Cardiac muscle differ from skeletal muscle by?

SCTIMST Staff Nurse - 2016

Applied Physiology

Easy

Appeared in: SCTIMST Staff Nurse - 2016

Explanation

The primary difference is that cardiac muscle has automaticity, meaning specialized pacemaker cells (like those in the SA node) can spontaneously generate electrical impulses without external nervous stimulation.
Cardiac muscle also has conductivity, where electrical impulses spread rapidly from cell to cell through intercalated discs and gap junctions.
This allows the heart muscle to function as a single, coordinated unit, known as a functional syncytium.
Skeletal muscle, in contrast, requires a nerve impulse from a motor neuron to initiate contraction, and its fibers are electrically isolated from one another.

Option A: This is a similarity, not a difference. Both cardiac and skeletal muscles are striated and use actin and myosin filaments as the fundamental proteins for contraction.
Option C: This is a shared requirement. Both muscle types depend on calcium ions to trigger the interaction between actin and myosin, leading to contraction.
Option D: This statement is factually incorrect. Cardiac muscle has a very high oxygen demand and relies almost exclusively on aerobic metabolism. It cannot thrive without oxygen; deprivation leads to ischemia and infarction.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Differences between Cardiac and Skeletal Muscle as background academic context rather than a clinical decision trigger.
The heart's automaticity and conductivity are fundamental to its function as a pump. Damage to the conduction system (e.g., from a myocardial infarction) can disrupt this rhythm, causing life-threatening arrhythmias.
An electrocardiogram (ECG) is a vital diagnostic tool that measures the electrical activity generated by the heart's conduction system, allowing nurses and doctors to assess its function.
What if a patient's SA node (the primary pacemaker) fails? Another part of the heart's conduction system, like the AV node, will take over as the pacemaker, but at a slower rate. This is a backup mechanism that can sustain life but often requires intervention, such as the implantation of an artificial pacemaker.

How to Approach the Question

First, identify the core of the question, which asks for a key difference between cardiac and skeletal muscle.
Evaluate each option to determine if it represents a true difference or a similarity.
Recall that both are striated muscles, so they share features like actin and myosin (eliminating option A).
Remember that calcium is the universal trigger for muscle contraction in both types (eliminating option C).
Consider the metabolic needs. Cardiac muscle is an endurance muscle that requires constant oxygen, making option D false.
This leaves option B. Recall that the heart has its own intrinsic electrical system (automaticity and conductivity), which is a unique feature not present in skeletal muscle, making it the correct answer.

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