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The Autonomic Nervous System

The Autonomic Nervous System. What does the autonomic nervous system do?. Regulate the viscera- cardiac muscle, smooth muscle, glands, blood vessels Involuntary control Preganglionic and postganglionic neurons Sympathetic and parasympathetic branches. The peripheral nervous system.

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The Autonomic Nervous System

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  1. The Autonomic Nervous System

  2. What does the autonomic nervous system do? • Regulate the viscera- cardiac muscle, smooth muscle, glands, blood vessels • Involuntary control • Preganglionic and postganglionic neurons • Sympathetic and parasympathetic branches

  3. The peripheral nervous system

  4. Features of the sympathetic nervous system • Preganglionic ganglia are myelinated, postganglionic are not • Mass activation of most postganglionic neurons • Collateral ganglia in abdominal area • Adrenal glands are part of the system • Thoracolumbar system

  5. Parasympathetic system • Craniosacral origin • Parasympathetic ganglia are very near the effector organs • Do not travel within spinal nerves (sympathetic nerves do) • No parasympathetic stimulation of cutaneous effectors • Some cranial nerves do contain parasympathetic fibers

  6. The autonomic nervous system

  7. Vagus nerve provides much parasympathetic stimulation of internal organs

  8. “Fight or Flight” vs “Rest and Digest” • Sympathethic system acts all at once; parasympathetic does not • All preganglionic fibers release Ach • Postganglionic: sympathetic- adrenergic; • Parasympathetic- cholinergic • Review Table 9.4

  9. Adrenergic stimulation • Epinephrine and norepinephrine can be excitatory or inhibitory • Receptor proteins are the differences • All G-protein linked; vary in distribution and effect

  10. Distribution of α and β receptors • Blood flow will be increased to some organs and reduced to others • β1 receptors increase muscular contraction • See Table 9.5 for distribution

  11. Cholinergic (parasympathetic) stimulation

  12. Sympathetic and parasympathetic effects tend to be opposite

  13. …but not always • Examples: • Digestion • PNS increase production of saliva and digestive glands; SNS constricts blood flow to digestive systemthickens saliva • Urination reflex • PNS promotes bladder contracttion • SNS enhances micturition reflex

  14. Some organs have SNS stimulation only (think fight or flight) • Adrenal medulla • Arrector pili muscles • Sweat glands • Most blood vessels • Important for thermoregulation

  15. Reflexes don’t do all the work • Medulla • Vagus nerve delivers sensory input (heart, lungs, aorta, digestive tract) • Hypothalamus • Responsible for thermoregulation, thirst, hunger..organ systems controlled by ANS • Limbic system…and visceral reactions • Cerebellum, cerebrum-modulate visceral responses

  16. Summary • Autonomic nervous system originates in brain and spinal cord • SNS: thoracolumbar, “fight or flight,” adrenergic receptors • PNS: craniosacral, “rest and digest,” cholinergic receptors • Autonomic responses are also controlled by higher centers in medulla, hypothalamus, limbic system cerebellum, and cerebrum.

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