prof. azaprof. aza

Autonomic Nervous SystemAutonomic Nervous System

prof. azaprof. aza

prof. azaprof. aza

the sympathetic nervous systemthe sympathetic nervous system

One division of the autonomic nervous system, One division of the autonomic nervous system, called the sympathetic nervous system, called the sympathetic nervous system, dominates in times of stress. It controls dominates in times of stress. It controls the "fight the "fight or flight"or flight" reaction, increasing blood pressure, reaction, increasing blood pressure, heart rate, breathing rate, and blood flow to the heart rate, breathing rate, and blood flow to the muscles. muscles.

Another division, called the parasympathetic Another division, called the parasympathetic nervous system, has the opposite effect. It nervous system, has the opposite effect. It conserves energyconserves energy by slowing the heartbeat and by slowing the heartbeat and breathing rate, and by promoting digestion and breathing rate, and by promoting digestion and elimination (of waste). elimination (of waste).

prof. azaprof. azaFigure 07 ANS Side ViewFigure 07 ANS Side View

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The CNS controlsThe CNS controls

Most glands, smooth muscles, and cardiac Most glands, smooth muscles, and cardiac muscles constantly get inputs from both the muscles constantly get inputs from both the sympathetic and parasympathetic systems. The sympathetic and parasympathetic systems. The CNS controls the activity CNS controls the activity by varying the ratio of by varying the ratio of the signals. the signals.

Depending on which motor neurons are selected Depending on which motor neurons are selected by the CNS, the net effect of the arriving signals by the CNS, the net effect of the arriving signals will will either stimulate or inhibit the organeither stimulate or inhibit the organ. .

Figure 07 shows the various organs and actions, Figure 07 shows the various organs and actions, which are related to the two different divisions. which are related to the two different divisions.

prof. azaprof. aza

prof. azaprof. aza

prof. azaprof. aza

Motor fibers that govern involuntary responses, do Motor fibers that govern involuntary responses, do not lead directly to the organs they innervate. not lead directly to the organs they innervate. Instead, they make their trips in two stages. Instead, they make their trips in two stages.

The first set of fibers The first set of fibers leads from the CNS to leads from the CNS to gangliaganglia (which are collections of nerve cell (which are collections of nerve cell bodies) that lie outside the CNS (the bodies) that lie outside the CNS (the preganglionic fibers). preganglionic fibers).

At the ganglia the fibers form synaptic junctions At the ganglia the fibers form synaptic junctions with the dendrites of as many as twenty different with the dendrites of as many as twenty different cell bodies. The axons of these cell bodies form cell bodies. The axons of these cell bodies form a second set of fibers, the postganglionic fibers. a second set of fibers, the postganglionic fibers.

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It is these postganglionic fibers that lead to the It is these postganglionic fibers that lead to the organs.organs.The chief ganglia involved in the autonomic The chief ganglia involved in the autonomic nervous system form two lines running down nervous system form two lines running down either side of the spinal column. They are either side of the spinal column. They are outside the bony vertebrae. outside the bony vertebrae.

These two lines of ganglia outside the column These two lines of ganglia outside the column resemble a pair of long beaded cords. At the resemble a pair of long beaded cords. At the lower end, the two cords join and finish in a lower end, the two cords join and finish in a single central stretch. single central stretch.

These lines of ganglia are sometimes called the These lines of ganglia are sometimes called the sympathetic trunks (used by the sympathetic sympathetic trunks (used by the sympathetic nervous system). Not all ganglia are located in nervous system). Not all ganglia are located in the sympathetic trunks. the sympathetic trunks.

prof. azaprof. aza

Not all ganglia are located in the sympathetic trunks. Not all ganglia are located in the sympathetic trunks. Some are not; and it is possible for a preganglionic fiber Some are not; and it is possible for a preganglionic fiber to go right through, making no synaptic junction there at to go right through, making no synaptic junction there at all, joining instead with ganglia located in front of the all, joining instead with ganglia located in front of the vertebrae. vertebrae.

For the parasympathetic nervous system, some of the For the parasympathetic nervous system, some of the ganglia separating the preganglionic fibers from the ganglia separating the preganglionic fibers from the postganglionic fibers are actually located within the postganglionic fibers are actually located within the organ the nerve is servicing. In that case, the organ the nerve is servicing. In that case, the preganglionic fiber runs almost the full length of the total preganglionic fiber runs almost the full length of the total track, whereas the postganglionic fiber is at most just a track, whereas the postganglionic fiber is at most just a few millimeters long.few millimeters long.

prof. azaprof. aza

the CNS (the preganglionic fibers). At the ganglia the fibers form the CNS (the preganglionic fibers). At the ganglia the fibers form synaptic junctions with the dendrites of as many as twenty different synaptic junctions with the dendrites of as many as twenty different cell bodies. The axons of these cell bodies form a second set of cell bodies. The axons of these cell bodies form a second set of fibers, the postganglionic fibers. It is these postganglionic fibers that fibers, the postganglionic fibers. It is these postganglionic fibers that lead to the organs.lead to the organs.The chief ganglia involved in the autonomic nervous system form The chief ganglia involved in the autonomic nervous system form two lines running down either side of the spinal column. They are two lines running down either side of the spinal column. They are outside the bony vertebrae. outside the bony vertebrae.

These two lines of ganglia outside the column resemble a pair of These two lines of ganglia outside the column resemble a pair of long beaded cords. At the lower end, the two cords join and finish in long beaded cords. At the lower end, the two cords join and finish in a single central stretch. These lines of ganglia are sometimes called a single central stretch. These lines of ganglia are sometimes called the sympathetic trunks (used by the sympathetic nervous system). the sympathetic trunks (used by the sympathetic nervous system). Not all ganglia are located in the sympathetic trunks. Some are not; Not all ganglia are located in the sympathetic trunks. Some are not; and it is possible for a preganglionic fiber to go right through, and it is possible for a preganglionic fiber to go right through, making no synaptic junction there at all, joining instead with ganglia making no synaptic junction there at all, joining instead with ganglia located in front of the vertebrae. located in front of the vertebrae.

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For the parasympathetic nervous system, some of the For the parasympathetic nervous system, some of the ganglia separating the preganglionic fibers from the ganglia separating the preganglionic fibers from the postganglionic fibers are actually located within the postganglionic fibers are actually located within the organ the nerve is servicing. In that case, the organ the nerve is servicing. In that case, the preganglionic fiber runs almost the full length of the total preganglionic fiber runs almost the full length of the total track, whereas the postganglionic fiber is at most just a track, whereas the postganglionic fiber is at most just a few millimeters long.few millimeters long.The splanchnic nerves, which originate from some of the The splanchnic nerves, which originate from some of the thoracic nerves, have their preganglionic fibers ending in thoracic nerves, have their preganglionic fibers ending in a mass of ganglia lying just behind the stomach. It a mass of ganglia lying just behind the stomach. It represents the largest mass of nerve cells that is not represents the largest mass of nerve cells that is not within the CNS and is sometimes called the "abdominal within the CNS and is sometimes called the "abdominal brain". It is a vital spot to be protected during boxing. brain". It is a vital spot to be protected during boxing. Figure 08 is the front view of a more detailed ANS Figure 08 is the front view of a more detailed ANS anatomy.anatomy.