Autonomic nervous system

• What do afferent fibres do?

  Bring information into the brain
• What is the function of efferent fibres?

  Take information away from the brain
• What does the autonomic nervous system control?

  Smooth muscle, cardiac muscle, glands, adipose tissue
• What type of muscle do somatic motor neurons control?

  Skeletal muscle
• What are the two branches of the autonomic nervous system?

  • Sympathetic (fight or flight)
  • Parasympathetic (rest & digest)
• What is the role of the autonomic nervous system in homeostasis?

  It maintains homeostasis with the endocrine system
• What physiological functions does the autonomic nervous system regulate?

  • Contraction and relaxation of smooth muscle
  • Heartbeat
  • Exocrine and endocrine secretions
  • Energy metabolism
• How do sympathetic and parasympathetic systems affect the heart?

  • Sympathetic: Increases rate and force of contraction
  • Parasympathetic: Lowers heart rate
• What are the effects of sympathetic and parasympathetic systems on the pancreas?

  • Sympathetic: Decreases insulin secretion
  • Parasympathetic: Increases insulin secretion
• How do sympathetic and parasympathetic systems affect the eye?

  • Sympathetic: Dilates pupil
  • Parasympathetic: Constricts pupil
• What are the effects of sympathetic and parasympathetic systems on the gastrointestinal tract?

  • Sympathetic: Decreases motility and secretion
  • Parasympathetic: Increases motility and secretion
• What is meant by antagonistic control in the autonomic nervous system?

  Branches have opposing effects on target tissue
• How can heart rate be increased?

  Stimulate sympathetic or inhibit parasympathetic
• What is tonic control in the autonomic nervous system?

  Variable response based on output level
• Why do different tissues have variable responses in the autonomic nervous system?

  Due to different receptor populations
• What are the components of the autonomic nervous system's neuron structure?

  • Preganglionic neuron: Cell body in CNS, extends to ganglion
  • Postganglionic neuron: Arises from ganglia, supplies tissues
• What is the main neurotransmitter in autonomic ganglia?

  Acetylcholine
• What receptors does acetylcholine act on in autonomic ganglia?

  Nicotinic ACh receptors
• What are the characteristics of parasympathetic pathways?


  • Originate from brain stem and sacral region
  • Ganglia near target organs
  • Neurotransmitter is ACh
  • Responses mediated by muscarinic ACh receptors
• What are the characteristics of sympathetic pathways?

  • Originate in thoracic and lumbar regions
  • Ganglia close to spinal cord
  • Neurotransmitter is usually norepinephrine
  • Responses mediated by alpha and beta adrenoreceptors
• What does the adrenal medulla secrete?

  Adrenaline
• What are non-adrenergic, non-cholinergic (NANC) neurons?

  Neurons that secrete alternative transmitters
• How is acetylcholine synthesized and removed?

  • Synthesized from choline and acetyl CoA
  • Broken down by acetylcholinesterase
  • Choline is recycled back into axon terminal
• What is the process of noradrenaline release?

  1. Action potential arrives
  2. Ca2+ channels open
  3. NE is released and binds to receptors
  4. NE is removed by uptake and metabolism
• What are the uses of drugs that modulate the autonomic nervous system?

  • Treat high blood pressure
  • Manage cardiac arrhythmias
  • Control asthma
  • Address incontinence
  • Treat glaucoma
  • Alleviate depression