Anatomy of Automatic Nervous System PDF

Anatomy of Autonomic Nervous System By: Dr. Kamal Motawei & Dr. Khulood Al-Khater Sunday, November 5, 2023 12:34 Learning Objectives At the end of this lecture students will be able to: • Comprehend the arrangement of the autonomic NS and its associated ganglia • Explain the distribution of auto...

Anatomy of Autonomic Nervous System By: Dr. Kamal Motawei & Dr. Khulood Al-Khater Sunday, November 5, 2023 12:34 Learning Objectives At the end of this lecture students will be able to: • Comprehend the arrangement of the autonomic NS and its associated ganglia • Explain the distribution of autonomic nerves Sunday, November 5, 2023 12:34 Functional Division L.tt85 1 IPrehiralN. E ani From body wall (soma): skin, sk. Muscles, joints, bones, & ligaments E Nervous System Somatic nervous system I sforyTotor Sensory SAFFRENT To Skeletal Muscles Motor belfrent From 5ham Sunday, November 5, 2023 Autonomic/visceral nervous system Sensory as on Motor if ga n From Viscera: internal organs, glands, & blood vessels To Smooth and Cardiac Muscles and Glands Difference between somatic & autonomic of motor nerve distribution Trent i.EE Somatic motor system: A single nerve Letry Autonomic motor system: Two nerves (pre & postganglionic) s Sunday, November 5, 2023 282 Autonomic System Fightorflight im out in a J jg Sunday, November 5, 2023 12:34 Divisions of the Autonomic Nervous System (ANS) ➢ Sympathetic division (fight or flight response) • Increases heart rate and blood pressure • Depresses digestive function • Increases sweating Sunday, November 5, 2023 ➢ Parasympathetic division (rest & digest response) • Slows heart rate, fall in pressure • Increases digestive functions • Stops sweating Sympathetic Nervous System (Thoracolumbar outflow) LET sa parasympathetic Spinal cord (lateral horn) T1-L2 0 Sympathetic Ganglia Sunday, November 5, 2023 Paravertebral Sympathetic Chain Ganglia Prevertebral Sympathetic Ganglia Preganglionic postganglionic Parasympathetic Nervous System (Craniosacral outflow) postganglionic CN III, VII, IX, X 3 7 9 10 S2-4 Sunday, November 5, 2023 Parasympathetic Autonomic nerves Motor autonomic control passes from the CNS to the effector organs in nerve fibers of a two-series neurons: A. Preganglionic neurons: their axons form preganglionic nerves B. Postganglionic neurons: their axons form postganglionic nerves Short preganglionic nerves Has and short preganglionic Eg postganglionic Long postganglionic nerves Has long preganglionic Long preganglionic nerves Sunday, November 5, 2023 andshortpostsynaptic short postganglionic nerves A. Autonomic preganglionic nerves white They are myelinated axons of autonomic preganglionic neurons which are situated in the CNS: preganglioni I 3 I – In the spinal cord: in the lateral horn of the gray matter (the intermediolateral cell column): In • T1 to L2 segments (sympathetic) and • S2-4 (parasympathetic). Ey – In the brainstem: parasympathetic nuclei of 4 cranial nerves (III, VII, IX, and X). Sunday, November 5, 2023 I parasympathetic 8 B. Autonomic postganglionic nerves Agray ▪ They are the unmyelinated axons of postganglionic neurons located in autonomic ganglia in PNS. eye ▪ Autonomic ganglia are of two types: i. ii. Sympathetic ganglia and Parasympathetic ganglia What is a GANGLION? Aggregation of neuronal cell bodies outside the CNS (that is in PNS) system Sunday, November 5, 2023 psiitiii.my ftp.stganglia Ganglia Is there any motor somatic ganglia in the PNS? Why should the autonomic motor nerves have ganglia? synapses c Autonomic ganglia provide a location for synapse in PNS Sunday, November 5, 2023 1 Somatic (Sensory) N to ganglia 2 Autonomic (Motor) ga Spinal (Spinal root ganglia) Sympathetic Cranial (Cranial nerves ganglia) Parasympathetic Sympathetic Ganglia These are located along the sympathetic trunk (chain) which extend alongside the whole length of the vertebral column from the base of skull to coccyx There are about 24 ganglia in each sympathetic trunk Sunday, November 5, 2023 Connection between spinal nerves and sympathetic ganglia ▪ White rami communicans: s pre-ganglionic fibers ▪ Gray rami communicans: spost-ganglionic fibers a Sunday, November 5, 2023 I Parasympathetic Ganglia • Parasympathetic ganglia tend to be smaller and located more peripherally than sympathetic ganglia. • They are typically situated adjacent to the viscera they supply. • 4 named ganglia in the head region • • • • IF Ciliary ganglion: supplying the eye Pterygopalatine ganglion: lacrimal and nasal glands Otic ganglion: parotid gland nerve Submandibular ganglion: submandibular and sublingual salivary glands •Scattered ganglia in the wall of the viscera Sunday, November 5, 2023 É Distribution of sympathetic nervous system ▪ The sympathetic nervous system has a wide distribution that covers the whole body, targeting: – peripheral effectors as skin glands, erector pili muscles, and blood vessels – Internal organs in the head, neck, thorax, abdomen, and pelvis. ▪ This is achieved by the propagation action of sympathetic chains and prevertebral ganglia. Sunday, November 5, 2023 Distribution of sympathetic nervous system (continued) ▪ Sympathetic preganglionic fibers exit the spinal cord at T1-L2 segments to join the sympathetic chain as white rami communicans. 