Autonomic Nervous System - Dr Valerio (2025).pdf

AUTONOMIC NERVOUS SYSTEM PHYSIOLOGY A: Midterms Lec 1 DR. GLORIA VALERIO |SEPT 13, 2021 OBJECTIVES 5. T...

AUTONOMIC NERVOUS SYSTEM PHYSIOLOGY A: Midterms Lec 1 DR. GLORIA VALERIO |SEPT 13, 2021 OBJECTIVES 5. Trigeminal At the end of the lecture, the student should be able to: 6. Abducens 1. Review the concepts in nervous transmission 7. Facial 2. Discuss functional division of the nervous system 8. Vestibulocochlear 3. Differentiate Somatic and Autonomic Nervous Systems. 9. Glossopharyngeal 4. Differentiate the divisions of autonomic nervous system. 10. Vagus a. Anatomic b. Biochemical 11. Spinal accessory nerve c. Physiologic/Functional 12. Hypoglossal d. Pharmacologic Cranial Nerves associated with the autonomic 5. Correlate with common clinical conditions nervous system References: o 3 (Oculomotor) Dr. Valerio’s 2021 Lecture o 7 (Facial) AUTONOMIC NERVOUS SYSTEM o 9 (Glossopharyngeal) Part of the nervous system that regulate visceral function o 10 (Vagus) or functions of different internal organs Spinal Nerves – originated from the different segments o Regulation of cardiovascular function of the spinal cord o Regulation of respiratory function o Spinal Nerves associated with the o Regulation of gastrointestinal function autonomic nervous system: o Regulate secretions of different exocrine glands § Thoracic (T1-T12) (including sweat glands and salivary glands) § Lumbar (L1-L3) Basically, almost all functions of the internal organs are § Sacral (S2-S4) regulated by the autonomic nervous system REFLEX ARC MAIN DIVISION OF HUMAN NERVOUS SYSTEM Organize all the activity of the nervous system Although the nervous system is divided into two, they are actually connected because the nerves that make up the PNS originates from the CNS. CENTRAL NERVOUS SYSTEM Made up of different parts of the brain and different segments of the spinal cord Different parts of the brain o Cerebral cortex o Hypothalamus o Thalamus FIVE COMPONENTS OF REFLEX ARC o Basal ganglia SENSORY RECEPTORS o Cerebellum Specialized structures located in almost all parts of the o Brainstem (midbrain, pons, and medulla) body that can be stimulated by changes inside or outside Different segments of the spinal cord the body o Cervical (8 pairs) In the body wall, walls of blood vessels, walls of different o Thoracic (12 pairs) internal organs, skin, muscle, intestinal wall, heart muscle o Lumbar (5 pairs) walls o Sacral (5 pairs) Examples: o Coccygeal (1 pair) o Skin – Thermoreceptors PERIPHERAL NERVOUS SYSTEM § stimulated by changes in temperature Made up of 12 pairs of Cranial Nerves and 31 pairs of o Eyes – Photoreceptors Spinal Nerves § stimulated by changes in the wavelength of light Cranial Nerves – originated from the nuclei located in the o Arterial wall – Baroreceptors brainstem § stimulated by the arterial wall stretch because of an 1. Olfactory increase in the blood pressure 2. Optic o Intestinal wall – Mechanoreceptors 3. Oculomotor § stimulated when intestinal wall is stretched 4. Trochlear because of retained food Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 1 of 14  AUTONOMIC NERVOUS SYSTEM o Mouth – Chemoreceptors A segment of the small intestine becomes distended § stimulated by the chemical composition of food because of retained food. The mechanoreceptors will Initially, when these receptors are stimulated, it will generate a sensory impulse to be transmitted by an generate a local potential, or which we call receptor afferent nerve to the spinal cord, which is the center. From potential. the spinal cord, a motor impulse is transmitted by an The receptor potential can then be converted into an efferent nerve to the effector, which is the smooth muscle action potential or sensory impulse. in the intestinal wall. The smooth muscle would response The sensory impulse will then be transmitted by an by contracting, which would cause retained food to be afferent nerve to the center (CNS: brain and spinal pushed along the small intestine. cord) AFFERENT NERVE A sensory nerve that transmits sensory impulses from sensory receptors to the center. CENTER The brain and the spinal cord It interprets and analyzes the sensory impulse transmitted to it. It responds by generating another type of action potential, which we now call a motor impulse From the center, the motor impulse