The automatic nervous system, also known as the autonomic nervous system, controls involuntary actions such as breathing, digestion, and heart rate. The word "automatic" is spelled /ɔːtəˈmætɪk/ according to the International Phonetic Alphabet, with stress on the second syllable. The "u" in automatic is pronounced as the sound "aw" in "saw". Additionally, "nervous" is spelled /ˈnɜːvəs/, with stress on the first syllable and a silent "e" at the end. The phrase "automatic nervous system" is commonly pronounced as /ɔːtəˈmætɪk ˈnɜːvəs ˈsɪstəm/.
The autonomic nervous system (ANS) is a complex network of nerves and ganglia that controls and regulates involuntary bodily functions, maintaining homeostasis and coordinating responses to internal and external stimuli.
Comprising two main divisions, the sympathetic and parasympathetic, the autonomic nervous system operates largely unconsciously, orchestrating processes such as heart rate, blood pressure, digestion, and respiration. The sympathetic division, often referred to as the "fight or flight" response, prepares the body for physical stress or emergencies by increasing heart rate, dilating pupils, and diverting blood to the muscles. Conversely, the parasympathetic division is associated with "rest and digest" functions, conserving energy and facilitating processes such as digestion and elimination.
The ANS is primarily controlled by a region in the brain called the hypothalamus, which receives information from various sensory receptors and triggers appropriate physiological responses. This information is transmitted through a complex circuitry involving the brainstem, spinal cord, ganglia, and peripheral nerves.
Disorders of the autonomic nervous system can have significant impact on a person’s health, leading to conditions such as orthostatic hypotension, gastroparesis, urinary retention, or excessive sweating. These conditions can disrupt normal bodily functions and require medical treatment to manage symptoms and improve quality of life.
In summary, the autonomic nervous system is responsible for regulating and coordinating involuntary processes in the body, ensuring efficient and appropriate responses to internal and external stimuli.