The Autonomic Nervous System

1. 15 The Autonomic Nervous System

2. I. The Autonomic Nervous System (ANS) A.The ANS is a system of motor neurons B. The ANS is the general visceral motor division of the PNS C. It innervates: Smooth muscle; Cardiac muscle; Glands D. It regulates visceral functions such as: 1. Heart rate 2. Blood pressure 3. Digestion 4. Urination E. It also contains the general visceral sensory system of the PNS

3. Central nervous system (CNS) Peripheral nervous system (PNS) Sensory (afferent) division Motor (efferent) division Somaticsensory Visceralsensory Somatic nervoussystem Autonomic nervoussystem (ANS) Sympatheticdivision Parasympatheticdivision

4. II. Comparison Autonomic and Somatic Motor Systems A. Somatic motor system 1. one motor neuron extends from the CNS to skeletal muscle 2. axons are well myelinated, conduct impulses rapidly B. Autonomic nervous system 1. Chain of two motor neurons to smooth muscle, cardiac muscle, glands a. preganglionic neuron► ►► postganglionic neuron 2. Conduction is slower than somatic nervous system because a. axons are thinly myelinated (white) or nonmyelinated (grey) b. motor neuron synapses in a ganglion outside the CNS

6. III. Divisions of the Autonomic Nervous System A. Sympathetic and parasympathetic divisions 1. chains of two motor neurons 2. innervate same structures - cause opposite effects 3. Sympathetic division - during extreme situations a. examples: fear, rage, exercise 4. Parasympathetic division - routine maintenance functions

7. B. Sympathetic -“fight or flight” 1. activated during EXTREME situations a. examples: exercise, excitement, emergencies 2. sympathetic responses help respond to dangerous situations a. increase heart rate and breathing rate b. increase blood and oxygen to skeletal muscles c. vasoconstriction of other blood vessels d. dilate pupils and bronchioles e. inhibit motility of the digestive tract and urinary tracts

8. C. Parasympathetic – “rest and digest” (“sit or shit”) 1. Active when the body is at rest 2. Concerned with conserving energy 3. Directs “housekeeping” activities a. digestion b. elimination of feces and urine c. heart rate, b.p. , respiration at low-normal levels

9. Parasympathetic Sympathetic   Eye(dilatespupil) Eye(constrictspupil) Brain stem   Salivaryglands Skin* Cranial  Salivaryglands Sympatheticganglia  Heart Cervical  Lungs(dilatesairways)  Lungs(constrictsairways) T1  Heart  Stomach Thoracic   Pancreas Stomach  Liver  Pancreas  Gall-bladder L1  Gall-bladder Lumbar  Adrenalgland   Bladder Bladder   Genitals(erection) Genitals(ejaculation) Sacral  stimulatory effect  inhibitory effect

10. A. Emerge from different regions of the CNS 1. sympathetic - also called the thoracolumbar division a. originate from spinal segments (T1–L2) 2. parasympathetic - also called the craniosacral division a. originate from III, VII, IX, X and (S2,3,4) B. Length of postganglionic fibers 1. sympathetic- long postganglionic fibers 2. parasympathetic- short postganglionic fibers IV. Anatomical Comparisons

11. C. Branching of fibers 1. sympathetic fibers a. highly branched; influence many organs at once 2. parasympathetic fibers a. few branches; only localized effect D. Neurotransmitter released by postganglionic axons 1. sympathetic - most release norepinephrine (adrenergic) 2. parasympathetic - release acetylcholine (cholinergic)

13. V. The Parasympathetic Division A. Cranial outflow 1. originates from the brain (III, VII, IX, X) 2. innervates - organs of the head, neck, thorax, and abdomen B. Sacral outflow 1. originates from spinal segments (S2,3,4) 2. “(S2,3,4) keeps your penis off the floor” 3. innervates - remaining abdominal and pelvic organs

14. Eye Ciliaryganglion CN III Lacrimalgland CN VII Pterygopalatineganglion Nasalmucosa CN IX CN X Submandibularganglion Submandibularand sublingualglands Otic ganglion Parotid gland Heart Cardiac andpulmonaryplexuses Lung Preganglionic Postganglionic CN Cranial nerve

15. Liver andgallbladder Celiacplexus Stomach Pancreas S2 Largeintestine S3 S4 Smallintestine Pelvicsplanchnicnerves Inferiorhypogastricplexus Rectum Urinarybladderand ureters Genitalia (penis, clitoris, and vagina) Preganglionic Postganglionic CN Cranial nerve

