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Autonomic Nervous System

Autonomic Nervous System. Ch 15. The ANS and Visceral Sensory Neurons. Figure 15.1. Terms. Synapse – junction between 2 neurons that communicates the message from the presynaptic neuron to the postsynaptic neuron Ganglion ( pl. ganglia) – a cluster of neuronal cell bodies in the PNS

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Autonomic Nervous System

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  1. Autonomic Nervous System Ch 15

  2. The ANS and Visceral Sensory Neurons Figure 15.1

  3. Terms • Synapse – junction between 2 neurons that communicates the message from the presynaptic neuron to the postsynaptic neuron • Ganglion (pl. ganglia) – a cluster of neuronal cell bodies in the PNS • Preganglionic neuron – cell body lies within the CNS - its axon, the preganglionic fiber synapses with the 2nd motor neuron, the ganglionic neuron, in a peripheral autonomic ganglion • Postganglionic fiber (axon) of the ganglionic neuron extends to the visceral organs

  4. Anatomical Differences • Issue from different regions of the CNS • Sympathetic - aka the thoracolumbar division • Parasympathetic – aka the craniosacral division Figure 15.3

  5. Anatomical Differences • Length of postganglionic fibers: sympathetic are long and parasympathetic are short • Branching of axons: sympathetic axons are highly branched to influence many organs while parasympathetic axons have few branches so have a localized effect • Sympathetic release norepinephrine (adrenergic) • Parasympathetic release acetylcholine (cholinergic)

  6. Comparison of Somatic & Autonomic Nervous System

  7. Anatomical Differences Figure 15.4a

  8. Anatomical Differences Figure 15.4b

  9. Neurotransmitters • Cholinergic fibers release the neurotransmitter ACh • All ANS preganglionic axons • All parasympathetic postganglionic axons • Adrenergic fibers release the neurotransmitter NE • Most sympathetic postganglionic axons • Exceptions: sympathetic postganglionic fibers secrete ACh at sweat glands and some blood vessels in skeletal muscles

  10. Autonomic Nervous System • Parasympathetic and Sympathetic Nervous System: • A subdivision of the PNS • Not under conscious control • Controlled by medulla oblongata and hypothalamus • PNS supplies stimulation via motor nerves to smooth and cardiac muscle and to glands

  11. Autonomic Nervous System • Biofeedback: • Conscious control of ANS • Ex. Yoga, meditation • Monitoring devices useful for: • epilepsy • digestive problems • chronic headaches • high blood pressure • generalized stress • anxiety • insomnia

  12. Autonomic Nervous System • Sympathetic • Parasympathetic Work antagonistically Myelinated motor neuron Unmyelinated motor neuron CNS ganglion effector

  13. Sympathetic Division Neurotransmitter is norepinephrine “fight or flight” E= exercise, excitement, emergency, and embarrassment

  14. Sympathetic Division • Fight or flight adaptive effects include: • increased cardiac activity, increased blood pressure, dilation of skeletal muscle blood vessels • constriction of blood vessels in skin • dilation of pupil • inhibition of gut and urinary bladder contractions • increase in blood glucose and free fatty acid levels • dilation of bronchial smooth muscle   • secretion of viscous saliva • sweating • lower threshold for reticular formation activation • liver produces glucose to provide energy for muscle contraction.

  15. Parasympathetic Division neurotransmitter is acetylcholine D= digestion, defecation, diuresis (urinating) • Parasympathetic activation results in: • decreased cardiac activity • secretion of watery saliva and stimulation of GI secretions • contraction of urinary bladder • increased insulin and glucagon secretion • bronchiole constriction

  16. Sympathetic Ganglia • Sites of synapses between pre and postsympathetic ganglia • sympathetic trunk ganglia • located from base of skull to coccyx • prevertebral ganglia • innervates organs below the diaphragm

  17. Parasympathetic Ganglia • Site of synapses between pre and post parasympathetic ganglia • terminal ganglia • Located close to or within the wall of a visceral organ

  18. Sympathetic

  19. Parasympathetic

  20. Autonomic Plexuses in the Thorax, Abdomen & Pelvis

  21. Types of connections bwtn ganglia & postganglia neurons in the sympathetic division

  22. Autonomic Reflexes • Examples: • Digestion • Blood pressure • Defecation • Urination • Components of an Autonomic Reflex: • Receptor • Sensory neuron • Integration center • Motor neuron • Effector (smooth or cardiac muscle, or a gland)

  23. Autonomic Control Hypothalamus & Medulla Major control and integration center of the ANS Medulla oblongata

  24. Inquiry • What neurotransmitter is produces from the Somatic nervous system, Sympathetic, and Parasympathetic nervous system? • What effector organs are targeted from the ANS? • Where does sensory input for the ANS come from? • List the components of an autonomic reflex arc. • What part of the brain is the major control and integration center of the ANS? • What effect does the parasympathetic nervous system have on the digestive system? • What effect does the sympathetic nervous system have on the liver?

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