Introduction To Autonomic Nervous System

ANS: INTRODUCTION

Dr.U.P.Rathnakar MD.DIH.PGDHM

Dr.U.P.Rathnakar

MD.DIH.PGDHM

ANS

Parasympathetic Sympathetic Enteric

 Autonomic

Somatic

• Supplies all innervated

Sk.Muscles

structures • Synapses outside CNS

Inside C.S.axis

• Ganglia

No ganglia

Absent

• Peripheral plexus + •

Post ganglionic fibres

Post ganglionic fibres

non-myelinated • Spontaneous activity

myelinated Nil

in effectors • Interruption of nerve supply Disuse Atrophy

-no atrophy • NA and Adrenaline

Acetylcholine

Flight, Fight and Fright

Sympathtic

Sit & Digest

P.Sympathtic

 Organ 

Sympathtic P.Sympathetic [Flight & Fright] [Sit &

Digest]

 Survival  Eye  Heart  Bronchi

Possible Mydriasis Stim. Dilation ↓Motility

 GIT

 ↓Secretion  Contracts spincter  UB 

Relaxes detrusor Contracts trigone

& spincter

 Sexual organs  Ejaculation  Sk.Muscles

Contractility increased

Not possible Miosis Dep. Spasm ↑Motility ↑Secretion Relaxes spincters Contracts detrusor, Relaxes trigone &

spincter

Erection

•The human nervous system can be divided into the •Central nervous system (CNS), •Consisting of the brain and spinal cord, •Peripheral nervous system, •Consisting of the cranial and spinal nerves and their branches. •The 12 pairs of cranial nerves (labeled I - XII) originate from the base of the brain. •The 31 pairs of spinal nerves include •8 pairs of cervical nerves (labeled Cl - C8), •12 pairs of thoracic nerves (labeled T1 - T12), • 5 pairs of lumbar nerves (labeled L1 - L5), • 5 pairs of sacral nerves (labeled S1 - S5), •1 pair of coccygeal nerves and roots. 

Sympathetic outflow:Thoracolumbar•Emerge with spinal • White ramigangliongrey rami •22 bilateral, paravertebra l gangia •15 connected to-T1-L3 •3 Prevertebral gangia •Ad.medulla gangion

Sympathetic outflow: Thoraco-lumbar outflow Cellbodies and preganglionic neurones

inside spinal cord 22 Paravertebral ganglioninterconnected Out flow from-Ti-L3-15 ganglia Preganglionic white rami & post ganglionic grey rami-to spinal nerves To sweat glands, Pilomotor, BV, of skin and skeletal muscles

Sympathetic outflow… First 3-ICG, MCG, SCG- supply dilator pupillae, BV of head & neck, and salivary glands Prevertebral, unilateral,- Celiac, S.mesenteric, Aorticorenal, inf mesenteric Adrenal medulla- embryo. Anatom-ganglion- N.transmittterAdrenaline Sacral ganglion

Adrenergic receptors Receptors:

α1a, α1b, α1d,



α 2a

α2b α2c



β1, β2, β3

Neurotransmitter- Nor adrenaline, Adrenaline

Parasympathetic outflow:Cranio-sacral

Parasympathetic:

Cranio-sacral

outflowMotor and secretory fibres to Thoracic, abd, and pelvic organs

Cranial: III N- →Circular muscles of Iris OCCULOMOTOR VII N- →Sal.and lachrimal glands FASCIAL

IX N- Mucus glands of nose, mouth,

pharynx and parotid gland.

GLOSSOPHARYNGEAL

X- Synapse near visceral

organs→Heart, lungs, intestine

VAGUS

Sacral: Nervi ergentes • Bladder,

• Rectum • Sexual organs

Parasympethetic CHOLINERGIC  Muscarinic= M1, M2, M3, M4, M5

 Nicotinic= NN, NM

 Neurotransmitter = Acetylcholine

transmission “ Nerve impulses elicit

responses in effector organs and post synaptic neurones through liberation of specific chemical transmitters”

Junctional transmission

conduction

 

Vs

Nerve

Neurotransmission Initially thought tobe

electrical. Otto Lewi → Frog hearts perfused in series →  Stim.vagosymp.trunk of I organ  →Perfusate produced inhibitory effect on II

Tachycardia or Bradycardia

Flow of Chemic al substan ce

Tachycardia Or Bradycardia Otto Lewi’s experiment

Neurotransmitter Should be

present in Presynaptic

Should be

Released on nerve impulse

neurones

Application of sub. Produces

response to nerve stimulation

Effects are antagonised or

Similar

potentiated by other sub. Which also have similar effect on nerve stimulation.

