The Autonomic Nervous System: Understanding the Body’s Automatic Functions
The autonomic nervous system (ANS) is a complex neural network that regulates the body’s involuntary movements and maintains essential bodily functions. From heart rate and digestion to pupil response and urination, the ANS controls a wide range of automatic processes that keep our bodies running smoothly.
The Autonomic Nerve Pathway
The autonomic nerve pathway involves two nerve cells connected by multiple nerve fibers, which are clustered in a group of nerve cells called an autonomic ganglion. These nerve fibers then connect to internal organs, allowing the ANS to control various bodily functions.
Divisions of the Autonomic Nervous System
The ANS has two main divisions: the sympathetic nervous system and the parasympathetic nervous system.
1. Sympathetic Nervous System: Responds to external stimuli by stimulating body processes, preparing the body for stressful situations or the “fight or flight” response.
2. Parasympathetic Nervous System: Inhibits certain actions in response to external stimuli, promoting relaxation and conservation of energy.
Functions of the Autonomic Nervous System
The ANS controls various internal organs to regulate:
1. Blood pressure
2. Heart and respiratory rates
3. Body temperature
4. Digestion
5. Metabolism and body weight
6. Balance of water and electrolytes
7. Regulation of saliva, sweat, and tears
8. Urination
9. Defecation
10. Sexual response
Sympathetic Division: Preparing for Stress
The sympathetic division prepares the body for stressful situations by:
1. Increasing heart rate and force of contractions
2. Dilating airways to increase respiration
3. Releasing stored energy
4. Increasing muscular strength and blood supply to muscles
5. Dilating pupils
6. Sweating of palms
7. Constricting intestinal and urinary sphincters
Parasympathetic Division: Conserving Energy
The parasympathetic division works to inhibit or control certain actions to conserve and restore energy by:
1. Slowing down heart rate
2. Decreasing blood pressure
3. Stimulating digestive tract to process food and eliminate waste
4. Using energy to restore, repair, and build tissues
5. Narrowing bronchiolar diameter when oxygen demand is reduced
6. Stimulating salivary gland secretion and increasing digestion and absorption of nutrients
Neurotransmitters: The Messengers
Chemicals called neurotransmitters act as messengers, transmitting information from one nerve cell to another. The two primary neurotransmitters of the ANS are:
1. Acetylcholine: Sends signals to neurons, muscle cells, and gland cells.
2. Norepinephrine: Regulates visceral functions and is produced by adrenal glands and certain neurons in the medulla oblongata.
References:
https://en.wikipedia.org/wiki/Autonomic_nervous_system
https://faculty.washington.edu/chudler/nsdivide.html
http://www.scholarpedia.org/article/Autonomic_nervous_system
https://www.msdmanuals.com/en-in/home/brain,-spinal-cord,-and-nerve-disorders/autonomic-nervous-system-disorders/overview-of-the-autonomic-nervous-system