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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 : [email protected] 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
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