The Visceral Nervous System

SHANDONG UNIVERSITY

Liu Zhiyu

The Visceral Nervous System

Composition Visceral motor nerves (autonomic nervous system)

Sympathetic part Parasympathetic part

Visceral sensory nerves

Somatic and Autonomic Nervous System

Main Differences Between Somatic Motor and Visceral Motor n.

  Somatic Visceral Effectors Skeletal muscles Cardiac, smooth muscles and glands

Control Voluntary (consciousness)

Involuntary (unconsciousness )

From lower center to effect require

Single neuron Two neurons: preganglionic neuron and postganglionic neuron

Kind of fibers One Two: sympathetic & parasympathetic

Fibers Thick myelinated Preganglionic: thin myelinated postganglionic: unmyelinated

Distributive form Nerve trunk Nerve plexuses

Somatic and Autonomic Nervous System

Somatic and Autonomic Nervous System

Somatic Skeletal muscle Conscious and unconscious

movement Skeletal muscle contracts One synapse Acetylcholine

Autonomic Smooth and cardiac muscle

and glands Unconscious regulation Target tissues stimulated or

inhibited Two synapses Acetylcholine by preganglio

nic neurons and ACh or norepinephrine by postganglionic neurons

Neurotransmitters

ACh AChSweatglands

Striatedmuscle

AChSOMATIC NERVOUS SYSTEM

HeartSm. mus.Glands

ACh AChParasympathetic

ACh E, NE

Ad. M.

HeartSm. mus.Glands

ACh NE

AUTONOMIC NERVOUS SYSTEMSympathetic

Sympathetic Part

Lower center: located in intermediolateral nucleus (lateral gray horn) of spinal cord segments T1~L3

Sympathetic ganglia Paravertebral ganglia Prevertebral ganglia

Paravertebral Ganglia

Arranged on either side of vertebral column

Consist of 19~22 of oval-shaped ganglia 3 cervical 10~12 thoracic 4 lumbar 2~3 sacral Ganglion impar : unpaired on

the anterior face of coccyx

Paravertebral Ganglia

Superior cervical ganglion: largest, situated in front of transverse processes of C1~C3 vertebra

Middle cervical ganglion: smallest, is at level of transverse processes of C6 vertebra

Inferior cervical ganglion: situated at level of C7 vertebra, and may be fused with first thoracic ganglion to form cervicothoracic ganglion

Paravertebral Ganglia

Sympathetic Trunk

Formed by paravertebral ganglia and interganglionic branches

Lie on either side of vertebral column from base of skull to coccyx

The trunks of two side unite in front of the coccyx at a small swelling, the ganglion impar

Prevertebral Ganglia

Lie anterior to vertebral column and near the arteries for which they are named

Celiac ganglion Aorticorenal ganglion Superior mesenteric ganglion Inferior mesenteric ganglion

Preganglionic Fibers

Preganglionic fibers 15 pairs white communicating branches

Sympathetic trunk (only spinal levels T1~L3 have

white communicating branch)

Three Fates of Preganglionic Fibers

1. Relay in corresponding ganglion

2. Ascend or descend in sympathetic trunk and relay in higher or lower ganglia

3. Pass without synapse to a prevertebral ganglion for relay

Preganglionic Fibers Greater splanchnic nerve

formed by preganglionic fibers from T5~T9 ganglia, and relay in celiac ganglion.

Lesser splanchnic nerve formed by preganglionic fibers from T10~T12 ganglia, and relay in aorticorenal ganglion.

The postganglionic fibers supply the liver, spleen, kidney and alimentary tract as far as the left colic flexure.

Preganglionic Fibers

Lumbar splanchnic nerve Formed by preganglionic fibers from

L1~L4 ganglia, and relay in preverte

bral ganglia.

The postganglionic fibers supply desc

ending and sigmoid colon, rectum, pe

lvic viscera and lower limbs.

