Page 326 - Atlas of Histology with Functional Correlations

Actin and myosin form lattice network, and they insert into dense bodies in

sarcoplasm and cytoplasm
Dense bodies contain α-actinin and other Z-disc proteins
The sarcoplasmic reticulum is not well developed for calcium storage
Sarcolemma contains invaginations called caveolae
Caveolae may control influx of calcium into the cell after stimulation

Following stimulation, calcium enters sarcoplasm from the caveolae and
sarcoplasmic reticulum
Calmodulin, a calcium-binding protein, stimulates actin and myosin

interaction
Actin and myosin contract muscle by a sliding mechanism similar to skeletal
muscle
Connection of dense bodies with adjacent cells transmits force of contraction
to all cells

Exhibit spontaneous activity and maintain tonus in hollow organs
Peristaltic contractions propel contents in the organs
Gap junctions couple muscles and allow ionic communication between all

fibers
Innervated by postganglionic neurons of sympathetic and parasympathetic
divisions
Involuntary muscles regulated by autonomic nervous system, hormones, and
stretching

Review Questions

QUESTIONS

In the following multiple-choice questions, choose the letter corresponding
to the one best answer.

1. What is the difference between T tubules in skeletal and cardiac
muscles?

A. There is no difference in T tubules between the different striated

muscles.

B. T tubules are larger and store more calcium in skeletal muscles.

C. T tubules in cardiac muscles are branched.

D. T tubules are larger in cardiac muscles than in the skeletal muscle.

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