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visceral effectors
smooth muscle, glands, cardiac muscle
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2 motor neurons in ANS
- Preganglionic neuron - in the CNS, myelinated axon
- Ganglionic neuron - peripheral ganglion outside CNS, unmyelinated postganglionc axon
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Arrangement of neurons
Preganglionic neuron's axon innervates ganglonic neuron outside CNS
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2 subdivisions of ANS with opposite effects
- Sympathetic - excitation, fright or fight
- Parasympathetic - inhibition , rest and digest
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Origin sites
- Parasympathetic - brain & sacral spinal cord
- Sympathetic - thoracolumbar spinal cord
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Length of fibers
Parasympathetic - long preganglionic, short postganglionic
Sympathetic - short pre, long post
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Location of ganglia
- Parasympathetic - near/in visceral effectors
- Sympathetic - near spinal cord
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Neurotramsmitters
- 1. All preganglionic fibers - Acetylcholine Ach (stimulae)
- 2. Postganglionic parasympathetic - Ach (stimulate or inhibit)
- Postganglionic sympathetic - Norepinephrine NE (stimulate)
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Parasympathetic division
- 1. Preganglionic fibers run in oculomotor, facial, glossopharygeal, vagus nerves
- 2. Innervates structures in head, organs in thoraic and abdominalpelvic cavity
- 3. effects - specific, localized, only last a few seconds, conserve energy
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Functions of Parasympathetic division
- Relaxation, energy absorption, food processing
- e.g. Person relaxing after a meal
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General increase in nutrient content of blood
(fun: of parasympathetic system)
- 1. Constriction of pupils
- 2. Secretion by digestive glands
- 3. Secretion of hormones that promote nutrient absorption
- 4. smooth muscle activity along digestive tract
- 5. stimulation and coordination of defecation
- 6. contraction of urinary bladder (urination)
- 7. reduction of heart rate and force of contraction
- 8. sexual arousal and stimulation of sex glands
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Sympathetic division
- 1. Preganglionic neurion in lateral gray horns, axons in ventral root
- 2. Ganglionic neuron near vertebral column
- Paired chain ganglia - each side of spinal cord
- body wall, head, thoraic cavity (heart & lungs)
- 3 collateral ganglia - anterior of spinal cord
- abdominalpelvic cavity
- 2 adrenal ganglia - in adrenal medulla
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Ganglionic neurons and their target organs
Sympathetic chain ganglia (paired) - target visceral effectors in throaic cavity, head, body wall and limbs
Collateral ganglia (unpaired) - visceral effectors in abdominalpelvic cavity
Adrenal medullae (paired) - organs and systems throughout the body
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Functions of sympathetic division
- 1. Stimulates dilator muscles of eyes
- 2. Inhibit salivary and digestive gland secretion
- 3. stimulates copious sweating
- 4. stimulates medulla cells to secrete epinephrine and norepinephrine
- 5. stimulates contraction of arrector pili
- 6. increase heart rate and force of contraction
- 7. vasodilation of heart blood vessels
- 8. dilates brochioles
- 9. inhibits urination
- 10. decrease activity of glands and muscles of digestivge system
- 11. contract anal sphincter
- 12. stimulates liver to release glucose to blood
- 13. constricts most vessels and increase blood pressure
- 14. increase alretness
- 15. increase metabolic rate
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