TOPIC OF THE LECTURE:TOPIC OF THE LECTURE:

Anatomy of vegetative part of Anatomy of vegetative part of nervous system. nervous system.

The central and peripheral The central and peripheral structures of the sympathetic and structures of the sympathetic and

parasympathetic parts. parasympathetic parts. Vegetative plexuses.Vegetative plexuses.

The autonomic nervous system The autonomic nervous system (ANS or visceral nervous system) is the part of the (ANS or visceral nervous system) is the part of the

peripheral nervous system that acts as a that acts as a control system functioning largely below the level of consciousness, and functioning largely below the level of consciousness, and controls controls visceral functions. The ANS affects functions. The ANS affects heart rate, , digestion, , respiration rate, , salivation, , perspiration, diameter of , diameter of the pupils, the pupils, micturition (urination), and (urination), and sexual arousal. . Whereas most of its actions are involuntary, some, such as Whereas most of its actions are involuntary, some, such as breathing, work in tandem with the conscious mind.breathing, work in tandem with the conscious mind.

It is classically divided into two subsystems: the It is classically divided into two subsystems: the parasympathetic nervous system (PSNS) and (PSNS) and sympathetic nervous system (SNS). Relatively recently, a (SNS). Relatively recently, a third subsystem of neurons that have been named 'non-third subsystem of neurons that have been named 'non-adrenergic and non-cholinergic' neurons (because they use adrenergic and non-cholinergic' neurons (because they use nitric oxide as a neurotransmitter) have been described and nitric oxide as a neurotransmitter) have been described and found to be integral in autonomic function, particularly in found to be integral in autonomic function, particularly in the gut and the lungs.the gut and the lungs.

General Characteristics of the ANS: General Characteristics of the ANS: 1. It is a two-neuron pathway.1. It is a two-neuron pathway.

2. Sensory signals from viscera and skin send signals 2. Sensory signals from viscera and skin send signals to autonomic neurons in brain and spinal cord. to autonomic neurons in brain and spinal cord. 3. A preganglionic neuron cell body is located within 3. A preganglionic neuron cell body is located within the CNS (brain stem or spinal cord).the CNS (brain stem or spinal cord).4. Preganglionic fibers (efferent fibers) synapse with a 4. Preganglionic fibers (efferent fibers) synapse with a ganglionic neuron located in the PNSganglionic neuron located in the PNS5. A postganglionic fiber terminates on the effector 5. A postganglionic fiber terminates on the effector organ (heart, stomach, etc).organ (heart, stomach, etc).

Divisions of the ANS Divisions of the ANS 1. Sympathetic Division 1. Sympathetic Division 2. Parasympathetic Division2. Parasympathetic Division

Sympathetic nervous Sympathetic nervous system ( function)system ( function)

Eye Eye – dilates pupil– dilates pupil Heart - iHeart - increases rate and force of ncreases rate and force of

contraction contraction Lungs - dLungs - dilates bronchioles ilates bronchioles Digestive tract - iDigestive tract - inhibits peristalsis nhibits peristalsis Kidney - iKidney - increases renin secretion ncreases renin secretion Penis – promotes Penis – promotes ejaculation ejaculation

The sympathetic nervous system is responsible for up- and The sympathetic nervous system is responsible for up- and down-regulating many homeostatic mechanisms in living down-regulating many homeostatic mechanisms in living organisms. Fibers from the SNS innervate tissues in almost organisms. Fibers from the SNS innervate tissues in almost every organ system, providing at least some regulatory function every organ system, providing at least some regulatory function to things as diverse as to things as diverse as pupil diameter, diameter, gut motility, and , and urinary output. It is perhaps best known for mediating the neuronal and output. It is perhaps best known for mediating the neuronal and hormonal stress response commonly known as the hormonal stress response commonly known as the fight-or-fight-or-flight responseflight response. .

This response is also known as This response is also known as sympatho-adrenal responsesympatho-adrenal response of of the body, as the the body, as the preganglionic sympathetic fibers that end in the sympathetic fibers that end in the adrenal medulla (but also all other sympathetic fibers) secrete adrenal medulla (but also all other sympathetic fibers) secrete acetylcholine, which activates the great secretion of adrenaline acetylcholine, which activates the great secretion of adrenaline (epinephrine) and to a lesser extent noradrenaline (epinephrine) and to a lesser extent noradrenaline (norepinephrine) from it.(norepinephrine) from it.

Therefore, this response that acts primarily on the Therefore, this response that acts primarily on the cardiovascular system is mediated directly via impulses is mediated directly via impulses transmitted through the sympathetic nervous system and transmitted through the sympathetic nervous system and indirectly via indirectly via catecholamines secreted from the adrenal secreted from the adrenal medulla. medulla.

