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Autonomic Nervous System

Autonomic Nervous System. Chapter 14. Human Nervous System Divisions. Info in & out. Integration & Command. Comparing Somatic and Autonomic. Effectors Innervates skeletal muscle Innervates visceral organs and glands Efferent pathways Single axon = faster signal

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Autonomic Nervous System

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  1. Autonomic Nervous System Chapter 14

  2. Human Nervous System Divisions Info in & out Integration & Command

  3. Comparing Somaticand Autonomic • Effectors • Innervates skeletal muscle • Innervates visceral organs and glands • Efferent pathways • Single axon = faster signal • Two axons = slower signal • Target organ responses • Cholinergic (ACh) synapses exite • Cholinergic, epinephrine, or norepinephrine synapses  excite or inhibit

  4. Autonomic Nervous System • Stabilize internal environments • Adjustments from changes to sensory stimuli • Dual innervation • 2 divisions counter the effects of each other • Parasympathetic • Nonstressful situations (rest and digest) • Sympathetic • Emergency or threatening situations (fight or flight) • Rare in actuality • Antagonistic relationship with continuous adjustments by both • Anatomical characterizations • Origin: craniosacral or thoracolumbar regions • Length of fibers: long preganglionic, short post- or opposite • Location of ganglia: in effectors or close to spinal cord

  5. Parasympathetic Roles • D division (digest, defecate, diuresis) • Pupils constrict • Stimulates salivary, lacrimal, and pancreas glands • Decrease heart rate • Causes contraction and emptying of hollow organs: • Bladder, gallbladder, stomach, intestines (peristalsis) • Vasodilation of penis (erection) • No effect on blood vessels

  6. Sympathetic Roles • E division (exercise, excitement, emergency, embarrassment) • Dilates pupils • Inhibits secretion of glands • Stimulates sweating • Stimulates arrectorpili • Stimulates medulla of adrenal gland to secrete epi- and norepinephrine • Increases heart rate • Decreases digestive processes • Decreases urine output • Causes ejaculation • Stimulates glycogenolysis in liver (glucose release) • Blood vessel constriction/dilation and blood coagulation • Bronchiole dilation

  7. Craniosacral Division • CN III (oculomotor) • From midbrain  ciliary ganglia • CN VII (facial) • From pons pterygopalatine and submandibular ganglia • CN IX (glossopharyngeal) • From medulla  otic ganglia • CN X (90%) (vagus) • From medulla  cardiac, pulmonary, and celiac plexuses • S2 – S4 • Lateral gray spinal mater  pelvic splanchnic nerves into the inferior hypogastric plexus

  8. Thoracolumbar Division • Pre- from gray matter in lateral horns of T1 – L2 to sympathetic trunk via rami communicates • Synapse varies • W/ a postganglionic neuron w/i same ganglion(1) • Ascend/descend w/i sympathetic trunk to another ganglion (2) • Pass through ganglion w/o synapsing (collateral ganglia or adrenal medulla)(3)

  9. Trunk Ganglia • Post- enter rami via rami communicates • Superior cervical ganglion • Dilates pupils • Inhibit nasal and salivary secretions • Stimulates sweating, arrectorpili muscles, and vasodilation • Middle cervical ganglion • Heart and skin • Inferior cervical ganglion • Heart, aorta, bronchiole dilation, and esophageal sphincter constriction

  10. Collateral Ganglia • Pre- form splanchnic nerves which synapse w/ collateral ganglia • Post- from collateral ganglia to effectors • Greater splanchnic nerve • Celiac ganglia • Stomach, adrenal medulla, liver, kidney, and intestine • Lesser splanchnic nerve • Superior mesenteric (via celiac) • Small intestine • Lumbar splanchnic nerve • Inferior mesenteric ganglion • Large intestine • Hypogastric ganglion • Bladder, urethra, and genitalia

  11. ANS Neurotransmitters • Acetylcholine (cholinergic fibers) • All pre- and all parasympathetic post- • Nicotinic receptors (stimulatory) • Skeletal muscle, all ganglionic neurons, and adrenal medulla • Muscarinic receptors (stimulatory or inhibitory) • All parasymapthetic targets and some sympathetic organs • Norepinephrine (adrenergic fibers) • Most sympathetic post- • Alpha (generally stimulatory) • Beta (generally inhibitory)

  12. Select ANS Effecting Drugs • Atropine • Anticholinergic (blocks muscarinic receptors) • Prevent salivation, dilate pupils, and dry up respiratory secretions • Neostigmine • Anticholinesterase • Treat myasthenia gravis by preventing ACh degradation • Ephedrine • Stimulates alpha adrenergic receptors • Beta-blockers • Inhibit beta receptors • Reduce heart rate and arrhythmias w/o disrupting other sympathetic effects

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