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1、Autonomic Nervous System (ANS) Chapter 3 The Peripheral Nervous SystemThe autonomic portion of the nervous system controls the visceral functions of the body (also called the visceral nervous system).Helps control arterial pressure, gastrointestinal motility and secretion, urinary bladder emptying,
2、sweating, body temperature, and many other activities.innervates organs whose functions are not usually under voluntary control, so its functions are involuntary.Although ANS is composed of portions of both the central nervous system and peripheral nervous system, it functions independently and with
3、out a persons conscious control.Organization of the Autonomic Nervous SystemSNS, PNS, and ANSnSNS and ANS are both part of the peripheral nervous system (PNS).nSNS operates under our conscious control.nANS functions are involuntary. Organization of the Autonomic Nervous SystemThe effectors that resp
4、ond to autonomic regulation include cardiac muscle tissue (within the heart), smooth muscle tissue (within the viscera), glandular epithelium. Organization of the Autonomic Nervous SystemThese effectors are part of the organs of the viscera, of blood vessels, and of specialized structures within oth
5、er organs. The involuntary effects of autonomic innervation contrast with the voluntary control of skeletal muscles by way of somatic motor innervation.In the somatic motor system, impulses are conducted along a single axon from the spinal cord to the neuromuscular junction, however, the autonomic m
6、otor pathway involves two neurons in the motor transmission of impulses. Organization of the Autonomic Nervous SystemThe first neurons has its cell body in the gray matter of the brain or spinal cord. Rather than directly innervating the effector organ, the axon of this neuron synapses with a second
7、 neuron within an autonomic ganglion. (A ganglion is a collection of neuron cell bodies outside the CNS.)Organization of the Autonomic Nervous SystemThe first neuron is thus called a preganglionic neuron.The second neuron in this pathway, called a postganglionic neuron, has an axon that extends from
8、 the autonomic ganglion and synapses with the cells of an effector organ.Organization of the Autonomic Nervous SystemPreganglionic autonomic neurons originate in the brainstem and from the upper thoracic to the fourth sacral portions of the spinal cord, with the exception of the area between L3 and
9、S1. Autonomic ganglia are located in the head, neck, and abdomen. Chains of autonomic ganglia also parallel the spinal cord along each side. The origin of the preganglionic neurons and the location of the autonomic ganglia help to differentiate the sympathetic and parasympathetic divisions of the au
10、tonomic system.Organization of the Autonomic Nervous SystemDivision of the Autonomic Nervous System ANS is subdivided into parasympathetic and sympathetic divisions. Divisions are similar in that they both use a preganglionic neuron and a ganglionic neuron to innervate effectors.Both contain the aut
11、onomic ganglia that house the ganglionic neurons.Both are involuntary and are concerned with the bodys internal environment. Divisions perform dramatically different functions. The Sympathetic DivisionnPrimarily concerned with preparing the body for emergencies.qreferred to as the “fight-or-flight”
12、division nIncreased sympathetic activity results in the increased alertness and metabolic activity necessary for these activities as well as in times of fear.Division of the Autonomic Nervous SystemThe sympathetic nervous system is stimulated by increased physical activity, resulting in elevated blo
13、od pressure, accelerated heart rate and respiratory rate, dilated pupils, raised hair, and increased perspiration. At the same time, the peristaltic activity of the gastrointestinal tract is suppressed and secretion by intestinal glands is reduced.The Parasympathetic Division nPrimarily concerned wi
14、th conserving energy and replenishing nutrient stores. nIs most active when the body is at rest or digesting a meal.qnicknamed the “rest-and-digest” divisionnParticipates along with the sympathetic division in maintaining homeostasis (a constant internal environment).Division of the Autonomic Nervou
15、s SystemWhen the parasympathetic system predominates, it increases peristaltic activity and intestinal secretion, stimulates defecation and urination, and reduces the heart rate and respiratory rate, while the pupils constrict.nLower center: located in lateral horn of gray mater of spinal cord in se
16、gments T1L3The sympathetic Division （thoracolumbar division）n The peripheral part Sympathetic ganglia - Paravertebral ganglia (to form sympathetic trunk) -Prevertebral ganglia (lie near arteries) The sympathetic Division （thoracolumbar division）The sympathetic neurons in the thoracic and lumbar late