would then be transmitted by an efferent nerve to the different effector Peripheral Nervous System – spinal nerves and cranial cells/organs in the body nerves are made up of bundle of nerve fibers EFFERENT NERVE 4 TYPES OF NERVE FIBES Motor nerve that transmits motor impulses from the SOMATIC AFFERENT center to the effector cell Sensory nerve that will transmit sensory impulses from EFFECTOR CELL sensory receptors (head, body walls, extremities) going to It will respond to whatever the impulse is, which could the center. either be excitatory or inhibitory. SOMATIC EFFERENT Effector cell receives and performs the action dictated by Motor nerve that transmits motor impulses from the the motor impulse. center to the effector cell Four types of effector cell: It only innervates one type of effector cell which is the o Skeletal / Striated Voluntary Muscle – present skeletal striated or voluntary muscle only mostly on the body wall VISCERAL AFFERENT o Cardiac Muscle – in the heart Sensory nerve that transmits sensory impulses from o Smooth Muscle – in the wall of the viscera sensory receptors located in the wall of different internal o Glands organs going to the center VISCERAL EFFERENT Motor nerve that transmits motor impulses from the center to effector cells. It innervates three types of effector cells, which are ALWAYS REMEMBER – cardiac muscle cells, visceral smooth muscle cells, Afferent – sensory, from receptor to center and glands Efferent – motor, from center to effector TWO MAIN DIVISIONS OF PNS Examples of a Reflex Activity Made up of 12 pairs of cranial nerves originating from the Food in the mouth, the chemical composition of the food brainstem and 31 pairs of spinal nerves originating from will stimulate the chemoreceptors present in the taste the spinal cord. buds. These receptors would then generate a sensory SOMATIC NERVOUS SYSTEM impulse which is transmitted by the afferent nerve to the Composed of somatic afferent and somatic efferent medulla, which is the center. From the medulla, a motor impulse is transmitted by an efferent nerve to the effector, which is the salivary glands. These effectors increase the production of saliva Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 2 of 14  AUTONOMIC NERVOUS SYSTEM AUTONOMIC/VISCERAL NERVOUS SYSTEM Composed of visceral afferent and visceral efferent TAKE NOTE: Although almost all of autonomic activity are involuntary, there are some autonomic activities that can be mostly involuntary and partly voluntary. Respiration – normal quiet respiration is involuntary, however once we’re told to breathe deeply, hold our breaths – it becomes voluntary. Micturition – you feel the urge to urinate, but you can still hold it voluntarily. However, if urinary bladder is already stretched – it will initiate an autonomic reflex, making you pee. Defecation – when rectal pressure reaches 18mmHg, you feel the urge to defecate but you can still contract your anal sphincter (voluntary control), but when it reaches 55mmHg – it will initiate an autonomic reflex, making you defecate. AUTONOMIC NERVOUS SYSTEM Enteric NS Sympathetic NS Parasympathetic NS ENTERIC NERVOUS SYSTEM Nervous system of the GIT (stomach, small intestine, large intestine, rectum, anus) Neurons in the GIT lies in the gastrointestinal walls from the esophagus all the way to the anus These neurons are grouped into two plexuses: o Myenteric § Auerbach’s Plexus § Located in the muscular layer of GI wall § Regulates motor activity of GIT (peristalsis motor activity) o Meissner’s Plexus § Located in the submucosal layer of GI wall § Regulates secretory activity of the GIT (secretion of gastrointestinal glands) § These are automatic cells that can regulate both motor and secretory activity of GIT Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 3 of 14  AUTONOMIC NERVOUS SYSTEM Activities of enteric neurons are regulated by: SYMPATHETIC POSTGANGLIONIC FIBERS à synapse with enteric neurons (effector cell: NMJ) à inhibits or decreases the activity of the ENS à decreasing GIT motor and secretory activity. PARASYMPATHETIC PREGANGLIONIC FIBERS à synapse with enteric neurons (peripheral ganglion: NEJ) à increases the activity of ENS à increasing GIT motor and secretory activity (excitatory) ANATOMICAL DIFFERENCE Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 4 of 14  AUTONOMIC NERVOUS SYSTEM From