Organisation of ans
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The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). The autonomic nervous system (ANS) is a division of the PNS that regulates involuntary body functions like heart rate and digestion. The ANS has sympathetic and parasympathetic divisions that originate in the CNS and synapse in peripheral ganglia. The sympathetic division originates from the thoracic and lumbar spinal cord and the parasympathetic from cranial and sacral regions. Together with the endocrine system, the ANS coordinates essential bodily functions.
Organisation of ans
- 3. BRIEF INTRODUCTION TO NERVOUS SYSTEM The nervous system is divided into anatomical divisions : CNS which is composed of composed of the brain and spinal cord, and PNS which includes neurons located outside the brain and spinal cord i.e. any nerve that enter or leaves the CNS. The peripheral nervous system is further subdivided into the efferent divisions , the neurons of which carry signals away from the brain and spinal cord to the peripheral tissues, and the afferent division, the neurons of which bring information from periphery to the CNS.
- 4. WHAT IS AUTONOMIC SYSTEM? The autonomic nervous system (ANS) is largely autonomous (independent) in that its activities are not under direct conscious control. It is concerned with visceral functions-cardiac output, blood flow to various organs, digestion, etc- that are necessary for life.
- 5. Autonomic Nervous System And Endocrine System The autonomic nervous system, along with the endocrine system coordinates the regulation and integration of bodily functions. The endocrine system sends signals to target tissues by varying the levels of blood borne hormones. In contrast, the nervous system exerts its influence by the rapid transmission of electrical impulses over nerve fibers that terminate at effector cells, which specifically respond to the release of neuromediator substances
- 6. Preganglionic neurons in the CNS send axons to synapse on ganglionic neurons in autonomic ganglia outside the CNS Preganglionic neuron’s body lies in the CNS Postganglionic axons of ANS are usually unmyelinated CNS (brain and Spinal Cord) PreganglionicGanglionPostganglionic
- 7. ORGANISATION OF AUTONOMIC NERVOUS SYSTEM
- 10. 1. EFFERENT NEURONS The ANS carries nerve impulses from the CNS to the effector organs by way of two types of efferent neurons. The first nerve cell is called a preganglionic neuron, and its cell body is located within the CNS . Preganglionic neurons emerge from the brainstem or spinal cord and make a synaptic connection in ganglia(an aggregation of nerve cell bodies located in the peripheral nervous system).
- 11. These ganglia function as relay stations between a preganglionic neuron and a second nerve cell, the postganglionic neuron . The latter neuron has a cell body originating in the ganglion .It is generally nonmyelinated and terminates on effector organs, such as smooth muscles of the viscera, cardiac muscle and the exocrine glands
- 12. 2. AFFERENT NEURONS The afferent neurons of the ANS are important in the reflex regulation of this system. For example:- By sensing pressure in the carotid sinus and aortic arch and in signaling the CNS to influence the efferent branch of the system to respond.
- 13. 3. SYMPATHETIC NEURONS Anatomically, the sympathetic and parasympathetic neurons originate in the CNS and emerge from two different spinal cord regions. The preganglionic neurons of the sympathetic system come from thoracic and lumbar regions (T1 and L2) of the spinal cord , and they synapse into two cord like chains of ganglia that run close to and parallel on each side of the spinal cord. Axons of the postganglionic neuron extend from these ganglia to the tissues that they innervate and regulate. The sympathetic nervous system is also called thoracolumbar division because of its origin. In most cases, the preganglionic endings of sympathetic nervous system are highly branched enabling one preganglionic neuron to interact with many postganglionic neurons. This arrangement enables them to activate numerous effector organs.
- 15. 4. PARASYMPATHETIC NEURONS The parasympathetic preganglionic fibers arise from cranial nerves 3 (oculomotor), 7(facial), 9 (glossopharyngeal) and vagus as well as from the sacral regions (S2 and S4) of the spinal cord and synapse in ganglia near or on the effector organ. They are also called as cranio-sacral division
- 16. 5. ENTERIC NEURONS The enteric nervous is the third division of the ANS. It is a collection of nerve fibers that innervate the gastro intestinal (GI) tract, pancreas, gallbladder. It constitutes the “BRAIN OF THE GUT” This system functions independently of the CNS and controls the motility, exocrine and endocrine secretions, and microcirculation of the GI tract.
- 18. FUNCTION OF ANS Autonomic because the autonomous autonomic nervous system regulates them. Regulating, adjusting, and coordinating vital visceral functions: Blood pressure and blood flow Body temperature Diameter of bronchi Digestion Metabolism Elimination