Chapter 14 Autonomic Nervous System Flashcards | Easy Notecards
Autonomic nervous system study guide by nrbain includes 53 questions The two divisions of the autonomic nervous system normally have a what relationship. The central nervous system is divided into two parts: the brain and the spinal cord In contrast, an adult human weighs approximately 70 kg and has a brain that. The two divisions of the autonomic nervous system (ANS) normally have a(n) ______ relationship. antagonistic. Which target organ is NOT affected by the .
The autonomic system usually is defined as a motor system that innervates three major types of tissue: However, it also relays visceral sensory information to the central nervous system and processes it so that alterations can be made in the activity of specific autonomic motor outflows, such as those that control the heartblood vessels, and other visceral organs. It also stimulates the release of certain hormones involved in energy metabolism e. These integrated responses maintain the normal internal environment of the body in an equilibrium state called homeostasis.
The autonomic system consists of two major divisions: These often function in antagonistic ways. The motor outflow of both systems is formed by two serially connected sets of neurons.
Autonomic Examples and Quiz
The first set, called preganglionic neuronsoriginates in the brainstem or the spinal cordand the second set, called ganglion cells or postganglionic neuronslies outside the central nervous system in collections of nerve cells called autonomic ganglia.
Parasympathetic ganglia tend to lie close to or within the organs or tissues that their neurons innervate, whereas sympathetic ganglia are located at more distant sites from their target organs. Both systems have associated sensory fibres that send feedback into the central nervous system regarding the functional condition of target tissues.
A third division of the autonomic system, the enteric nervous system, consists of a collection of neurons embedded within the wall of the gastrointestinal tract and its derivatives. This system controls gastrointestinal motility and secretion.
AUTONOMIC NERVOUS SYSTEM
Sympathetic nervous system The sympathetic nervous system normally functions to produce localized adjustments such as sweating as a response to an increase in temperature and reflex adjustments of the cardiovascular system. Under conditions of stress, however, the entire sympathetic nervous system is activated, producing an immediate, widespread response called the fight-or-flight response. This response is characterized by the release of large quantities of epinephrine from the adrenal glandan increase in heart rate, an increase in cardiac outputskeletal muscle vasodilation, cutaneous and gastrointestinal vasoconstriction, pupillary dilation, bronchial dilation, and piloerection.
The overall effect is to prepare the individual for imminent danger. Sympathetic preganglionic neurons originate in the lateral horns of the 12 thoracic and the first 2 or 3 lumbar segments of the spinal cord.
For this reason the sympathetic system is sometimes referred to as the thoracolumbar outflow. The axons of these neurons exit the spinal cord in the ventral roots and then synapse on either sympathetic ganglion cells or specialized cells in the adrenal gland called chromaffin cells. Sympathetic ganglia Sympathetic ganglia can be divided into two major groups, paravertebral and prevertebral or preaorticon the basis of their location within the body.
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Paravertebral ganglia generally are located on each side of the vertebrae and are connected to form the sympathetic chainor trunk. There are usually 21 or 22 pairs of these ganglia—3 in the cervical region, 10 or 11 in the thoracic region, 4 in the lumbar region, and 4 in the sacral region—and a single unpaired ganglion lying in front of the coccyxcalled the ganglion impar.
The three cervical sympathetic ganglia are the superior cervical ganglion, the middle cervical ganglion, and the cervicothoracic ganglion also called the stellate ganglion. The superior ganglion innervates viscera of the head, and the middle and stellate ganglia innervate viscera of the neck, thorax i.
The thoracic sympathetic ganglia innervate the trunk region, and the lumbar and sacral sympathetic ganglia innervate the pelvic floor and lower limbs.
- Sympathetic nervous system
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- Parasympathetic nervous system
All the paravertebral ganglia provide sympathetic innervation to blood vessels in muscle and skin, arrector pili muscles attached to hairs, and sweat glands. The three preaortic ganglia are the celiac, superior mesenteric, and inferior mesenteric. Lying on the anterior surface of the aortapreaortic ganglia provide axons that are distributed with the three major gastrointestinal arteries arising from the aorta.
Thus, the celiac ganglion innervates the stomachliverpancreasand the duodenumthe first part of the small intestine; the superior mesenteric ganglion innervates the small intestine ; and the inferior mesenteric ganglion innervates the descending colonsigmoid colonrectumurinary bladderand sexual organs. Therefore, the brain was only 0. In contrast, an adult human weighs approximately 70 kg and has a brain that weighs approximately 1. This makes the brain to body ratio of the human times greater than that of the stegosaurus.
Peripheral Nervous System The peripheral nervous system is divided into two major parts: Somatic Nervous System The somatic nervous system consists of peripheral nerve fibers that send sensory information to the central nervous system AND motor nerve fibers that project to skeletal muscle. The picture on the left shows the somatic motor system.
Autonomic Examples and Quiz
The cell body is located in either the brain or spinal cord and projects directly to a skeletal muscle. Autonomic Nervous System The autonomic nervous system is divided into three parts: The autonomic nervous system controls smooth muscle of the viscera internal organs and glands.
This picture shows the general organization of the autonomic nervous system. The preganglionic neuron is located in either the brain or the spinal cord. This preganglionic neuron projects to an autonomic ganglion.
The postganglionic neuron then projects to the target organ. Notice that the somatic nervous system has only one neuron between the central nervous system and the target organ while the autonomic nervous system uses two neurons. The enteric nervous system is a third division of the autonomic nervous system that you do not hear much about.
The enteric nervous system is a meshwork of nerve fibers that innervate the viscera gastrointestinal tract, pancreas, gall bladder.