Quiz 5: Autonomic Nervous System


The central nervous system (CNS) is the organ system controlling and coordinating all the systems in the body. It is a vast and complicated, but a well-arranged for the integration of the whole living body. CNS has divisions to control the voluntary and involuntary actions separately. Peripheral nervous system (PNS) aids CNS in its function. CNS constitutes 2 structures - brain and spinal cord. It sends and receives information through the structures called nerves. PNS constituting cranial and spinal nerves are divided into somatic and visceral nerves. Visceral nervous system is also called autonomic nervous system (ANS). ANS is again divided into sympathetic and parasympathetic nervous systems. The parasympathetic division is also called craniosacral division. This is comprised of nerves from the brain (cranial nerves) and spinal cord (sacral nerves). The cranial nerves 3, 7, 9 and 10; and the sacral nerves S2, S3 and S4, form the parasympathetic system. The upper portion of the abdominal cavity is innervated by cranial nerves whereas the lower portion of the abdominal cavity and the pelvic cavity are innervated by sacral nerves. The cranial nerves supply the glands of the head, thoracic cavity and the internal organs too. The sympathetic nervous system which is also called thoracolumbar division originate from thoracic and lumbar spinal nerves spanning from T1 to L3. The thoracic nerves of the sympathetic system innervate the body regions similar to cranial nerves, and the lumbar nerves innervate just like sacral nerves. Almost all the body organs and glands except most of the blood vessels are supplied by one division of sympathetic nerve and one division of parasympathetic nerve. The blood vessels are supplied only by sympathetic nerves.

The categories of drugs included in cholinergic agonists are: directly-acting muscarinic agonists or nicotinic agonists and indirectly-acting cholinergic agonists. The drugs that bind directly to the muscarinic receptors located in the various tissues and organs throughout the body are known as directly-acting muscarinic agonists. Since the action produced is similar to the action of the parasympathetic nervous system; therefore they are also known as parasympathomimetics agents. The examples of drugs are carbachol and neostigmine. These drugs cause miosis like morphine. The drugs that block the effects of parasympathetic nervous system are known as Para sympatholytic or cholinergic antagonists. The examples include atropine and cyclopentolate. These drugs are also known by the name of anti-cholinergics. These drugs are divided into two important categories: anti-muscarinic and anti-nicotinic drugs. For example: atropine is an anti-cholinergic drug that specifically targets the muscarinic cholinergic receptors.

The sensory information is transmitted from the peripheral organs to the brain and spinal cord i.e. central nervous system (CNS) by an afferent nerve. The nerve impulses are send to the skeletal muscles by the somatic nerves. On the other side, an appropriate motor response is carried from the brain and spinal cord to the peripheral organs by an efferent nerve. The neuron for which the neurotransmitter is adrenaline, nor-adrenaline or dopamine is known as adrenergic nerve fibre. The basis of classification of nerves in the somatic nervous system is their location either in the head regions or spine region. Hence the incorrect options are a, b, d and e. The autonomic nerve is known to conduct nerve impulses to skeletal muscles. The two nerve cells are involved in an autonomic nerve pathway. One of the cells is located in the brain stem or spinal cord which is connected by nerve fibers to the other cell. Hence the correct option is img .

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