lecture 10

• Autonomic Nervous System


  • Ganglia
  • Synapses
  • Neurotransmitters

  
• Signal Transmission


  • Parasympathetic nervous system
  • Sympathetic nervous system

  
• Nervous System


  • Somatic
  • Autonomic
  • Enteric

  
• Somatic


  • Voluntary actions
  • Skeletal muscles
  • Movement, speech, etc.
• Autonomic


  • Involuntary actions
  • Smooth muscles, glands
  • Salivation, vessel constriction, etc.
• Autonomic Nervous System


  • Sympathetic System: Fight or flight
  • Parasympathetic System: Rest and digest

  
• Ganglia


  • Swelling of nerve fibre containing a cluster of nerve bodies
  • E.g. spinal ganglion: cluster of nerve bodies along spinal cord at dorsal and ventral roots of a spinal nerve
  • Function: carry nerve signals between PNS and CNS

  
• Synapses


  Meeting point / "junction" between two nerve cells where impulses are carried using neurotransmitters
• Neurotransmitters


  • Acetylcholine
  • Norepinephrine (noradrenaline)
• Acetylcholine


  • Binds to cholinergic receptors
  • Seen in preganglionic neurons
  • Nicotinic, muscarinin (M1-M5)
• Norepinephrine (noradrenaline)


  • Binds to adrenergic receptors
  • Postganglionic neurons
  • Also a stress hormone!
• Signal Transmission in the Autonomic NS


  Ganglionic synapses: Neurotransmitter: acetylcholine, All ganglionic receptors: nicotinic, Nicotinic receptors also found on skeletal muscle, Nicotinic modulation: Activation: fasciculation (twitch), Blockade: paralysis

  
• Parasympathetic Nervous System


  Major effector neurotransmitter: acetylcholine, Receptors: Muscarinic (subtypes: M1-M5), M1, M4, M5 = brain, M2 = heart (slows it down), M3 = most other locations involved in parasympathetic nervous system (blood vessels, lungs, salivary glands)

  
• Sympathetic Nervous System


  Sympathetic ganglia: paravertebral (close to vertebrae), Major effector transmitter: norepinephrine, Binds to adrenergic receptors, Alpha 1, Alpha 3, Beta 1, 2, 3, Exceptions: renal muscles (dopamine), sweat glands (acetylcholine), adrenal glands

  
• Adrenal Glands


  Innervated by sympathetic nervous system, Neurotransmitter: acetylcholine, Receptor: nicotinic (neuronal subtype), Amplifies sympathetic response by releasing Norepinephrine and Epinephrine when simulated, Fight or flight

  
• Sympathetic activation (PANIC!)


  Pupil diameter increases (dilate), More light let in, Accommodation (altered lens shape) not really involved, See further
• Parasympathetic activation (Don't panic!)


  Pupil diameter decreases (constricts), Ciliary muscles contract, Near vision improves
• Sympathetic activation


  Bronchodilation, Widen airways, makes breathing easier
• Parasympathetic activation


  Bronchoconstriction
• Sympathetic activation


  Beta 1 receptors, Increase heart rate
• Parasympathetic activation


  M2 receptors, Slow heart rate to normal sinus rhythm
• Sympathetic activation


  GI Blood flow: Vasoconstriction, Less blood flow, Sphincter muscles: Constriction, Slows transit/motility
• Parasympathetic activation


  GI Sphincter muscles: Relaxation, Motility increases
• Anticholinergic drugs = constipation, cholinergic excess = diarrhoea