Cardiac muscle differs from skeletal muscle by?

BSF Staff Nurse - 2021

Applied Physiology

Medium

Appeared in: BSF Staff Nurse - 2021

Explanation

Cardiac muscle possesses automaticity, meaning it can generate its own electrical impulses via pacemaker cells, a property skeletal muscle lacks.
It is an involuntary muscle, controlled by the autonomic nervous system, whereas skeletal muscle is under voluntary control.
Cardiac muscle cells are connected by intercalated discs and gap junctions, allowing them to conduct impulses and contract as a coordinated unit (functional syncytium), which is different from the isolated nature of skeletal muscle fibers.
Since all three listed properties (conductivity mechanism, automaticity, and involuntary control) are distinct features of cardiac muscle compared to skeletal muscle, the most comprehensive answer is 'All the above'.

Option A: This statement is a correct difference, but it is incomplete. The unique conductivity via intercalated discs is a key feature, but automaticity and involuntary control are also major differences.
Option B: This statement is a correct difference, but it is incomplete. Automaticity is a hallmark of cardiac muscle, but it's not the only difference listed.
Option C: This statement is a correct difference, but it is incomplete. Involuntary control is a fundamental distinction, but other listed properties are also correct.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Properties of Cardiac Muscle vs. Skeletal Muscle as background academic context rather than a clinical decision trigger.
The property of automaticity is clinically significant because defects in pacemaker cells can lead to arrhythmias (abnormal heart rhythms), sometimes requiring an artificial pacemaker.
The heart's specialized conduction system can be affected by disease or injury, leading to heart blocks, where the electrical signal is delayed or stopped.
Because cardiac muscle is involuntary and highly resistant to fatigue, the heart can beat continuously throughout a person's life. If it fatigued like skeletal muscle, sustained life would be impossible.

How to Approach the Question

First, identify the core of the question, which is to find the differences between cardiac and skeletal muscle.
Evaluate each option individually. Ask yourself: 'Is this property true for cardiac muscle and false for skeletal muscle, or is there a significant difference?'
Analyze Option A (Conductivity): Both conduct, but cardiac muscle does so as a syncytium. This is a difference.
Analyze Option B (Automaticity): Cardiac muscle has it; skeletal muscle does not. This is a clear difference.
Analyze Option C (Involuntary muscle): Cardiac is involuntary; skeletal is voluntary. This is a clear difference.
Since options A, B, and C all represent valid differences, look for an 'All the above' option. If present, it is the most complete and therefore the best answer.

Concept Tested & Keywords

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