Cardiac muscle differ from skeletal muscle by

JIPMER Nursing Officer-2017

Applied Physiology

Easy

Appeared in: JIPMER Nursing Officer-2017

Explanation

The key difference is that cardiac muscle possesses automaticity, meaning it can generate its own electrical impulses spontaneously, primarily through its pacemaker cells.
Cardiac muscle also has high conductivity due to intercalated discs and gap junctions, which allow electrical signals to spread rapidly, ensuring the heart contracts as a coordinated unit (functional syncytium).
Skeletal muscle lacks both automaticity and this type of cell-to-cell conductivity, requiring direct stimulation from a motor neuron for every contraction.

Option A: This is a similarity, not a difference. Both cardiac and skeletal muscles are composed of actin and myosin filaments, which are the fundamental proteins responsible for muscle contraction.
Option C: This is a similarity. Both muscle types depend on an increase in intracellular calcium ions to trigger the interaction between actin and myosin, leading to contraction.
Option D: This is factually incorrect. Cardiac muscle is highly aerobic and has a critical, continuous need for oxygen. It cannot survive, let alone thrive, without it. Lack of oxygen leads to myocardial ischemia and infarction.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Physiological differences between cardiac and skeletal muscle as background academic context rather than a clinical decision trigger.
The property of automaticity is the basis for the heart's intrinsic rhythm. When the natural pacemaker cells fail, it can lead to arrhythmias, sometimes requiring an artificial pacemaker.
The heart's high dependence on oxygen makes it extremely vulnerable to ischemia (reduced blood flow), as seen in coronary artery disease. Unlike skeletal muscle, which can endure temporary oxygen deficits, even brief interruptions in oxygen supply can cause irreversible damage to cardiac tissue (myocardial infarction).
What if? - If a patient's SA node (the primary pacemaker) fails, other parts of the cardiac conduction system (like the AV node or Purkinje fibers) can take over as secondary pacemakers due to their own, albeit slower, automaticity. This is a crucial backup mechanism.

How to Approach the Question

First, identify the core task of the question, which is to find a key difference between cardiac and skeletal muscle.
Evaluate each option systematically. For each option, ask: 'Is this statement true for cardiac muscle? Is it true for skeletal muscle? Is it a similarity or a difference?'
Option A (actin/myosin) and Option C (calcium) describe features common to both muscle types, so they are similarities, not differences. Eliminate them.
Option D (thrives without oxygen) is a false statement about cardiac muscle, which is highly oxygen-dependent. Eliminate it.
Option B (automaticity/conductivity) describes a unique, fundamental property of cardiac muscle not present in skeletal muscle, making it the correct answer.

Concept Tested & Keywords

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