Functions of the ANS

• Mediates output from the whole body except skeletal muscle
  • Output modulated by external and internal sensory input, often via reflexes
    • Reflexes: negative feedback loops within PNS and CNS
• Regulates functions essential to human health and life that do not require conscious effort e.g. contraction and relaxation of vascular and visceral smooth muscle, heartbeat, metabolism, immune system
• Training allows some conscious influence over some ANS reflexes

Basic organisation of the motor ANS

• Regulates essential physiological functions, helping to maintain homeostasis via complementary actions of the sympathetic and parasympathetic divisions

Sympathetic ANS

• ‘Fight or flight’
• Preganglionic neurones originate in the thoracolumbar region

Parasympathetic ANS

• ‘Rest and digest’
• Preganglionic neurons originate in the craniosacral region

Chemical transmission in the ANS

Sympathetic division

• Transmitter for preganglionic neurons - acetylcholine (ACh)
• Transmitter for postganglionic neurons - noradrenaline (NA)

Parasympathetic division

• Transmitter for preganglionic neurons - acetylcholine (ACh)
• Transmitter for postganglionic neurons - acetylcholine (ACh)

Other transmitters