Sympathetic nervous systemSympathetic nervous system

1. Central part1. Central part 2. Peripheral part2. Peripheral part Sympathetic centers:Sympathetic centers: Over segmental: Cortical: located in Over segmental: Cortical: located in

cerebral cortex ( frontal lobecerebral cortex ( frontal lobe,, limbic limbic system)system)

Subcortical – in diencephalon are Subcortical – in diencephalon are common for sympathetic and common for sympathetic and parasympathetic partsparasympathetic parts

The The limbic systemlimbic system (or Paleomammalian brain) (or Paleomammalian brain) is a set of brain structures including the is a set of brain structures including the hippocampus, , amygdala, , anterior thalamic nuclei, , septum, , limbic cortex and fornix, which and fornix, which seemingly support a variety of functions seemingly support a variety of functions including including emotion, , behavior, , long term memory, , and and olfaction..

The term "limbic" comes from the The term "limbic" comes from the Latin limbuslimbus, , for "border" or "edge". Some scientists have for "border" or "edge". Some scientists have suggested that the concept of the limbic system suggested that the concept of the limbic system should be abandoned as should be abandoned as obsolete, as it is , as it is grounded more in transient tradition than in grounded more in transient tradition than in facts.facts.

Segmental level – in lateral horns of spinal cord Segmental level – in lateral horns of spinal cord ( intermediolateral nucleus)( intermediolateral nucleus) Nucleus include: tropicNucleus include: tropic,, functional functional,, vasomotor vasomotor,,

visceromotorvisceromotor,, secretory secretory ссenters.enters.

The The parasympathetic parasympathetic nervous system ( (PSNSPSNS) is one ) is one of the two main divisions of the of the two main divisions of the autonomic nervous system (ANS). (ANS).

The ANS is responsible for regulation of internal The ANS is responsible for regulation of internal organs and glands, which occurs unconsciously. The organs and glands, which occurs unconsciously. The parasympathetic system specifically is responsible for parasympathetic system specifically is responsible for stimulation of "rest-and-digest" activities that occur stimulation of "rest-and-digest" activities that occur when the body is at rest, including sexual arousal, when the body is at rest, including sexual arousal, salivation, , lacrimation (tears), (tears), urination, , digestion and and defecation. .

Its action is described as being complementary to that Its action is described as being complementary to that of one of the other main branches of the ANS, the of one of the other main branches of the ANS, the sympathetic nervous system, which is responsible for , which is responsible for stimulating activities associated with the stimulating activities associated with the fight-or-flight response. .

SYMPATHETIC NERVOUS SYMPATHETIC NERVOUS SYSTEM.SYSTEM.

Diverts blood flow away from the gastro-intestinal Diverts blood flow away from the gastro-intestinal (GI) tract and (GI) tract and skin via vasoconstriction. via vasoconstriction.

Blood flow to Blood flow to skeletal muscles and the and the lungs is is enhanced (by as much as 1200% in the case of enhanced (by as much as 1200% in the case of skeletal muscles). Dilates bronchioles of the lung, skeletal muscles). Dilates bronchioles of the lung, which allows for greater alveolar oxygen exchange. which allows for greater alveolar oxygen exchange.

Increases Increases heart rate and the and the contractility of cardiac of cardiac cells (cells (myocytes), thereby providing a mechanism for ), thereby providing a mechanism for the enhanced blood flow to skeletal muscles.the enhanced blood flow to skeletal muscles.

Dilates pupils and relaxes the ciliary muscle to the Dilates pupils and relaxes the ciliary muscle to the lens, allowing more light to enter the eye and far lens, allowing more light to enter the eye and far vision. Provides vasodilation for the vision. Provides vasodilation for the coronary vessels of the of the heart. .

Constricts all the intestinal Constricts all the intestinal sphincters and the urinary sphincter. and the urinary sphincter.

Inhibits Inhibits peristalsis. .

Parasympathetic nervous systemParasympathetic nervous system

Dilates blood vessels leading to the GI tract, Dilates blood vessels leading to the GI tract, increasing blood flow. This is important following increasing blood flow. This is important following the consumption of food, due to the greater the consumption of food, due to the greater metabolic demands placed on the body by the gut. metabolic demands placed on the body by the gut.

The parasympathetic nervous system can also The parasympathetic nervous system can also constrict the bronchiolar diameter when the need constrict the bronchiolar diameter when the need for oxygen has diminished. for oxygen has diminished.

