Introduction to the Autonomic Introduction to the Autonomic Nervous system (ANS)Nervous system (ANS)

• Dr. Taha Sadig Ahmed

• MBBS , PhD ( England )• MAANEM ( USA) • Consultant , Clinical Neurophysiology, King

Abdulaziz University Hospital , Riyadh • Medical Advisor to the Saudi Board of

Neurophysiology • Associate Professor , College of Medicine

• ANS has two subdivisions: Sympathetic and

Parasympathetic Higher (CNS)controller of

ANS is the Hypothalamus : Posterior hypothalamus

controls Sympathetic NS Anterior hypothalamus

controls Parasympathetic NS These hypothalamic centers

exert their effects via the motor centers of he brainstem & spinal cord .. Moreover , the

hypothalamic centers are influenced by impulses from the Cerebral Cortex and Limbic System .

Q Q :What are the main differences between the:What are the main differences between the Somatic ( Voluntary ) Nervous SystemSomatic ( Voluntary ) Nervous System

and Autonomic( Involuntary ) Nervous Systemand Autonomic( Involuntary ) Nervous System ??

Somatic NS Somatic NS Controls skeletal muscles Controls skeletal muscles الهيكلية الهيكلية العضالت which , which , العضالت

are voluntaryare voluntaryإراديةإرادية , & considered a somatic , & considered a somatic structures structures

There is one lower ( efferent ) motor neuron There is one lower ( efferent ) motor neuron that directly innervates the skeletal muscle. that directly innervates the skeletal muscle.

The cell-body ( soma ) of this motoneuron is The cell-body ( soma ) of this motoneuron is located inside the CNS , either located inside the CNS , either

(a) in the brain (a) in the brain in case of cranial nerves , or in case of cranial nerves , or (b) in the spinal cord (b) in the spinal cord in case of spinal nerves in case of spinal nerves

.. The axon of the somatic motor neuron is The axon of the somatic motor neuron is

myelinated, therefore fast-conducting . myelinated, therefore fast-conducting .

Autonmic Nervous System ( ANS ) Autonmic Nervous System ( ANS ) :: Controls smooth and skeletal muscles , both of which Controls smooth and skeletal muscles , both of which

are involuntary . They are parts of the visceral organs are involuntary . They are parts of the visceral organs There are 2 lower motor neurons arranged in series :There are 2 lower motor neurons arranged in series :

(1)Preganglionic neuron :(1)Preganglionic neuron : , whose cell-body is situated , whose cell-body is situated inside the CNS ) , arising from inside the CNS ) , arising from

(a) spinal cord ( thoracolumbar segments ) (a) spinal cord ( thoracolumbar segments ) in case of in case of sympathetic sytem , sympathetic sytem ,

(b) brain ( cranial nerve autonomic nuclei ) + spinal cord ( (b) brain ( cranial nerve autonomic nuclei ) + spinal cord ( sacral segments ) sacral segments ) in case of parasympathetic system in case of parasympathetic system ..

The preganglionic fiber synapses within a ganglion with a 2The preganglionic fiber synapses within a ganglion with a 2ndnd

(2) (2) Postganglionic nerve : Postganglionic nerve : whose cell-body is situated whose cell-body is situated outside the CNS , in a ganglion . outside the CNS , in a ganglion .

Axons of preganglionic nerves are myelinated , but Axons of preganglionic nerves are myelinated , but those of postganglionic nerves are myelinated .those of postganglionic nerves are myelinated .

That is why postganglionic nerves are slower-That is why postganglionic nerves are slower-conducting than preganglionic nerves .conducting than preganglionic nerves .

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Somatic NS : one motor fiber that directly innervates to the skeletal muscle

ANS : Two motor neurns in series : preganglionic & postganglionic They supply the target cell , which can be a an involuntary muscle ( cardiac or smooth ) , or a gland ( e.g., salivary , gastric , sweat gland , etc )

Unmyelinated Fiber

Myelinated Fiber

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1. Preganglionic nerves in exit the CNS from the thoracic and lumbar segments of the spinal cord therefore , the sympathetic system is also called : “ Thoraco-lumbar Outflow “

2.Preganglionic fibers are myelinated 3.The postganglionic neuron cell-bodies are located in

paravertebral sympathetic ganglia , distant from their target tissues .

