Cardiovascular_innervation_2021-2_FINAL23 (2).pptx

Anatomy of Cardiovascul ar Innervation Preparation demonstrating profuse neural innervation of the left atrium. Kapa, et al., 201 Session Goals 1. Gain an understanding of the patterns and functions of innervation to the heart and vascular tree. 2. Appreciate the role of autonomic pathways in mediating specific patterns of referred pain from the heart. Learning Objectives 1. Describe the origins of the sympathetic and parasympathetic innervation of the cardiovascular system, the general pathways for each, and their general effects on target organs. • involves: both CNS and PNS structures • two divisions: parasympathetic and sympathetic • supplies: 1. smooth muscle 2. glands (including adipose tissue) 3. specialized cardiac muscle • primarily a motor (efferent) system, characterized by a 2-neuron efferent pathway BUT: efferent fibers of the ANS run in company with visceral sensory (afferent) fibers hich of these apply to CV autonomics? The Autonomic Efferent Pathway Neuron 1 1st synapse 2nd synapse Cell body Cell body Neuron 2 CNS PNS © Nancy Minugh-Purvis, 2007 Autonomic Ganglion target organ The Autonomic Efferent Pathway 1st synapse 2nd synapse Cell body Cell body CNS PNS © Nancy Minugh-Purvis, 2007 Autonomic Ganglion target organ Consisting Consisting of: of: 1. 1. aa preganglionic preganglionic portion, portion, comprised comprised of of neurons neurons originating originating in in (i.e., (i.e., with with their their cell cell bodies bodies located located in) in) the the CNS; CNS; 2. 2. aa peripheral peripheral ganglion; ganglion; 3. 3. an an entirely entirely postganglionic postganglionic portion, portion, comprised comprised of of neurons neurons entirely entirely within within the the PNS PNS (and (and whose whose cell cell bodies bodies collectively collectively make make up up aa peripheral peripheral ganglion ganglion in in the the pathway) pathway) Parasympathetic Sympathetic T h o r a c o l u m b a r C r a n i o s a c r a l PNS CNS PNS ources of Cardiovascular Autonomics Parasympathetics • Supply exclusively from Vagus N. (CN X) • A few parasympathetics from vagus are vasomotor to blood vessels in some regions of the body • Majority supply heart - Indirectly, decrease rate and strength of contraction - Cause constriction of coronary vessels at times of decreased demand for blood Sympathetics • Cardiopulmonary splanchnic nerves supply heart - Indirectly, increase rate, force, and output of cardiac contractions • Vasomotor to vast majority of blood vessels (and lymphatic vessels!) in  Note: Allbody; sympathetics cardiac structures are already maintain supplying tone and regulate lumen diameter postganglionic when they leave the sympathetic chain. Kapa, et al., 2016 What about blood vessels? Autonomics (=involuntary motor) - contraction of the musculature in vessels regulates - diameter of vessel - tone of muscular wall This most pronounced in arteries. WHY? : most arteries provide routes along which nerves run to reach peripheral target organs/structures. are known as paravascular nerves. They do not supply the arteries themselves, but if the vessel is d or cut, the nerves running along it in that location will commonly be injured as well. In surgical procedure ometimes possible to lift such nerves away from the vessel as they lie superficial to the adventitia. ascular nerves, in contrast, form a profuse meshwork of nerves that runs in the adventitia of arteries and de innervation to the arterial muscle tissue. Injuries to the vessel always involves perivascular nerves, with that autonomic innervation to the smooth muscle of the vessel is interrupted. Learning Objective 1: Application Describe the origins of the sympathetic and parasympathetic innervation of the cardiovascular system, the general pathways for each, and their general effects on target organs. Ask yourself: • Which parts of the parasympathetic division of the ANS supply blood vessels? The heart? • Which parts of the sympathetic division of the ANS supply blood vessels? The heart? • What is the difference between an injury to a perivascular nerve bundle vs. Learning Objectives 2. Describe the composition and organization of the glossopharyngeal and vagus nerves; name, locate, and describe their course, associated peripheral ganglia, and branches to destinations in the neck and thorax – particularly those to cardiovascular structures. Course