12985678-Autonomic-Nervous-System-Lect-5.ppt

ANS PHYSIOLOGY

1. 06:59 1

2. DefinitionDefinition
The portion of the nervous The portion of the nervous
system that controls most system that controls most
visceral functions of the body visceral functions of the body
is called the is called the autonomic autonomic
nervous system (ANS).nervous system (ANS).
06:59 [email protected]

3. DefinitionDefinition
Or it is the motor nervous Or it is the motor nervous
system that controls glands, system that controls glands,
cardiac muscle, and smooth cardiac muscle, and smooth
muscle. muscle.
06:59 [email protected]

4. DefinitionDefinition
It is also called the visceral It is also called the visceral
motor system to distinguish it motor system to distinguish it
from the somatic motor from the somatic motor
system that controls the system that controls the
skeletal muscles. skeletal muscles.
06:59 [email protected]

5. The primary target organs of the ANSThe primary target organs of the ANS
The viscera of the thoracic and The viscera of the thoracic and
abdominal cavities and abdominal cavities and
some structures of the body some structures of the body
wall, including cutaneous blood wall, including cutaneous blood
vessels, sweat glands, and vessels, sweat glands, and
piloerector muscles.piloerector muscles.
06:59 [email protected]

6. ControlControl
Autonomic literally Autonomic literally
means “self-governed.”.means “self-governed.”.
The The ANS usually carries out its actions ANS usually carries out its actions
involuntarily, without our conscious involuntarily, without our conscious
intent or awareness, in contrast to the intent or awareness, in contrast to the
voluntary nature of the somatic motor voluntary nature of the somatic motor
system. system.
06:59 [email protected]

7. ControlControl
This voluntary involuntary distinction is This voluntary involuntary distinction is
not, however, as clear-cut as it once not, however, as clear-cut as it once
seemed. Some skeletal muscle responses seemed. Some skeletal muscle responses
are quite involuntary, such as the somatic are quite involuntary, such as the somatic
reflexes, and some skeletal muscles are reflexes, and some skeletal muscles are
difficult or impossible to control, such as difficult or impossible to control, such as
the middle-ear muscles. the middle-ear muscles.
06:59 [email protected]

8. ControlControl
On the other hand, therapeutic On the other hand, therapeutic
uses of biofeedback show that uses of biofeedback show that
some people can learn to some people can learn to
voluntarily control such visceral voluntarily control such visceral
functions as blood pressure.functions as blood pressure.
06:59 [email protected]

9. Visceral effectorsVisceral effectors
Visceral effectors do not Visceral effectors do not
depend on the ANS to depend on the ANS to
function, but only to adjust function, but only to adjust
their activity to the body’s their activity to the body’s
changing needs. changing needs.
06:59 [email protected]

10. Visceral effectorsVisceral effectors
The heart, for example, goes on The heart, for example, goes on
beating even if all autonomic beating even if all autonomic
nerves to it are severed, but the nerves to it are severed, but the
ANS ANS modulates (adjusts) the modulates (adjusts) the
heart rate in conditions of heart rate in conditions of rest rest
or exercise. or exercise.
06:59 [email protected]

11. Visceral effectorsVisceral effectors
If the somatic nerves to a If the somatic nerves to a
skeletal muscle are severed, skeletal muscle are severed,
the muscle exhibits flaccid the muscle exhibits flaccid
paralysis—it no longer paralysis—it no longer
functions. functions.
06:59 [email protected]

12. Visceral effectorsVisceral effectors
But if the autonomic nerves to But if the autonomic nerves to
cardiac or smooth muscle are cardiac or smooth muscle are
severed, the muscle exhibits severed, the muscle exhibits
exaggerated responses exaggerated responses
(denervation (denervation
hypersensitivity).hypersensitivity).
06:59 [email protected]

13. 06:59 [email protected]

14. striking characteristics of the ANS
The rapidity and intensity.
For instance,
Within 3 to 5 seconds it can increase the heart rate to
twice normal.
Within 10 to 15 seconds the arterial pressure can be
doubled.
The arterial pressure can be decreased low enough within
10 to 15 seconds to cause fainting.
Sweating can begin within seconds, and the urinary
bladder may empty involuntarily, also within seconds.
06:59 [email protected]

