasympathetic neurones release acetylcholine as a neurotransmitter. It is released into the tissues from parasympathetic nerve endings
  • All nerve pathways begin in the brain, at the top of the spinal cord or the very base of the spinal cord
• The autonomic nervous system:

  • the ANS is part of the nervous system controlling "automatic" processes, so controls the functioning of internal organs without conscious intervention.
  • This includes heart rate (beating of cardiac muscle cells), ventilation rate, blood pressure (contraction of smooth muscle in arteries), digestion and temperature regulation
  • the hypothalamus is the main controlling region of the ANS and provides a link between the brain and endocrine systems via the pituitary gland.
  • The medulla oblongata contains many important centres of the ANS