AUTONOMIC NERVOUS SYSTEM

Transcription

1 AUTONOMIC NERVOUS SYSTEM assoc. prof. Edyta Mądry MD, PhD Department of Physiology Poznań University of Medical Sciences

2 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))

3 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

4 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

5 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.

6 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.

7 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.

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9 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)

10 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!!!

11 Efferent pathways of ANS (Th1-12 i L1-3) (III, VII, IX, X, S2-4)

12 Autonomic ganglion

13 Ganglionic transmision

14 Autonomic and somatic efferent innervation

15 Effectors of ANS smooth muscles heart glands nervous tissue adipose tissue

16 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)

17 Autonomic Nervous System: controls visceral functions conscious control minimal (UNVOLUNTARY) Somatic Nervous System: controls skeletal muscles under conscious control (VOLUNTARY)

18 Autonomic Nervous System AUTONOMIC NERVOUS 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

19 Adrenal medulla 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

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21 Lie detection, truth verification Polygraphy

22 Autonomic Nervous System AUTONOMICZNY UKŁAD Techniques based on meditation allow, to a certain degree, consciously control AUN. The relaxation response - in oxygen consumption, HR, RR, respiration rate

23 Regulatory systems of of 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

24 General characteristics of ANS 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

25 Comparison of efferent pathways SNS and PNS Sympathetic Anatomical localization Thoracolumbar segments (Th1-12; L1-3) Preganglionic fibers Postganglionic fibers Transmitter (ganglia) Short Long ACh NE Transmitter (nerve fiber ends) Parasympathetic Cranial and sacral segments (III, VII, IX, X; S2-4) Long Short ACh ACh

26 Different nerve endings in ANS Discrete ( precise ) synapses of PNS Diffuse synapses of SNS activate large surface area of one cell or large number of cells

27 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!!!

28 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

29 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

30 Paradoxical fear

31 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

32 Acetylcholine metabolism Acetylcholine Choline acetyltransferase (ChAT) Acetylcholinesterase (AchE) Acetyl-CoA + Choline Acetate + Choline

33 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

34 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

35 Reflexes of ANS Viscero-visceral Viscero-somatic Somato-visceral From interoreceptors to internal organs (effectors) e.g. micturition, defecation From internal organs to SNS e.g. reffered pain or muscular defense (convergention of the afferent pathways onto one spinal segment) From exteroreceptors to internal organs e.g. acupuncture, warm compresses

36 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

37 Referred Pain

38 Referred Pain Referred Pain Dr n. med. Edyta Mądry

39 Receptors for autonomic transmitters Cholinergic: - nicotinic (N) - muscarinic (M) Adrenergic: - alpha - beta

40 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)

41 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

42 Adrenergic receptors Alpha receptors norepinephrine Beta receptors - epinephrine

43 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)

44 Adrenergic receptors 2 Adrenergic receptors 2 Rec 2 mainly in the presynaptic terminals - autoreceptors; their activation controls the amount of neurotansmitter that is released (inhibition of reuptake-feedback inhibition) Inhibition of adenylate cyclase and inhibition of camp generation Agonist clonidine Antagonist - yohimbine

45 Adrenergic receptors 1 and heart, kidney, adipose tissue; 2 smooth muscles of airways second messenger - camp Activation of presynaptic 2 receptors increases release of NE (feedback excitation) Agonist - phenoterol ( 2) Antagonist - propranolol (nonselective), metoprolol ( 1)

46 Ganglionic transmission Which of the autonomic receptors is most important in ganglionic transmission?

47 Phase 1: ACh binds to N receptor on ganglionic cell causes depolarization (fepsp); ACh binds to M1 receptor (SIF cells) causes dopamine release; Dopamine binds to D1 receptor causing K + permeability and hyperpolarization (IPSP) Phase 2: ACh binds to M1 and M4 receptors causing K + permeability and slow depolarization (sepsp) Phase 3: (lsepsp) Gn-RH as a neuromodulator causes slow depolarization

48 The effects of ANS 1. Which system is responsible for stress response? 2. Describe the changes in fight-orflight reaction

49 Adrenergic and cholinergic stimulation Organ SNS PNS Heart Bronchi rate and force (β1) dilation (β2) mucus inhibition (α1) rate and force (M1) constriction (M3) mucus-increase (M1) Pupil dilation (α1) constriction (M1) Adipose tissue lipolysis (β3) no effect Kidney External male reproductive organs urine production (α1, β1) ejaculation (α1) urine production erection (M1)

50 Adrenergic and cholinergic stimulation Organ SNS PNS Bladder Rectum Gastrointestinal system Salivary glands relaxation of detrusor (β2, β3), contraction of internal sphincter(α) contraction of internal sphincter, relaxation of smooth muscles peristalsis (β2 ) and gastric juice production (α1, α2) production of high viscosity saliva (α1) contraction of detrusor (M2, M3), relaxation of internal sphincter relaxation of internal sphincter contraction of smooth muscles peristalsis (M1) and gastric juice production (M1) production of watery saliva (M1)

51 Disorders of the Autonomic Nervous System: Raynaud s Disease Raynaud s disease characterized by constriction of blood vessels Provoked by exposure to cold or by emotional stress

52 Disorders of the Autonomic Nervous System: Hypertension Hypertension high blood pressure Can result from overactive sympathetic vasoconstriction

53 Disorders of the Autonomic Nervous System: Achalasia of the Cardia Achalasia of the cardia Defect in the autonomic innervation of the esophagus

54 Quick repetition camp receptors: ATP Adenylate cyclase camp Protein kinase A Cellular effects: e.g. increased influx of Ca ++ in heart; activation of lipase in the adipose tissue lipolysis

55 Phosphatidylinositol cycle receptors: Quick repetition T+R+G s +GTP Phosphatidylinositol biphosphate (PIP 2 ) Phospholipase C Phosphatidylinositol (PIP) IP 3 Inositol triphosphate - release of Ca ++ from ER Protein kinase C - proton pump activation DG diacylglycerol - protein phosphorylation

56 Quick repetition Convertion of an extracellular event - the binding of a signal molecule into an intracellular response that modifies the behavior of target cell Phase I binding of first messenger (transmitter) to the receptor (T+R) Phase II transduction of a signal into the intracellular compartment. T+R complex interacts with a specific G-protein; T+R+G complex binds GTP, which activates subunit of G protein Phase III activated subunit of G protein activates (or inhibits) a specific enzyme (eg. adenylate cyclase or phospholipase C), which causes synthesis of second messenger

57 Quick repetition When a first messenger binds to a G-protein coupled receptor, the receptor changes its conformation and activates several G-protein subunits. Each subunit breaks away from the complex, and activates a single effector protein, which in turn, generates many intracellular second -messenger molecules. One second messenger activates many enzymes, and each activated enzyme can regulate many target proteins (amplification)

58 Quick repetition Action of Epinephrine Action of Epinephrine 9yaEUbv8Sz1AMve45

59 Amplification

60 Quick repetition When a first messenger binds to a G-protein coupled receptor, the receptor changes its conformation and activates several G-protein subunits. Each subunit breaks away from the complex, and activates a single effector protein, which in turn, generates many intracellular second -messenger molecules. One second messenger activates many enzymes, and each activated enzyme can regulate many target proteins (amplification)

61 Quick repetition Parasympathetic Responses Enhance rest-and-digest activities Mechanisms that help conserve and restore body energy during times of rest Normally dominate over sympathetic impulses SLUDD type responses = salivation, lacrimation, urination, digestion & defecation and 3 decreases --- decreased HR, diameter of airways and diameter of pupil 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

62 Quick repetition

63 Quick repetition Reflexes Reflex is a fast, involuntary, unplanned sequence of actions that occurs in response to a particular stimulus. Some reflexes are inborn ( pulling your hand away from a hot) Other reflexes are learned or acquired. 63

64 Quick repetition Reflex arc The pathway followed nerve impulses that produce a reflex is a reflex arc. A reflex arc includes the following five function components: sensory receptor sensory neuron integrating center motor neuron effector