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Anatomy Lecture Notes Chapter 15 ANS = general visceral motor portion of PNS sympathetic "fight or flight" prepares body for emergencies and intense division muscular activity parasympathetic "rest and digest" maintains body, conserves and stores energy division both divisions innervate cardiac m., smooth m., and glands (dual innervation) divisions usually cause opposite effects in effector organs A. ANS pathway has 3 components 1. preganglionic neuron - CNS to ganglion 2. ganglion (autonomic motor) 3. postganglionic neuron - ganglion to effector B. anatomical comparison 1. origin (location of preganglionic neuron cell bodies) S: lateral gray horn, thoracic and lumbar spinal cord P: brain stem and sacral spinal cord Strong/Fall 2008 page 1 Anatomy Lecture Notes Chapter 15 2. relative length of pre- and postganglionic neurons sympathetic parasympathetic preganglionic postganglionic 3. location of ganglia a. sympathetic paravertebral (sympathetic chain) ganglia - chain lateral to spinal column prevertebral (collateral) ganglia - ventral body cavity b. parasympathetic terminal (intramural) ganglia in effector organs cranial ganglia 4. divergence of preganglionic neurons a. sympathetic - extensive b. parasympathetic - minimal Strong/Fall 2008 page 2 Anatomy Lecture Notes Chapter 15 C. neurotransmitters cholinergic neurons - acetylcholine (Ach) adrenergic neurons - norepinephrine (NE) preganglionic sympathetic parasympathetic * except in skeletal blood vessels and sweat glands postganglionic D. parasympathetic outflow 1. cranial nerves a. oculomotor preganglionic neurons in midbrain ganglion = ciliary ganglion postganglionic neurons innervate intrinsic muscles of eye: ciliary and iris b. facial nerve preganglionic neurons in pons ganglia = pterygo-palatine and submandibular postganglionic neurons innervate : submandibular & sublingual salivary glands lacrimal gland nasal mucus glands c. glossopharyngeal nerve preganglionic neurons in medulla oblongata ganglion = otic postganglionic neurons innervate parotid gland d. vagus nerve preganglionic neurons from medulla via plexuses ganglia = intramural postganglionic neurons innervate most visceral organs of thorax and abdomen 2. sacral preganglionic neurons in S2-S4 pelvic splanchnic nerves ganglia = intramural postganglionic neurons innervate pelvic organs Strong/Fall 2008 page 3 Anatomy Lecture Notes Chapter 15 E. sympathetic outflow 1. preganglionic neuron cell bodies in lateral gray horn of segments T1-L2 axons leave spinal nerve in white ramus 2. pathways of preganglionic neurons a. synapse with postganglionic neuron in paravertebral ganglion; return to spinal nerve in gray ramus same segment inferior or superior segment b. pass through paravertebral ganglia to synapse with postganglionic neuron in a prevertebral ganglion splanchnic nerves Strong/Fall 2008 page 4 Anatomy Lecture Notes Chapter 15 F. adrenal medulla specialized sympathetic ganglion chromaffin cells are modified postganglionic cells without axons secrete norepinephrine and epinephrine into circulation G. control of ANS 1. reticular formation contains vital reflex centers that control organs via autonomic nerves 2. hypothalamus integrates both ANS divisions and links ANS to limbic system 3. cerebral cortex can be used to indirectly and temporarily control some autonomic functions H. visceral sensory neurons general visceral sensory neurons monitor viscera for pain, temperature, chemicals, stretch neuron cell bodies are in dorsal root ganglia axons project to thalamus and cerebral cortex Strong/Fall 2008 page 5