Steps in neurotransmission:  Impulse conduction  Arrival of impulse  Synthesis Storage & release

of transmitter

 Combination of transmitter

with P.J. receptors

 Postjunctional activity:  Excitatory[EPSP] or  Inhibitory[IPSP]  Termination of

neurotransmitter action [Diffusion, destruction, reuptake]

•I. Synthesis and storage of N (neurotransmitter) •II. Release of N (exocytosis) •III. Interaction with postjunctional cell and initiation of activity •IV. Deactivation of N.  i. diffusion  ii. enzymatic destruction  iii. reuptake 

Postjunctional Cells:  Postganglionic neuron at synapses in peripheral ganglia  Effector cell at autonomic neuroeffector junctions  Striated muscle cell at somatic neuromuscular junctions 

Impulse conduction:

Arrival of impulse→ ↑ Na conductance→

Depolarization→Inside (+)ve→(K flows out→Repolarization) →Action potential→Impulse propogation.

Storage & release of

transmitter:  Neurotransmitter synthesized and

stored in pre junctional nerve endings in “Synaptic Vesicles”  Arrival of nerve impulse→Fuses vesicular and axonal membrane(small amounts constantly released without impulse) Ca entry fluidizes membrane→Contents of vesicle released→Exocytosis Other protiens also participate in docking and fusion. 

Combination of transmitter with P.J.

receptors and P.J.potential:

Excitatory post synaptic potential(EPSP):

↑ permeability to cations-Na or Ca→ Depolarization→ EPSP IPSP: ↑ permeability to K or Cl→

Hyperpolarization→ IPSP

Postjunctional activity: EPSP more than threshold level

→AP→Activity IPSP(neurones, smooth muscles not in Sk.muscles) → Opposes excitatory impulses Final response depends on summation of all responses

Termination of

neurotransmitter action: Dissipation or destruction ACHE(acetylcholinesterase)

→Hydrolyzes Ach. →if ACHE is inhibited action prolonged Adrenergic- Diffusion, Reuptake

NON-Electrogenic functions

of neurotransmitter:  Continuos low grade release→No P.J.

activity→ But imp. For turn over of enzymes of synthesis, inactivation, maintainance of pre and post synaptic transmission. These are trophic actions of neurotransmitter.

Co-Transmitter: Other transmitters

released along with principal transmitter

Ach-VIP,

Other cotransmitters- Adenosine,

NA-ATP

neuropeptide-Y, NO, Somatostatin etc.  NANC: Nonadrenergic-noncholinergic transmission-exists in ANS. Principal transmitter is not Ach or NA. Eg. In GIT, GUT, (adenosine, ATP)

Neurotransmitters:Adrenerg ic and Cholinergic

N N

α 1α2 β1β2β

N N

NN

α 1α2

NM

β1β2β 3

M1 M2 M3

What is the link?

Cholinergic drugs

Drugs act like ACh

[Agonists of Ach Rec.] Cholinomimitics OR Directly acting cholinergics OR Indirectly acting Cholinomimitic s

Act at sites & receptors Where Ach acts

Ganglia-NN Sk.muscles-NM Heart,Lungs, Int.]Musc Eve, Sweat glands]M12345

Inhibit degradation of AntiIncrease duration Ach Cholinesterases of By Action of ACh AChE[Cholinesterase] Antagonist Anti-cholinergics Musc.Rec.Antagonis s ts Antagonists at N.M.Blockers N.M.Junction

Adrenergic drugs

α1, 2 - Agonists

and antagonists [Blockers] β1, 2, 3 – Agonists and antagonists [Blockers]