of the Vagus Nerve anial nerve X ts the CNS at the medulla aves skull through the jugular foramen ns inferiorly in the neck through he carotid sheath ters the superior mediastinum proaches the esophagus in the posterior mediastinum and runs along it aves the thorax by passing through the thoracoabdominal diaphragm in company with the esophagus, at the T10 vertebral level ntinues in the abdomen by following along the GI tract as far as 2/3 of the way along the transverse colon Vagus nerve in the neck N. Vagus N. Lateral view Posterior view Path of the Vagus N. in the thorax Right • Gives off right recurrent laryngeal just before entering thorax • Descends from carotid sheath to enter superior mediastinum • Runs deep to the arch of the azygous vein • Approaches the esophagus and becomes plexiform as it contributes to the esophageal plexus • Runs posteriorly to become the posterior vagus N. • Passes through the diaphragm with the esophagus at the T10 vertebral level Left • Descends from carotid sheath to enter superior mediastinum • Runs superficial to the arch of the aorta • Gives off the left recurrent laryngeal at the inferior border of the aorta • Approaches the esophagus and becomes plexiform as it contributes to the esophageal plexus • Runs anteriorly to become the anterior vagus N. • Passes through the diaphragm with the esophagus at the T10 vertebral level Vagal fibers to the heart and Great vessels Parasympathetic input (GVE; or general visceral efferent) and Visceral Sensation (GVA, or general visceral afferent) • Left and right vagus nerve via • Superior and inferior cervical cardiac branches -these are two long, slender branches arising from each vagus in the neck • Thoracic cardiac branches - variable in number - arise either from the vagal trunks or the recurrent laryngeal branches of X The Vagus Nerve, many destinations & functions Supplies: • Skeletal muscle • Smooth muscle • Cardiac muscle • Glands • Skin • Dura mater • Baroreceptor and chemoreceptors • Mucosa • Taste buds How does it do this? • Contains 5 types of fibers (ie., neuronal axons): - GSA (general somatic afferent) = general sensation such as pain/temperature ry- GVA (general visceral afferent) o ns = visceral sensation, such as pressure e s - SVA (special visceral afferent) = special sense related to GI function (e.g., taste) - GVE (general visceral efferent) = autonomic (i.e., visceral or involuntary motor) = different places; different tissues; numerous functions r o t mo -  Different combinations of these 5 fiber types are carried to their destinations by vagal branches. SVE (special visceral efferent) = motor to head and neck skeletal muscle derived from pharyngeal arches of the embryo halic, cervical, and thoracic Branches of the Vagus Nerve Head - meningeal branch - auricular branch Neck - pharyngeal branch - sinus nerve - superior laryngeal branch - inferior (recurrent) laryngeal branch - cervical cardiac nerves Thorax - cardiac branches - pulmonary branches  Different combinations of the 5 vagal fiber types are carried to appropriate destinations by these branches. Clemente, 6th ed. X. Vagus Nerve GSA fibers carry somatic sensations from skin of external ear, tympanic membrane, and dura. SVA carry taste fibers from epiglottis. GVA carry visceral sensations from the neck, thorax, and abdomen. GVE carry preganglionic parasympathetics to terminal ganglia for thoracic and abdominal glands and smooth muscle, and the conduction SVE innervate skeletal muscles of the palate, pharynx, system of the heart. and larynx.  Remember: a ganglion is a collection of neuronal cell bodies in the PNS. The autonomic synapse of the two-neuron pathway of GVE neurons occurs at the peripheral ganglia. From CNS to PNS Central Process (of axon; runs from cell body to CNS) Direction of signal Peripheral Process muscle Motor Neuron From PNS to CNS (of axon; runs from periphery to cell body) Sensory Neuron Modified from Kandel, et al., 1995 Remember: if autonomic, there would be two neurons in this efferent pathway from CNS to PNS. X. Vagus Nerve GSA carry somatic sensations from skin of external ear, tympanic membrane, and dura. SVA carry taste fibers from epiglottis. GVA carry visceral sensations from the neck, thorax, and abdomen. CELL BODIES IN NODOSE GANGLION. [includes fibers from carotid sinus nerve] GVE carry preganglionic parasympathetics to terminal (peripheral) ganglia for thoracic and abdominal glands