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Transcript of ANS
Introduction to
AUTONOMIC NERVOUS SYSTEM
Nervous system---------------Anatomical classificationNervous system---------------Anatomical classificationCNS……….Brain……Forebrain………...Cerebrum (Telencephalon) (Prosencephalon) Diencephalon……….Thalamus (Interbrain) Epithalamus Metathalamus Hypothalamus Subthalamus Midbrain (Mesencephalon) Hindbrain………..Metencephalon……...Pons (Rhombencephalon) Cerebellum Mylencephalon……...Medulla oblongata Spinal cord
PNS……….Cranial nerve Spinal nerve
Nervous system---------------Functional classificationNervous system---------------Functional classificationSomatic nervous systemAutonomic nervous system………. Sympathetic nervous system Parasympathetic nervous system Enteric nervous system
• Somatic nervous system-
The part of nervous system which controls somatic/voluntary structures of the body. Its target structures are skeletal muscle and skin.
• Autonomic nervous system-
The part of nervous system which controls involuntary structures of the body. Its target structures are smooth muscle, cardiac muscle, glands (exocrine) and mucus membrane of viscera.
Autonomic vs. Somatic NS
• Somatic nervous system– excitation of skeletal muscle– consciously perceived sensations– one neuron connects CNS to organ
• Autonomic nervous system– involuntary inhibition or excitation of smooth muscle,
cardiac muscle or glandular secretion – unconsciously perceived visceral sensations – two neurons needed to connect CNS to organ
CharacteristicSomatic Nervous
SystemAutonomic Nervous System
EffectorsVoluntary(skeletal) muscle
Smooth muscle, Cardiac Muscle, Glands
General functionAdjustment to
external environment.
Adjustment within the internal environment (homeostasis)
Number of neurons fromCNS to effector
1 2
Ganglia outside the CNS 0 Chain ganglia, collateral ganglia or terminal ganglia
Neurotransmitter Acetylcholine Acetylcholine, adrenaline, noradrenaline
Effect of nerve damage onthe effector
Paralysis and muscle wastage (atrophy)
Effector remains functional but not able to quickly respond to the changing needs of the body.
Autonomic vs. Somatic• Somatic NS motor pathway only contains one neuron.• Autonomic NS motor pathway is a 2 neuron pathway
• Endocrine system and autonomic nervous system control internal environment of the body. They bring about fine internal adjustments necessary for the optimal internal environment (milieu interior of Claude Bernard/homeostasis of Canon) of the body.
• These control effect is extremely rapid, widespread and occurs at subconscious level.
• Distribution of autonomic nervous system occurs through somatic nervous system.
• ANS is controlled by hypothalamus and it receives input from limbic system.
Autonomic nervous system has 3 subdivisions-1. Sympathetic nervous system
2. Parasympathetic nervous system
3. Enteric nervous system Sympathetic and parasympathetic division of ANS produce opposite effects in most organs, thus considered as physiological antagonists. However they operate in conjunction with one another and it is the balance in activities that maintains a stable internal environment.
Exception: Both sympathetic and parasympathetic increase salivation.
Enteric nervous systemEnteric neurons form plexuses that surround and extend along the length of the gut, including stomach, small and large intestines.
Enteric system activate coordinated contraction of smooth muscles to cause peristaltic constriction of the gut.
Most of enteric nervous system functions independently of higher CNS control.
ANS has motor/efferent component and
sensory/afferent components.
Motor componentsThey represent GVE functional components.2 sets of neuron which synapse at ganglion.
