Autonomic Nervous System PDF

(006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 OUTLINE Final common pathway...

(006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 OUTLINE Final common pathway linking the CNS to the skeletal muscle is I. INTRODUCTION TO AUTONOMIC NERVOUS SYSTEM the alpha motor neuron while on the autonomic nervous system, the A. Difference Between Somatic & Autonomic Nervous final common pathways are the sympathetic and parasympathetic System motor neurons B. Comparison Between Somatic & Nervous System C. Autonomic Nervous System D. Subdivisions of Autonomic Nervous System E. Video: Autonomic Nervous System – Introduction A. DIFFERENTIATION BETWEEN SOMATIC AND (Anatomy Zone) AUTONOMIC NERVOUS SYSTEM II. SYMPATHETIC DIVISION A. Sympathetic Division 1. SOMATIC (VOLUNTARY) B. Sympathetic Chain Ganglia C. Collateral Ganglia a. Consists of a single neuron between central nervous D. Specialized Neurons system and skeletal muscle cells(effector organ) E. Pathways of Sympathetic Division b. Innervates skeletal muscles F. Adrenal Medulla of the Adrenal Gland c. Can lead only to muscle contraction G. Summary H. Video 2. AUTONOMIC (INVOLUNTARY) III. PARASYMPATHETIC NERVOUS SYSTEM a. Has 2 neuron chain (connected by a synapse) between A. Parasympathetic Division central nervous system and effector organ B. Parasympathetic Outflow b. Innervates smooth & cardiac muscle, glands & GI neurons C. Organization & anatomy of the parasympathetic c. Can either be excitatory or inhibitory division D. Functions of the Parasympathetic Division E. Parasympathetic activation & Neurotransmitters F. Video IV. ANATOMICAL AND PHYSIOLOGICAL DIFFERENCES BETWEEN THE PARASYMPATHETIC AND SYMPATHETIC DIVISION Figure 2. Somatic Nervous System Neuron A. Origin B. Location of ganglia C. Relative length of axons D. Rami communicantes E. Degree of branching F. Functional role G. Neurotransmitters H. Video Figure 3. Autonomic Nervous System Neuron V. TEST YOUR KNOWLEDGE VI. REFERENCES VII. APPENDICES I. NERVOUS SYSTEM FIGURE 4. Somatic Nervous System Main neurotransmitter is acetylcholine Involve the ventral horn of the spinal cord that give rise to the ventral root and goes to the peripheral nerve which is myelinated and synapses in the neuromuscular junction with the skeletal muscle through the acetylcholine receptors Single neuron pathway Cholinergic Highly myelinated; Faster conduction Figure 1. Nervous System Page 1 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 e. Effectors Skeletal Muscles f. Responses Contraction of Skeletal Muscle g. Type of Nerve Fibers Alpha motor neuron is large diameter and rapidly conducting (highly myelinated) FIGURE 5. Autonomic Nervous System 2. AUTONOMIC NERVOUS SYSTEM Chain of two motor neuron a. Sensory Input Preganglionic axon/fiber synapses with the second motor Mostly, some somatic senses & special senses neuron which is the postganglionic neuron in a peripheral b. Control of Motor output ganglia (Cell bodies in PNS). Post ganglionic neuron INVOLUNTARY CONTROL, hypothalamus, limbic system, therefore will extend to the visceral or effector organ. brainstem limited from cerebral cortex Functionally, preganglionic neuron signals the c. Motor neuron pathway postganglionic neuron, then the postganglionic neuron will Two motor-neuron pathway stimulate the effector organs d. Neurotransmitters and Hormones Preganglionic neurons are thinly myelinated and has slow All PREGANGLIONIC fibers release ACETYLCHOLINE conduction; Postganglionic neurons are unmyelinated and POST GANGLIONIC fibers release different has even slower conduction. neurotransmitters incasein case of SYMPATHETIC and Autonomic ganglia are motor ganglia containing motor PARASYMPATHETIC neurons e. Effectors Smooth muscles, cardiac muscles & glands f. Responses B. COMPARISON BETWEEN SOMATIC AND Contraction & relaxation of smooth muscle, cardiac muscle, control of gland secretion AUTONOMIC NERVOUS SYSTEM g. Type of Nerve Fibers Pre-ganglionic fibers : B fibers (myelinated, small and slow conducting) Post-Ganglionic fibers: C fibers (unmyelinated, smaller and slower-conducting) C. AUTONOMIC NERVOUS SYSTEM Figure 5. Comparison of Somatic and Autonomic Nervous System 1. SOMATIC NERVOUS SYSTEM a. Sensory Input somatic & special senses (5 special senses) b. Control of Motor output VOLUNTARY CONTROL, cerebral cortex, basal ganglia, cerebellum, spinal cord c. Motor