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Lecturer: Dr Lucy Patston lpatston@unitec.ac.nz Slide 2 Lundy: Chapter 9 Tortora PDF on Moodle 3x word documents of ANS systems Lundy-Ekman. Neuroscience: Fundamentals for Rehabilitation, 4th Edition. W.B. Saunders Company, 2013. Kandel et al. Principles of Neural Science, 5 th Edition. McGraw Hill, 2012. Tortora & Derrickson. Principles of anatomy and physiology, 13 th Edition. Wiley. 2012. Slide 3 Comparison of somatic and autonomic nervous systems Anatomy of autonomic motor pathways Anatomical Components Structure of the Sympathetic Division Structure of the Parasympathetic Division Physiology of the ANS Slide 4 Understand the function of the ANS as a whole and how it differs from the somatic NS Have an idea about the types of receptors found in the ANS Understand the functions and innervations of the parasympathetic system Understand the functions and innervations of the sympathetic system Be able to compare and contrast the two systems Have an appreciation for some of the disorders associated with the ANS Slide 5 Slide 6 Main input to ANS comes from autonomic (visceral) sensory neurons (sensory receptors located in blood vessels, visceral organs, muscles) ANS monitors the internal environment E.g., chemoreceptors monitoring blood CO2 levels, mechanoreceptors monitoring stretch in walls of organs (bladder) Sensory signals not normally consciously perceived Slide 7 Autonomic motor neurons regulate visceral activity by increasing OR decreasing activity in effector tissues (smooth muscle, glands) E.g., constriction of pupils, dilation of blood vessels, adjustment of rate and force of heartbeat (ANS motor responses) Most motor responses cannot be consciously altered (difficult to slow own heart) Signals from somatic/special senses via limbic system influence response of ANS (e.g., being grabbed; hearing wheels squeal) Slide 8 Somatic motor neuron: single, myelinated axon extend from CNS to skeletal muscle Autonomic motor neuron: Two neuron series with autonomic ganglion as synapse point Autonomic Ganglion (in PNS) Effector organ (in PNS) First neuron: Preganglionic neuron - myelinated Second neuron: Postganglionic neuron - unmyelinated Spinal cord (in CNS) Slide 9 Somatic motor neurons release only acetylcholine (ACh) as their neurotransmitter Autonomic motor neurons release either ACh or norepinephrine (NE) Slide 10 Somatic efferents: innervate only muscle dependent on CNS input activation usually voluntary use one neuron Autonomic efferents: innervate all other parts of the body can function independently of CNS input usually non-conscious use two neurons with a synapse outside the CNS Slide 11 Somatic system Autonomic system Slide 12 Slide 13 ANS has two divisions Sympathetic division Parasympathetic division Most organs have dual innervation they receive inputs from both sympathetic and parasympathetic neurons Innervation by one division may stimulate organ, whereas innervation by the other division may inhibit organ E.g., heart rate: sympathetic increases, parasympathetic decreases Slide 14 Divisions of the autonomic nervous system. Note that although the sympathetic pathways are separate from the parasympathetic pathways, most autonomic effectors are innervated by both pathways. Slide 15 Known as fight-or-flight division Sympathetic activities result in increased alertness and metabolic activities to prepare body for emergency situation Rapid heart rate; dilation of pupils; dry mouth; sweaty, cool skin; dilation of blood vessels to organs involved in combating stress (heart, skeletal); constriction of blood vessels to organs NOT involved (gut, kidneys) Slide 16 Known as rest-and-digest division Parasympathetic activities conserve and restore body energy during rest times Conserves energy, replenishes nutrient stores Slide 17 Preganglionic Neurons Autonomic Ganglia Sympathetic Parasympathetic Postganglionic Neurons Autonomic Plexuses Slide 18 Preganglionic Neurons (Sympathetic) Cell bodies in spinal cord (lateral horns) in 12 thoracic segments and first 3 lumbar segments Known as thoracolumbar outflow Preganglionic Neurons (Parasympathetic) Cell bodies located in nuclei of 4 cranial nerves (III, VII, IX, X) and lateral gray matter of S2-S4 in spinal cord Known as craniosacral outflow Slide 19 Sympathetic Ganglia synapse sites