Principles of Anatomy and Physiology: The Autonomic Nervous System PDF

Principles of Anatomy and Physiology Gerard Tortora and Bryan Derrickson Sixteenth Edition Chapter 15 The Autonomic Nervous System This slide deck contains animations. Please disable animations if they...

Principles of Anatomy and Physiology Gerard Tortora and Bryan Derrickson Sixteenth Edition Chapter 15 The Autonomic Nervous System This slide deck contains animations. Please disable animations if they cause issues with your device. Copyright ©2021 John Wiley & Sons, Inc. Introduction The purpose of this chapter is to: 1. Examine the structure and function of the autonomic nervous system (ANS) 2. Compare and contrast the somatic and ANS 3. Examine ANS neurotransmitters 4. Compare and contrast the sympathetic and parasympathetic nervous systems Copyright ©2021 John Wiley & Sons, 2 Inc. Comparison of Somatic and Autonomic Nervous Systems Copyright ©2021 John Wiley & Sons, 3 Inc. Comparison of Somatic and Autonomic Nervous Systems (1 of 6) The somatic nervous system includes sensory and motor neurons. Sensory neurons are related to touch, pain, temperature, and proprioception (sense of self position), sight, hearing, taste, smell and equilibrium. Motor neurons innervate skeletal muscles excitatory or inhibitory. Voluntary. The autonomic nervous system receives input from sensory receptors located in organs, blood Copyright ©2021 vessels, John Wiley & Sons, muscles 4 Inc. Comparison of Somatic and Autonomic Nervous Systems (2 of 6) The axon of a single, myelinated somatic motor neuron extends from the central nervous system to the skeletal muscle fiber it innervates Copyright ©2021 John Wiley & Sons, 5 Inc. Anatomy of Autonomic Motor Pathways (1 of 16) Item Somatic Nervous Autonomic Nervous System System Sensory From somatic senses Mainly from interoceptors; some from input and special senses. somatic senses and special senses. Control of Voluntary control Involuntary control from hypothalamus, motor from cerebral cortex, limbic system, brainstem, and spinal output with contributions cord; limited control from cerebral from corpus cortex. striatum, cerebellum, brainstem, and spinal cord. Motor One-neuron Usually two-neuron pathway: neuron pathway: Somatic Preganglionic neurons extending from pathway motor neurons CNS synapse with postganglionic extending from CNS neurons in autonomic ganglion, and synapse directly postganglionic neurons extending from with effector. ganglion synapse with visceral effector. Alternatively, preganglionic neurons may extend from CNS to synapse with chromaffin cells of adrenal medullae. Copyright ©2021 John Wiley & Sons, 6 Inc. Anatomy of Autonomic Motor Pathways (2 of 16) Item Somatic Autonomic Nervous System Nervous System Neurotr All somatic All sympathetic and ansmitte motor neurons parasympathetic preganglionic rs and release only neurons release ACh. Most hormone acetylcholine sympathetic postganglionic neurons s (ACh). release NE; those to most sweat glands release ACh. All parasympathetic postganglionic neurons release ACh. Chromaffin cells of suprarenal medullae release epinephrine and norepinephrine (NE). Effectors Skeletal muscle. Smooth muscle, cardiac muscle, and glands. Respons Contraction of Contraction or relaxation of smooth es skeletal muscle. muscle; increased or decreased rate and Copyright ©2021 force John Wileyof & contraction Sons, of cardiac 7 muscle; Inc. increased or decreased  Introduction to the ANS The ANS usually operates without conscious control, though centers in the hypothalamus and brain stem do provide regulation for ANS reflexes. Sensory receptors called interoceptors located in blood vessels, visceral organs, muscles, and the nervous system monitor conditions in the internal environment. Examples of interoceptors are chemoreceptors that monitor blood CO2 level and mechanoreceptors that detect the degree of stretch in the walls of organs or blood vessels.  ANS Motor Pathways Autonomic motor neurons regulate visceral activities by either increasing (exciting) or decreasing (inhibiting) ongoing activities in their effector tissues. Because autonomic responses cannot be consciously altered to any great degree, some autonomic responses are the basis for polygraph (“lie detector”) tests. However, practitioners of yoga and biofeedback techniques may learn how to regulate at least some of their autonomic activities through long practice. Comparison of Somatic and Autonomic Nervous Systems (3 of 6) Most autonomic motor pathways consist of two motor neurons in series. A preganglionic neuron has its cell body in the central nervous system and the axon extends to an autonomic ganglion. A postganglionic neuron has its unmyelinated axon extending from the ganglion to the effector Copyright ©2021 John Wiley & Sons, 10 Inc. Comparison of Somatic and Autonomic Nervous Systems (4 of 6) Effector Copyright ©2021 John Wiley & Sons, 11 Inc.  