and smooth muscle, and the SVE innervate skeletal muscles of the palate, pharynx, conduction system of the heart. and larynx. Note: the vagus has two associated sensory ganglia: the superior and Nodose (inferior). The GVA monitoring fibers have their cell bodies in the Sensory ganglia of the Vagus Nerve Neck - superior (Jugular) ganglion - inferior (Nodose) ganglion emember: a ganglion is a collection of neuronal cell bodies the PNS. Fibers (axons) running from an innervated structure to sensory ganglion are the peripheral processes of the axons; fibers nning from the ganglion to the CNS are the central processes the axons. ote: this is a single neuron pathway. There are no synapses on the ell bodies in these ganglia. Just like a DRG! Clemente, 6th ed. Summary: Vagus Nerve supply to the heart • Left and right vagus descend in the neck after leaving the cranial cavity • Among their branches are several to the heart: - Upper cervical cardiac N. - Branches off above the C6 vertebra - Lower cervical cardiac N. - Branches off at base of the neck - Thoracic cardiac branches Drake, et al., 2nd ed. Course of the Glossopharyngeal Nerve • • • • • • Cranial nerve IX Contains both motor and sensory fibers Exits the CNS at the medulla Passes through the jugular foramen at skull base Begins to branch as passing through foramen Supplies structures in the head and neck as far inferiorly as the lower pharynx BRANCHES: - Tympanic - Lesser petrosal - Carotid sinus - Pharyngeal - Muscular - Tonsillar - Lingual The Glossopharyngeal Nerve, many destinations & functions Supplies: • Auditory structures • Skeletal muscle • Glands • Skin • Baroreceptor (carotid sinus) • Chemoreceptor (carotid body) • Mucosa • Tongue • Pharynx How does it do this? • Contains 5 types of fibers (ie., neuronal axons): - GSA (general somatic afferent) = general sensation such as pain/temperature ry- GVA (general visceral afferent) o ns = visceral sensation, such as pressure e s - SVA (special visceral afferent) = special sense related to GI function (e.g., taste) - GVE (general visceral efferent) = autonomic (i.e., visceral or involuntary motor) = different places; different tissues; numerous functions r o t mo -  Different combinations of these 5 fiber types are carried to their destinations by various branches of IX. SVE (special visceral efferent) = motor to head and neck skeletal muscle derived from pharyngeal arches of the embryo IX. Glossopharyngeal Nerve GSA carry somatic sensations from skin of external ear and oropharynx. SVA carry taste fibers from posterior 1/3 of tongue. GVA carry visceral sensations from the middle ear, oropharynx, posterior 1/3 of tongue, carotid sinus and carotid body. CELL BODIES IN INFERIOR (PETROSAL) GANGLION. GVE carry preganglionic parasympathetics to otic ganglion for parotid salivary gland. SVE carry motor signals to skeletal muscle from the 3rd pharyngeal arch of the embryo. Note: the glossopharyngeal has two associated sensory ganglia: the superior and inferior (petrosal) ganglia. The GVA fibers carrying sensory information from the carotid sinus and body have their cell bodies in the petrosal ganglion. The Carotid Sinus Nerve - Branches off the glossopharyngeal N., just below the base of the skull - Courses anterior to the internal carotid A., running inferiorly along this vessel to reach the wall of the carotid sinus and carotid body - Communicates with - Sympathetic fibers from superior cervical ganglion - A twig of X which may arise independently or from a laryngeal branch of the vagus - Peripheral processes of axons terminate at - Carotid sinus - Carotid body - Intercarotid plexus - Contains: 1. Afferent fibers (GVA) from chemoreceptors in carotid body 2. Afferent fibers (GVA) from baroreceptors in the wall of the carotid sinus Porzionato, et al., 2019 - Cell bodies located in: inferior ganglion of IX (petrosal ganglion) The carotid sinus nerve (indicated by the black arrows), coursing inferiorly on the anterior aspect of the internal carotid artery (ICA). Nerve supply to carotid sinus • IX • X • Sympathetics from superior cervical ganglion (not shown) Carotid body Common carotid anterior Carotid Body Situated near carotid sinus in neck near bifurcation of common carotid artery Tiny: each approx. 