between pre- and postganglionic neurons Two types of sympathetic ganglia Sympathetic trunk ganglia (aka: vertebral chain ganglia or paravertebral ganglia) Prevertebral ganglia (aka: collateral ganglia) Parasympathetic Ganglia (later) Slide 20 Lie in vertical row either side of vertebral column From base of skull to coccyx Trunk ganglia in neck have specific names: Superior cervical ganglia Middle cervical ganglia Inferior cervical ganglia Postganglionic neurons from these innervate heart and head/neck/shoulders Preganglionic axons SHORT, postganglionic axons LONG Slide 21 Lie anterior to vertebral column Innervate organs below the diaphragm There are five: 1.The celiac ganglion 2.The superior mesenteric ganglion 3.The inferior mesenteric ganglion 4.The aorticorenal ganglion 5.The renal ganglion Slide 22 Parasympathetic Ganglia pre- and postganglionic neurons in parasympathetic division synapse in terminal ganglia These ganglia located close to or in visceral organ Terminal ganglia in head have specific names: 1.Ciliary ganglion 2.Pterygopalatine ganglion 3.Submandibular ganglion 4.Otic ganglion Preganglionic axons LONG, postganglionic axons SHORT Slide 23 Sympathetic Division: Preganglionic neurons connect with postganglionic neurons in one of the following ways (see next slide for diagram): 1.Synapse in ganglion it first reaches 2.Ascend or descend the sympathetic chain 3.Continue, without synapsing, to a prevertebral ganglion 4.Continue, without synapsing, to adrenal medulla One sympathetic preganglionic neuron may have many branches and may synapse with 20+ postganglionic neurons. Projection of divergence explains why sympathetic responses can affect many effectors at once Slide 24 Different types of connections between ganglia and postganglionic neurons in the sympathetic division of the ANS Slide 25 Parasympathetic Division: Because postganglionic neurons are short (parasym. ganglia are located near effectors), stimulation involves only one visceral effector (organ) Slide 26 Axons form tangled networks autonomic plexuses Major ones are Cardiac plexus, which supplies the heart Pulmonary plexus, which supplies the bronchial tree There are also plexuses in the abdomen and pelvis Slide 27 Pathway for thoracic and L1-3: Myelinated axon exits lateral gray horn via ventral root & spinal nerve Then passes through white ramus communicans and on to sympathetic trunk ganglion white refers to myelinated Slide 28 Sympathetic trunk ganglia: lie anterior and lateral to vertebral column Typically 3 cervical, 11 or 12 thoracic, 4 or 5 lumbar, 4 or 5 sacral, and 1 coccygeal ganglion Although trunk extends to the neck, ganglion only receive preganglionic axons from the thoracic and lumbar segments Slide 29 Cervical portion of trunk divided into: Superior ganglia: innervate head and heart Middle ganglia: innervate the heart Inferior ganglia: innervate the heart Slide 30 The thoracic and lumbar portions innervate most other viscera, sweat glands, blood vessels and arrector pili muscles of hair follicles Slide 31 Axons leave the sympathetic trunk in 4 possible ways: 1.They can enter spinal nerves 2.They can form cephalic periarterial nerves 3.They can form sympathetic nerves 4.They can form splanchnic nerves They innervate different parts of the body (no need to know details) Slide 32 Postganglionic axons leaving the sympathetic trunk ganglia enter the gray ramus communicans gray because unmyelinated Slide 33 Craniosacral outflow: Cell bodies found in 1) brain stem nuclei (axons emerge as part of a cranial nerve) and 2) lateral gray matter of sacral segments S2-S4 (axons emerge as sacral spinal nerves) All preganglionic axons of both cranial and sacral outflows end in terminal ganglia (the head terminal ganglia are named (see previous slide), the sacral terminal ganglia are not named and are found in the walls of the innervated viscera Slide 34 Cranial Outflow: (CNs III, VII, IX, & X) CN III innervates: Ciliary muscle (lens) pupillary sphincter (pupil) CN VII innervates: Lacrimal (tear film) Submandibular and sublingual (salivary) glands CN IX innervates: Parotid (salivary) gland CN X innervates: Heart, Larynx, Trachea, Bronchi, Lungs, Liver, Gallbladder, Stomach, Pancreas, Small intestine (and part of large intestine) Slide 35 Slide 36 Sacral Outflow: (S2, S3, S4) Form pelvic splanchnic nerves