Divisions of the ANS Most body organs have dual ANS innervation; that is, they receive impulses from both sympathetic and parasympathetic neurons. Usually the nerve impulses from one division stimulate an organ, while impulses from the other division decrease activity. Comparison of Somatic and Autonomic Nervous Systems (6 of 6) The autonomic nervous system is divided into two divisions: The sympathetic nervous system is often referred to as the fight-or- flight division because its stimulation leads to increased alertness and metabolism to be ready for an emergency. The parasympathetic nervous system is referred to as the rest-and-digest division as its stimulation slows down most body activity. Copyright ©2021 John Wiley & Sons, 13 Inc. Anatomy of Autonomic Motor Pathways Copyright ©2021 John Wiley & Sons, 14 Inc. Comparison of Somatic and Autonomic Nervous Systems (5 of 6) Copyright ©2021 John Wiley & Sons, 15 Inc. Anatomy of Autonomic Motor Pathways (3 of 16) Each division of the autonomic nervous system has two motor neurons: The preganglionic (cell body in the brain or spinal cord) and the postganglionic (cell body and dendrites located in an autonomic ganglion where it synapses with preganglionic axons) Copyright ©2021 John Wiley & Sons, 16 Inc. Anatomy of Autonomic Motor Pathways (4 of 16) In the sympathetic division, the cell bodies of preganglionic neurons are in the lateral horns of the gray matter in the 12 thoracic and first 2 or 3 lumbar segments Copyright ©2021 John Wiley & Sons, 17 Inc. Anatomy of Autonomic Motor Pathways (5 of 16) A much faster response system then the parasympathetic system due to divergence. Copyright ©2021 John Wiley & Sons, 18 Inc. Anatomy of Autonomic Motor Pathways (6 of 16) In the parasympathetic division, cell bodies of the preganglionic neurons are in the nuclei of four cranial nerves (III, VII, IX and X) in the brain stem and in the lateral gray matter of sacral segments 2–4 of the spinal cord. 80% of the parasympathetic flow goes through the vagus nerve. Copyright ©2021 John Wiley & Sons, 19 Inc. Anatomy of Autonomic Motor Pathways (7 of 16) Copyright ©2021 John Wiley & Sons, 20 Inc. Anatomy of Autonomic Motor Pathways (8 of 16) There are two types of autonomic ganglia: o Sympathetic o Parasympathetic There are 2 major types of sympathetic ganglia: o Sympathetic trunk ganglia Lie in a vertical row on either side of the vertebral column o Prevertebral ganglia Lie anterior to ©2021 Copyright theInc. vertebral John Wiley & Sons, column and 21 Anatomy of Autonomic Motor Pathways (12 of 16) Copyright ©2021 John Wiley & Sons, 22 Inc. Anatomy of Autonomic Motor Pathways (10 of 16) Copyright ©2021 John Wiley & Sons, 23 Inc. Anatomy of Autonomic Motor Pathways (9 of 16) After axons of sympathetic preganglionic neurons enter sympathetic trunk ganglia, they may connect with postganglionic neurons in one of 4 ways. 1. An axon may synapse with postganglionic neurons in the first ganglion it reaches. 2. An axon may ascend or descend to a higher or lower ganglion before synapsing with postganglionic neurons. 3. An axon may continue, without synapsing, through the sympathetic trunk ganglion to end at a prevertebral ganglion and synapse with postganglionic neurons. 4. An axon may also pass, without synapsing, through the sympathetic trunk ganglion and a prevertebral ganglion and then extend to the adrenal medullae. Copyright ©2021 John Wiley & Sons, 24 Inc. Anatomy of Autonomic Motor Pathways (11 of 16) The abdomen and pelvis contain major autonomic plexuses which are often named after the artery along which they are distributed These include the celiac (solar) plexus, the superior mesenteric plexus, the inferior mesenteric plexus, the renal plexus and the hypogastric plexus Copyright ©2021 John Wiley & Sons, 25 Inc. The Sympathetic Division Major groups of sympathetic Anatomy of Autonomic Motor Pathways (13 of 16) Cell bodies of the sympathetic preganglionic neurons are part of the lateral gray horns of all thoracic segments and of the first two lumbar segments of the spinal cord The paired sympathetic trunk ganglia are anterior and lateral to the vertebral column o Usually, there are 2 cervical, 11 or 12 thoracic, 4 or 5 lumbar, 4 or 5 sacral sympathetic trunk Copyright ©2021ganglia and 1 coccygeal27 John Wiley & Sons, Inc.  