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Autonomic Nervous System

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Aims of session

• To review the basic structure and function of the Autonomic Nervous System (ANS)

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Objectives

Learners should be able to:

1. Describe the basic structure and general functions of the sympathetic and parasympathetic divisions of the autonomic nervous system

2. Describe the fight’/’flight’ responses and cooperative effects of the sympathetic and parasympathetic sysyem on different organs.

Nervous System Divisions

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Encased in the Cranium and vertebral column

allows nerve connections between the CNS and the organs and tissues of the body i.e. the nerve trunks, plexus and

nerve fibres

Nervous System - Physiology

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E.G Skeletal muscle and

joint movement

Regulating: Cardiorespiratory ,Gastrointestinal,Genitourinary Reproductive , Integumentary Neurological , Endocrine systems

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Ganglia- e.g..

Part of the nervous system that carries out its functioning automatically i.e. without conscious control. With such organs and tissue are able to function in either a decreased or increased manner in order to maintain homeostasis

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GanglionA mass of nerve cell bodies RECAP Dorsal root ganglia – sensory nerves connect CNS with

PNS

Autonomic GangliaAutonomic ganglia -clusters of neurones and a junction

between autonomic nerves originating from the CNS and autonomic neurones serving peripheral target organs.

CNS to ganglia = Preganglionic

Ganglia to effector organ = Postganglionic

Many sympathetic and parasympathetic ganglions run from the top to the bottom of the spine. 21/04/23 : obrienmp@cf.ac.uk 8

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Physiological Similarities and Differences

Sympathetic

nerve type

Myelinated /

Unmyelinated

Distribution Neurotransmitter

(normally)

Function

Preganglionic Myelinated CNS to Ganglion

Acetylcholine Fight’ or ‘Flight’ response

Postganglionic Unmyelinated. Throughout body

Noradrenaline.

Parasympathetic

nerve type

Myelinated /

Unmyelinated

Distribution Neurotransmitter

(normally)

Function

Preganglionic MyelinatedCNS to Ganglion

Acetylcholinereturns body to normal state after a fight/flightPostganglionic Unmyelinated.

Throughout body

acetylcholine.

Postganglionic fibres i.e. between the Ganglion and target tissue ganglion) Preganglionic fibres i.e. between the CNS and the ganglion anglionic fibres i.e. between the Ganglion and target tissue ganglion)

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What would be happening to an arteriole with sympathetic nerve

stimulation?

What would be happening to the Gut wall with parasympathetic

nerve stimulation?

Sympathetic Inhibitory and Excitatory Functions

2 types of receptors to Sympathetic nerve excitation - Alpha and Beta

Adrenaline excites both alpha and beta receptors equally

Noradrenaline excites mainly alpha receptors.

There are also subtypes of each – more of this later on21/04/23 13

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Autonomic Nervous System EffectsStructure Sympathetic Stimulation Parasympathetic Stimulation

Iris (eye muscle) Pupil Dilation Pupil Constriction

Salivary Glands Saliva production reduced Saliva production increased

Oral/Nasal Mucosa

Mucus production reduced Mucus production increased

HeartHeart rate and force increased

Heart rate and force decreased

Lung Bronchial muscle relaxed Bronchial muscle contracted

Stomach Peristalsis reducedGastric juice secreted; motility increased

Small Intestine Motility reduced Digestion increased

Large Intestine Motility reduced Secretions and motility increased

LiverIncreased conversion ofglycogen to glucose

Reduction in conversion of glycogen to glucose

Kidney Decreased urine secretion Increased urine secretion

Adrenal medullaNoradrenaline andadreanaline secreted

Secretion of Adrenaline and noradrenalin

BladderWall relaxedSphincter closed

Wall contractedSphincter relaxed

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OrganOrgan Sympathetic StimulationSympathetic Stimulation Parasympathetic StimulationParasympathetic Stimulation

HeartHeart

Increased heart rate beta1 (& beta2) Decreased heart rate

Increased force of contraction beta1

(& beta2)Decreased force of contraction

Increased conduction velocity Decreased conduction velocity

ArteriesArteriesConstriction (alpha1) Dilation

DilationDilation (beta2)

VeinsVeinsConstriction (alpha1)

 Dilation (beta2)

LungsLungs Bronchial muscle relaxation (beta2)

Bronchial muscle contraction

Increased bronchial gland secretions

GastroGastroIntestinalIntestinal tracttract

Decreased motility (beta2) Increased motility

Contraction of sphincters (alpha) Relaxation of sphincters

Major Organ Responses to Autonomic ImpulsesMajor Organ Responses to Autonomic Impulses

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LiverLiver

Glycogenolysis (beta2 & alpha)

Glycogen synthesisGluconeogenesis (beta2 & alpha)

Lipolysis (beta2 & alpha)

KidneyKidney Renin secretion (beta2)  

BladderBladderDetrusor relaxation (beta2) Detrusor contraction

Contraction of sphincter (alpha) Relaxation of sphincter

UterusUterus

Contraction of pregnant uterus (alpha)

 Relaxation of pregnant and non-pregnant uterus (beta2)

EyeEye Dilates pupil (alpha) Constricts pupil

Increased lacrimal gland secretions

Submandibular Submandibular & parotid & parotid glandsglands

Viscous salivary secretions (alpha) Watery salivary secretions

Major Organ Responses to Autonomic ImpulsesMajor Organ Responses to Autonomic ImpulsesOrganOrgan Sympathetic StimulationSympathetic Stimulation Parasympathetic StimulationParasympathetic Stimulation

SkinSkin Pilomotor muscles contractSweat glands secrete slightly