left to right SYMPATHETIC Short Red Lines (Left) – Sympathetic preganglionic Almost all visceral organs receive dual innervation nerve fibers (T1-L3) including celiac ganglion, superior (sympathetic and parasympathetic) mesenteric ganglion, inferior mesenteric ganglion Whenever sympathetic and parasympathetic are present (Collateral ganglion) in one organ, almost always they have opposite effects Sympathetic Chain - Peripheral ganglia (superior (not antagonistic because they regulate) but not always. cervical, middle cervical) Examples: Collateral ganglia – Celiac ganglion, superior mesenteric o if sympa ↑heart rate; parasympa ↓ heart rate o If you cut the vagus nerve innervating the SA node of ganglion, inferior mesenteric ganglion heart, there will be tachycardia (sympa ↑ heart rate) Long Red Lines – postganglionic o if sympa ↑ intestinal motility; parasympa ↓ intestinal Effector organs motility o if sympa causes pupillary dilatation; parasympa PARASYMPATHETIC causes pupillary constriction o if sympa causes bronchodilatation; parasympa causes bronchoconstriction Cranial Nerve III (Oculomotor nerve) – blue line from brain stem to the ciliary ganglion (Parasympathetic BIOCHEMICAL TRANSMISSION preganglionic nerve) NEUROTRANSMITTER AGENT (NTA) Oculomotor nerve synapses with the ciliary ganglion Chemical substance that mediates transmission of motor Lighter blue line from the ciliary ganglion is the post impulses in both somatic and autonomic pathways ganglionic nerve which goes to the effectors (ciliary Released in 3 locations: muscles in the eye, pupillary constrictor in the iris) o Somatic NMJ o Autonomic ganglion o Autonomic NEJ Acetylcholine (Ach) – mediates cholinergic transmission Norepinephrine (NEP) – mediates noradrenergic/adrenergic transmission SITE OF TRANSMISSION In the somatic efferent pathway – NTA is released into NMJ o NMJ – mediate transmission of motor impulses from a somatic efferent nerve ending to the Nicotinic 1 receptor membrane of the skeletal muscle In autonomics – there are two sites where NTA are released. Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 5 of 14  AUTONOMIC NERVOUS SYSTEM o Peripheral Ganglion – mediates transmission of FOUR STEPS IN BIOCHEMICAL TRANSMISSION impulses from autonomic efferent pre-ganglionic nerve 1. Synthesis and Storage of NTA that will occur at ending to the membrane of the peripheral ganglion the nerve ending o NEJ – where NTA will mediate transmission of Neurotransmitter impulses from an autonomic efferent post ganglionic o Synthesized by a neuron nerve ending to the membrane of the effector cell o Stored temporarily in vesicles located at the nerve or membrane of the visceral smooth muscle cell, cardiac axon terminal muscle, or glands. When an action potential or motor impulse is generated: o It travels along an axon o Depolarizes when it reaches the axon terminal o voltage-gated calcium channel will open that will allow calcium influx o Ca will bind to synaptotagmin on the vesicular membrane – making vesicles heavy, duct into membrane of axon terminal o Interaction between vesicular proteins o Fusion of vesicular membrane to membrane of nerve terminal o TAKE NOTE: Proteins in the membrane of the nerve terminal: § SNAP 25 § Syntaxin (nerve terminal membrane) § Synaptobrevin (vesicular membrane) 2. Release of NTA Exocytosis of NTA to the synaptic cleft NTA will bind with membrane receptors on the effector that will elicit a physiologic response from the effector 3. Interaction Between neurotransmitter agent and membrane receptors on the effector NTA will not remain permanently bound to the receptor After eliciting a physiologic response from the effector, the Photo labels neurotransmitter will now be deactivated and that will Axon terminal terminate effects of the neurotransmitter on the effector Somatic Nerve Ending 4. Deactivation o Effector: skeletal muscle Enzymatic Deactivation o Junction: Somatic NMJ o Enzymes destroy NTA at synaptic cleft Autonomic Preganglionic Nerve ending o There are enzymes that are located near the receptor, o Effector: peripheral ganglion so after eliciting a physiologic response from the o Junction: bet. Autonomic preganglionic fiber & PG effector, NTA is immediately deactivated by the Autonomic Postganglionic nerve ending enzyme o Effector: Smooth muscle cell, cardiac muscle cell, glands Vesicles (containing