Autonomic nervous systemAutonomic nervous system

المالح فاضل محمد ثامر المالح حسان فاضل محمد ثامر حسان

Group – B -Group – B -

Dr. Maha Talal Dr. Maha Talal

THE NERVOUS SYSTEMTHE NERVOUS SYSTEM The nervous system is a The nervous system is a complex part of the complex part of the

human body human body concerned with the concerned with the regulation regulation and coordination and coordination of body activities of body activities such as such as movement, digestion of food, sleep, and movement, digestion of food, sleep, and elimination of waste products.elimination of waste products.

The nervous system has The nervous system has two main two main divisionsdivisions:: the central nervous system (CNS) and the the central nervous system (CNS) and the peripheral nervous system (PNS).peripheral nervous system (PNS).

Autonomic nervous systemAutonomic nervous system: : The component of The component of the NS ( Nervous System) that functions below the the NS ( Nervous System) that functions below the conscious level, controlling several physiological conscious level, controlling several physiological processes:processes:

1. Distribution of blood flow & tissue perfusion1. Distribution of blood flow & tissue perfusion

2. Regulation of blood pressure2. Regulation of blood pressure

3. Control of visceral smooth muscle ( bladder, 3. Control of visceral smooth muscle ( bladder,

bowels)bowels)

4. Control of endocrine and exocrine glands4. Control of endocrine and exocrine glands

5. Control of metabolic energy (glycolysis, glucogenesis 5. Control of metabolic energy (glycolysis, glucogenesis

etc)etc)

Autonomic nervous system division Autonomic nervous system division to : to :

1.1. Sympathetic or Sympathetic or (adrenergic)(adrenergic)

(thoracolumber) (thoracolumber)

NeurotransmitterNeurotransmitter: : ))epinephrine, epinephrine, norepnephrine)norepnephrine)

ReceptorReceptor : α1 , : α1 , α2 α2 , , ββ1,1, β β22

2. Parasympathetic or2. Parasympathetic or (cholinergic): (cholinergic): (craniosacral)(craniosacral)

NeurotransmitterNeurotransmitter :(acetylcholine) :(acetylcholine)

ReceptorsReceptors: M1, M2 , N1, N2: M1, M2 , N1, N2

NEURONAL INNERVATION TO ORGANSNEURONAL INNERVATION TO ORGANS

Classify of autonomic nervous Classify of autonomic nervous system system

1.release of n.t1.release of n.t 2.on structure2.on structure 3.from origin 3.from origin 4.according to the receptor 4.according to the receptor

INNERVATION AT MOST SITESINNERVATION AT MOST SITES

Functionally,Functionally, the two are the two are generally generally antagonisticantagonistic..

The The sympathetic division sympathetic division stimulates stimulates functions involved in functions involved in “fight or flight”“fight or flight” reactions (fear, anger, etc), whereas the reactions (fear, anger, etc), whereas the parasympathetic division parasympathetic division stimulates stimulates more tranquil functions (“more tranquil functions (“rest-and-rest-and-digest”).digest”).

NeurotransmittersNeurotransmitters are chemical are chemical substances called neurohormones. substances called neurohormones.

These are released at the nerve endings These are released at the nerve endings that facilitate the transmission of nerve that facilitate the transmission of nerve impulses.impulses.

Norepinephrine (mainly) and epinephrine Norepinephrine (mainly) and epinephrine

(in adrenal gland)(in adrenal gland) released at the released at the postganglionic sympathetic neuron postganglionic sympathetic neuron . These . These neurons are also called ‘Adrenergic’.neurons are also called ‘Adrenergic’.

..

Cholinergic Nervous System:Cholinergic Nervous System:Acetylcholine neurotransmitter releasing nerve fibers Acetylcholine neurotransmitter releasing nerve fibers

(parasympathetic).(parasympathetic). Acetylcholine is the preganglionic neurotransmitter in

the sympathetic system.A few sympathetic (sweat glands and salivary glands)

have Acetylcholine as the postganglionic neurotransmitter

Parasympathetic Parasympathetic Nervous SystemNervous System

Parasympathetic:Parasympathetic:

The The parasympathetic nervous system parasympathetic nervous system helps helps conserve body energy conserve body energy and is partly and is partly responsible for such activities as responsible for such activities as slowing the slowing the heart rate, digesting food, and eliminating heart rate, digesting food, and eliminating body wastes.body wastes.

The ganglia are usually The ganglia are usually close to or embedded close to or embedded in the target organ.in the target organ.