neuron pathway one-neuron pathway Figure 6. Role of the Autonomic Division in Homeostasis d. Neurotransmitters and Hormones All Somatic neuron secretes ACETYLCHOLINE (cholinergic) Page 2 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 Part of the Peripheral nervous system 2. PARASYMPATHETIC NERVOUS SYSTEM Responsible for regulating involuntary body functions - Such as heartbeat, blood flow, breathing and CRANIOSACRAL DIVISION digestion Rest and digest - A.k.a. VISCERAL or AUTONOMIC NERVOUS Concerned with conserving energy SYSTEM All preganglionic fibers release ACETYLCHOLINE. Function outside of our conscious awareness The effects are STIMULATORY. Postganglionic fibers release ACETYLCHOLINE but Makes routine adjustments in our body’s systems the effects CAN BE INHIBITORY. (homeostasis) Parasympathetic nervous system – Craniosacral division - Regulates body temperature - Coordinates cardiovascular, respiratory, digestive, excretory and reproductive functions 1. AUTONOMIC (SELF-GOVERNING) -operates in certain amount of independence Together with the endocrine system, control the internal environment of the body. Provides a fine discrete control over the functions of many organs and tissues including heart, smooth muscles, and exocrine glands. Functions outside of our conscious awareness (INVOLUNTARY) Makes routine adjustments in our body’s systems Regulates body temperature Coordinates cardiovascular, respiratory, digestive, excretory and reproductive. Afferent, connector and efferent neuron Divided into two parts, the Sympathetic and parasympathetic Rapid control Widespread (since one preganglionic axon may synapse with several postganglionic neurons) Contribution to homeostasis D. SUBDIVISION AUTONOMIC NERVOUS SYSTEM Balance between these divisions gives our system running smoothly 1. SYMPATHETIC NERVOUS SYSTEM Figure 7. Autonomic Innervation. THORACOLUMBAR DIVISION E. VIDEO Fight, flight or fright Activated during exercise, excitement and emergencies All preganglionic fibers release ACETYLCHOLINE. The effects are STIMULATORY. Most postganglionic fibers release NOREPINEPHRINE. The effects are STIMULATORY. Not all postganglionic fiber in the sympathetic division are ADRENERGIC: Those that INNERVATE the SWEAT GLANDS and BLOOD VESSELS in skeletal muscle are CHOLINERGIC. Sympathetic nervous system – Thoracolumbar division Page 3 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 II. SYMPATHETIC DIVISION A. SYMPATHETIC DIVISION “FIGHT OR FLIGHT” Larger of the 2 parts – more diverse compared to the parasympathetic Widely distributed throughout the body Innervates the heart and lungs, muscle if the blood vessels, hair follicles and the sweat glands, abdominopelvic viscera “PREPARE the body for emergency” Increase heart rate – to deliver more oxygen and blood to the skeletal muscle Pupillary dilation – let more light for clearer vision Bronchodilation – let more air for more oxygenation Liver releases more sugar into the blood to provide energy Arterioles of the skin and intestines are constricted – leads to cold skin, blood is being diverted to more vital organs, such as the brain Arterioles of the skeletal muscle are dilated Blood pressure is raised The hair is made to stand on end, and sweating occurs. Figure 8. Sympathetic Pathway These are the signs that the sympathetic division has been mobilized, that are response for any dangerous situation. THE SYMPATHETIC DIVISION: This means that non-vital organs, such as intestine or non-essential More complex than parasympathetic functions, are inhibited or temporarily stopped. Innervates more organs Supplies not only all visceral organs in the internal cavities 1. PREGANGLIONIC NEURONS but visceral structures in the superficial region of the body Thoraco-Lumbar Division - Sweat glands - Hair raising arrector pili muscles of the skin (Scared) between T1 and L2 - Smooth muscles in the walls of arteries and vein Cell bodies are in the lateral gray horns It has more ganglia compared to parasympathetic Axons enter the ventral roots - Sympathetic trunk ganglia (lateral to the vertebral 2. GANGLIONIC NEURONS (GANGLIA) column) a. SYMPATHETIC CHAIN GANGLIA (Paravertebral - Collateral Ganglia (anterior to the vertebral column) ganglia) Lateral to the vertebral column Control effectors in the body wall, head, neck, limbs, and thoracic cavity b. COLLATERAL GANGLIA (Prevertebral ganglia) Anterior to the vertebral