1. Preganglionic neuron/1st set/primary neuron2. Postganglionic neuron/2nd set/secondary neuron
Target structure-Target structure-•Smooth muscle•Cardiac muscle•Glands (exocrine)
GVEGVE
GVEGVE
Preganglionic neuron• Cell body in brain or spinal cord • Axon is myelinated type B fiber that extends to autonomic ganglion• Sympathetic preganglionic neurons are located in lateral horn of
T1-L2/L3 spinal segments------THORACOLUMBAR OUTFLOWTHORACOLUMBAR OUTFLOW• Parasympathetic preganglionic neurons are located partly in the
brain stem in connection 3rd, 7th, 9th and 10th cranial nerves and partly in S2, 3, 4 spinal segments---------------------CRANIOSACRAL CRANIOSACRAL OUTFLOWOUTFLOW
Postganglionic neuron• Cell body lies outside the CNS in an autonomic ganglion• Axon is unmyelinated type C fiber that terminates in a visceral
effector
Structure of autonomic ganglion
Connective tissue capsule
Cell bodies of post ganglionic neurons
Interneurons – SIF cells
Satellite/capsular cells
Nerve fibers-Pre- and postganglionic fibers
and fibers traversing the ganglion without synapse
Postganglionic neuron• Sympathetic postganglionic neuronsSympathetic postganglionic neurons
Lateral (paravertebral) ganglia- Ganglionated sympathetic trunk
Subsidiary ganglia
Collateral (prevertebral) ganglia Celiac ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion
Aorticorenal ganglion (renal)
Superior hypogastric ganglion
Terminal ganglia- Adrenal medulla
• Parasympathetic postganglionic neuronsParasympathetic postganglionic neurons
Collateral ganglia (cranial parasympathetic ganglia) Ciliary ganglion
Pterygopalatine ganglion
Submandibular ganglion
Otic ganglion
Terminal ganglia-close to or within wall of viscera
Cardiac plexusPulmonary plexusMyenteric plexusSubmucosal plexusInferior hypogastric (ganglion) plexus
Sensory componentsThey represent GVA functional components.
• Sympathetic sensory component- Their cell bodies are located within DRG of T1-L2/3 spinal nerves Conveys mainly visceral pain sensations from abdominal cavity
• Parasympathetic sensory component- Their cell bodies are located within- For cranial part -Sensory ganglia of facial, glossopharyngeal and vagus nerve
For sacral part -DRG of S2, 3, 4 spinal nerves
Convey- General visceral sensations- like nausea, hunger Sensations for normal visceral reflexes- like carotid sinus reflex, Hering Breuer’s reflex, micturition reflex and defecation reflex. Visceral pain sensations from some pelvic organs
Sympathetic nervous system(Adrenergic system, Thoracolumbar part of ANS/ Thoracolumbar outflow)
• It is the larger part of ANS• Presents definite anatomical entity• Widely distributed throughout body• Prepares body for emergency-nerve of emergency-works during stress and strain to fright,
fight or flight• A catabolic nervous system• Effect is widespread and produce a mass reaction• Works for today• Not essential for life
Components-• Efferent outflow from spinal cord• 2 Ganglionated sympathetic trunks (lateral ganglia)• Important branches• Plexuses• Subsidiary ganglia
Structures having only sympathetic supply- no parasympathetic supply:
Cutaneous viscera
JG cells of nephron
Pineal gland
Adrenal medulla
Follicular cells of thyroid gland
Efferent nerve fiber (sympathetic outflow)Efferent nerve fiber (sympathetic outflow)
Cell bodies of primary neuron in lateral gray horn of T1-L2/3 segment of spinal cord
Myelinated axon in anterior root………spinal nerve trunk……anterior ramus……..ganglionated sympathetic trunk through white rami communicantes (14/15 in number)
Fate of preganglionic fibers in the ganglion of sympathetic trunk-
• Some fibers make synapse with (cell bodies of postganglionic) neurons of corresponding ganglion. Post ganglionic fibers enter ventral ramus of spinal nerve through gray rami communicantes (31 in number). Distributed through spinal nerves to cutaneous viscera as vasomotor, pilomotor and sudomotor branches.
T1-L2/3 spinal nerve
Cervical Spinal nerve
Below L2/3Spinal nerve
1
Subsidiary ganglia
deep seated viscera
• Some fibers leave the corresponding ganglion without making synapse as medial branch and synapse in subsidiary ganglia. These long preganglionic fibers are called splanchnic nerve. Postganglionic fibers from these subsidiary ganglia supply deep seated viscera.
T1-L2/3 spinal nerve
Cervical Spinal nerve
Below L2/3Spinal nerve
12
Subsidiary ganglia
deep seated viscera
• Some fibers travel upward to reach upper ganglia. Here they synapse. Some postganglionic fibers return back to corresponding spinal nerve through gray rami communicantes and distributed to skin viscera. Some postganglionic fibers are distributed along blood vessels to important structures of head-neck region.