Dedicated cardiac branches of the Dedicated cardiac branches of the Vagus and and thoracic thoracic Spinal Accessory nerves impart nerves impart Parasympathetic control of the control of the Heart or or Myocardium. .

During During accommodation, the parasympathetic , the parasympathetic nervous system causes constriction of the nervous system causes constriction of the pupil and contraction of the ciliary muscle to pupil and contraction of the ciliary muscle to the lens, allowing for closer vision. the lens, allowing for closer vision.

The parasympathetic nervous system The parasympathetic nervous system stimulates salivary gland secretion, and stimulates salivary gland secretion, and accelerates accelerates peristalsis, so, in keeping with the , so, in keeping with the rest and digest functions, appropriate PNS rest and digest functions, appropriate PNS activity mediates digestion of food and activity mediates digestion of food and indirectly, the absorption of nutrients. indirectly, the absorption of nutrients.

Is also involved in erection of genitals, via the Is also involved in erection of genitals, via the pelvic splanchnic nerves 2–4. 2–4.

Stimulates sexual arousal. Stimulates sexual arousal.

TheThe sympathetic trunkssympathetic trunks ( (sympathetic chainsympathetic chain, , gangliated gangliated cordcord) ) are a paired bundle of nerve fibers that run from the are a paired bundle of nerve fibers that run from the base of the base of the skull to the to the coccyx. .

The sympathetic trunk travels in a downward direction The sympathetic trunk travels in a downward direction from the skull, just lateral to the vertebral bodies. It from the skull, just lateral to the vertebral bodies. It interacts with the interacts with the spinal nerves or their ventral rami by way or their ventral rami by way of of rami communicantes..

The superior end of it is continued upward through the The superior end of it is continued upward through the carotid canal into the skull, and forms a into the skull, and forms a plexus on the on the internal carotid artery; the inferior part travels in front of ; the inferior part travels in front of the the coccyx, where it converges with the other trunk at a , where it converges with the other trunk at a structure known as the structure known as the ganglion impar..

Along the length of the sympathetic trunk Along the length of the sympathetic trunk are are ganglia known as known as paravertebral ganglia..

FunctionFunction The sympathetic trunk is a fundamental The sympathetic trunk is a fundamental

part of the sympathetic division of the part of the sympathetic division of the autonomic nervous system. It allows nerve . It allows nerve fibers to travel to spinal nerves that are fibers to travel to spinal nerves that are superior and inferior to the one in which superior and inferior to the one in which they originated. Also, a number of nerves, they originated. Also, a number of nerves, such as most of the such as most of the splanchnic nerves, arise , arise directly from the trunks.directly from the trunks.

The sympathetic division (thoracolumbar The sympathetic division (thoracolumbar outflow) consists of cell bodies in the outflow) consists of cell bodies in the lateral horn of spinal cord (intermediolateral cell (intermediolateral cell columns) of the spinal cord from T1 to L2. columns) of the spinal cord from T1 to L2. These cell bodies are GVE (general visceral These cell bodies are GVE (general visceral efferent) neurons and are the preganglionic efferent) neurons and are the preganglionic neurons. There are several locations upon which neurons. There are several locations upon which preganglionic neurons can synapse for their preganglionic neurons can synapse for their postganglionic neurons:postganglionic neurons:

Paravertebral ganglia of the sympathetic chain of the sympathetic chain (these run on either side of the vertebral bodies) (these run on either side of the vertebral bodies)

Prevertebral ganglia (celiac ganglia, superior (celiac ganglia, superior mesenteric ganglia, inferior mesenteric ganglia) mesenteric ganglia, inferior mesenteric ganglia)

Chromaffin cells of of adrenal medulla (this is the one (this is the one exception to the two-neuron pathway rule: synapse is exception to the two-neuron pathway rule: synapse is direct onto cell bodies) These ganglia provide the direct onto cell bodies) These ganglia provide the postganglionic neurons from which innervation of target postganglionic neurons from which innervation of target organs follows. Examples of splanchnic (visceral) nerves organs follows. Examples of splanchnic (visceral) nerves are:Cervical cardiac nerves & thoracic visceral nerves are:Cervical cardiac nerves & thoracic visceral nerves which synapse in the sympathetic chain which synapse in the sympathetic chain

Thoracic splanchnic nerves (greater, lesser, least) which Thoracic splanchnic nerves (greater, lesser, least) which synapse in the prevertebral ganglion synapse in the prevertebral ganglion

Lumbar splanchnic nerves which synapse in the Lumbar splanchnic nerves which synapse in the prevertebral ganglion prevertebral ganglion

Sacral splanchnic nerves which synapse in the inferior Sacral splanchnic nerves which synapse in the inferior hypogastric plexus hypogastric plexus

These all contain afferent (sensory) nerves as well, also These all contain afferent (sensory) nerves as well, also known as GVA (general visceral afferent) neurons.known as GVA (general visceral afferent) neurons.

