Question

Mark the following statements as true for smooth muscle tissue, cardiac muscle tissue, and/or skeletal muscle tissue.
a. _____ Actin attaches to dense bodies.
b. _ Cells are joined by intercalated discs.
c. _ The thick and thin filaments are arranged into sarcomeres.
d. _ The thick filaments contain myosin heads along their entire length.
e. _ The cells depolarize and contract as a unit.
f. _ Ca²⁺ binding to troponin is the initiating event of contraction.
g. _ Ca²⁺ binding to calmodulin is the initiating event of contraction.
h. _____ The sarcolemma has a distinct motor end plate.

Accepted Answer

Understand the characteristics of the three types of muscle tissue: smooth, cardiac, and skeletal. Smooth muscle is non-striated and involuntary, cardiac muscle is striated and involuntary, and skeletal muscle is striated and voluntary. This foundational knowledge will help match the statements to the correct muscle type. For statement (a), 'Actin attaches to dense bodies,' recall that dense bodies are a feature of smooth muscle tissue. These structures serve as anchoring points for actin filaments, similar to Z-discs in striated muscle. For statement (b), 'Cells are joined by intercalated discs,' recognize that intercalated discs are unique to cardiac muscle tissue. These structures allow for electrical and mechanical coupling between cardiac muscle cells. For statement (c), 'The thick and thin filaments are arranged into sarcomeres,' note that sarcomeres are the repeating structural units of striated muscle, found in both skeletal and cardiac muscle tissue, but not in smooth muscle. For statement (d), 'The thick filaments contain myosin heads along their entire length,' understand that this is a characteristic of smooth muscle tissue. In contrast, skeletal and cardiac muscle have myosin heads only in specific regions of the thick filaments.

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Key Concepts

Muscle Tissue Types

Contraction Mechanisms

Cellular Structures