17、ral horn send their axons via the communicating branches to the sympathetic trunk. The sympathetic DivisionThe sympathetic trunk consists of a chain of paravertebral ganglia and interganglionic branches, which lie on each side of the vertebral column, in front of the transverse processes of each ver
18、tebra, and extend from the base of the skull to the coccyx. The sympathetic Division- sympathetic trunk Except in the cervical region, where several paravertebral ganglia fuse together to form 3-4 lager ganglia, the anterior root of each spinal nerve generally has a chain ganglion associated with it
19、. The sympathetic Division-sympathetic trunk Superior cervical ganglionMiddle cervical ganglioninferior cervical ganglionSince most of the preganglionic sympathetic nerve fibers are myelinated, the short pathways they form in passing from the anterior root of each spinal nerve to the sympathetic tru
20、nks appear white and are called white rami communicantes. There are 14 pairs of white rami communicantes connecting the first thoracic through the second lumbar spinal nerves to the paravertebral ganglia.The sympathetic Division-sympathetic trunk The sympathetic Division Upon entering the chain gang
21、lia, the preganglionic fibers follow one of there courses:Some fibers synapse with neurons in the corresponding paravertebral ganglion at the same level at which the fibers entered the chain; The postganglionic fibers return to the spinal nerve (gray rami communicantes). Along with the spinal nerve,
22、 the fibers innervate effectors in the skin, including smooth muscles in the walls of the blood vessels of the skin, sweat glands, and the arrector pili muscles of the hairs.The sympathetic DivisionSome fibers pass up or down in sympathatic trunk before terminating in the paravertebral ganglion at a
23、 higher or lower level; Some postganglionic fibers enter the cervical and sacral spinal nerves through gray rami communicantes, and finally innervate the skin of the region supplied by those nerves. Some postganglionic fibers in the thoracic and cervical ganglia pass directly from the ganglion to in
24、nervate the thoracic viscera and structures in the head, rather than entering the spinal nerve.The sympathetic DivisionThe others just pass through the paravertebral ganglion and terminate in prevertebral ganglion. Some preganglionic fibers from the thoracic region form splanchnic nerves, that pass
25、through the diaphragm and lead to prevertebral ganglia located on the front of the abdominal aorta. The major prevertebral ganglia, which are named for the vascular branches of the aorta nearest them, are the Celiac ganglion Superior mesenteric ganglion Inferior mesenteric ganglion, G. splanchnic nL
26、.splanchnic nCeliac ganglionSuperior mesenteric ganglionInferior mesenteric ganglionThe postganglionic fibers leave the prevertebral ganglia, interconnect to form autonomic plexus, and supply the vicera of the abominopelvic cavity.The sympathetic DivisionnLower center1.Cranial portion: four pairs pa
27、rasympathetic nuclei in brain stem accessory oculomotor nucleus superior salivatory nucleus inferior salivatory nucleus dorsal nucleus of vagus n.2.Sacral portion: sacral parasympathetic nucleus of spinal cord in segments S2S4The parasympathetic Division (craniosacral division) -Para-organ ganglia l
28、 Ciliary ganglionl Pterygopalatine ganglionl Submandibular ganglion l Otic ganglionIntramural ganglian The peripheral part Parasympathetic ganglia- are called terminal gangliaThe parasympathetic Divisionciliary ganglionsphincter pupillae and ciliary musclesaccessory oculomotor nucleusThe parasympath
29、etic Division-Cranial portion superior salivatory nucleuspterygopalatine ganglionSubmandibular ganglionlacrimal glandsubmandibular glandSublingual glandThe parasympathetic Division-Cranial portion inferior salivatorynucleusotic ganglionparotid glandThe parasympathetic Division-Cranial portion dorsal
30、 nucleus of vagus nterminal gangliaheart, lungs, liver, spleen, kidneys, alimentary tract as far as left colic flexure The parasympathetic Division-Cranial portion Sacral n.Pelvic splanchnic n.Pelvic plexusSynapse with terminal gangliasupply the descending and sigmoid colon, rectum and pelvic viscer
31、a sacral parasympathetic nucleusS2-S4Postganglionic fibersThe parasympathetic Division- Sacral portion Sympathetic Parasympathetic Lower centerLateral gray horn of spinal cord segments T1L3Four pairs parasympathetic nuclei and sacral parasympathetic nucleusGanglia Paravertebral, prevertebralTerminal
32、 (Para-organ ganglia; Intramural ganglia)Preganglionic f.Shorter LongerPostganglionic f.Longer Shorter Distributions Throughout the bodyLimited primarily to head and viscera of thorax, abdomen, and pelvisDifferent actionPrepares for emergency situation (fight or flight)Conserve and restore body energy (rest and relaxation)Main differences between sympathetic and parasympathetic
