What is the effect of the parasympathetic stimulation on bronchus?

Appeared in: UPUMS Nsg officer-2023

Explanation

The parasympathetic nervous system is responsible for the body's 'rest and digest' functions.
Stimulation of parasympathetic nerves (part of the vagus nerve) releases the neurotransmitter acetylcholine (ACh) in the lungs.
Acetylcholine acts on muscarinic receptors in the smooth muscle of the bronchial walls.
This action causes the smooth muscle to contract, leading to a narrowing of the airways, which is known as bronchoconstriction.

Option A: Flexibility is a physical property related to the elasticity of tissues and cartilage in the airways, not a direct physiological response to nerve stimulation.
Option B: Relaxation of the bronchial smooth muscle (bronchodilation) is the primary effect of the sympathetic nervous system, which is antagonistic to the parasympathetic system.
Option D: Distension refers to the act of being stretched or expanded. While the lungs distend during inhalation, this is a passive process driven by pressure changes, not a direct action of parasympathetic nerves on the bronchi.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Autonomic nervous system control of bronchial smooth muscle as background academic context rather than a clinical decision trigger.
This physiological principle is fundamental to respiratory pharmacology. In conditions like asthma and Chronic Obstructive Pulmonary Disease (COPD), excessive parasympathetic tone can lead to bronchoconstriction and difficulty breathing.
Medications known as anticholinergics (e.g., ipratropium, tiotropium) are used to block these parasympathetic effects, leading to bronchodilation and relief of symptoms.
Conversely, some irritants like smoke or dust can trigger a reflex parasympathetic response, causing acute bronchoconstriction.

How to Approach the Question

First, identify the key physiological system in the question: the parasympathetic nervous system.
Recall the general function of the parasympathetic system, often summarized as the 'rest and digest' state.
Consider the body's needs during a 'rest' state. Oxygen demand is lower compared to a 'fight or flight' situation.
Logically deduce that to conserve energy and match airflow to lower demand, the airways would narrow.
Scan the options and select the term that means narrowing or tightening: 'Constriction'.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 2A p. 58-60

E6 Pharmacology Katzung 16e p. 174-176

Practise the full UPUMS Nsg officer-2023

Attempt every question from this paper in a timed mock, then review the full solution for each one.