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.
Generally, the Gastrointestinal tract (GI Tract) controls the digestion, absorption, and excretion of wastes. This tract consists of multiple organs such as the stomach, small and large intestines, liver, gallbladder, and more, making it possible to perform its functions. In terms of major nerve supply, the parasympathetic (PNS) and sympathetic(SNS) division of the autonomic nervous system supports the listed organs. The enteric nervous system is also involved in the process. On top of that, here are some effects of the nervous system on the specific organs involved:
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Stomach and the intestines: M1 and M3 receptors in the PNS cause an increase in motility and relaxation of the sphincters. Additionally, M receptors assist digestion by increasing gastric secretions.
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Liver: both systems support the function of the liver (regeneration, hepatic fibrosis, circadian rhythm)
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Gallbladder: PNS stimulates the M3 receptor, causing the stimulation of the peristalsis of ureters, relaxation of the internal sphincter (flow and excretion of urine), contraction to release bile, and the contraction of the detrusor muscle
The enteric and autonomic nervous systems are involved in the “after-dinner activities.” In a nutshell, the enteric nervous system is the large division of the PNS that controls gastrointestinal behavior, independent from the control of CNS. On the other hand, the autonomic nervous system controls the digestive tract’s tone.
2. Your friend is driving home from work, listening to her favorite music, when suddenly a bicycle came out of nowhere. She manages to swerve avoiding hitting the bicycle. She continued to drive home but she noticed that her heart is beating fast, she had goosebumps, and her heads were sweaty. How would you explain these effects?
The threat from the near collision serves as a stimulus, activating the fight-or-flight response of my friend. This response consists of 3 stages: Alarm, Resistance, and Exhaustion. During the Alarm stage, the Central nervous system is activated, which explains how she manages to swerve her car to avoid the bicycle as a defense against a future threat(collision). Meanwhile, in the Resistance stage is where she calms down after that stressful event. She might feel tired when she reaches the Exhaustion stage.
Furthermore, my friend’s racing heartbeat, goosebumps, and sweating are caused by fear triggered by the accident she experienced. With that in mind, the amygdala (known as the fear center) triggers the fear response and sends information to alert the different brain structures. Because of this, the brain becomes more alert, the pupil dilates, and breathing accelerates. The amygdala also causes classic fear responses (heartbeat racing, goosebumps, sweating).