AcetylcholineAcetylcholine is both preganglionic and is both preganglionic and postganglionic neurotransmitter (Cholinergic).postganglionic neurotransmitter (Cholinergic).

Biologic responses to parasympathetic Biologic responses to parasympathetic stimulation:stimulation:

Constriction of pupil (miosis), ciliary body Constriction of pupil (miosis), ciliary body (“accommodation” of lens)(“accommodation” of lens)

Contraction of smooth muscle in the GI Contraction of smooth muscle in the GI (“peristalsis”) and urinary tract(“peristalsis”) and urinary tract

Constriction of the bronchioles Constriction of the bronchioles (“bronchoconstriction”)(“bronchoconstriction”)

Slowing of heart rate (“bradycardia”)Slowing of heart rate (“bradycardia”) Increased secretion by the glandsIncreased secretion by the glands

Acetylcholine release Acetylcholine release in cholinergic in cholinergic neuron involve 6 stepsneuron involve 6 steps: :

1.1. Synthesis of AchSynthesis of Ach

2.2. Storage of Ach in vesiclesStorage of Ach in vesicles

3.3. Release of AchRelease of Ach

4.4. Binding to receptor Binding to receptor

5.5. Degradation of AchDegradation of Ach

6.6. Recycling of cholineRecycling of choline

AGENTS AFFECTING AGENTS AFFECTING CHOLINERGIC TRANSMISSIONCHOLINERGIC TRANSMISSION

HemicholiniumHemicholiniumLatrotoxinLatrotoxinVesamicolVesamicolBotulinus toxinBotulinus toxinCalciumCalciumPhysostigminePhysostigmineAtropineAtropined-Tubocurarined-Tubocurarine

DRUG ACTING ON DRUG ACTING ON A.N.SA.N.S

1- cholinergic drugs 1- cholinergic drugs

A- Parasympathomimetic DA- Parasympathomimetic D

B- Parasympathlytic DB- Parasympathlytic D 2- 2- adrenergic drugs adrenergic drugs

A- sympathomimetic DA- sympathomimetic D

B- sympatholytic D B- sympatholytic D

Parasympathetic drugs : Parasympathetic drugs : A- Parasympathomimetic DA- Parasympathomimetic D

Cholinergic agonist: Cholinergic agonist: Agents that bind to Agents that bind to acetylcholine receptors and stimulates theacetylcholine receptors and stimulates the

parasympathetic system parasympathetic system (“parasympathomimetic”).(“parasympathomimetic”).

B- parasympathlytic DB- parasympathlytic DCholinergic antagonistCholinergic antagonist: Agents that bind to : Agents that bind to acetylcholine receptors but exhibit no intrinsic acetylcholine receptors but exhibit no intrinsic activity (“parasympatholytic” – competitive to activity (“parasympatholytic” – competitive to endogenous Ach)endogenous Ach)

Parasympathomimetic Parasympathomimetic drug:drug:

1- 1- direct acting cholinergic agentdirect acting cholinergic agent

2- Indirect acting cholinergic agent: 2- Indirect acting cholinergic agent: divided divided

into reversible & irreversible into reversible & irreversible

Parasymathomimetic Parasymathomimetic drugdrug

direct

Cholin esteraseNaturally occurrence

alkaloid

A- A- cholin esterasecholin esterase1-Acetylcholine1-Acetylcholine

Prototypical muscarinic (and nicotinic) Prototypical muscarinic (and nicotinic) agonist, Nonselective action.agonist, Nonselective action.

poor therapeutic agent.poor therapeutic agent. Chemical/enzymatic instability; Low Chemical/enzymatic instability; Low

bioavailability (poorly absorbed); Quick bioavailability (poorly absorbed); Quick onset and short duration of action.onset and short duration of action.

Use: In ocular surgery, causes complete Use: In ocular surgery, causes complete miosis in seconds. miosis in seconds.

Effect of ACH :Effect of ACH :

1.on the intestine 1.on the intestine : Increase S.M : Increase S.M contractioncontraction

2.on the urinary tract 2.on the urinary tract : Increase in : Increase in muscle muscle

tone and contraction tone and contraction

3. on blood vessels 3. on blood vessels : vasodilatation : vasodilatation

4.on the 4.on the secretary gland secretary gland :increase secretion :increase secretion

5. on the 5. on the S.M of trachea S.M of trachea :contract , increase :contract , increase

bronchial secretion, bronchial secretion, bronchoconstriction , 6.on the skeletal Muscle : increase Muscle tone7. On the heart : bradycardia 8. On the eye : miosis , decrease in I.O.P

9 .On the adrenal gland