Transcript Lecture 9
Chapter 9 The Autonomic Nervous System “Fight or Flight Response System” The Autonomic Nervous System Autonomic nervous system • Sympathetic nervous system • 1. neurotransmitter = • 2. secretes • 3. effects on physiology: – – – – a) b) c) d) Autonomic nervous system • Parasympathetic nervous system • • 1. Neurotransmitter = • • 2. effects on physiology – a) – b) – c) Neural Control of Involuntary Effectors • Autonomic nervous system (ANS): • Innervates _______ whose functions are not usually under voluntary control. • Effectors include _________ and _____________ and __________. • Effectors are part of visceral organs and blood vessels. Autonomic Control Centers of the Brain • • • • • 1. 2. 3. 4. 5. Hypothalamus Pituitary Mamillary Body Pons Medulla Autonomic Neurons BSE Visceral Effector Organs • Involuntary effectors are somewhat independent of their innervation. • _________________________________ • . • Example of this???? • Cardiac and many smooth muscles can ___________rhythmically in absence of nerve stimulation. Sympathetic Division (continued) Sympathetic and Parasympathetic Divisions • All fibers within S and P secrete 1 of 2 transmitter substances: 1. Acetylcholine – _______________ 2. Noerpinephrine - ________________ Sympathetic vs Parasympathetic Organ Sympathetic Parasympathetic Eye Dilated Constricted Heart Increased rate, increased force of contraction Decreased peristalsis Ejaculation Decreased rate, decreased force of contraction Increased peristalsis Erection Increase in glucose Increase in Lipolysis None Gut Penis Blood Fat cells None Effects on Major Organs Nasal, lacrimal, salivary, GIT Parasympathetic: Glands: ___________________ Sympathetic Glands: constricts blood vessels going to gland = _____________ quantity of secretion Sweat Glands Parasympathetic: ______________ Sympathetic: _________________ Adrenal Glands • Located above _____________ • Each adrenal is divided into 2 parts: • Cortex_____________ • Medulla________________ • Adrenal medulla secretes epinephrine (_____) and norepinephrine (_____) when stimulated by the _______________ • _______ is mainly secreted from nerve endings • _______ can be converted to Epi in adrenal medulla Parasympathetic Division •Preganglionic fibers originate in __________, medulla, pons; sacral levels of the spinal column. •Preganglionic fibers synapse in terminal ganglia located next to or within organs innervated. •Most parasympathetic fibers do not travel within spinal nerves. •Do not ____________ vessels, sweat glands, and arrector pili muscles. Parasympathetic Division (continued) • Vagus (X): • Innervates _________, ___________,___________, stomach, pancreas, liver, small intestine and upper half of the large intestine. • ________________ fibers from the sacral level innervate the lower half of large intestine, the rectum, urinary and reproductive systems. Sympathetic Effects • Fight or flight response. • Release of ___________________ from postganglionic fibers and ____________________ from adrenal medulla. • Mass activation prepares for intense activity. • Heart rate (HR) _____________ • Bronchioles _______________ • Blood [glucose] _________________. Parasympathetic Effects • Normally not activated as a whole. • Stimulation of separate parasympathetic nerves. • Release ACh as NT. • Relaxing effects: • __________________ HR. • _______________ visceral blood vessels. • ____________________ digestive activity. Adrenergic and Cholinergic Synaptic Transmission •ACh is NT for all preganglionic fibers of both sympathetic and _____________________ nervous systems. •Transmission at these synapses is termed cholinergic: •ACh is NT released by most postganglionic parasympathetic fibers at synapse with effector. •Axons of postganglionic neurons have numerous varicosities along the axon that contain NT. Adrenergic and Cholinergic Synaptic Transmission (continued) •NT released by most postganglionic _______________ nerve fibers is NE. •Epi, released by the adrenal medulla is synthesized from the same precursor as NE. •Collectively called ________________. Responses to Adrenergic Stimulation • Beta adrenergic receptors: • Produce their effects by stimulating production of cAMP. • NE binds to receptor. • G-protein dissociates into a subunit or bgcomplex. • Depending upon tissue, either a subunit or bgcomplex produces the effects. • Alpha subunit activates adenylate cyclase, producing cAMP. • cAMP activates protein kinase, opening ion channels. • ___________________ – parasympathetic postganglionic fibers = cholinergic • ___________________– sympathetic postganglionic fibers = adrenergic Responses to Adrenergic Stimulation (continued) • Alpha1 adrenergic receptors: • Produce their effects by the production of ___________________ • Epi binds to receptor. • Ca2+ binds to ____________________. • Calmodulin activates protein kinase, modifying enzyme action. • Alpha2 adrenergic receptors: • Located on ________________terminal. • Decreases release of ___________. ___________________________ feedback control. • Located on postsynaptic membrane. • When activated, produces vasoconstriction. Responses to Adrenergic Stimulation (continued) • Has both excitatory and inhibitory effects. • Responses due to different membrane receptor proteins. a1 : constricts __________smooth muscles. a2 : contraction of ____________muscle. b1 : ___________ HR and force of contraction. b2 : __________bronchial smooth muscles. b3: adipose tissue, function unknown. Responses to Cholinergic Stimulation • All somatic motor neurons, all preganglionic and most postganglionic parasympathetic neurons are cholinergic. • Release _____________ as NT. • Somatic motor neurons and all preganglionic autonomic neurons are excitatory. • Postganglionic axons, may be excitatory or inhibitory. • Muscarinic receptors: • __________ binds to receptor. • Requires the mediation of G-proteins. bg-complex affects opening or closing a channel, or activating enzymes. Responses to Cholinergic Stimulation (continued) •Nicotinic receptors (ligand-gated): •ACh binds to 2 nicotinic receptor binding sites. •Causes ion channel to open within the receptor protein. •Opens a _____________ channel. •Always _____________. Responses to Cholinergic Stimulation (continued) Other Autonomic NTs • Certain nonadrenergic, noncholinergic postganglionic autonomic axons produce their effects through other NTs. • _________. • _________. • NO. Organs With Dual Innervation • Most visceral organs receive dual innervation (innervation by both sympathetic and parasympathetic fibers). • Antagonistic effects: • Sympathetic and parasympathetic fibers innervate the same cells. • Actions counteract each other. • _______________________. • Complementary: • Sympathetic and parasympathetic stimulation produces similar effects. • _________________________________. • Cooperative: • Sympathetic and parasympathetic stimulation produce different effects that work together to produce desired effect. • _____________________. Organs Without Dual Innervation • Regulation achieved by increasing or decreasing firing rate. • Adrenal medulla, arrector pili muscle, sweat glands, and most blood vessels receive only sympathetic innervation. • _________________________________ Control of the ANS by Higher Brain Centers • Sensory input transmitted to brain centers that integrate information. • Can modify activity of preganglionic autonomic neurons. • Medulla: • Most directly controls activity of _____________ system. • Location of centers for control of cardiovascular, pulmonary, urinary, reproductive and digestive systems. • Hypothalamus: • _____________________________. • Cerebral cortex and limbic system: • Responsible for visceral responses that are characteristic of emotional states. Ractopamine • _______________________ agonist • Approved for improving growth in meat animals • _____________________ and feed conversion but do not affect feed intake in feedlot cattle. • Hogs -