Anatomy of Autonomic Motor Pathways (14 of 16) Cell bodies of the parasympathetic preganglionic neurons are located in nuclei in the brain stem and in the lateral gray matter of the 2nd through 4th sacral segments of the spinal cord Cranial parasympathetic outflow extends from the brain stem in 4 cranial nerves Sacral parasympathetic outflow extends from the 2nd through 4th sacral spinal nerves Copyright ©2021 John Wiley & Sons, 28 Inc. Anatomy of Autonomic Motor Pathways (15 of 16) Copyright ©2021 John Wiley & Sons, 29 Inc. Anatomy of Autonomic Motor Pathways (16 of 16) Anatomy Overview: Nervous System: Organization of the ANS Copyright ©2021 John Wiley & Sons, 30 Inc. ANS Neurotransmitters and Receptors Copyright ©2021 John Wiley & Sons, 31 Inc. ANS Neurotransmitters and Receptors (1 of 2) Based on the neurotransmitter they produce and release, autonomic neurons are considered as either cholinergic or adrenergic Cholinergic neurons release the neurotransmitter acetylcholine o Cholinergic receptors include nicotinic receptors and muscarinic receptors Adrenergic neurons release norepinephrine (noradrenalin) Copyright ©2021 John Wiley & Sons, 32 Inc. ANS Neurotransmitters and Receptors (2 of 2) Copyright ©2021 John Wiley & Sons, 33 Inc. Receptors of the ANS (1 of 6) Type of Major Locations Effects of Receptor Receptor Activation CHOLINERGI Integral proteins in C postsynaptic plasma membranes; activated by the neurotransmitter acetylcholine. Nicotinic Plasma membrane of Excitation → impulses in postganglionic sympathetic postganglionic neurons. and parasympathetic neurons. Nicotinic Chromaffin cells of Epinephrine and suprarenal medullae. norepinephrine secretion. Nicotinic Sarcolemma of skeletal Excitation → contraction. muscle fibers (motor end plate). Copyright ©2021 John Wiley & Sons, 34 Inc. Receptors of the ANS (2 of 6) Type of Major Locations Effects of Receptor Receptor Activation CHOLINERGI Integral proteins in C postsynaptic plasma membranes; activated by the neurotransmitter acetylcholine. Muscarinic Effectors innervated by In some receptors, excitation; parasympathetic in others, inhibition. postganglionic neurons. Muscarinic Sweat glands innervated by Increased sweating. cholinergic sympathetic postganglionic neurons. Muscarinic Skeletal muscle blood Inhibition → relaxation → vessels innervated by vasodilation. cholinergic sympathetic postganglionic neurons. Copyright ©2021 John Wiley & Sons, 35 Inc. Receptors of the ANS Don’t need to know just the applications of the concepts of the possible side effects. Type of Major Locations Effects of Receptor Receptor Activation ADRENERGIC Integral proteins in postsynaptic plasma membranes; activated by the neurotransmitter norepinephrine and the hormones norepinephrine and epinephrine. 𝞪1 Smooth muscle fibers in Excitation → contraction, blood vessels that serve which causes salivary glands, skin, mucosal vasoconstriction, dilation of membranes, kidneys, and pupil, and closing of abdominal viscera; radial sphincters. muscle in iris of eye; sphincter muscles of stomach and urinary bladder. 𝞪1 Salivary gland cells. Secretion of K+ and water. 𝞪1 Sweat glands on palms and Increased sweating. soles. Copyright ©2021 John Wiley & Sons, 36 Inc. Receptors of the ANS Don’t need to know just the applications of the concepts of the possible side effects. Type of Major Locations Effects of Receptor Receptor Activation ADRENERGIC Integral proteins in postsynaptic plasma membranes; activated by the neurotransmitter norepinephrine and the hormones norepinephrine and epinephrine. 𝞪2 Smooth muscle fibers in some Inhibition → relaxation → blood vessels. vasodilation. 𝞪2 Cells of pancreatic islets (beta Decreased insulin secretion. cells) that secrete the hormone insulin. 𝞪2 Pancreatic exocrine acinar Inhibition of digestive cells. enzyme secretion. 𝞪2 Platelets in blood. Aggregation to form platelet plug. Copyright ©2021 John Wiley & Sons, 37 Inc.  Beta blockers Beta blockers, also known as beta- adrenergic blocking agents, are medications that reduce blood pressure. Beta blockers work by blocking the effects of the hormone epinephrine (adrenaline). Beta blockers cause the heart to beat more slowly and with less force, which lowers blood pressure. Beta blockers also help widen veins and arteries to improve blood flow. i.e. propranolol Copyright ©2021 John Wiley & Sons, Inc. 38 Physiology of the ANS Copyright ©2021 John Wiley & Sons, 39 Inc.  