Innervate smooth muscle and glands in the walls of: Colon and rectum Urinary bladder External genitals Uterus Slide 37 Please read half page section on page 593 of Tortora pdf This system is FYI only Slide 38 Anatomy & Physiology: Patton & Thibodeau Slide 39 Primary role of the sympathetic NS is to maintain optimal blood supply in organs Normal activity of the sympathetic NS will stimulate smooth muscle in vessel walls (just at the right amount) Increase in sympathetic NS constricts vessels, decrease dilates vessels E.g., lying to standing: BP increased to prevent fainting Slide 40 Role of sympathetic NS described using fight or flight responses System prepares for vigorous muscle activity when under threat Vasoconstriction in skin and gut all blood to muscles Blood glucose increases Bronchi/coronary vessel dilate BP/heart rate increase (Digestion reduces) Slide 41 Sympathetic activity regulates temperature through effectors on skin Signals control Diameter of blood vessels Secretion of sweat glands Erection of hairs Slide 42 Blood pools in skeletal muscle vessels when their walls are relaxed If pooling of blood in the lower limbs and abdomen is not prevented when a person assumes an upright position, the resulting drop in blood pressure can deprive the brain of adequate blood supply, causing syncope (fainting) Normally, the pooling of blood is prevented by vasoconstriction of the capacitance vessels, before the change in position Slide 43 Sympathetic signals dilate the pupil of the eye and assist in elevating the upper eyelid. The levator palpebrae superioris muscle consists of both smooth and skeletal muscle fibers Only the smooth muscle fibers are innervated by the sympathetic nervous system (The skeletal muscle fibers are innervated by the oculomotor cranial nerve) Sympathetic fibers also innervate salivary glands; their activation causes secretion of thick saliva, which causes a sensation of dryness in the mouth Slide 44 Sym and parasym work together in normal conditions E.g., para tends to slow/weaken heartbeat so sym functions to maintain normal beat/strength Sym dominates during times that require fight or flight Parasym dominates during inbetween times to rest and repair Slide 45 Some organs have synergistic activity of the two systems (opposing actions are balanced to provide optimal organ function): Actions on thoracic & abdominal viscera Bladder and bowels Pupil of eye Some independent functions: Sym: e.g., elevation of upper eyelid Para: e.g., increasing convexity of lens Slide 46 Parasympathetic cell bodies in brainstem and sacral spinal cord: craniosacral outflow Sympathetic cell bodies located T1-L2 levels: thoracolumbar outflow Slide 47 Parasympathetic activity decreases cardiac activity; facilitates digestion; increases secretions in the lungs, eyes, and mouth; controls convexity of the lens in the eye; constricts the pupil; controls voiding of the bowels and bladder; and controls the erection of sexual organs The sympathetic nervous system optimizes blood flow to the organs, regulates body temperature and metabolic rate, and regulates the activity of viscera Slide 48 Horners Syndrome Syncope Tests of Autonomic Function Slide 49 If a lesion affects the sympathetic pathway to the head, sympathetic activity on one side of the head is decreased This leads to ipsilateral drooping of the upper eyelid, constriction of the pupil, and skin vasodilation, with absence of sweating on the ipsilateral face and neck Slide 50 Interruption of blood supply, trauma, tumor, cluster headache, or stellate ganglion block may cause Horner's syndrome Cluster headache is a severe headache on one side of the head that lasts a few minutes to 3 hours and occurs as a series of headaches Slide 51 Slide 52 Loss of consciousness due to inadequate blood flow to the brain Blood flow to head restored when person is horizontal Vasovagal attack: Vagal stimulation to heart follow the intramuscular vasodilation Slows heart, further decreasing BP, nausea, salivation, increased perspiration Excessive activity of both sympathetic and parasympathetic systems Scary for bystanders!! Slide 53 BP in supine position, then in standing position Sweat test (filter paper placed on skin and then weighed) Hand vasomotor test (skin temp recorded before and after hands in cold water vasoconstriction) Valsalva test Slide 54