column Neurons innervates effectors in the abdominopelvic cavity 3. SPECIALIZED NEURONS (Direct Innervation of the Adrenal Gland) neurons in the interior of the suprarenal gland Modified sympathetic ganglion in the suprarenal gland (Adrenal Gland) Neurons release neurotransmitters (Epinephrine and Norepinephrine) that act like hormones (adrenergic Rush) Figure 9. Sympathetic Division of Autonomic Nervous System Page 4 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 1. ANATOMY OF THE SYMPATHETIC GANGLIA B. SYMPATHETIC CHAIN GANGLIA (PARAVERTEBRAL GANGLIA) Each spinal nerve consists of: Preganglionic and postganglionic fibers - Control effectors in the body wall, head, neck, limbs, and There are: thoracic cavity 1. Cervical sympathetic chain ganglia 2. Thoracic sympathetic chain ganglia 3. Lumbar sympathetic chain ganglia 4. Sacral sympathetic chain ganglia 5. Coccygeal sympathetic chain ganglia Figure 10. Locations of Ganglia Figure 12. Autonomic Nerves, plexuses and Ganglia Figure 11. Sympathetic Chain Ganglia. Originates form the ventral horn cells, and enters ventral root then to the spinal nerve, it give rise to the white ramus comunicantes, which communicates with your ganglion. This preganglionic fibers, comunicates with the sympathetic ganglia and that it gives rise to the post ganglionic neuron which enters the gray ramus comunicantes, which will enters again in the spinal nerve to innervates the visceral effectors. Figure 13. Anatomic Division of Sympathetic Postganglionic Fibers Page 5 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 2. FUNCTION OF SYMPATHETIC CHAIN GANGLIA Neurons release neurotransmitters (Epinephrine and Reduction of circulation to the skin Norepinephrine) that act like hormones More circulation to skeletal muscles Stimulates more energy production by skeletal muscles 1. SUPRARENAL MEDULLAE Releases stored adipose Stimulation of arrector pili muscles Fibers pass through sympathetic chain and the Dilation of pupils Celiac ganglion without synapsing Increase heart rate Proceed to the suprarenal medulla Dilation of respiratory tubes Fibers then synapse on modified neurons that when stimulated will release neurotransmitters that act as - Neurons innervate effectors in the abdominopelvic cavity hormones: The collateral ganglia, or prevertebral ganglia, differ from the - Epinephrine and norepinephrine sympathetic trunk ganglia in at least three ways: 1. They are not paired and not segmentally arranged 2. They occur only in the abdomen and pelvis 3. They all lie anterior to the vertebral column (hence the name pre-vertebral) The main collateral ganglia - The Celiac - Superior mesenteric - Inferior mesenteric - Inferior hypogastric ganglia 3. COLLATERAL GANGLIA Reduction of flow of blood to the visceral organs Decrease in activity of the digestive organs Stimulation of the release of glucose from glycogen in the Figure 15. The Suprarenal Medullae liver Stimulates adipose cells to release energy reserves Relaxation of smooth muscle in the urinary bladder 2. FUNCTIONS OF THE SUPRAMEDULLA Causes ejaculation in males Increase alertness by activating the reticular activating system Increase cardiovascular and respiratory activity Increase muscle tone Increase the mobilization of energy reserves Increase release of lipids from adipose cells Increase breakdown of glycogen in liver 5. THREE PATHWAYS OF SYMPATHETIC DIVISION 1. SYNAPSE IN TRUNK GANGLION AT THE SAME LEVEL From the lateral horn, ventral horn goes to the ventral root to the spinal nerve, into the ventral ramus (which is the only involved Figure 14. Collateral Ganglia here) then to white ramus (white ramus are white because the nerve fibers are covered with white myelin) comunicantes and synapses with the neurons in the sympathethic ganglion, and it releases the post ganlionic neuron thru the gray ramus comunicates and then enters again in the spinal nerve and goes 4. SPECIALIZED NEURON to your effector organs Modified sympathetic ganglion in the suprarenal gland (Adrenal Gland) Page 6 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 Figure 16. Synapse in trunk ganglion at the same level 2. SYNAPSE IN THE TRUNK GANGLION AT A HIGHER OR LOWER LEVEL - The preganglionic axon ascends or descends in the sympathetic trunk to synapse in another trunk ganglion. The postganlionic fiber exits the sympathetic trunk via the gray ramus communicans at the level of the