4.Postganglionic fibers are unmyelinated & longer than preganglionic fibers .

5.There is much divergence . The ratio (pre/post) being = 1:10 ;

6.This considerable divergence results in generalized and widespread effects on body functions when this system is activated .

Sympathetic (Thoracolumbar) System

Parasympathetic (Craniosacral ) system

1. Preganglionic nerves exit the CNS from the cranium and sacral segments of the spinal cord .Therefore , the paraympathetic system is also called “ Craniosacral Outflow “ .

2. Preganglionic fibers are myelinated 3. The postganglionic neuron cell-bodies are located in

parasympathetic ganglia , close to their target tissues or embedded in their walls

4. Postganglionic fibers are unmyelinated & shorter than preganglionic fibers .

5 . There is little divergence , the ratio of pre- to postgaglionic fibers is 1:3

6. This little divergence results in more specific ,discrete and localized effects in the body when this system is activated .

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General Effect of Sympathetic Activation ( Stimulation )

• Sympathetic system is active during stress and physical activity , such as physical exercise ( as in sport ) ; and during increased mental & emotional activity such as in fear, anger , worry , anxiety, severe pain preparing the body for fight or flight

• And promoting mechanisms which increase energy production & accelerate metabolism

Alternating fight & flight

Is this fight or flight ?

Is this fight or flight ?

العصبي الجهاز دراسة تجريو الحيوانات في الالإرادي

معامل في ااألنسانهذا معملنا مثل الفسيولوجيا

إنجلترا غرب في

Electrodes palced in special brain locations can make the animal aggressive ( fight ) عدواني or placid وديع

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General Effect of Parasympathetic Stimulation

• Parasympathetic system activities is related to the relaxed state and rest

• Conservation of body energy ,and • vegetative functions ( nutritive , body-building ,

restorative anabolic functions & tissue repair ) , & is more active during feeding , digestion & rest & sleep .

• The parasympathetic system is more active during feeding , digestion , leisure , rest

• & sleep

Ach is secreted by (1) all preganglionic nerves, (2) all postganglionic parasympathetic nerves , & (3) postganglionic sympathetic nerves that innervate sweat glands & blood vessels in skeletal muscle .The rest of postganglionic sympathetic nerves secrete norepinephrine Adrenal medulla secretes epinephrine ( 80%) and norepinephrine ( 20%)

The adrenal medulla is considered integral part of the sympathetic NS .

80% of its secretion is epinephrine ( EP) and

20% of it NE . EP (epinephrine ) in the

bloodstream comes from the adrenal medulla . Postganglionic sympathetic nerves can not synthesize epinephrine from its precursor which is norepinephrine .

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Effect of sympathetic & parasympathetic Effect of sympathetic & parasympathetic

stimulationstimulationOrgan sympathetic parasympathetic

العين في العين البؤبؤ في Pupilالبؤبؤ Dilatation of توسعpupil

Constrictionضيق

Heart Increased heart rateالقلب

النبضات سرعة النبضات زيادة سرعة زيادةIncreased force of contraction ةXقّو قّوXة زيادة زيادة

من : : األنقباض األنقباض أكبر كمية من ضخ أكبر كمية ضخ الدمالدم

Decreased heart rate

القلب دقات سرعة القلب تباطؤ دقات سرعة تباطؤ

No effect

Systemic blood vessels

Constriction ( specially arterioles) ضيق

Little or no effect

Blood Pressure Raised الدم ضغط Little or no effec إرتفاع

Lung ( Bronchioles) Dilation المجاري توسعالتنفسية

التنفسية المجاري ضيقConstriction

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Organ sympathetic parasympatheticGlands

األنفية المخاطNasal

Lacrimal الدمّوعSalivaryاللعاب

Gastricالمعدة Intestinal األمعاء

Pancreatic البنكرياس-----------------

العرق SweatغددGlands

Slight ( small volume ) secretion

---------------------Increased secretion

Copious ( large volume) secretion

--------------------No effect

Digestive system muscles

Promotes retention

(relaxation of wall muscles & contraction of sphincters)

Promotes emptying

(contraction of wall muscles & relaxation of sphincters)

Urinary bladder Promote retention

(relaxation of wall & constriction of sphincter

Promotes emptying

(contraction of wall& relaxation of sphincter

Blood sugar Raised No effect

Thanks !

