Question at position 40 Which feature is more abundant in cardiac contractile cells compared to skeletal muscle fibers?Glycogen reservesCell sizeSarcoplasmic reticulum triadsMitochondria

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BlackTom AI · Accepted Answer

To begin, let's lay out the options and what each feature represents in muscle cells.
Option 1: Glycogen reserves. Skeletal muscle typically stores substantial glycogen to fuel rapid, repeated contractions, whereas cardiac muscle relies more on oxidative metabolism and not primarily on large glycogen stores. So cardiac cells generally do not have greater glycogen reserves than skeletal muscle; this option is unlikely.
Option 2: Cell size. Cardiac contractile cells (cardiomyocytes) are indeed elongated but roughly similar in size to skeletal muscle fibers and do not characteristically exceed skeletal fibers in size. Therefore, saying cardiac cells are more abundant in cell size is not accurate.
Option 3: Sarcoplasmic reticulum triads. In skeletal muscle, the triad structure at the A-I junction consists of a T-tubule flanked by two terminal cisternae of the sarcoplasmic reticulum, enabling synchronized calcium release. Cardiac muscle, by contrast, has primarily dyads (a T-tubule with a single terminal cisterna), not the classic skeletal triad arrangement. Thus, sarcoplasmic reticulum triads are less abundant in cardiac cells.
Option 4: Mitochondria. Cardiac muscle has a high demand for continuous ATP production to support persistent, rhythmic contractions. This leads to a high density of mitochondria in cardiomyocytes, significantly more than in skeletal muscle fibers. Therefore, mitochondria are more abundant in cardiac contractile cells.
In summary, considering energy needs and the structural differences, the feature that is more abundant in cardiac contractile cells compared to skeletal muscle fibers is mitochondrial content. The other options either reflect traits more characteristic of skeletal muscle or contradict the known cellular organization of cardiomyocytes.

Question at position 40 Which feature is more abundant in cardiac contractile cells compared to skeletal muscle fibers?Glycogen reservesCell sizeSarcoplasmic reticulum triadsMitochondria

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Question at position 40 Which feature is more abundant in cardiac contractile cells compared to skeletal muscle fibers?Glycogen reservesCell sizeSarcoplasmic reticulum triadsMitochondria

View Explanation

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