T1-L2/3 spinal nerve
Cervical Spinal nerve
Below L2/3Spinal nerve
12
3
Subsidiary ganglia
deep seated viscera
T1-L2/3 spinal nerve
Cervical Spinal nerve
Below L2/3Spinal nerve
12
43
Subsidiary ganglia
deep seated viscera
• Some fibers travel downward to reach lower ganglia. Here they may synapse. Some postganglionic fibers return back to corresponding spinal nerve through gray rami communicantes and distributed to skin viscera. Some postganglionic fibers are distributed along splanchnic nerve. Some preganglionic fibers leave the ganglion as medial branch of the ganglion called lumber or sacral splanchnic nerve which synapse with subsidiary ganglia and distributed to viscera.
T1-L2/3 spinal nerve
Cervical Spinal nerve
Below L2/3Spinal nerve
12
34
5
Subsidiary ganglia
deep seated viscera
T1-L2/3 spinal nerve
Cervical Spinal nerve
Below L2/3Spinal nerve
12
34
6
5
Subsidiary ganglia
deep seated viscera
Splanchnic nerves-Splanchnic nerves-Sympathetic splanchnic nerve-
• Thoracic splanchnic nerve Greater splanchnic nerve-T5-9 ganglia
Lesser splanchnic nerve-T10-11ganglia
Lowest/least splanchnic nerve-T-12 ganglia
• Lumbar splanchnic nerve
• Sacral splanchnic nerve
Parasympathetic splanchnic nerve-Pelvic splanchnic nerve
(Nervi erigentes)
Ganglionated sympathetic trunk-Ganglionated sympathetic trunk-• Paravertebral in position
• Extends from base of the skull to 1st coccygeal vertebra---
where 2 trunks unite to form coccygeal ganglion/ganglion impar
• Initially number of ganglia of each sympathetic trunk corresponds with number of spinal nerve. (31 each)
• Later a number of fusion occurs. Ultimately the trunk presents- 3 ganglia in cervical region- Superior, Middle and Inferior 11/12 ganglia in thoracic region 4/5 ganglia in lumbar region 4/5 ganglia in sacral region
• Superior cervical ganglion is formed by fusion of upper 4 cervical ganglia
• Middle cervical ganglion is formed by fusion of 5th and 6th cervical ganglia
• Inferior cervical ganglion is formed by fusion of 7th and 8th cervical ganglia
• Sometimes inferior cervical and 1st thoracic ganglia fuse to form cervicothoracic/stellate ganglion
DCP
SCP
SupCervicalGanglion
MiddleCervicalGanglion
InfCervicalGanglion
EC Br
Pharyngeal Br
IC Br
Vertebral Artery Br
Subclavian Br
Thyroid Br
Tracheal Br
Esophageal Br
Ansa subclavia
G
R
C
Rami communicantes-Each of T1-L2/3 gangliaT1-L2/3 ganglia is connected to ventral ramus of corresponding spinal nerve
through 2 bundles of nerve fibers.
1. White rami communicantes: the lateral bundle containing myelinated preganglionic nerve fibers. 14/15 in number.
2. Gray rami communicantes: the medial bundle containing unmyelinated postganglionic nerve fibers. 31 in number.
Rest of the gangliaRest of the ganglia are connected to ventral ramus of corresponding spinal nerve only through gray rami communicantes.
