1. You have been to an ‘eat all you can’ buffet and have consumed large amounts of food. After returning home, you recline on the couch to watch television. Which division of the nervous system will be handling your body’s after-dinner activities? List several organs involved, the major nerve supply to each organ, and the effects of the nervous system on their functions.
The description of the situation above is linked to the parasympathetic division of the nervous system, also specifically known as “rest-and-digest”.
The following organs, nerve supplies, and functions are as follows:
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Mouth (Salivary Gland)
Major Nerve Supply: Cranial Nerve 9 - Glossopharyngeal (IX)
Effects of the Nervous System on their Function: Acetylcholine, a substance released by the parasympathetic nervous system, stimulates the glands to produce more saliva, increasing salivation. Saliva begins to break down the meal into a form that our body can absorb and utilize. M1 and M3 receptors also lead to high volume secretion of potassium ions, water, and amylase.
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Esophagus
Major Nerve Supply: Cranial Nerve 10 - Vagus (X)
Effects of the Nervous System on their Function: Allows contraction of the sphincter and prevents the contents of the stomach from flowing back into the esophagus. Food then enters our stomach by a process called peristalsis, which involves a sequence of muscle contractions in the esophagus.
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Heart
Major Nerve Supply: Cranial Nerve 10 - Vagus (X)
Effects of the Nervous System on their Function: Receptors allow the release of the hormone acetylcholine to slow the heart rate.
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Lungs
Major Nerve Supply: Cranial Nerve 10 - Vagus (X)
Effects of the Nervous System on their Functions: It causes your bronchial tubes to narrow and the pulmonary blood vessels to widen and slows our breathing rate.
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Stomach and Intestines
Major Nerve Supply: Cranial Nerve 10 - Vagus (X)
Effects of the Nervous System on their Function: Parasympathetic stimulation increases gastric secretions to aid in digestion and leads to increased motility and relaxation of sphincters. Stimulation of M receptors also increases gastric secretions to aid in digestion. These enzymes continue the process of turning food into a form that can be consumed. The breakdown process is carried out by strong acids and potent enzymes secreted by cells in the lining of our stomach.
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Pancreas
Major Nerve Supply: Cranial Nerve 10 - Vagus (X)
Effects of the Nervous System on their Function: Receptors lead to the release of digestive enzymes that break down protein, fats and carbohydrates and insulin, the chief hormone in your body for metabolizing sugar.
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Liver
Major Nerve Supply: Cranial Nerve 10 - Vagus (X)
Effects of the Nervous System on their Function: Allows the small intestine's absorbed nutrients to be processed. Digesting fat and several vitamins requires the help of bile, which the liver secretes into the small intestine.
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Gallbladder
Major Nerve Supply: Cranial Nerve 10 - Vagus (X)
Effects of the Nervous System on their Function: Receptors allow the concentration of bile from the liver, and then releases it into the duodenum in the small intestine to help absorb and digest fats.
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Colon
Major Nerve Supply: Cranial Nerve 10 - Vagus (X)
Effects of the Nervous System on their Function: Receptors allow the regulation of propulsive colonic motility, particular prior to defecation.
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Rectum
Major Nerve Supply: Pelvic Splanchnic Nerves (S2-4)
Effects of the Nervous System on their Function: Allows the sphincters to relax and the rectum contracts, disposing its contents. If the contents cannot be disposed of, the sphincter contracts and the rectum accommodates so that the sensation temporarily goes away.
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Browning, K. N., & Travagli, R. A. (2014, October). Central Nervous System control of gastrointestinal motility and secretion and modulation of gastrointestinal functions. Comprehensive Physiology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4858318/#:~:text=The%20parasympathetic%20neural%20innervation%20to,dysregulated%20colonic%20motility%20and%20constipation.
Digestive system: Function, Organs & Anatomy. Cleveland Clinic. (n.d.). https://my.clevelandclinic.org/health/body/7041-digestive-system
Neuroanatomy, parasympathetic nervous system - statpearls - NCBI bookshelf. (n.d.). https://www.ncbi.nlm.nih.gov/books/NBK553141/
2. Your friend is driving home from work, listening to her favorite music, when suddenly a bicycle comes out of nowhere. She manages to swerve avoiding hitting the bicycle. She continued to drive home but she noticed that her heart was beating fast, she had goosebumps, and her head was sweaty. How would you explain these effects?
The description of the situation above is linked to the sympathetic nervous system, specifically the “fight or flight” response. It is an active defense reaction in which we either fight or run away. It could be accompanied with the manifestation of goosebumps caused by the skin's minuscule muscles contracting, which causes the hair follicles to slightly raise. Hairs start to stick up as a result. It is an uncontrollable reaction, brought on by sympathetic nervous system nerves, which also regulate the fight-or-flight response. Our heartbeat quickens, increasing the amount of oxygen getting to our main muscles. Our ability to feel pain lessens while our hearing gets better which then allows us to act quickly and appropriately.
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Robert H. Shmerling, M. D. (2020, October 2). Wondering about goosebumps? of course you are. Harvard Health. https://www.health.harvard.edu/blog/wondering-about-goosebumps-of-course-you-are-2020080320688#:~:text=Goosebumps%20are%20the%20result%20of,response%20%E2%80%94%20control%20these%20skin%20muscles.
Nunez, K. (2020, February 21). Fight, flight, or freeze: How we respond to threats. Healthline. Retrieved October 7, 2022, from https://www.healthline.com/health/mental-health/fight-flight-freeze