Autonomic

• The autonomic nervous system is a part of the nervous system concerned with regulation and control of all involuntary processes in the body.
• The autonomic nervous system helps to control arterial pressure, gastrointestinal motility and secretion, urinary bladder emptying, sweating, body temperature and many other body activities.
• The nervous system is divided into two main systems: the Somatic nervous system, which controls the activity of voluntary skeletal muscles, and the Autonomic nervous system, which is concerned with the unconscious control of visceral activity.
• The peripheral motor portion of the Autonomic nervous system, the efferent, is made up of preganglionic and postganglionic neurons and is divided into the sympathetic nervous system, which arises from lateral horn cells of T1-L3 (thoracolumbar) segments of the spinal cord, and the parasympathetic system, which arises from the cranial and sacral areas of the CNS.
• The sympathetic nervous system is also called "Thoracolumbar outflow" and is further divided into the thoracic outflow, which arises from T1-T4 (thoracic) segments of the spinal cord, and the lumbar outflow, which arises from L1-L3 (lumbar) segments of the spinal cord.
• Most sympathetic preganglionic fibers are very short, synapse with postganglionic neurons within ganglia that lie in a sympathetic chain located on either side of the spinal cord and the long postganglionic fibers originating from this ganglion chain terminate in the effector organ.
• Some preganglionic fibers pass through the sympathetic chain without relay and terminate in collateral ganglia located between the spinal cord and innervated organ.
• The parasympathetic system, also called "Cranio-sacral outflow", arises from the cranial and sacral areas of the CNS and supplies the visceral structures in the head via the oculomotor, facial, glossopharyngeal nerves and those in the thorax and upper abdomen via the vagus nerves.
• The parasympathetic system also supplies the pelvic viscera.
• The preganglionic fibers in both outflows end on short postganglionic neurons located on or near the visceral structures.
• Autonomic ganglia are collections of nerve cells outside the CNS and contain the nerve cells of the postganglionic neurons.
• The glossopharyngeal nerve of the Parasympathetic System secretes parotid gland and vasodilates blood vessels.
• The facial nerve of the Parasympathetic System secretes profuse watery saliva and vasodilates blood vessels of the salivary glands.
• In the GIT, the vagus nerve of the Parasympathetic System contracts the gall bladder, helps evacuation of food, and is secretory to the stomach, pancreas, and liver for digestion.
• Noradrenaline (Norepinephrine) is released by all sympathetic post-ganglionic neurons except those which innervate sweat glands and blood vessels of skeletal muscles.
• The origin of preganglionic fiber in the sympathetic system is the Thoraco-Lumbar and Cranio-Sacral segments of the spinal cord.
• The type of receptors in the sympathetic system are α (alpha) and β (beta) adrenergic receptors.
• The type of fiber in the parasympathetic system is Long cholinergic preganglionic and short cholinergic postganglionic.
• The type of fiber in the sympathetic system is Short cholinergic preganglionic and long adrenergic(most) postganglionic.
• Chemical Transmission at Autonomic Junctions is mediated by neurotransmitters such as acetylcholine and nor-epinephrine.
• The origin of postganglionic fiber in the parasympathetic system is the terminal ganglia or collateral ganglia.
• The type of receptors in the parasympathetic system are α (alpha) and β (beta) adrenergic receptors.
• The cranial outflow of the Parasympathetic System includes the occulomotor nerve which contracts the constrictor pupillae muscle, producing miosis, and the ciliary muscle, increasing the convexity of the lens to allow near vision.
• The ANS can be divided into the Cholinergic system, which releases acetylcholine, and the Noradrenergic system, which releases noradrenaline.
• The origin of preganglionic fiber in the parasympathetic system is the Thoraco-Lumbar and Cranio-Sacral segments of the spinal cord.
• The origin of postganglionic fiber in the sympathetic system is the sympathetic chain or collateral ganglia.
• The vagus nerve of the Parasympathetic System inhibits all cardiac properties, decreases the heart rate, and decreases the contractility of cardiac muscles in the heart.
• In the lungs, the vagus nerve of the Parasympathetic System causes bronchoconstriction and vasodilates blood vessels.
• Acetylcholine is released by all preganglionic neurons (autonomic ganglia), all parasympathetic post-ganglionic neurons, and sympathetic post-ganglionic neurons which innervate sweat glands and blood vessels of skeletal muscles.
• The sacral outflow of the Parasympathetic System includes the urinary bladder, where it is motor to the wall and inhibitory to the internal urethral sphincter, and the colon and rectum, where it is motor to the wall and inhibitory to their sphincters, helping defecation.
• Collateral ganglia are present in the abdomen, near the big branches of the aorta and are the site of relay of preganglionic sympathetic and parasympathetic fibers but mainly sympathetic.
• Lateral ganglia (paravertebral) form the sympathetic chain on both sides of the vertebral column and are the sites of relay of preganglionic sympathetic fibers only.
• The functions of the Autonomic nervous system (ANS) include relay stations for preganglionic nerves and origin for postganglionic nerves, distributing centers, and sites of action of drugs.
• The functions of the Sympathetic Nervous System include the Cervical division which controls the eye, the Cardio-Pulmonary division which controls the heart and lungs, the Splanchnic division which controls the digestive system, and the Sympathetic supply to the pelvis which controls the urinary bladder and rectum.</
• The functions of the Parasympathetic Nervous System include the Cervical division which controls the eye, the Cardio-Pulmonary division which controls the heart and lungs, the Splanchnic division which controls the digestive system, and the Sympathetic supply to the pelvis which controls the urinary bladder and rectum.
• Terminal ganglia are present near or on the wall of effector organs and are the site of relay of preganglionic parasympathetic fibers only.
• The main ganglia for preganglionic sympathetic fibers are the lateral ganglia.
• The Autonomic nervous system (ANS) is divided into three divisions: the Sympathetic nervous system, the Parasympathetic nervous system, and the Divisions of Autonomic nervous system (ANS).
• The main ganglia for preganglionic parasympathetic fibers are the terminal ganglia.
• The functions of the Sympathetic Nervous System include the Cervical division which controls the eye, the Cardio-Pulmonary division which controls the heart and lungs, the Splanchnic division which controls the digestive system, and the Sympathetic supply to the pelvis which controls the urinary bladder and rectum.