Autonomic nervous system sympathetic and parasympathetic system

Autonomic nervous system

1. Autonomic nervous system By Shama Praveen Physiology dept.

2. Autonomic nervous system Regulates activity of smooth muscle, heart, glands of GIT, sweat glands, adrenal gland and of certain endocrine organs. Its main aim is to maintain the optimal internal environment of the body. It governs the body function which are normally carried out without conscious control or awareness. This is why ANS is also called vegetative or efferent visceral or involuntary nervous system.

3. Difference between somatic and ANS SOMATIC NERVOUS SYSTEM AUTONOMIC NERVOUS SYSTEM POLYSYNATIC PATHWAY (3neurons involved) Afferent neuron, connector neuron, efferent neuron Also 3 neurons involved. Afferent neuron( cell body lie in dorsal root ganglion), interneuron called preganglionic neuron (cell body lie in intermediolateral columnof spinal cord. Sensory input from general and special senses. From interoceptors ’ One motor neuron from CNS to effector organ 2 motor neurons involved Neurotransmitters: Ach Ach, NE Always lead to muscle contraction It may increase or decrease activity or parameter of organ and gland. Control of output: Voluntary from cerebral cortex Involuntary from hypothalamus, limbic system, brain stem and spinal cord

4. Organization of ANS ANS is divided into two divisons : Sympathetic and parasympathetic Sympathetic preganglionic fibers leave the spinal cord with the central roots of the spinal nerves only b/w the 1 st thoracic and 2 nd lumbar segment, therefore, sympathetic division is also called thoraco lumbar division. Preganglionic fibers pass via white rami communicates to the Paravertebral sympathetic ganglia lies close to the spinal cord, form 2chains of ganglia, one on each side of cord called sympathetic trunk. Postganglionic fibers: Pass to viscera in the various sympathetic nerves, others re enter the spinal nerves via the Grey rami communicates from chain ganglia Some preganglionic fibers pass through the paravertebral ganglion chain (sympathetic trunk) and end on the postganglionic neurons located in the collateral ganglia (prevertebral ganglia).

5. Exceptions Myometrium of the uterus is innervated by a special system of short adrenergic neurons, with cell bodies in the uterus and preganglionic fibers to these postgsnglionic neurons go a’l the way to uterus. Preganglionic fibers directly supply the adrenal medulla, where the postganglionic neurons have lost their axons and become specialized for secretion directly into the blood. Sympathetic ganglia can act either as automatic relay stations and integrating centers.

6. Parasympathetic division of ANS CRANIOSACRAL DIVISION Parasympathetic ganglia located near the effector organ (exceptional: Sphenopalatine and otic ganglia) Cranial outflow. It supplies the visceral structures in the head via oculomotor (III)nerve, facial nerve and glossopharyngeal nerve, those in thorax and upper abdomen via vagus nerve. Sacral outflow. It supplies the pelvic viscera via pelvic branches of the 2 nd to 4 th sacral spinal nerves.

7. Chemical transmission at autonomic junctions On the basis of chemical transmitters released, the neurons in the entire nervous system are either cholinergic or adrenergic

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