16. VI. Cranial Outflow (Parasympathetic) A. Preganglionic fibers run via 1. oculomotor nerve (III) 2. facial nerve (VII) 3. glossopharyngeal nerve (IX) 4. vagus nerve (X) B. Cell bodies of preganglionic neurons located in motor cranial nerve nuclei in gray matter of the brain stem

17. C. Oculomotor Nerve (III) 1. innervate smooth muscles in the eye 2. cause pupil constriction D. Facial Nerve (VII) 1. stimulate secretions of glands in the head 2. examples: lacrimal gland, submandibular salivary glands E. Glossopharyngeal Nerve (IX) 1. stimulate secretion of other salivary glands

18. F. Vagus Nerve (X) 1. innervate visceral organs of the thorax and most of the abdomen 2. stimulates digestion, lower heart rate, and lower blood pressure 3. sends branches through autonomic nerve plexuses a. cardiac plexus b. pulmonary plexus c. esophageal plexus d. celiac plexus e. superior mesenteric plexus

19. Left vagus nerve Superior cervicalganglion Cardiac branchesof the vagus Middle cervicalganglion Stellate ganglion Cardiac plexus Pulmonary plexus Vagus nerve Esophageal plexus Stomach with vagus nerve Celiac plexus Superior mesentericplexus

20. A. Emerges from S2 toS4 B. Innervates organs of the pelvis and lower abdomen 1. contraction of urinary bladder for urination 2. erection of the penis - (S2,3,4) 3. inhibits contraction of uterine smooth muscles 4. vasodilation - clitoris and contraction of smooth m. of vagina VI. Sacral Outflow (Parasympathetic)

21. VI. The Sympathetic Division A. Issues from T1 to L2 B. Preganglionic fibers form the lateral gray horn of spinal cord C. Supplies visceral organs in internal body cavities and structures of superficial body regions D. Contains more ganglia than the parasympathetic division E. Located on both sides of the vertebral column F. Linked by short nerves into sympathetic trunks G. Sympathetic trunk ganglia also called: 1. chain ganglia or 2. paravertebral ganglia

22. VII. Sympathetic Trunk Ganglia A Joined to ventral rami by white and grayrami communicantes (the next picture will show what this actually means) B. Fusion of ganglia  there are fewer ganglia than spinal nerves C. Sympathetic ganglia form a “chain” along the vertebral column 1. most apparent in the cervical region a. superior cervical ganglia b. middle cervical ganglia c. inferior cervical ganglia

23. 1. preganglionic nerve cell body in lateral horn of spinal cord 2. axon goes through ventral root of spinal nerve 3. to ventral ramusof spinal nerve 4. through white communicans (myelinated) 5. synapses on postganglionic nerve cell body in sympathetic ganglion 6. postganglionic axon through grey communicans (unmyelinated!!!) 7. to effector organ Lateral horn(visceralmotor zone) Ventral ramus ofspinal nerve Gray ramuscommunicans Ventral root Sympathetictrunk ganglion White ramuscommunicans Skin (arrectorpili musclesand sweatglands) Sympathetic trunk To effector Blood vessels

24. 1. Synapses with a postganglionic neuron at the same level and exit on a spinal nerve at that same level or Lateral horn(visceralmotor zone) Ventral ramus ofspinal nerve Gray ramuscommunicans Ventral root Sympathetictrunk ganglion White ramuscommunicans Skin (arrectorpili musclesand sweatglands) Sympathetic trunk To effector Blood vessels

25. 1 2 3 4 6 5 2. Synapses with a postganglionic neuron at a different level and exits on a spinal nerve at that same level Skin (arrectorpili musclesand sweatglands) To effector Blood vessels 1. Preganglionic nerve in lateral horn 2. Ventral root of spinal nerve 3. White ramus communicans 4. Sympathetic chain ganglion 5. Grey ramus communicans 6. Postganglionic nerve axon

26. Ventral root Sympathetictrunk ganglion Sympathetictrunk Ventral ramusof spinal nerve Gray ramuscommunicans White ramuscommunicans Location of the sympathetic trunk Dissection of posterior thoracic wall, right side

27. D. Pathways to Body Periphery 1. innervate sweat glands, arrector pili muscles, blood vessels E. Pathways to the Head 1. originate from T1–T4 2. synapse in superior cervical ganglion 3. innervate glands, smooth muscles, blood vessels of head F. Pathways to Thoracic Organs 1. originate from T1–T6 2. run directly to the effector organ

28. G. Pathways to Thoracic Organs 1. originate from T1–T6 2. run directly to the effector organ 3. functions in this region are to: a. increase heart rate b. dilate the bronchioles c. dilate arteries of the heart d. inhibit muscles and glands of the digestive system H. Pathways to Pelvic Organs 1. originate from T5–L2 2. inhibit activity of smooth m. and glands in the visceral organs