neurotransmitters) Receptors Effector Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 6 of 14  AUTONOMIC NERVOUS SYSTEM Reuptake G-PROTEIN x SECONDARY MESSENGER SYSTEM o Bumabalik sa pinanggalingan cAMP o NTA is actively transported back into the nerve NTA + R à Activate G-protein à (+) adenylyl cyclase à terminal (no longer enclosed by vesicle) à destroyed ­ cAMP à (+) Protein kinase A à phosphorylation of secondarily by enzymes in the nerve terminal [MAO specific IC enzymes à stimulation/inhibition of (Mono Amine Oxidase)] intracellular biochemical reactions in the cell Example o Catecholamines (EP & NEP) + b receptors o Acetylcholine + muscarinic receptors Phospholipase C (enzyme) NTA + receptor à Activate G protein à Phospholipase C stimulated and catalyzes reaction à breakdown of Phosphoinositol Biphosphate (PIP2) à Increase Inositol triphosphate (IP3) (increases Intracellular Calcium) and Diffusion away from the synapse diacylglycerol (DAG) à stimulates (+) Protein Kinase C o Aalis na yung neurotransmitter à phosphorylation of specific Intracellular proteins (IC o Circulates in the blood, will go to the liver where it will CHONs) à stimulation of specific intracellular biochemical be destroyed secondarily by hepatic enzymes [COMT reactions (Cathecol Omethyl Transferase)] NOTE: In the visceral and vascular smooth muscles, Ca binds with calmodulin to initiate contraction Example o Catecholamines + a receptors o Acetylcholine + muscarinic receptors TYPES OF MEMBRANE RECEPTORS ION CHANNELS/LIGAND-GATED ION CHANNELS Ionophores/Ionotropic Nicotinic receptors NTA + receptor: § open specific ligand-gated ion channels § depolarization & excitation of the effector § when stimulated by NTA, the response of the effector is immediate but short in duration § Response is always excitatory § Ex. Ach + nicotinic receptor G-PROTEIN COUPLED RECEPTOR Metabophore/Metabotropic o Metabotropic because of change in metabolism in the cell Muscarinic and Adrenergic o NTA + receptor: o activate g-protein o stimulate/activate specific intracellular enzymes o formation of second messengers (Intracellular ligands) o Intracellular ligands mediate the actions of the NTA on the effector o When stimulated, response of effector is delayed but longer in duration o Either excitatory or inhibitory Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 7 of 14  AUTONOMIC NERVOUS SYSTEM CHOLINERGIC TRANSMISSION CHOLINERGIC TRANSMISSION Mediated by acetylcholine 4 steps – Synthesis and Storage, Release, Interaction, When is it present? Where will acetylcholine mediate Deactivation transmission of impulses? 1. Synthesis and Storage of Acetylcholine o All somatic NMJ Acetylcholine is synthesized from Choline and Acetyl Co- o All autonomic ganglia Enzyme A o All parasympathetic NEJ Reaction is catalyzed by Choline acetyltransferase o Sympathetic Cholinergic NEJ Takes place on nerve terminals of: § Sweat glands o Somatic efferent nerve terminal – effector: skeletal § Vascular smooth muscles or blood vessels in the muscle skeletal muscle o Autonomic pre ganglionic (Sympathetic and NORADRENERGIC TRANSMISSION Parasympathetic) nerve terminal – effector: All sympathetic Adrenergic NEJ peripheral ganglion Mediated by norepinephrine o Parasympathetic Post Ganglionic – effectors: Cardiac muscle cell, visceral smooth muscle cell visceral smooth muscle, cardiac muscle, glands most sympathetic effects to different effector organs are o Sympathetic Cholinergic Post Ganglionic nerve mediated by NEP; ending – effectors: sweat glands and blood vessels in Sympathetic NS = Adrenergic division skeletal muscle o Except sweat glands and smooth muscle cell or blood 2. Release of Acetylcholine vessels of skeletal muscle Acetylcholine is released by exocytosis from the synaptic cleft 3. Interaction – Acetylcholine Binding to Specific Receptors Two types of cholinergic receptors that will bind to acetylcholine: Nicotinic receptors o Can be stimulated by small doses of nicotine o Can be classified as ligand gated ion channels (proteins) or ionophores – when stimulated by acetylcholine the response of the effectors is immediate, short in duration, always excitatory o When stimulated by acetylcholine à open up ligand gated sodium channels à depolarization à excitation of the effector Two subtypes: § Nicotinic 1 or NM Receptors – present in all somatic NMJ (membrane of skeletal muscle cell) binding of acetylcholine and N1 receptors can be blocked by curare (chemical compound) § Nicotinic 2 or NN Receptors – present in all autonomic ganglia in small doses of nicotine, it is excitatory in high doses of nicotine, it is inhibitory, becomes ganglionic blocker Muscarinic receptors o can be stimulated by small doses of Muscarine from a specific type of mushroom o present in all parasympathetic NEJ o Present also in sympathetic cholinergic NEJ o G-protein coupled receptors (glycoproteins) o When stimulated with acetylcholine, the response of effector is delayed, but longer in duration and can be excitatory or inhibitory Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 8 of 14  AUTONOMIC NERVOUS SYSTEM Five subtypes: NEGATIVE FEEDBACK EFFECT: § M1: Brain, stomach Regulate formation of norepinephrine § M2: Heart, Visceral smooth muscles Excess dopamine and norepinephrine – inhibit enzyme § M3: Visceral smooth muscle and glands tyrosine hydroxylase § M4: Visceral smooth muscle and glands Happens in sympathetic adrenergic postganglionic nerve § M5: Sphincter muscle or pupillary constrictor of ending the iris, esophagus, parotid gland, cerebral blood vessels Mechanism of action: o When acetylcholine binds with M2 receptor in the heart à decrease formation of CAMP à increase K conductance à hyperpolarization = effect on the heart: inhibitory o For M3 and M5, when acetylcholine binds à increase formation of Inositol triphosphate (IP3) and diacetyl glycerol (DAG)= effect: excitatory STEP 3: NOREPHINEPRINE BINDS TO ADREGENIC 4. Deactivation of Acetylcholine RECEPTORS Depends on location Adrenergic receptors – receptors that bind specifically with Two mechanisms: NE Enzyme Destruction / Deactivation All adrenergic receptors are G-coupled receptors o In somatic NMJ and autonomic NEJ Beta receptors is mediated by cAMP o Enzyme: acetylcholinesterase Five Types of Adrenergic Receptors: § Acetylcholine à Choline + Acetate Alpha 1 Re-uptake o Present in visceral smooth muscles and glands o Main mechanism in autonomic ganglia o Action is mediated by IP3 and DAG o Acetylcholine is re-uptake by preganglionic and then o When NE binds with alpha 1 receptor to vascular destroyed secondarily by the acetylcholinesterase smooth muscle à contraction à vasoconstriction o When NE binds with alpha 1 receptor in the radial muscle of the iris à contraction à pupillary dilatation (excitatory) Alpha 2 o Present in nerve terminals o When NE binds with alpha 2 à cAMP decrease à inhibits release of NE (negative feedback mechanism) Beta 1 o Present in heart Beta 2 o Present in visceral smooth muscle and glands ADREGERGIC TRANSMISSION o When NE binds with Beta 2 receptor in the bronchial STEP 1: SYNTHESIS OF NOREPINEPHRINE muscle à relaxation à bronchodilatation Norepinephrine is synthesized from the amino acid o When NE binds with Beta 2 receptor in vascular Phenylalanine à initially converted to Beta Tyrosine by smooth muscle à relaxation à vasodilatation the enzyme phenylalanine hydroxylase à converted to Beta 3 DOPA by the enzyme tyrosine hydroxylase à converted o Present in adipose cells to Dopamine by the enzyme DOPA decarboxylase à converted to Norepinephrine by the enzyme dopamine beta hydroxylase Happens only in sympathetic adrenergic postganglionic nerve ending – effectors: internal organs (cardiac muscle, visceral smooth muscle, glands) STEP 2: STORAGE AND RELEASE OF NOREPINEPHRINE Norepinephrine is temporarily stored in vesicles Release of Norepinephrine by exocytosis Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 9 of 14  AUTONOMIC NERVOUS SYSTEM POTENCY Norepinephrine o Strong stimulator of alpha and beta 1 receptors o Weak stimulators of beta 2 receptors Epinephrine o Strong stimulator of alpha, beta 1 and beta 2 receptors STEP 4: DEACTIVATION OF NOREPINEPHRINE If you have NEP released at the neuroeffector junction, the main Mechanism is Reuptake by Sympathetic Adrenergic Postganglionic Nerve When the NEP goes back to the postganglionic nerve, it will be destroyed secondarily by the enzyme Mono-Amine Oxidase (MAO) Others (Circulating NEP & EP from adrenal medulla) o Deactivated mainly by diffusion away from the junction and transported to the liver, where they will be destroyed secondarily by the enzyme catechol-O- methyl transferase (COMT) AUTONOMIC INNERVATION FIRST