Chapter 15: Flashcards
The nervous system has two main divisions
- the central nervous system (CNS)
- The PNS.
PNS has two major subdivisions:
- Somatic motor system
Controls voluntary
movement of muscles - Autonomic nervous system
Somatic motor system
Controls voluntary
movement of muscles
The autonomic nervous system is further subdivided into
- The parasympathetic nervous system and
- The sympathetic nervous system
The two subdivisions of the ANS regulate?
The two subdivisions of the autonomic nervous system regulate many involuntary processes
The autonomic nervous system has three principal functions:
- Regulation of the heart;
- Regulation of secretory glands
- Regulation of smooth muscles
Regulation of secretory glands
(salivary, gastric, sweat, and bronchial glands);
Regulation of smooth muscles
(muscles of the bronchi, blood vessels, urogenital system, and gastrointestinal [GI] tract).
The parasympathetic nervous system performs seven regulatory functions
Stimulation of appropriate parasympathetic nerves causes:
- Slowing of heart rate
- Increased gastric secretion
- Emptying of the bladder
- Emptying of the bowel
- Focusing the eye for near vision
- Constricting the pupil
- Contracting bronchial smooth muscle
Therapeutic agents that alter parasympathetic nervous system function are used primarily for
effects on the GI tract, bladder, and eye.
Occasionally, these drugs are also used for effects on the heart and lungs.
The sympathetic nervous system has three main functions:
- Regulating the cardiovascular system
- Regulating body temperature
- Implementing the acute stress response (commonly called a “fight-or-flight” reaction)
Stimulation of sympathetic nerves to the heart
Stimulation of sympathetic nerves to the heart increases cardiac output.
Stimulation of sympathetic nerves to arterioles and veins
Stimulation of sympathetic nerves to arterioles and veins causes vasoconstriction.
Release of epinephrine from the adrenal medulla results in
Release of epinephrine from the adrenal medulla results in vasoconstriction in most vascular beds and vasodilation in certain others.
By influencing the heart and blood vessels, the sympathetic nervous system can achieve three homeostatic objectives:
- Maintenance of blood flow to the brain
- Redistribution of blood flow during exercise
- Compensation for loss of blood, primarily by causing vasoconstriction
The sympathetic nervous system helps regulate body temperature in three ways:
- By regulating blood flow to the skin, sympathetic nerves can increase or
decrease heat loss. - Sympathetic nerves to sweat glands promote secretion of sweat, thereby helping the body cool.
- By inducing piloerection (erection of hair), sympathetic nerves can promote heat conservation.