synapse. Figure 18.. Pass through sympathetic trunk in a collateral ganglion anterior to the vertebral column D.ADRENAL MEDULLA OF THE ADRENAL GLAND - The internal portion of this gland- the adrenal medulla- is a major organ of the sympathetic nervous system. - These neuron-derived cells secrete great quantities of two excitatory hormones into the blood of neaby capillaries during the fight-or-flight response - Hormones secreted are norepinephrine (the chemical secreted by other postganglionic sympathetic neurons as a neurotransmitter) and greater amounts of a related excitatory molecule called epinephrine (adrenaline) - A “surge of adrenaline” Figure 17. Synapse in trunk ganglion at a higher or lower level E.SUMMARY 3. PASS THROUGH SYMPATHETIC TRUNK IN A COLLATERAL GANGLION ANTERIOR TO THE ✓ consists of parallel chain on either side of the spinal cord VERTEBRAL COLUMN ✓ preganglionic fibers are short and extend from the spinal cord to the body organs ✓ the sympathetic division shows considerable divergence - The preganlionic axon passes through the sympathetic trunk, exits ✓ all preganglionic neurons release ACh/ most post ganlionic on a splanchnic nerve, and synapses in a collateral ganglion. neurons release norepinephrine - The postsynaptic fiber extends from the collateral ganglion to the visceral organ vio an autonomic nerve plexus. Page 7 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 post ganglionic neurons are near (terminal) the target organ or within (intramural) the target organ. Eg. Organs coming from the sacral division (s2-s4) B. PARASYMPATHETIC OUTFLOW 1. CRANIAL OUTFLOW -originates from the brainstem and innervates head, neck, thorax, and most of the abdomen CRANIAL NERVES: III: Oculomotor (Edinger-Westphal nucleus) VII: Facial (Superior salivatory nucleus & lacrimal nucleus) IX: Glossopharyngeal (Inferior salivatory nucleus) X: Vagus (Dorsal nucleus of vagus) Remember: 1973 2. SACRAL OUTFLOW -originates from S2, S3, S4 supplies the distal portion of digestive/pelvic organs Figure 19. The Adrenal Medulla - SACRAL OUTFLOW Sacral Spinal Cord S2, S3, S4 F.VIDEO C. ORGANIZATION & ANATOMY OF THE PARASYMPATHETIC DIVISION -preganglionic fibers leave the brain via: A. CRANIAL NERVE III To the intrinsic eye muscles, pupil and lens B. CRANIAL NERVE VII To the tear (Lacrimal) glands and salivary glands (submandibular/sublingual) C. CRANIAL NERVE IX To the parotid salivary glands D. CRANIAL NERVE X To the visceral organs of the thoracic cavity and abdominal cavity III. PARASYMPATHETIC DIVISION -preganglionic fibers leave the sacral region via: PELVIC NERVES : to the visceral organs in the inferior portion of the abdominopelvic cavity. A. PARASYMPATHETIC DIVISION Most ACTIVE when the body is at REST Concerned with conserving energy Direct vital “housekeeping” activities (digestion, elimination of feces and urine) “REST and DIGEST” Preganglionic neurons are in the brain stem and sacral segments S2-S4 Pre ganglionic neurons do not diverge as mucsh as the sympathetic division (SymphateticSympathetic division is much more diverse) - Therefore, the parasympathetic division is more localized and specific as compared to the sympathetic division Figure 20. Parasympathetic Division of Autonomic Nervous System Page 8 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 Most stimulations are short lived due to the immediate breakdown of Acetylcholine by ACETYLCHOLINESTERASE (within 2-3 msec, ACh is hydrolysed into acetic acid and choline by the enzyme (AChE, which is located on the surface of the nerve and receptor membrane. The choline is reabsorbed into the nerve ending and used again for synthesis of ACh). F. SUMMARY OF THE PARASYMPATHETIC DIVISION Involves CN III, CN VII, CN IX and CN X Involves sacral segments S2 to S4 All parasympathetic neurons are cholinergic Release of Ach stimulates nicotinic receptors on ganglionic neurons Release of Ach on neuroeffector junctions stimulates muscarinic receptors Figure 21. Autonomic Distribution of the Parasympathetic Output Sacral outflow emerges from segments s2-s4 continuing where the G. VIDEO vagus nerve ends, innervating the organs of the pelvis including: Distal parts of intestines Urinary bladder Uterus Ovaries Erectile tissues/external genitalia Parasympathetic effects therefore on these organs include: Digestion Stimulation of defacation Voiding of urine Erection III. ANATOMICAL AND PHYSIOLOGICAL