BIOS 252 Week 4 Case Study: ANS

Grace J.
August 5, 2025August 5, 2025
BIOS-252, CU BSN

Student Name

Chamberlain University

BIOS-252: Anatomy & Physiology II with Lab

Prof. Name

Date

Signs and Symptoms of Autonomic Nervous System Activation

Looking at the signs and symptoms, you notice that one of the two branches of the autonomic nervous system (ANS) is highly upregulated. Which one is it? Name three signs or symptoms that clued you in on it and why.

Based on the clinical presentation, the branch of the autonomic nervous system (ANS) that is significantly upregulated is the parasympathetic nervous system. This branch is primarily responsible for conserving energy and maintaining normal physiological functions. Three key symptoms that indicated parasympathetic overactivity include bradycardia, excessive sweating, and vomiting.

Bradycardia, or a slower than normal heart rate, occurs due to increased vagal tone, which is mediated by parasympathetic stimulation. Vomiting is linked to enhanced gastrointestinal motility and secretions, also under parasympathetic control. Although sweating is often associated with sympathetic activation, certain sweat glands, particularly eccrine glands in the palms and soles, are actually stimulated via cholinergic fibers associated with the sympathetic nervous system, but they respond to acetylcholine, a neurotransmitter prominent in the parasympathetic system as well. This overlapping function can sometimes make parasympathetic dominance more complex to interpret (Guy-Evans, 2021).

Symptom	Linked to Parasympathetic Activation	Reason
Bradycardia	Yes	Increased vagal stimulation lowers heart rate.
Vomiting	Yes	Elevated gastrointestinal motility and secretions.
Sweating	Indirectly	Muscarinic activation in eccrine glands via cholinergic fibers.

Muscarine and Receptor Binding in the ANS

What receptor do you think muscarine binds to in the ANS? What neurotransmitter usually binds to the receptor?

Muscarine binds to muscarinic receptors, a subtype of cholinergic receptors located throughout the parasympathetic nervous system. These receptors play a crucial role in mediating the effects of parasympathetic stimulation on various organs. The primary neurotransmitter that naturally activates these receptors is acetylcholine (Kudlak & Tadi, 2021).

Muscarinic receptors are categorized into subtypes (M1–M5), each of which is responsible for different physiological responses. For instance, M2 receptors affect cardiac function, while M3 receptors regulate glandular secretions, smooth muscle contraction, and even sweating, which is relevant to this case.

Receptor	Ligand (Natural)	Ligand (Toxin/Drug)	Function
Muscarinic (M1–M5)	Acetylcholine	Muscarine	Regulates parasympathetic organ functions.

Understanding Excessive Sweating

At first, it seemed odd that three out of four of your patients were sweating. It makes sense now that you know what they ate. Why?

The unusual observation of excessive sweating in three out of four patients can be attributed to the activation of M3 muscarinic receptors, which are present not only in the gastrointestinal tract but also in eccrine sweat glands. These receptors, when stimulated by acetylcholine—whether endogenous or exogenous, such as from muscarine ingestion—lead to increased secretion from sweat glands.

The food consumed likely contained muscarine, which mimics acetylcholine and overstimulates the M3 receptors, causing profuse sweating. Though sweating is commonly linked with sympathetic responses, its mechanism is cholinergic, which connects it indirectly to parasympathetic pathways (Guy-Evans, 2021; Kudlak & Tadi, 2021).

Treatment and Role of Anticholinergics

Treatment for this issue includes the use of atropine. Atropine is anticholinergic. Define anticholinergic and determine why you would use it in this case.

Anticholinergic medications are agents that block the action of acetylcholine at muscarinic receptors in the parasympathetic nervous system. This inhibition helps to reduce or completely stop excessive involuntary functions such as glandular secretion, gastrointestinal activity, and muscle spasms.

Atropine is a classic anticholinergic drug and is particularly effective in counteracting muscarine poisoning. It works by competitively inhibiting muscarinic receptors, thus preventing acetylcholine from binding and exerting its parasympathetic effects. In this clinical scenario, atropine would help normalize the patient’s heart rate, reduce vomiting, and stop excessive sweating, providing symptomatic relief and preventing further complications (Gal, 2022; National Institute of Diabetes and Digestive and Kidney Diseases, 2012).

Drug	Type	Mechanism of Action	Effect in This Case
Atropine	Anticholinergic	Blocks acetylcholine at muscarinic receptors	Reduces bradycardia, vomiting, and sweating caused by muscarine.

References

Gal, K. (2022). Anticholinergic drugs: What to know. https://www.medicalnewstoday.com/articles/323514

Guy-Evans, O. (2021). Peripheral Nervous System. Definition, Parts, and Function. https://www.simplypsychology.org/peripheral-nervous-system.html

Kudlak, M., & Tadi, P. (2021). Physiology, Muscarinic Receptor. https://www.ncbi.nlm.nih.gov/books/NBK555909/