Parasympathetic divisionParasympathetic division The parasympathetic division (craniosacral outflow) consists of The parasympathetic division (craniosacral outflow) consists of

cell bodies from one of two locations: cell bodies from one of two locations: brainstem (Cranial Nerves (Cranial Nerves III, VII, IX, X) or sacral spinal cord (S2, S3, S4). These are the III, VII, IX, X) or sacral spinal cord (S2, S3, S4). These are the preganglionic neurons, which synapse with postganglionic preganglionic neurons, which synapse with postganglionic neurons in these locations:neurons in these locations:

Parasympathetic ganglia of the head (Ciliary (CN III), of the head (Ciliary (CN III), Submandibular (CN VII), Pterygopalatine (CN VII), Otic (CN Submandibular (CN VII), Pterygopalatine (CN VII), Otic (CN IX) IX)

In or near wall of organ innervated by Vagus (CN X), Sacral In or near wall of organ innervated by Vagus (CN X), Sacral nerves (S2, S3, S4)) nerves (S2, S3, S4))

These ganglia provide the postganglionic neurons from which These ganglia provide the postganglionic neurons from which innervations of target organs follows. Examples are:innervations of target organs follows. Examples are:

The preganglionic parasympathetic splanchnic (visceral) nerves The preganglionic parasympathetic splanchnic (visceral) nerves Vagus nerve, which wanders through the thorax and abdominal , which wanders through the thorax and abdominal

regions innervating, among other organs, the heart, lungs, liver regions innervating, among other organs, the heart, lungs, liver and stomachand stomach..

VEGETATIVE PLEXUSESVEGETATIVE PLEXUSES

The The abdominal aortic plexusabdominal aortic plexus (aortic plexus) is (aortic plexus) is formed by branches derived, on either side, formed by branches derived, on either side, from the from the celiac plexus and and ganglia, and , and receives filaments from some of the receives filaments from some of the lumbar ganglia..

It is situated upon the sides and front of the It is situated upon the sides and front of the aorta, between the origins of the superior and , between the origins of the superior and inferior mesenteric arteries. arteries.

From this plexus arise part of the From this plexus arise part of the spermatic, , the inferior mesenteric, and the the inferior mesenteric, and the hypogastric plexuses; it also distributes filaments to the plexuses; it also distributes filaments to the inferior vena cava..

The celiac plexus includes a number of The celiac plexus includes a number of smaller plexuses:smaller plexuses:

Hepatic plexus Splenic plexus Gastric plexus Pancreatic plexus Suprarenal plexus Other plexuses that are derived from Other plexuses that are derived from

the celiac plexus:the celiac plexus: Renal plexus Testicular plexus / / ovarian plexus Superior mesenteric plexus Inferior mesenteric plexus

The The celiac plexusceliac plexus or or coeliac plexuscoeliac plexus, also known as the , also known as the solar plexussolar plexus, is a complex network of nerves (a , is a complex network of nerves (a plexus) ) located in the abdomen, where the located in the abdomen, where the celiac trunk, , superior mesenteric artery, and , and renal arteries branch branch from the from the abdominal aorta. It is behind the . It is behind the stomach and and the the omental bursa, and in front of the , and in front of the crura of the of the diaphragm, on the level of the first , on the level of the first lumbar vertebra, L1., L1.

The plexus is formed (in part) by the greater and lesser The plexus is formed (in part) by the greater and lesser splanchnic nerves of both sides, and also parts of the of both sides, and also parts of the right right vagus nerve..

The celiac plexus proper consists of the The celiac plexus proper consists of the celiac ganglia with a network of interconnecting fibers. The with a network of interconnecting fibers. The aorticorenal ganglia are often considered to be part of are often considered to be part of the celiac ganglia, and thus, part of the plexus.the celiac ganglia, and thus, part of the plexus.

The The renal plexusrenal plexus is formed by filaments is formed by filaments from the from the celiac plexus, the , the aorticorenal ganglion, and the , and the aortic plexus . .

It is joined also by the It is joined also by the least splanchnic nerve.. The nerves from these sources, fifteen or The nerves from these sources, fifteen or

twenty in number, have a few twenty in number, have a few ganglia developed upon them.developed upon them.

They accompany the branches of the They accompany the branches of the renal artery into the into the kidney; some filaments ; some filaments are distributed to the are distributed to the spermatic plexus and, and, on the right side, to the on the right side, to the inferior vena cava..

