The nerve that provides parasympathetic stimulation to the heart and reduces heart rate is called which of th… - NHM UP Staff Nurse-2023 shift 1st

NHM UP Staff Nurse-2023 shift 1st

Applied Physiology

Easy

Appeared in: NHM UP Staff Nurse-2023 shift 1st

Explanation

The vagus nerve (Cranial Nerve X) is the main nerve of the parasympathetic nervous system that innervates the heart.
Stimulation of the vagus nerve causes the release of the neurotransmitter acetylcholine.
Acetylcholine acts on the sinoatrial (SA) and atrioventricular (AV) nodes to slow the heart's intrinsic pacemaker and decrease the rate of electrical conduction, resulting in a reduced heart rate.
This function is part of the body's 'rest and digest' response, conserving energy.

Option A: The optic nerve is Cranial Nerve II, which is a sensory nerve responsible for transmitting visual information from the retina to the brain.
Option C: The accessory nerve is Cranial Nerve XI, a motor nerve that innervates the sternocleidomastoid and trapezius muscles, controlling head and shoulder movements.
Option D: The cardiac accelerator nerve is part of the sympathetic nervous system. It increases heart rate and contractility, which is the opposite of the function described in the question.

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 cardiac function as background academic context rather than a clinical decision trigger.
Nurses may instruct patients to perform vagal maneuvers (e.g., bearing down as if having a bowel movement, coughing, or carotid sinus massage in a controlled setting) to stimulate the vagus nerve and slow down a dangerously fast heart rate, as seen in supraventricular tachycardia (SVT).
Understanding vagal tone is crucial. High vagal tone leads to a lower resting heart rate, often seen in athletes. Conversely, conditions like vasovagal syncope involve an overactive vagal response, causing a sudden drop in heart rate and blood pressure, leading to fainting.
What if? If a patient presented with symptomatic bradycardia (a dangerously slow heart rate), the clinical goal would be the opposite. Treatment would involve medications like atropine, which is an anticholinergic that blocks the vagus nerve's effect, thereby increasing the heart rate.

How to Approach the Question

First, break down the question. The key phrases are 'parasympathetic stimulation' and 'reduces heart rate'.
Recall the two main divisions of the autonomic nervous system and their general functions: Sympathetic ('fight or flight', increases heart rate) and Parasympathetic ('rest and digest', decreases heart rate).
The question directly links 'parasympathetic' with 'reduces heart rate', which is a core physiological concept.
Evaluate the options based on this understanding:
Optic nerve: Relates to vision. Eliminate.
Vagus nerve: Known as the primary parasympathetic nerve that innervates the heart. This is a strong candidate.

Concept Tested & Keywords

QjFwyZlfa7rKOM-UlVSApQ

E6 Physiology Ganong 27e Vol 2 Part 1 p. 134-136

E6 Physiology Review Sembulingam 5e p. 120-122

E6 Anatomy Applied Ashalatha 4e p. 431-433