Sympathetic vs. Parasympathetic (1 of 3) Comparison of Sympathetic and Parasympathetic Divisions of the ANS Characteristic Sympathetic Parasympathetic (Thoracolumbar) (Craniosacral) Distribution Wide regions of body: skin, Limited mainly to head and to sweat glands, arrector viscera of thorax, abdomen, muscles of the hair, adipose and pelvis; some blood tissue, smooth muscle of vessels. blood vessels. Location of preganglionic Lateral gray horns of spinal Nuclei of cranial nerves III, VII, neuron cell bodies and cord segments T1–L2. IX, and X and lateral gray site of outflow Axons of preganglionic matter of spinal cord neurons constitute segments S2–S4. Axons of thoracolumbar outflow. preganglionic neurons constitute craniosacral outflow. Associated ganglia Sympathetic trunk ganglia Parasympathetic ganglia. and prevertebral ganglia. Ganglia locations Close to CNS Copyright andJohn ©2021 distant Typically near or within wall of40 Wiley & Sons, from visceral effectors. Inc. visceral effectors. Sympathetic vs. Parasympathetic (2 of 3) Characteristi Sympathetic Parasympathetic c (Thoracolumbar) (Craniosacral) Axon length Preganglionic neurons Preganglionic neurons with and with short axons long axons usually divergence synapse with many synapse with four to five postganglionic neurons postganglionic neurons with long axons that with short axons that pass pass to many visceral to single visceral effector. effectors. White and Both present; white Neither present. gray communicating rami communicati contain myelinated ng rami preganglionic axons; gray communicating rami contain unmyelinated postganglionic axons. Copyright ©2021 John Wiley & Sons, 41 Inc. Sympathetic vs. Parasympathetic (3 of 3) Characteristi Sympathetic Parasympathetic c (Thoracolumbar) (Craniosacral) Neurotransmi Preganglionic neurons Preganglionic neurons tters release acetylcholine release ACh, which is (ACh), which is excitatory and stimulates excitatory and postganglionic neurons; stimulates postganglionic neurons postganglionic release ACh. neurons; most postganglionic neurons release norepinephrine (NE); postganglionic neurons that innervate most sweat glands and some blood vessels in skeletal muscle release ACh. Physiological Fight-or-flight Rest-and-digest activities. effects responses Copyright ©2021 John Wiley & Sons, 42 Inc. Autonomic Tone Autonomic tone is the balance between sympathetic and parasympathetic nervous system activity It is regulated by the hypothalamus Effects body organs differently When sympathetic input increases, parasympathetic input decreases and vice versa Copyright ©2021 John Wiley & Sons, 43 Inc.  Physiology of the ANS Sympathetic stimulation leads to secretion of norepinephrine by the adrenal glands, an increase in the rate and strength of the heartbeat, constriction of blood vessels of non- essential organs, dilation of vessels of essential organs (skeletal muscle and the cerebral cortex), an increase in the rate and depth of breathing, hepatic conversion of glycogen to glucose, and decrease in GI activity.  Physiology of the ANS SLUDD is as an acronym used to describe the responses of the parasympathetic nervous system: Salivation (increased) Lacrimation (increased) Urination (increased) Digestion (increased) Defecation (increased) … and 3 decreases (in the rate and force of the heart beat, airway size and rate of breathing, and pupil size) Integration and Control of Autonomic Functions Copyright ©2021 John Wiley & Sons, 46 Inc. Integration and Control Functions such as heart rate and force of ventricular contraction, blood pressure and blood vessel diameter are controlled by autonomic reflexes that occur when nerve impulses pass through an autonomic reflex arc The reflex arc is composed of a receptor, a sensory neuron, an integrating center, motor neurons and an effector Copyright ©2021 John Wiley & Sons, 47 Inc. The Stress Response (2 of 2) Parasympatheti c NS Salivation Lacrimation Urination Defecation digestion Copyright ©2021 John Wiley & Sons, 48 Inc. The Nervous System and Homeostasis (1 of 2) Copyright ©2021 John Wiley & Sons, 49 Inc. The Nervous System and Homeostasis (2 of 2) Copyright ©2021 John Wiley & Sons, 50 Inc.  Raynaud Phenomenon o Occurs due to excessive sympathetic stimulation of smooth muscle in arterioles of digits. o Vasoconstriction leads to numbness and ischemia in digits. Copyright ©2021 John Wiley & Sons, 51 Inc. Copyright ©2021 John Wiley & Sons, 52 Inc.