CONDITION Dual innervation of the same structure in the same organ of the sympathetic and parasympathetic NS and they will exert opposite or antagonistic effects Ex. Heart Sweat glands has 2 innervations – Alpha 1 and M3 SA node is the automatic cell in the heart: primary Generalized sweating – sympathetic cholinergic pacemaker in the heart that determines heart rate. It is Localized sweating (underarm, hands) – sympathetic innervated by a sympathetic nerve and parasympathetic adrenergic nerve There are some sympathetic preganglionic fibers that o Sympathetic nerve originates from T3, T4 and T5 synapse directly with the membrane of the adrenal Sympathetic preganglionic fiber will first synapse with medullary cells stellate ganglion of the sympathetic chain Adrenal medullary cells are histologically the same as Postganglionic fiber from stellate ganglion will release an autonomic ganglion Norepinephrine binding to Beta 1 receptor to the heart and Sympathetic preganglionic fibers release Ach à binds causes an ­cAMP=­Ca conductance=­heart rate with nicotinic receptors on the membrane of adrenal SA node can also be innervated by a parasympathetic medullary cells – Nicotinic 2 receptors nerve Upon sympathetic stimulation, adrenal medulla is also o Originate from vagus nerve of the medulla that stimulated and will release 80% Epinephrine and only 20% releases Acetylcholine, binding to M2 receptor of à released into circulating blood before transported in heart causing ¯cAMP =­K conductance =¯Heart rate NEJ where they will stimulate Adrenergic receptors à § Causing hyperpolarization so that the reinforcing sympathetic adrenergic effects parasympathetic or vagal effect of the SA node is Although adrenal medulla is an endocrine gland, it is inhibitory considered as part of sympathetic adrenergic nervous SAME STRUCTURE: SA node system SAME ORGAN: heart SYMPATHETIC EFFECTS Opposite effects of sympathetic and parasympathetic Direct – sympathetic nerve directly stimulates effector nerve organ o Sympathetic = increase heart rate Indirect – stimulated by circulating Epinephrine and o Parasympathetic / vagus = decrease heart rate Norepinephrine from adrenal medulla Sympathetic and parasympathetic are said to be in tone o Both regulate at the same time, the activity of the SA node Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 10 of 14  AUTONOMIC NERVOUS SYSTEM o Continuously active that fires impulses simultaneously Sympathetic innervation ONLY to maintain in a balance effect so that the heart rate will o Blood Vessels neither increase or decrease o Sweat Glands o The normal level of the heart rate will be maintained o Pyro-erector muscles in the skin (hair follicles) § About 60-100 per min o Kidneys SECOND CONDITION PHYSIOLOGIC DIFFERENCES Dual innervation of two different structures in the same organ à opposite effects Sympathetic and Parasympathetic are present but will innervate TWO DIFFERENT STRUCTURES in the SAME ORGAN and will have OPPOSITE EFFECTS Ex. Iris – has 2 types of smooth muscles Radial o Innervated by the sympathetic nerve originating from T1 and T2 o Sympathetic preganglionic fiber will synapse with the superior cervical ganglion à release NE and bind to Alpha 1 receptor in the radial muscle Sphincter/Constrictor pupillae o Parasympathetic nerve originating from C3 Oculomotor nerve from the midbrain o NTA: Acetylcholine o Receptor: M5 The pupil is the space in the middle of the iris o The action of the smooth muscle in the iris can affect the size of the pupil In the absence of light, SYMPATHETIC NS will predominate that will cause the radial muscle to contract FIGHT OR FLIGHT RESPONSE (CATABOLIC) and increases pupillary size o PUPILLARY DILATATION OR MIDRIASIS In the presence of light, PARASYMPATHETIC NS predominates and causes sphincter muscle to contract and decreases pupillary size o PUPILLARY CONSTRICTION OR MYOSIS OPPOSITE EFFECTS BUT BOTH EXCITATORY (BOTH CONTRACTION) THIRD CONDITION Dual innervation of the same structures in the same organ à synergistic effects Ex. Salivary Glands SYMPATHETIC stimulation will cause a mild to moderate increase in thick salivary secretion PARASYMPATHETIC stimulation will cause a profuse increase in watery salivary secretion Ex. Male Genitals SYMPATHETIC stimulation will cause ejaculation PARASYMPATHETIC stimulation will cause penile erection FOURTH