Ach is secreted by (1) all preganglionic nerves, (2) all postganglionic parasympathetic nerves , & (3) postganglionic sympathetic nerves that innervate sweat glands & blood vessels in skeletal muscle .The rest of postganglionic sympathetic nerves secrete norepinephrine Adrenal medulla secretes epinephrine ( 80%) and norepinephrine ( 20%)

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It should be noted thatIt should be noted that Under physiological conditions , nearly all sympathetic and Under physiological conditions , nearly all sympathetic and

parasympathetic activities are opposite to each other ; parasympathetic activities are opposite to each other ; however , the two systems cooperate (however , the two systems cooperate ( & may act in & may act in unison/accord ) in unison/accord ) in

(1) Salivary secretion (1) Salivary secretion sympathetic sympathetic small amount (volume) secretion but rich in small amount (volume) secretion but rich in

enzymes enzymes parasympathetic parasympathetic copious ( big volume ) , watery secretion , copious ( big volume ) , watery secretion ,

(2) Emotional stress :(2) Emotional stress : sympathetic sympathetic increased heart-rate , BP , etc. increased heart-rate , BP , etc. parasympathetic parasympathetic increased secretion from the tear and increased secretion from the tear and

nasal glands .nasal glands .

(3) Sexual intercourse : (3) Sexual intercourse : parasympathetic parasympathetic erection of the penis or clitoris , erection of the penis or clitoris , sympathetic sympathetic ejaculation or orgasm ejaculation or orgasm

Blood vessels Blood vessels to skeletal to skeletal

musclesmuscles

داخل الدمّوية داخل األوعية الدمّوية األوعيةالهيكلية الهيكلية العضالت العضالت

Dilatation Dilatation (cholinergic)(cholinergic)

تّوسXعتّوسXع

NoneNone

تأثير تأثير ال ال

Bronchial Bronchial musclesmuscles

في الملساء في العضالت الملساء العضالتXة التنفسي Xة المجاري التنفسي المجاري

Relaxation Relaxation

يؤدي : يؤدي : إرتخاء إرتخاءالمجاري المجاري لتّوسع لتّوسع

الرئّويةالرئّوية

Constriction Constriction

كان : لّو كان : إنقباض لّو إنقباضلضيق يؤدي لضيق كثير يؤدي كثير

و التنفسية و المجاري التنفسية المجاريجريان جريان صعّوبة صعّوبةبالتالي ) بالتالي ) الهّواء الهّواء

) التنفس (صعّوبة التنفس صعّوبة

البهضمي الجهاز البهضمي إفرازات الجهاز إفرازاتGastrointestinal Tract (GIT) secretionsSalivary glands

اللعاب اللعاب غدد غدد

Pancreasالبنكرياسالبنكرياس Stomach المعدةالمعدة Intestine األمعاء

Decreased Increased

GIT motility ( CONTRACTIONS )

الجهاز جدران الجهاز إنقباضات جدران إنقباضات البهضميالبهضمي

Sphincters صمXامات في القابضة صمXامات العضالت في القابضة العضالت

) المخارج) ( منافذ المخارج) منافذ

Decreased

Constriction

إنقباضإنقباض

Increased

Relaxation

إرتخاءإرتخاء

البّولي البّولي الجهاز الجهاز

Ureters & urinary bladderUreters & urinary bladder wallwall

المثانة جدار و المثانة الحالبين جدار و الحالبين

Internal bladder Internal bladder sphinctersphincter ) المثانة ) صمXام ( عضلة المثانة ) صمXام عضلةالالإرادي ) ( الالإرادي ) (الداخلي الداخلي

