AUTONOMIC NERVOUS SYSTEM assoc. prof. Edyta Mądry MD, PhD Department of Physiology Poznań University of Medical Sciences Basic Functions of the Nervous System 1. Sensation ▪ Monitors changes/events occurring in and outside the body. Such changes are known as stimuli and the cells that monitor them are receptors. 2. Integration ▪ The parallel processing and interpretation of sensory information to determine the appropriate response 3. Reaction ▪ Motor output. – The activation of muscles or glands (typically via the release of neurotransmitters (NTs)) Nervous System’s Organization ◼ 2 big initial divisions: 1. Central Nervous System ▪ The brain + the spinal cord – The center of integration and control 2. Peripheral Nervous System ▪ The nervous system outside of the brain and spinal cord ▪ Consists of: – 31 Spinal nerves ▪ Carry info to and from the spinal cord – 12 Cranial nerves ▪ Carry info to and from the brain Peripheral Nervous System ◼ Responsible for communication btwn the CNS and the rest of the body. ◼ Can be divided into: Sensory Division =Afferent division – Conducts impulses from receptors to the CNS – Informs the CNS of the state of the body interior and exterior – Sensory nerve fibers can be somatic (from skin, skeletal muscles or joints) or visceral (from organs) Motor Division=Efferent division – Conducts impulses from CNS to effectors (muscles/glands) – Motor nerve fibers Motor Efferent Division ◼ Can be divided further: – Somatic nervous system ▪ Somatic nerve fibers that conduct impulses from the CNS to skeletal muscles – Autonomic nervous system ▪ Conducts impulses from the CNS to smooth muscle, cardiac muscle, and glands. Autonomic Nervous System ◼ Can be divided into: – Sympathetic Nervous System – Parasympathetic Nervous System These 2 systems are antagonistic. Typically, we balance these 2 to keep ourselves in a state of dynamic balance. Autonomic Nervous System – Sympathetic Nervous System ▪ “Fight or Flight” – Parasympathetic Nervous System ▪ “Rest and Digest” These 2 systems are antagonistic. Typically, we balance these 2 to keep ourselves in a state of dynamic balance. Principal components of ANS ◼ Central components: hypothalamus, certain brain stem regions and nuclei, spinal cord ◼ Peripheral components: ganglia and nerves (both sensory and efferent neurons) Functional anatomy of ANS ◼ Sympathetic division of ANS – central neurons (preganglionic nerve cells) in the intermediolateral cell column of the spinal cord (Th1-12 i L1-3) ◼ Parasympathetic division of ANS - central neurons in the nuclei of cranial nerves: oculomotor (III), facial(VII), glossopharyngeal(IX), vagus(X) and in the intermediolateral cell column of the spinal cord (S2-4) ◼ Enteric nervous system (ENS) – neurons lying within the walls of the gastrointestinal system (control of motility, secretion and blood flow) ◼ adrenal medulla !!! Efferent pathways of ANS (Th1-12 i L1-3) (III, VII, IX, X, S2-4) Autonomic ganglion Ganglionic transmision Autonomic and somatic efferent innervation Effectors of ANS ◼ smooth muscles ◼ heart ◼ glands ◼ nervous tissue ◼ adipose tissue Principal components of ANS ◼ Central components: hypothalamus, certain brain stem regions and nuclei, spinal cord ◼ Peripheral components: ganglia and nerves (both sensory and efferent neurons) Autonomic Nervous System: ◼ controls visceral functions ◼ conscious control – minimal (UNVOLUNTARY) Somatic Nervous System: ◼ controls skeletal muscles ◼ under conscious control (VOLUNTARY) AUTONOMICAutonomic NervousNERVOUS System SYSTEM ◼ Function of ANS is reflex (see the end of presentation) and simple autonomic reflexes in the peripheral parts of ANS may occur within one organ AdrenalAdrenal medullamedulla ◼ Functionally related to the symathetic nervous system. ◼ It is regarded as a sympathetic ganglion in which the postganglionic neurons have lost their axons and become secretory cells ◼ After hypothalamic stimulation it releases catecholamines, which may affect autonomic adrenic receptors Polygraphy Lie detection, truth verification AutonomicAUTONOMICZNY Nervous UKŁAD System ◼ Techniques based on meditation allow, to a certain degree, consciously control AUN. The relaxation response - in oxygen consumption, HR, RR, respiration rate RegulatoryRegulatory systemssystems of of ANS ANS ◼ Limbic system - „cerebral cortex of the ANS” (cortically stored past experiences can be evoked by external stimuli (smells, sounds, sights).They can cause emotional reactions leading to strong visceral responses coordinated by ANS) ◼ Hypothalamus ◼ Solitary nucleus of the medulla – coordinates heart and respiratory functions ◼ Circulating catecholamines – affect adrenergic receptors GeneralGeneral characteristicscharacteristics ofof ANSANS ◼ usually dual and antagonistic innervation