DIFFERENCES BETWEEN THE PARASYMPATHETIC AND SYMPATHETIC D. FUNCTIONS OF THE PARASYMPATHETIC DIVISION DIVISION Pupil Constriction Secretion of digestive enzymes from digestive glands Increased smooth muscle activity of the digestive system Stimulation and coordination of defecation A. ORIGIN Contraction of the urinary bladder Constriction of respiratory passages SYMPATHETIC Reduced heart rate - Thoracolumbar outflow Sexual arousal - Lateral horn of the gray matter of Spinal cord segments T1-L2 PARASYMPATHETIC E. PARASYMPATHETIC ACTIVATION & - Craniosacral outflow NEUROTRANSMITTER RELEASE - Brain stem nuclei of CN 3, 7, 9 and 10 - Spinal cord segments S2-S4 All preganglionic and postganglionic fibers release Acetylcholine at their synapses and neuroeffector junctions Page 9 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 Figure 23. Autonomic Nervous System Differences D. RAMI COMMUNICANTES SYMPATHETIC - Gray and White Rami Communicantes - White contain Myelinated Preganglionic Axons - Gray contain Unmyelinated Postganglionic axons (nerve fibers are devoid of myelin) PARASYMPATHETIC - NONE Figure 22. Autonomic Innervation B. LOCATION OF GANGLIA SYMPATHETIC - Ganglia close to CNS - Alongside vertebral column (Sympathetic Trunk Ganglia) and anterior to Vertebral Column (Collateral Ganglia) PARASYMPATHETIC - Ganglia in (Intramural) or close to visceral organ serve Figure 24. Rami communicantes C. RELATIVE LENGTH OF PRE- AND POSTGANGLIONIC AXONS E. DEGREE OF BRANCHING SYMPATHETIC - Short preganglionic (Splanchic Nerves are exceptions) SYMPATHETIC - Long Postganglionic - Extensive - Branch Profusely - Visceral organs mobilize simultaneously during PARASYMPATHETIC Fight or Flight situation - Long Preganglionic - Short Postganglionic PARASYMPATHETIC - Minimal - DO NOT Branch Profusely - More localized reaction and more discreet Page 10 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 Figure 25. Degree of Branching F. FUNCTIONAL ROLE SYMPATHETIC Figure 26. Neurotransmitters - Prepares body to cope with emergencies and intense muscular activity - Fight or Flight response PARASYMPATHETIC TEST YOUR KNOWLEDGE - Maintenance functions - Conserves and stores energy 1. Which is not a part of parasympathetic origin? - Rest and Digest response a. Oculomotor b. Vagus c. Trigeminal G. NEUROTRANSMITTERS d. Facial SYMPATHETIC 2. Type of Nerve fiber in post-ganglionic fibers? - All preganglionic axons release Ach a. A - Most postganglionic axons release b. B Norepinephrine (Adrenergic Axons) - Postganglionic Axons to sweat glands and blood c. C vessels of skeletal muscles release Ach d. D - Neurotransmitter activity augmented by release of Adrenal Medullary Hormones (Epinephrine and 3. Neurotransmitter stimulating sweat glands and Norepinephrine) smooth muscle of small arteries? a. Dopamine PARASYMPATHETIC - All axons, preganglionic and postganglionic b. Norepinephrine release Ach (Cholinergic Axons) c. Acetylcholine d. Serotonin 4. Organophosphates causes inhibition of this enzyme resulting into prolonged contraction of muscle a. Monoamine oxidase b. Cyclooxygenase c. Acetylcholinesterase d. Glutamate dehydrogenase Page 11 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 5. Which is true of sympathetic division? a. It promotes conservation of energy and GIT smooth muscle contraction b. Originates from the sacral segments of spinal cord c. Releases acetylcholine to stimulate the salivatory glands d. Has special fibers synapsing with the chromaffin cells for Norepi release (S) Sympathetic or (P) Parasympathetic: 6. Bronchodilation: 7. Promotes Intestinal peristalsis: 8. Ejaculation: 9. Contraction of the arrector pili: 10. Cutaneous vasoconstriction: 11. Mydriasis 12. Contraction of the gallbladder 13. Salivation 14. Detrusion of the urinary bladder 15. Long post-ganglionic fiber: Answer: 1.C 2.C 3.C 4.C 5. D 6. S 7. P 8. S 9. S 10.S 11.S 12. S 13.P 14.P 15.S REFERENCES 1. PPT-Doc Allan Viado 2. Snell’s Clinical Anatomy by R. Splittgerber. 8th EDITION. Chapter 14: Autonomic Nervous System. Pages 387-411. Page 12 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 APPENDICES Page 13 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 Page 14 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 Page 15 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 Page 16 of 17 CMED 1_B_4  (006) AUTONOMIC NERVOUS SYSTEM DR. A. VIADO | 01/11/21 Page 17 of 17 CMED 1_B_4