RelaxationRelaxation

إرتخاءإرتخاء

Constriction Constriction

مسك ) مسك ) إنقباض إنقباضالبّول(البّول(

ConstrictioConstrictionn

إرتخاءإرتخاء

Relaxation Relaxation

إرتخاءإرتخاء

Genital System Genital System التكاثر التكاثر جهاز جهاز EjaculatiEjaculationon

قذفقذفErection Erection

إنتصابإنتصاب

Adrenal medullaAdrenal medulla

الكظرية الغدة الكظرية لب الغدة لبSecretion of Secretion of adrenaline & adrenaline & noradrenalinnoradrenalin

NoneNone

Blood: Blood:

CoagulationCoagulation

Glucose Glucose

LipidsLipids

IncreasedIncreased None None

تأثير تأثير ال ال

Basal metabolism

Increased None

تأثير تأثير ال ال

Mental activity لتحفيز ا

الذهني

Increased القلق إلي يؤدي مما

None

تأثير تأثير ال ال

Skeletal muscle

Increased glycogenolysisإلي تحّويله و الجاليكّوجين تكسير

جلّوكّوز

None

Fat cells Lipolysis None

Applied Neurophysioloy (1)Applied Neurophysioloy (1)

Epinephrine ( adrenaline ) :Epinephrine ( adrenaline ) : Stimulates both beta1 and beta2 receptorsStimulates both beta1 and beta2 receptors Useful in Tt of Asthma Useful in Tt of Asthma Contraindcated ( C/I ) in Hypertension or Heart disease . Why Contraindcated ( C/I ) in Hypertension or Heart disease . Why

??

Salbutamol (ventolin ) :Salbutamol (ventolin ) : Stimlates mainly beta 2 receptorsStimlates mainly beta 2 receptors Used in Tt of Bronchial asthma Used in Tt of Bronchial asthma Safer than epinephrine . Why ? Safer than epinephrine . Why ?

Applied Neurophysioloy (2)Applied Neurophysioloy (2) Propranolol ( Inderal ) :Propranolol ( Inderal ) : Blocks both beta1 (Blocks both beta1 (ββ11) and beta2 () and beta2 (ββ22 ) receptors . ) receptors . Used in Tt of hypertensionUsed in Tt of hypertension Should not be given to a patient with Bronchial Asthma . Why Should not be given to a patient with Bronchial Asthma . Why

??

Atenolol ( Tenormin ) :Atenolol ( Tenormin ) : Blocks only Blocks only ββ11 receptor receptor Used in Tt (treatment) of hypertensionUsed in Tt (treatment) of hypertension Safer than propranolol . Why ?Safer than propranolol . Why ?

Atropine :Atropine : Blocks muscarinic receptors ( of Ach ) Blocks muscarinic receptors ( of Ach ) Used in Tt of colicsUsed in Tt of colics Better use Hyoscine ( Buscopan ) ; especially if the patient Better use Hyoscine ( Buscopan ) ; especially if the patient

has heart disease or glaucoma . Why ?has heart disease or glaucoma . Why ?

Agonists and Antagonists of Cholinergic ReceptorsAgonists and Antagonists of Cholinergic Receptors

Receptor Agonists Antagonists

Other

Cholinergic Acetylcholine AChE inhibitors e.g., Neostigmine, Prostigmine

Ach release blocker Botulinum toxin

Muscarinic Muscarine Atropine, scopolamine

Nicotinic Nicotine a-bungarotoxin (muscle only)Tetraethylammonium (TEA)

Agonists and Antagonists of Adrenergic ReceptorsAgonists and Antagonists of Adrenergic Receptors

Receptor Agonists Antagonists Other

Adrenergic NorepinephrineEpinephrine

Stimulate NE release Ephedrine, AmphetaminesPrevent NE uptake Cocaine

Alpha (a) Phenylephrine Alpha receptor blockers ( T? Phentolamine & Phenoxybenzamine )

Beta ( β ) Isoprenaline Beta-adrenergic receptor blockers propranolol (β1 and β2)

Metoprolol (β1 only)