CONDITION Single innervation Parasympathetic ONLY o Lacrimal glands o Nasal glands o Sublingual glands Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 11 of 14  AUTONOMIC NERVOUS SYSTEM REST OR DIGEST RESPONSE (ANABOLIC) BARORECEPTOR REFLEX Example of an autonomic reflex Regulates Arterial BP Stimulus is an increase in the ABP à will stretch the arterial walls à stimulate the baroreceptors à generate action potential à transmitted by sensory nerves to cranial nerve IX and X (Sensory division) à impulses to vasomotor center located in the medulla à from the center, impulses will be generated à transmitted by efferent nerve (sympathetic, parasympathetic) à Response: Decrease sympathetic outflow, increase parasympathetic outflow o With decrease sympathetic outflow § Vasodilation § Decreased cardiac activity § Decreased arterial blood pressure o With increase parasympathetic outflow § Decreased cardiac activity NOTE: No receptor for peripheral vasodilation and § Decreased arterial blood pressure lipolysis because they DO NOT have any parasympathetic Complete components of reflex arc = same sensory and innervations. Innervation is ONLY SYMPATHETIC. motor parts Parasympathetic predominates since no sympathetic. PHARMACOLOGIC DIFFERENCES CHOLINERGIC DRUGS Parasympathomimetic Drugs o Increase/potentiate cholinergic or parasympathetic effects o Mechanism: 1. Increase synthesis of ACh 2. Increase release of ACh 3. Increase interaction between ACh and cholinergic receptors 4. Decrease deactivation of Ach *By doing of those 4 steps, the drugs will mimic parasympathetic effects Examples: o Pilocarpine o Neostigmine *Both inhibiting the enzyme acetylcholinesterase à decrease deactivation of Ach *If you instill pilocarpine to the eye, there will be pupillary constriction § Pilocarpine is parasympathomimetic, it HYPOTHALAMUS inhibits acetylcholinesterase à mimics Highest center that regulates autonomic activities parasympathetic à constriction o Anterior: regulates cholinergic / PSNS activities * In pesticides, organophosphate is a component o Postero-Lateral: regulates adrenergic / SNS activities which also inhibits acetylcholinesterase. If there is Can still receive inputs from other parts of the brain – from pesticide poisoning cortex, thalamus, basal ganglia, etc. § Bradycardia o Reflex still has sensory § Pupillary constriction These is still no specific center in the cortex that can § Diarrhea identify as an autonomic center – since it is voluntary There is very little evidence that a localized autonomic center exists Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 12 of 14  AUTONOMIC NERVOUS SYSTEM Parasympatholytic Drugs *Drug that potentiate the action of MAO (Monoamine o Decrease or block cholinergic or parasympathetic oxidase) à Increase intestinal motility effects o Mechanism: 1. Decrease synthesis of ACh 2. Decrease or block release of ACh 3. Block the interaction between ACh and cholinergic receptors 4. Increase activation of ACh o Example: Atropine § Blocks the interaction between ACh and muscarinic receptors § When you instill atropine intravenously Tachycardia Constipation Dilation of pupil ADRENERGIC DRUGS Sympathomimetic Drugs o Increase or potentiate sympathetic adrenergic effects o Mechanism: 1. Increase synthesis of NEP 2. Increase the release of NEP 3. Increase the interaction between NEP and adrenergic receptors 4. Decrease the inactivation of NEP o Mimics sympathetic adrenergic effects o Example 1. Adrenaline (Epinephrine) o When you instill adrenaline to the eye § Dilation of pupil 2. Phenylephrine: alpha 1 agonist 3. Salbutamol *What will you give a patient with Asthma? 1. There is bronchoconstriction so there should be bronchodilation, which is a sympathetic effect 2. Administer Salbutamol o Will stimulate beta 2 receptors Sympatholytic Drugs o Inhibits/decreases/blocks sympathetic or adrenergic effects o Mechanism: 1. Decreases the synthesis of NEP 2. Blocks the release of NEP 3. Blocks the interaction between NEP and adrenergic receptors 4. Increase the activation of NEP o Example: Mostly cardiovascular drugs 1. Alpha-blockers 2. Beta-blockers 3. Calcium blockers o Increase reuptake of NEP which will decrease the heart rate. Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 13 of 14  AUTONOMIC NERVOUS SYSTEM Trans Makers: 1A-GURAY|LACANIN|MARQUEZ|NAPALANG|REYES Page 14 of 14