29. Eye Lacrimal gland Nasal mucosa Pons Sympathetic trunk(chain) ganglia Blood vessels;skin (arrector pilimuscles andsweat glands) Superiorcervicalganglion Salivary glands Middlecervicalganglion Heart Inferiorcervicalganglion Lung T1 Liver andgallbladder Celiac ganglion L2 Stomach Superiormesentericganglion Spleen Adrenal medulla Kidney Smallintestine Inferiormesentericganglion Largeintestine Rectum Preganglionic Postganglionic Genitalia (uterus, vagina, andpenis) and urinary bladder

30. VIII. The Role of the Adrenal Medulla A. Major organ of the sympathetic nervous system B. Constitutes largest sympathetic ganglia C. Secretes large amounts of norepinephrine and epinephrine D. Stimulated to secrete by preganglionic sympathetic fibers Remember: “Fight or Flight” Example: bear running out of the woods to eat your child!!!!

31. Sympathetic trunk Ventralroot Spinal cord:T8–L1 Thoracicsplanchnicnerves Kidney Adrenal gland Adrenalmedulla Epinephrine andnorepinephrine Capillary Adrenalmedulla cells

35. IX. Visceral Sensory Neurons A. General visceral sensory neurons monitor these sensations 1. stretch 2. temperature 3. chemical changes 4. irritation B. Nerve cell bodies are located in the dorsal root ganglion

36. C. Visceral pain 1. no pain results when visceral organs are cut 2. visceral pain results from chemical irritation or inflammation 3. visceral pain often perceived to be of somatic origin ► phenomenon of referred pain

37. A map of referred pain Lungs anddiaphragm Heart Liver Gallbladder Stomach Appendix Pancreas Small intestine Ovaries Colon Kidneys Urinary bladder Ureters

38. X. Visceral Reflexes A. Visceral sensory/autonomic neurons role in visceral reflex arcs: 1. defecation reflex 2. micturition reflex (urination impulse) B. NOTE: you do not “think” these reflexes; like patellar tendon reflex C. Some visceral reflexes are simple spinal reflexes D. Others do not involve the CNS - strictly peripheral reflexes

39. A visceral reflex 1 2 3 4 5 Stimulus Dorsal root ganglion Sensoryreceptor in viscera Spinal cord Visceral sensoryneuron Integration center• May be preganglionicneuron (as shown)• May be a dorsal horninterneuron• May be within wallsof gastrointestinaltract Autonomic ganglion Efferent pathway(two-neuron chain)• Preganglionic neuron• Postganglionic neuron Visceral effector Response

40. The baroreceptor reflex 1 1 2 2 3 3 4 4 5 5 Increased blood pressure Baroreceptors in carotidsinus are simulated. Sensory impulses arecarried on visceral sensoryfibers in the glosso-pharyngeal nerves (CN IX). Integration occurs incardiac center of medullaoblongata. Efferent pathway via thevagus nerves (CN X) Parasympatheticstimulation of heartdecreases heart rate. Blood pressure decreases

41. XI. CNS Control of the ANS A. The ANS is not under direct voluntary control B. Some parts of the CNS help coordinate the ANS 1. brain stem 2. spinal cord 3. hypothalamus 4. amygdala 5. cerebral cortex

42. C. Hypothalamus—the main integration center of the ANS A. medial and anterior parts ► direct parasympathetic functions B. lateral and posterior parts ► direct sympathetic functions D. People can exert some control over autonomic functions 1. feelings of calm during meditation a. influence of cerebral cortex on parasympathetic centers in hypothalamus 2. voluntary sympathetic response a. recalling scary event

43. Communication atsubconscious level Cerebral cortex(frontal lobe) Limbic system(emotional input) HypothalamusThe “boss”: Overallintegration of ANS Brain stem(reticular formation, etc.)Regulates pupil size, heart,blood pressure, airflow,salivation, etc. Spinal cordReflexes for urination,defecation, erection,and ejaculation

44. XII. Disorders of the ANS A. Raynauds disease - characterized by constriction of blood vessels 1. provoked by exposure to cold or by emotional stress B. Achalasia of the cardia 1. defect in the autonomic innervation of the esophagus C. Congenital megacolon (Hirschsprung’s disease) 1. birth defect 2. parasympathetic innervation of distal large intestine fails to develop correctly 3. feces and gas accumulate proximal to defect

45. D. Achalasia of the cardia 1. defect in the autonomic innervation of the esophagus E. Congenital megacolon (Hirschsprung’s disease) 1. birth defect 2. parasympathetics of distal large intestine fails to develop correctly 3. feces and gas accumulate proximal to defect