ans .the autonomic nervous system (ans )

.The autonomic nervous system (ANS ) coordinates cardiovascular,

respiratory, digestive, urinary and reproductive functions

• Preganglionic neurons in the CNS send axons to synapse on postganglionic neurons in autonomic ganglia outside the CNS

ANS

Components of the ANS

• Sympathetic division (thoracolumbar, “fight or

flight”)• Thoracic and lumbar segments outflow of

the spinal cord

• Parasympathetic division (craniosacral, “rest and

repose”)• Preganglionic fibers leaving the brain

and sacral segments of the spinal cord

I. The Sympathetic Division

• Preganglionic neurons between segments T1 and L2 of the spinal cord• Ganglionic neurons in ganglia near vertebral column• Specialized neurons in adrenal glands

Sympathetic division anatomy

The Organization of the Sympathetic Division of the ANS

• Sympathetic chain ganglia (paravertebral ganglia)

• Collateral ganglia (prevertebral ganglia)

Sympathetic ganglia

Sympathetic Pathways

Sympathetic Pathways

Sympathetic Pathways

• Segments T1-L2, ventral roots give rise to myelinated white ramus

• Leads to sympathetic chain ganglia

Organization and anatomy of the sympathetic division

The Distribution of Sympathetic Innervation

• Rejoin spinal nerves and reach their destination by way of the dorsal and ventral rami

• Those targeting structures in the thoracic cavity form sympathetic nerves• Go directly to their destination

Postganglionic fibers

• Sympathetic innervation via preganglionic fibers that• synapse within collateral ganglia

•Splanchic nerves

Abdominopelvic viscera

• Celiac ganglion• Innervates stomach, liver, gall

bladder, pancreas, spleen• Superior mesenteric ganglion• Innervates small intestine and initial

portion of large intestine• Inferior mesenteric ganglion• Innervates kidney, urinary bladder,

sex organs, and final portion of large intestine

Abdominopelvic viscera

• In crises, the entire sympathetic division responds• Sympathetic activation• Affects include increased alertness,

energy and euphoria, increased cardiovascular and respiratory activities, elevation in muscle tone, mobilization of energy resources

Sympathetic activation

• Stimulation of sympathetic division has two distinct results• Release of ACh or NE at specific

locations• Secretion of E and NE into general

circulation• Most postganglionic fibers are adrenergic, a

few are cholinergic or nitroxidergic• Two types of receptors are alpha

receptors and beta receptors• Sympathetic ganglionic neurons end in

telodendria studded with varicosities filled with neurotransmitter

Neurotransmitters and sympathetic function

Sympathetic Variosities

II.The Parasympathetic Division

• Preganglionic neurons in the brainstem and sacral segments of spinal cord

• Ganglionic neurons in peripheral ganglia located within or near target organs

Parasympathetic division of A.N.S

The Organization of the Parasympathetic Division of the ANS

• Preganglionic fibers leave the brain as cranial nerves III, VI, IX, X

• Sacral neurons form the pelvic nerves• S2,3,4

Organization and anatomy of the parasympathetic division

The Distribution of Parasympathetic Innervation

• Effects produced by the parasympathetic division • relaxation• food processing• energy absorption

Parasympathetic activation

• All parasympathetic fibers release ACh• Short-lived response as ACH is broken down by AChE and tissue cholinesterase• Postsynaptic membranes have two kinds of receptors• Muscarinic• Nicotinic

Neurotransmitters and parasympathetic functions

• Sympathetic• Widespread influence on visceral and

somatic structures• Parasympathetic• Innervates only visceral structures

serviced by cranial nerves or lying within the abdominopelvic cavity

• Dual innervation = organs that receive input from both systems

Sympathetic and parasympathetic divisions

• Sympathetic and parasympathetic systems intermingle to form autonomic plexuses• Cardiac plexus• Pulmonary plexus• Esophageal plexus• Celiac plexus• Inferior mesenteric plexus• Hypogastric plexus

Anatomy of dual innervation

The Autonomic Plexuses

• Important physiological and functional differences exist

Comparison of the two divisions

The Anatomical Differences between the Sympathetic and Parasympathetic Divisions

Integration and Control of Autonomic Functions

Visceral Reflexes

•Activity in the ANS is controlled by centers in the brainstem that deal with visceral functioning

Higher levels of autonomic control

Levels of Autonomic Control

A Comparison of Somatic and Autonomic Function

Memory Storage

• Deep sleep, the body relaxes and cerebral cortex activity is low• REM sleep active dreaming occurs• The reticular activating system (RAS) is important to arousal and maintenance of consciousness

Consciousness

The Reticular Activating System