Inferior hypogastric plexusInferior hypogastric plexus

Parasympathetic Parasympathetic centerscenters

A A nerve fibernerve fiber is a threadlike extension of a nerve cell is a threadlike extension of a nerve cell and consists of an and consists of an axon and and myelin sheath (if present) (if present) in the in the nervous system. There are nerve fibers in the . There are nerve fibers in the central nervous system and and peripheral nervous system. . A nerve fiber may be myelinated and/or unmyelinated. A nerve fiber may be myelinated and/or unmyelinated. In the central nervous system (CNS), myelin is In the central nervous system (CNS), myelin is produced by produced by oligodendroglia cells. cells.

Schwann cells form myelin in the peripheral nervous form myelin in the peripheral nervous

system (PNS). Schwann cells can also make a thin system (PNS). Schwann cells can also make a thin covering for an axon which does not consist of myelin covering for an axon which does not consist of myelin (in the PNS). A peripheral nerve fiber consists of an (in the PNS). A peripheral nerve fiber consists of an axon, myelin sheath, Schwann cells and its axon, myelin sheath, Schwann cells and its endoneurium. There are no endoneurium and Schwann . There are no endoneurium and Schwann cells in the central nervous systemcells in the central nervous system. .

In the In the autonomic nervous system, fibers from the , fibers from the CNS to the to the ganglion are known as are known as preganglionic preganglionic fibersfibers..

All preganglionic fibers, whether they are in the All preganglionic fibers, whether they are in the sympathetic division or in the or in the parasympathetic division, are , are cholinergic (that is, (that is, these fibers use these fibers use acetylcholine as their as their neurotransmitter).).

Sympathetic preganglionic fibers tend to be Sympathetic preganglionic fibers tend to be shorter than parasympathetic preganglionic fibers shorter than parasympathetic preganglionic fibers because sympathetic ganglia are often closer to because sympathetic ganglia are often closer to the spinal cord than are the parasympathetic the spinal cord than are the parasympathetic ganglia.ganglia.

In the In the autonomic nervous system, fibers from the ganglion to the , fibers from the ganglion to the effector organ are called effector organ are called postganglionic fiberspostganglionic fibers..

NeurotransmittersNeurotransmitters The neurotransmitters used for postganglionic fibers The neurotransmitters used for postganglionic fibers

differ:differ: In the parasympathetic division, they are In the parasympathetic division, they are cholinergiccholinergic

(that is, they use acetylcholine as their (that is, they use acetylcholine as their neurotransmitters.) neurotransmitters.)

In the sympathetic division, most are In the sympathetic division, most are adrenergicadrenergic (that is, (that is, they use norepinephrine as their neurotransmitters.) One they use norepinephrine as their neurotransmitters.) One exception of this is the sympathetic innervation of sweat exception of this is the sympathetic innervation of sweat glands, which uses acetylcholine as a neurotransmitter, glands, which uses acetylcholine as a neurotransmitter, at both pre and post ganglionic synapses. Furthermore, at both pre and post ganglionic synapses. Furthermore, another exception is the sympathetic innervation of the another exception is the sympathetic innervation of the adrenal glands, which is done directly by the adrenal glands, which is done directly by the preganglionic fiber, and subsequently uses acetylcholine preganglionic fiber, and subsequently uses acetylcholine as a neurotransmitter. as a neurotransmitter.

CCeliac plexus injury fundoplicationeliac plexus injury fundoplication

BLOOD SUPPLY OF LIVER.BLOOD SUPPLY OF LIVER. The liver receives a blood supply from two sources. The The liver receives a blood supply from two sources. The

first is the hepatic artery which delivers oxygenated first is the hepatic artery which delivers oxygenated blood from the general circulation. The second is the blood from the general circulation. The second is the hepatic portal vein delivering deoxygenated blood from hepatic portal vein delivering deoxygenated blood from the small intestine containing nutrients.the small intestine containing nutrients.

The blood flows through the liver tissue to the hepatic The blood flows through the liver tissue to the hepatic cells where many metabolic functions take place. The cells where many metabolic functions take place. The blood drains out of the liver via the hepatic vein.blood drains out of the liver via the hepatic vein.

The liver tissue is not vascularised with a capillary The liver tissue is not vascularised with a capillary network as with most other organs, but consists of blood network as with most other organs, but consists of blood filled sinusoids surrounding the hepatic cellsfilled sinusoids surrounding the hepatic cells. .

By- Dr. Pradeep JangirBy- Dr. Pradeep Jangir