Three Fates of Postganglionic Fibers

Back to a spinal nerve along gray communicating branches to terminate in blood vessels, arrector pili muscles and sweat glands of head, neck, trunk and limbs

The fibers form their networks around blood vessels passing to visceral end organs

Terminate directly in certain organs

Postganglionic Fibers

Distribution of Sympathetic Nerve

Preganglionic fibers Postganglionic fibers

T1~T5 Head, neck, upper limb and thoracic viscera

T5~T12 Abdominal viscera

L1~L3 Pelvic viscera and lower limb

Parasympathetic Part Lower center: located in four pairs parasympathetic nuclei in b

rain stem and in sacral parasympathetic nucleus of spinal cord segments S2~S4

Parasympathetic ganglia: terminal ganglia are near or within the wall of a visceral organ Para-organ ganglia

Ciliary ganglion Pterygopalatine ganglion Submandibular ganglion Otic ganglion

Intra-organ ganglia

Cranial Portion of Parasympathetic Nerve

Ⅲ

ciliary ganglion

sphincter pupillae and ciliary muscles

pterygopalatine ganglionⅦlacrimal gland

submandibular ganglion

sublingual glandsubmandibular glandⅨ

otic ganglionparotid glandⅩ

terminal ganglia

heart, lungs, liver, spleenkidneys,alimentary tractas far as left colic flexure

Cranial Portion of Parasympathetic Nerve

Ⅲaccessory oculomotor nucleus 〈○ sphincter pupillae and ciliary muscles

ciliary ganglion

pterygopalatine ganglion Ⅶ 〈○ lacrimal glandsuperior salivatory nucleus 〈○ sublingual gland submandibular ganglion submandibular gland

Ⅸinferior salivator nucleus 〈○ parotid gland otic ganglion

Ⅹ heart, lungs, liver, spleen, dorsal nucleus of vagus n. 〈○ kidneys,alimentary tract terminal ganglia as far as left colic flexure

Sacral Portion of Parasympathetic Nerve

Preganglionic fibers from sacral parasympathetic nucleus leave spinal cord with anterior roots of the spinal nerves S2~S4,

Then leave sacral nerves and form pelvic splanchnic nerve and travel by way of pelvic plexus to terminal ganglia in pelvic cavity

Postganglionic fibers terminate in descending and sigmoid colon, rectum and pelvic viscera

Main Differences Between Sympathetic and Parasympathetic

Sympathetic Parasympathetic

Lower center Intermediolateral nucleus (lateral gray horn) of spinal cord segments T1~L3

Four pairs parasympathetic nuclei and sacral parasympathetic nucleus

Ganglia Paravertebral, prevertebral Terminal

Preganglionic f. Shorter Longer

Postganglionic f. Longer Shorter

Pre: Postganglionic 1: many more 1: a few

Distributions Throughout the body Limited primarily to head and viscera of thorax, abdomen, and pelvis

Different action Prepares for emergency situation (expends energy)

Conserve and restore body energy (conserves energy)

Main Differences Between Sympathetic and Parasympathetic

Sympathetic Parasympathetic

Different action Prepares for emergency situation (fight or flight)

Conserve and restore body energy (rest and relaxation)

Pupil Dilates Constricts

Heart Increases force of contraction

Decreases force of contraction

Rhythm of the heart To become more rapid To make slow

Blood pressure Heighten Depress

Bronchi Dilates bronchi Constricts bronchi

Main Differences Between Sympathetic and Parasympathetic

Sympathetic neurone

Dilator pupillae

Sphincter pupillaePupil

GanglionParasympathetic neurone

Normal light

Low light:-iris dilates

Bright light:-iris constricts

FUNCTION OF THE IRIS

Visceral Plexuses Cardiac plexuses

Superficial , below aortic arch

Deep, anterior to bifurcation of trachea

Pulmonary plexus

Visceral Plexuses Celiac plexus Abdominal aortic plexus Hypogastric plexus

Superior hypogastric plexus Inferior hypogastric plexus

(pelvic plexus)

Visceral Sensory Nerves

Enteroceptors

Ⅶ ，Ⅸ , Ⅹ

Nucleus of solitary tract

Sympathetic nerve Pelvic splanchnic nerve

Posterior horn

Thalamus

Hypothalamus

Cerebral cortex

Somatic motor neurons visceral motor neuclei

Effectors

Referred Pain

Pain originating from organs perceived as coming from skin

Site of pain may be distant from organ

Referred Pain

Convergence theory: This type of referred pain occurs b

ecause both visceral and somatic afferents often converge on the same interneurons in the pain pathways.

Excitation of the somatic afferent fibers is the more usual source of afferent discharge, so we “refer” the location of visceral receptor activation to the somatic source even though in the case of visceral pain.

The perception is incorrect.The convergence of nociceptor input from the viscera and the skin.

Referred Pain