of the visceral organs ◼ ganglia in the efferent pathways ◼ large quantity of synapses in the ganglia ◼ cotransmitters and neuromodulators (they may coexist at most ganglionic synapses ) ◼ postganglionic unmyelinated nerve fibers in the efferent pathways Comparison of efferent pathways SNS and PNS Anatomical Pre- Post- Transmitter Transmitter localization ganglionic ganglionic (ganglia) (nerve fiber fibers fibers ends) Sympathetic Thoraco- Short Long ACh NE lumbar segments (Th1-12; L1- 3) Para- Cranial and Long Short ACh ACh sympathetic sacral segments (III, VII, IX, X; S2-4) Different nerve endings in ANS Discrete („precise”) synapses of Diffuse synapses of SNS activate PNS large surface area of one cell or large number of cells SNS – fight-or-flight respons ◼ in the emergency situations; mobilization of energy sources ◼ increase in heart rate and force; RR ◼ redistribution of blood from viscera to active skeletal muscles and heart ◼ inhibition of gastrointestinal activity ◼ ACTH secretion and secretion of catecholamines ◼ dilation of respiratory airways ◼ widening of pupil and accomodation for far vision ◼ „cold” sweating ◼ total activation !!! PNS – feeding and vegetative behavior “rest-and-digest” ◼ energy accumulation from food (intestinal digestion and absorption); waste products removal ◼ increases intestinal motility ◼ urination and defecation ◼ activated partially according to body demands !!!! ◼ dominates during the night Sympathetic Trunks and Pathways A preganglionic fiber follows one of three pathways upon entering the paravertebral ganglia: 1. Synapses with the ganglionic neuron within the same ganglion 2. Ascends or descends the sympathetic chain to synapse in another chain ganglion 3. Passes through the chain ganglion and emerges without synapsing Paradoxical fear ◼ PNS- normally dominates over sympathetic impulses Paradoxical fear when there is no escape route or no way to win – causes massive activation of parasympathetic division – loss of control over urination and defecation Acetylcholine metabolism Acetylcholine Choline acetyltransferase (ChAT) Acetylcholinesterase (AchE) Acetyl-CoA Acetate + + Choline Choline Norepinephrine metabolism -NE may be recycled back into vesicles for later release (80%) -NE they may be degraded by the enzymes: monoamine oxidase (MAO) or catechol-O-methyltransferase (COMT) -NE may travel to the blood NON-adrenergic sympathetic fibers - examples ◼ Cholinergic: - sweat glands (except hands) - vascular smooth muscles in skeletal muscle - salivary glands - vascular smooth muscles of penis (erection) ◼ Histaminic: - vascular smooth muscles of skeletal muscle, skin, brain Reflexes of ANS Viscero-visceral Viscero-somatic Somato-visceral From interoreceptors From internal organs From exteroreceptors – to internal organs to SNS to internal organs (effectors) e.g. reffered pain or e.g. acupuncture, e.g. micturition, muscular defense warm compresses defecation (convergention of the afferent pathways onto one spinal segment) Referred Pain Pain stimuli arising from the viscera are perceived as somatic in origin - due to the fact that visceral pain afferents travel along the same pathways as somatic pain fibers Referred Pain Referred Pain Referred Pain Dr n. med. Edyta Mądry Receptors for autonomic transmitters ◼Cholinergic: ◼Adrenergic: - nicotinic (N) - alpha - muscarinic (M) - beta Cholinergic nicotinic receptors( N) ◼ ionotropic receptors are ion channels to which neurotransmitters bind directly in order to open them. ◼ localization: - autonomic ganglia - adrenal medulla - motor end plate ◼ activation (via Ach) produces fEPSP of the ganglionic neurons ◼ The effect of ACh binding to nicotinic receptors is always stimulatory ◼ agonist - nicotine ◼ antagonist - atropine, hexamethonium (ANS), curare (motor end plate) Cholinergic muscarinic receptors (M1-M8) ◼ Work via the second messenger system (IP3 and DAG) ◼ M1 – postsynaptic membranes; M2 – presynaptic membranes ◼ Agonist - muscarine ◼ Antagonist – - atropine,scopolamine M2), -pirenzepine (M1, M4) ◼ The effect of ACh binding: – Can be either inhibitory or excitatory – Depends on the receptor type of the target organ Receptor type M2 – inhibition of adenylate cyclase – outflux of K ions – membrane hyperpolarization Amanita muscaria-source of muscarine Adrenergic receptors ◼ Alpha receptors – norepinephrine ◼ Beta receptors - epinephrine Adrenergic receptors 1 ◼ Rec 1 - salivary glands, mucus glands of bronchi, muscles of: blood vessels, uterus, gastrointestinal tract ◼ They work via the second messenger system (IP3) ◼ Agonist – methoxamine, phenylephrine ◼ Antagonist – prazosin (1) and phentolamine (nonselective) AdrenergicAdrenergic receptorsreceptors 22 ◼ Rec 2 – mainly in the presynaptic terminals - autoreceptors;