The autonomic nervous system
The autonomic nervous system
The autonomic nervous system (ANS) is concerned with control of visceral functions such as digestion, blood flow, temperature regulation, and reproduction.
Most functions of the ANS are carried out without conscious awareness.
The ANS
has three divisions:
- The sympathetic nervous system is generally excitatory and is associated with “fight or flight” responses.
- The parasympathetic nervous system is generally antagonist to the sympathetic nervous system and is associated with “rest and digest” functions.
- The enteric nervous system is a large system of neural networks within the walls of the gastrointestinal tract .
The autonomic and somatic nervous systems both consist of afferent and efferent nerves, and both have structures located within the CNS and PNS.
The higher centers of autonomic nervous system (ANS) are located in the spinal cord, medulla, midbrain, hypothalamus, pons, cerebellum, reticular formation, basal ganglia, and cerebral cortex.
The activation of the sympathetic division is characterized by a widespread pattern of activation and occurs in response to stress.
- In the cardiovascular system, heart rate and vascular tone increase and blood is redistributed to the muscles, heart, and brain (blood flow is increased) by constriction of arterioles in the skin and viscera (blood flow is decreased).
- Tissue metabolism (catabolism) is increased: energy utilization by glycogenolysis in the liver and lipolysis in adipose tissue (body temperature, serum glucose and lipids are increased). Anabolism is decreased.
- Respiratory rate is increased.
- Skeletal muscle tone is increased.
- Digestive functions are inhibited
The functions of the parasympathetic division generally act to conserve and restore energy reserves. Heart rate is decreased, but the digestive functions system are stimulated.
The major differences between the ANC and the somatic nervous system