1in ▪ In the sympathetic chain the preganglionic fiber may take the following four pathways to target tissues: 1. Relay in the sympathetic chain ganglia T1-L2, then, postganglionic fibers rejoin the corresponding spinal nerve (as gray rami communicans) to be distributed to peripheral viscera ftp.ffgioniFinan rejoin Sunday, November 5, 2023 Distribution of sympathetic nervous system (continued) 2. Some preganglionic fibers of T1-T5 ascend without relay in corresponding ganglia, to relay in cervical sympathetic chain ganglia and be distributed along cervical spinal nerves to head, neck, part of upper limbs and the heart (see next slide). 3. Some preganglionic fibers of T5-L2 descend in the sympathetic trunk to relay in its lumbar, sacral, and coccygeal ganglia, supplying peripheral structures in lower limbs Sunday, November 5, 2023 Distribution of sympathetic nervous system (continued) Sympathetic innervation of cranial, cervical, and thoracic viscera: Postganglionic sympathetic fibers from the cervical sympathetic ganglia join arteries to reach head and cervical viscera. Heart receives postganglionic sympathetic cardiac nerves from the three cervical ganglia and upper four thoracic ganglia Other thoracic viscera receive postganglionic sympathetic fibers from T1T4 which join parasympathetic fibers to form plexuses before supplying the target organ Sunday, November 5, 2023 Distribution of sympathetic nervous system (continued) 4. Fibers that bypass the paravertebral ganglia and synapse with prevertebral ganglia (sympathetic innervation of abdominopelvic viscera): Preganglionic sympathetic fibers may pass through the sympathetic trunk and paravertebral ganglia without synapsing and form splanchnic nerves: ➢ greater splanchnic (T5-T9), ➢ lesser splanchnic (T9-T10 or T10-T11), ➢ least splanchnic (T12), ➢ lumbar splanchnic (L1-L2), and ➢ sacral splanchnic (T12, L1, L2) They relay on prevertebral sympathetic ganglia and the postganglionic fibers supply the abdomen and pelvic organs. Sunday, November 5, 2023 Distribution of Parasympathetic Nervous System ▪ Parasympathetic distribution is limited to the trunk. So, it does not follow spinal nerves. D ▪ Its preganglionic fibers are long, while postganglionic fibers are short A. Sacral outflow: Preganglionic parasympathetic motor fibers exit the lateral horn of sacral spinal segments S2-S4. They form Pelvic splanchnic nerves, which relay on parasympathetic ganglia adjacent to hindgut and pelvic organs. Also, they supply cavernous tissue of penis and clitoris in the perineum. Sunday, November 5, 2023 Distribution of Parasympathetic Nervous System B. Cranial outflow: CN III, VII, and IX: have preganglionic parasympathetic motor fibers that relay on one of four distinct ganglia, which house postganglionic motor neurons. These four ganglia are near major branches of CN V. Postganglionic fibers leave the ganglia, join the branches of CN V, and are carried to target tissues (salivary, mucous, and lacrimal glands; constrictor muscle of the pupil; and ciliary muscle in the eye) with these branches. CN X (vagus): has preganglionic parasympathetic fibers which relay on parasympathetic ganglia adjacent to the target organs (all thoracic organs, and most of abdominal organs). Sunday, November 5, 2023 Higher control of ANS ▪ Preganglionic autonomic neurons are controlled by: – local reflex circuits with visceral sensory neurons – ipsilateral descending input from hypothalamus and brainstem reticular formation ▪ Reticular formation and hypothalamus receive inputs from insular cortex, limbic system, basal ganglia and other higher brain areas. Sunday, November 5, 2023 Visceral sensory innervation (visceral afferents) ▪ Visceral sensory fibers that accompany sympathetic fibers have cell bodies in the dorsal root ganglia and are mainly concerned with detecting pain ▪ Visceral sensory fibers accompanying parasympathetic fibers are carried mainly in IX and X and in spinal nerves S2 to S4. ▪ Visceral sensory fibers associated with parasympathetic fibers primarily relay information to the CNS about the status of normal physiological processes and reflex activities. ▪ Sensation from viscera (pain & stretch) is received by insular cortex. Sunday, November 5, 2023 Referred pain ▪ Some axons carrying pain sense from the viscera synapse on neurons in the dorsal horn that also receive somatosensory pain fibers from the skin. ▪ Our mind interprets visceral pain as arising from parts of the body served by the somatosensory system. We call this referred pain. Sunday, November 5, 2023 Enteric Nervous System ▪ The enteric nervous system (ENS) is one of the main divisions of the autonomic nervous system (ANS) and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract (GIT). ▪ Neurons of the enteric nervous system are in the wall of the GIT ▪ They are highly interconnected in local circuits which are controlled by sympathetic and parasympathetic input. Sunday, November 5, 2023 Clinical Modification of the Activities of the Autonomic Nervous System ▪ Many drugs and surgical procedures that can modify the activity of the autonomic nervous system are available. ▪ For example, drugs can be administered to lower the blood pressure by blocking sympathetic nerve endings and causing vasodilatation of peripheral blood vessels Sunday, November 5, 2023 Examples of SAQ ▪ Mention cranial nerves that contain parasympathetic preganglionic fibers. ▪ Mention the types of sympathetic ganglia Sunday, November 5, 2023 Study Guide ▪ Gray’ Anatomy for students, 4th edition: – Pages: 36-45 Sunday, November 5, 2023 12:34 Thank You Sunday, November 5, 2023