5-7mm high and 2.5-4mm wide Develop from mesenchyme from the 3rd pharyngeal arch of the embryonic head and neck Innervated primarily by Carotid sinus nerve, a branch of the glossopharyngeal and, by a plexus of glossopharyngeal, vagal, and sympathetic fibers Well-vascularized by tiny branches from the external carotid artery Function: arterial chemoreceptor brainstem, cross section Histological preparation of the Carotid body. Note the cells. Williams, et al., 1995 Learning Objective 2: Application Describe the composition and organization of the glossopharyngeal and vagus nerves; name, locate, and describe their course, associated peripheral ganglia, and branches to destinations in the neck and thorax – particularly those to cardiovascular structures. Ask yourself: • Which fibers of X synapse in peripheral ganglia? Which ganglia of X are not sites of synapses? • Which fibers of IX have a cardiovascular function? Where are their peripheral cell bodies? Are they autonomic? • What type(s) of fibers supply the carotid body? What is their CNS origin? Learning Objectives 3. Describe the sympathetic innervation of the heart, including: spinal levels of origin; pathways through the sympathetic chain; and cardiopulmonary splanchnic nerves supplying the heart. Sympathetics reach the heart via Cardiopulmonary Splanchnic nerves -originate at T1-5 spinal levels in IML column -synapse in sympathetic chain -exit sympathetic chain at cervical and upper thoracic levels as postganglionic fibers -called “splanchnic” but these splanchnics synapse in the sympathetic chain -2nd neuron synapses on nodal cells upon reaching the heart Sympathetic Supply to the Heart Origin: spinal levels T1-5 - Some of these axons ascend through the sympathetic chain and synapse at either the Stellate Ganglion or the Middle Cervical Ganglion, then leave the chain via gray rami to pass, as cardiopulmonary splanchnics, to the cardiac plexus - Other synapse in the sympathetic chain at their same spinal level then leave the chain via gray rami to pass, as cardiopulmonary splanchnic nerves, to the cardiac plexus Cardiopulmonary splanchnics  All autonomic fibers to the heart are funneled through a large meshwork of nerves: the cardiac plexus Drake, et al., 2nd ed. Learning Objective 3: Application Describe the sympathetic innervation of the heart, including: spinal levels of origin; pathways through the sympathetic chain; and cardiopulmonary splanchnic nerves supplying the heart. Ask yourself: • Where do the cardiopulmonary splanchnic nerves synapse in the sympathetic chain? In other words, where are their 2nd cell bodies located? • Where do they originate in the spinal cord? Learning Objectives 4. Describe, identify, and locate the autonomic plexuses of the thorax, including the types of fibers and ganglia participating in each. Cardiac Plexus Contains: Autonomic nerve axons (fibers) (GVE) -parasympathetic (preganglionics from X) -sympathetics (postganglionics from cardiopulmonary splanchnics) • Visceral sensory fibers (GVA) of X and of upper thoracic spinal levels Tiny ganglia containing parasympathetic cell bodies Williams, et al., 1995 Cardiac Plexus Location: base of the heart Two connected parts: 1. superficial (or ventral) 2. deep (or dorsal) Deep cardiac plexus - Superficial portion lies below aortic arch and anterior to R. pulmonary artery - Deep portion anterior to tracheal bifurcation Continuous with: • Aortic plexus • Pulmonary plexuses Superficial cardiac plexus Cardiac Plexus tends from anterior trachea to aortic arch, pulmonary trunk, and ligamentum arteriosum; extends along ulmonary arteries; some fibers continue to the lungs, others to the epicardium Drake, et al., 2nd ed. • Function: coordinate heart function with body activity - Parasympathetics: decrease rapidity and force of contractions; ‘puts the brakes on’ - Sympathetic fibers : increase rapidity and strength of heartbeat Learning Objective 4: Application Describe, identify, and locate the autonomic plexuses of the thorax, including the types of fibers and ganglia participating in each. Ask yourself: • What is the location of the cardiac plexus? What other structures is it near and thus vulnerable to injury if they are affected by a disease process? Learning Objectives 5. Explain referred pain associated with the heart. Visceral Sensation (GVA) • Stretch/distension • Spasms or violent contractions • Ischemia • Mechanical or chemical stimulation or irritants an be painful or imperceptible ollows autonomic PATHWAYS (pain typically follows sympathetic thways; reflex-related sensation follows parasympathetic pathways) Note: Quality of visceral pain: dull, diffuse, rather than sharp or easily localized What is Referred Pain? Often, pain related to visceral distress is felt at a site other than the actual anatomical location of the problem; this phenomenon is known as referred pain. For example, the pain of a heart attack may be initially felt over the entire chest wall and down the left upper limb. In this diagram, note that the sensory information (pain) from the heart is relayed via interoreceptors to the exact same level of the spinal cord as sensory information from exteroreceptors located in the skin. The brain cannot (immediately) distinguish the true source of the painful stimulus and initially interprets the pain as coming from dermatomes (in the case of the heart, dermatomes T1 – T4/T5 are involved) since these associated exteroreceptors are commonly stimulated on a daily basis. Visceral Pain Afferents (GVA fibers) - trace the pathway from the heart  For most of their pathway, these follow along sympathetic pathways BUT the pain pathways are afferents, so they run from peripheral to central… - Peripherals processes of sensory neuronal axons travel back along the sympathetic pathway and into the sympathetic chain - these axons run through the sympathetic chain without synapsing - axons travel via a ramus communicans into the spinal nerve - here they diverge from the sympathetic fibers they have been following and travel into the dorsal root to reach their sensory cell bodies (in the dorsal root ganglion) - central processes of sensory axons enter the dorsal horn of the spinal cord - pain signals are then transmitted to the brain as if they are coming from the T 1-5 dermatomes Pain from cardiac distress typically reflects the spinal level of origin of the sympathetic pathways they follow (T 1 -5), but there are unexplained variations. A: most common dermatome pattern B and C: variations erred pain from cardiac distress in females commonly involves the neck and back Shows more variations from the expected pattern than in males Heart Monitoring Visceral Afferent (GVA) fibers – continually send signals to the brain regarding status of functioning in a given organ; imperceptible sensory information GVA fibers Follow parasympathetic pathways For most of the body these travel in cranial nerves IX and X Visceral monitoring fibers from the pelvis accompany the sacral parasympathetics • Carry information regarding stretch (baroreceptors such as the carotid sinus and receptors in aortic arch); chemoreceptors (such as carotid body or para-aortic body); etc. back to the CNS • This visceral sensory information is primarily involved in mediating simple reflex arcs and peristalsis. • • • • Comparison of sensation Related to heart. Sensory neuronal cell body in Nodose gangion of X Sensory neuronal cell body in dorsal root ganglion Vagal Ganglion 3. Somatic afferents (GSA) from body wall and limbs carry somatic pain sensation (pain, temperature, etc.) Involved with cardiac referred pain. Sensory neuronal cell body in DRG Visceral afferent PARASYMPATHETIC pathway 1. Cardiac afferents (GVA) running in Vagus N. - Reflex depression of cardiac activity Visceral afferent SYMPATHETIC pathway 2. Cardiac afferents (GVA) running along sympathetics carrying visceral Sensory neuronal cell body in Nodose gangion of X Sensory neuronal cell body in dorsal root ganglion Vagal Ganglion 3. Somatic afferents (GSA) from body wall and limbs - carrying somatic pain sensation (pain, temperature, etc.) Sensory neuronal cell body in DRG Visceral afferent PARASYMPATHETIC pathway 1. Cardiac afferents (GVA) running in Vagus N. - Reflex depression of cardiac activity Visceral afferent SYMPATHETIC pathway 2. Cardiac afferents (GVA) running along sympathetics - carrying visceral pain Summary: Composition of Cardiac Plexus • GVE fibers from vagus • GVE fibers from T1-5 (sympathetics) • GVA fibers of vagus • GVA fibers of T1-5 (traveling along sympathetics to reach their spinal level) • Tiny ganglia Drake, et al., 2nd ed. Learning Objectives 5. Explain referred pain associated with the heart. Ask yourself: • What dermatomes are most likely to produce discomfort in cases of cardiac distress? • What pathway do GVA fibers from the T3 spinal level take to run from the heart to the spinal gray matter? • What pathway would monitoring fibers take from the heart to the CNS? From

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