15. General Organization of the ANSGeneral Organization of the ANS
The autonomic nervous system is ACTIVATEDACTIVATED
mainly by centers located in the spinal cord, spinal cord,
brain stem, and hypothalamus. brain stem, and hypothalamus.
Also, portions of the cerebral cortex, especially of
the limbic cortexlimbic cortex, can transmit signals to the
lower centers and in this way influence
autonomic control.
06:59 [email protected]

16. General Organization of the ANSGeneral Organization of the ANS
The autonomic nervous system also often
operates by means of VISCERAL REFLEXESVISCERAL REFLEXES .
That is, subconscious sensory signals from a
visceral organ can enter the autonomic
ganglia, the brain stem, or the hypothalamus
and then return subconscious reflex responses
directly back to the visceral organ to control
its activities.
06:59 [email protected]

17. General Organization of the ANSGeneral Organization of the ANS
The EFFERENTEFFERENT autonomic signals are
transmitted to the various organs of the body
through two major subdivisions called
The sympathetic nervous system.sympathetic nervous system.
The parasympathetic nervous parasympathetic nervous
systemsystem.
06:59 [email protected]

18. Physiologic Anatomy of the Sympathetic NSPhysiologic Anatomy of the Sympathetic NS
06:59 [email protected]

19. Each sympathetic pathway sympathetic pathway from the cord
to the stimulated tissue is composed of
two neuronstwo neurons, a preganglionic neuron preganglionic neuron
and a postganglionic neuronand a postganglionic neuron, in
contrast to only a single neuron in the
skeletal motor pathway.
06:59 [email protected]

20. Physiologic Anatomy of thePhysiologic Anatomy of the
Parasympathetic Nervous SystemParasympathetic Nervous System
 Parasympathetic fibers leave the CNS
through cranial nerves III, VII, IX, and XIII, VII, IX, and X.
 Additional parasympathetic fibers leave
the lowermost part of the spinal cord through
the second and third sacral spinalsecond and third sacral spinal nerves and
occasionally the first and fourth sacral nerves.
06:59 [email protected]

21. Physiologic Anatomy of thePhysiologic Anatomy of the
Parasympathetic Nervous SystemParasympathetic Nervous System
About 75 per cent of all parasympathetic
nerve fibers are in the vagus nerves vagus nerves (cranial
nerve X), passing to the entire thoracic and
abdominal regions of the body.
Therefore, a physiologist speaking of the
parasympathetic nervous system often
thinks mainly of the two vagus nerves.
06:59 [email protected]

22. Neurotransmitters in the ANSNeurotransmitters in the ANS
Sympathetic NS
Preganglionic neuron neurotransmitter: Ach
Postganglionic neuron neurotransmitter: Norepinephrine,
Epinephrine
Parasympathetic NS
Preganglionic neuron neurotransmitter: Ach
Postganglionic neuron neurotransmitter: Ach
06:59 [email protected]

23. 06:59 [email protected]

24. Sympathetic Sympathetic
Nervous SystemNervous System
06:59 [email protected]

25. Parasympathetic Parasympathetic
Nervous SystemNervous System
06:59 [email protected]

26. Comparison of Somatic and ANSComparison of Somatic and ANS
06:59 [email protected]

27. Comparison of Comparison of
Sympathetic and Parasympathetic NSSympathetic and Parasympathetic NS
06:59 [email protected]

28. Effects of Sympathetic and Parasympathetic NSEffects of Sympathetic and Parasympathetic NS
06:59 [email protected]

29. Effects of Sympathetic and Parasympathetic NSEffects of Sympathetic and Parasympathetic NS
06:59 [email protected]

30. Effects of Sympathetic and Parasympathetic NSEffects of Sympathetic and Parasympathetic NS
06:59 [email protected]

31. Effects of Sympathetic and Parasympathetic NSEffects of Sympathetic and Parasympathetic NS
06:59 [email protected]