Autonomic Nervous System

1. Autonomic Nervous System

2. I. Comparison between somatic and autonomic nervous system • A. Effectors differ • 1. somatic system • 2. ans • B. Number of neurons between CNS and effector • 1. somatic • 2. ans • C. Location of nerve cell bodies • 1. somatic • 2. ans • D. Ganglia present • 1. somatic • 2. ans

3. E. Nature of response • 1. Somatic • 2. Ans • F. Presence of myelin • 1. somatic • 2. ans • G. Transmitter substance • 1. somatic is acetycholine • 2. ans:acetycholine from preganglionic fiber, either acetycholine or norepinephrine from postganglionic fiber

4. Comparison between somatic and autonomic nervous systems

5. II. Structure of the ANS-Sympathetic Division • A. Location of preganglionic nerve cell bodies • B. Two ganglia in system • 1. sympathetic chain or paravertebral ganglia • 2. collateral ganglia • C. Relative length of fibers

6. D. Outflow from CNS • 1. Gray ramus communicans • 2. sympathetic nerves to thoracic organs • 3. splanchnic nerves • 4. special case of the adrenal medulla

7. III. Structure of the parasympathetic division • A. Location of the preganganglionic nerve cell bodies • B. Craniosacral division • C. Lengths of fibers • D. Location of ganglia • E. Terminal or intramural ganglia • F. Very little divergence in the parasympathetic division when compared to the sympathetic

8. IV. Physiology of ANS • A. Transmitter substances • 1. All presynaptic fibers-acetycholine • 2. postsynaptic fibers of para=acetycholine • 3. postsynaptic of sym=most are adrenergic but a few are cholinergic to sweat glands

9. B. Receptor sites in the ANS • 1. Cholinergic receptors • a. Bind acetycholine • b. Two categories-nicotinic and muscarinic • c. Nicotinic sites all postganglionic membranes and skeletal muscle-possess an excitatory affect • d. Muscarinic sites- membranes of effectors responding to acetycholine released from postganglionic fibers of ANS-response to binding of acetycholineto these receptors may be inhibitory or excitatory • e. Effects relatively short-lived because it is destroyed by cholinesterase

10. 2. Adrenergic receptor sites • a. Located on membranes of effectors innervated by sympathetic division • b. Respond to epinephrine or norepinephrine • c. May be excitatory or inhibitory depending on effector • d. These receptors can respond to ANS or to adrenalin released from the adrenal medulla • e. Sympathetic stimulations tend to be more widespread • f. Sympathetic reactions tend to be longer lasting because transmitter substance is not directly broken down but diffuses away

11. V. Generalizations about the ANS • A. Many organs possess dual innervation • 1. two divisions will have opposing effects • 2. if one is stimulatory, other is inhibitory • 3. parasympathetic is rest and recovery • 4. sympathetic produces the effects of “fight or flight”

12. B. Sympathetic division produces longer lasting and more widespread effects • 1. The adrenergic receptor sites of the sympathetic division can respond to adrenal gland secretions • 2. if adrenalin is circulating in the blood stream, disperses to many glands • 3. one sympathetic preganglionic fiber synapses with multiple postganglionic fibers travelling to many different effectors • 4. the transmitter substances of the sympathetic fibers degrades by diffusing from the receptor site

13. C. Blood vessel diameter is regulated solely by the sympathetic division of ANS • 1. always basal level of sympathetic activity • 2. if greater sympathetic activity, generally vasoconstriction • 3. less sympathetic activity, vasodilation • 4. generalizations don’t always hold when considering blood vessels • 5. during fight or flight • a. Blood vessels in skeletal muscle dilate • b. Blood vessels in digestive system constrict to limit flow