Parasympathetic nervous systemParasympathetic nervous system(Cholinergic system, Craniosacral part of ANS/Craniosacral outflow)
• It is the smaller part of ANS• Presents no definite anatomical entity• Less widely distributed throughout body (pre-post ratio-1:3)• Conserves and restores energy -nerve of tranquillity• Anabolic nervous system• Effect is localized and produce isolated effects• Works for tomorrow• Essential for life
Efferent pathway
NUCLEUS CRANIAL NERVE GANGLION THROUGH TARGET
EDINGER WESTPHAL
NUCLEUS
C3:
OCCULOMOTOR NERVE
CILIARY
GANGLION
SHORT CILIARY NERVE •CONSTRICTOR PUPILLAE
•CILIARY MUSCLE
LACRIMATORY
NUCLEUS
C7:
FACIAL NERVE
PTERYGOPALATINE GANGLION
LACRIMAL NERVE •LACRIMAL GLAND
•Other glands
SUPERIOR SALIVATORY
NUCLEUS
C7:
FACIAL NERVE
SUBMANDIBULAR GANGLION
LINGUAL NERVE •SUBMANDIBULAR GLAND
•SUBLINGUAL GLAND
INFERIOR SALIVATORY
NUCLEUS
C9:
GLOSSOPHARYNGEAL NERVE
OTIC GANGLION AURICULOTEMPORAL NERVE
PAROTID GLAND
DORSAL NUCLEUS
C10:
VAGUS NERVE
ORGAN WALL
(Intramural ganglion) -
•SMOOTH MUSCLE
•CARDIAC MUSCLE
•GLANDS
Cranial outflow
For vagus nerve
Preganglionic myelinated fibers synapse in neurons of terminal ganglia lying close to or within organ wall.
Terminal ganglia are located in-
• Cardiac plexus
• Pulmonary plexus
• Myenteric plexus
• Submucosal plexus
Postganglionic unmyelinated fibers supply heart, lung, foregut and midgut portion of alimentary tract.
Sacral outflow
Cell bodies of preganglionic neurons lie in the gray matter of S2, 3, 4 spinal segments.
Myelinated preganglionic fibers….enter anterior root…sacral nerve trunk……leave sacral nerve and form pelvic splanchnic nerve (nervi erigentes).
Pelvic splanchnic nerve ultimately synapse in ganglia in the hypogastric plexuses (close to target structure). Post ganglionic unmyelinated fibers supplies pelvic viscera and hindgut part of alimentary tract.
Pre-post ratio-1:3
ANS Neurotransmitters
• Classified as either cholinergic or adrenergic neurons based upon the neurotransmitter released
• Adrenergic
• Cholinergic
Ach
Ach
Ach
Ach Ach
Ach
Epinephrine
NorepinephrineNeurotransmittersNeurotransmitters
Everywhere
Adrenal medulla
Sweat gland
Everywhere
M receptor
N receptor
N receptor
N receptor
A>B receptor
B>A receptor
M receptor
N receptor
Receptors•Adrenergic receptors- Alpha (A) receptor- A1-------for contraction A2 Beta (B) receptor- B1-------in heart B2-------for relaxation•Cholinergic receptors Muscarinic (M) receptor- M1 M2 M3 Nicotinic (N) receptor-
NM
NN
Functions of ANSFunctions of ANS
Physiological Effects of the ANS
Hypothalamus
• Some organs have only sympathetic innervation– sweat glands, adrenal
medulla, arrector pili mm & many blood vessels
– controlled by regulation of the “tone” of the sympathetic system
• Most body organs receive dual innervation– innervation by both
sympathetic & parasympathetic
• Hypothalamus regulates balance (tone) between sympathetic and parasympathetic activity levels
Sympathetic nervous system
Parasympathetic nervous system
Difference between sympathetic and parasympathetic nervous system
Sym Para
Anatomical entity
Efferents
•Outflow
•Preganglionic neuron
•Ganglia
•Preganglionic fibers
•Pre-post ratio
•Action
•Anabolic/catabolic
•Works for
•Postganglionic transmitter
•Nerve of
•Necessity
Afferents
Central control
Horner’s syndrome• Miosis• Ptosis (slight)• Enophthalmos• Anhydrosis• Vasodilatation of skin arteriole• Loss of ciliospinal/ pupillary skin reflex
Cause: due to interruption of sympathetic nerve supply to the head and neck region.
Types:1. Central Horner’s syndrome2. Preganglionic Horner’s syndrome3. Postganglionic Horner’s syndrome
• Argyll Robertson pupil
• Adie’s tonic pupil syndrome
• Frey’s syndrome
• Crocodile tear syndrome
• Hirschsprung’s disease (megacolon)
• Atonic, automatic and autonomous bladder
T1-L2/3 spinal nerve
Cervical Spinal nerve
Below L2/3Spinal nerve
12
34
5
6
Subsidiary ganglia
deep seated viscera