College of Massage Therapists of British Columbia (CMTBC) Practice Exam

Do skeletal muscles have gap junctions?

1. Yes, they have numerous gap junctions

2. No, they do not have gap junctions

3. Only during times of high activity

4. They have gap junctions but only in the heart

The correct answer is: No, they do not have gap junctions

Skeletal muscles do not have gap junctions, which is a defining characteristic of their structure and function. Unlike cardiac and smooth muscle tissues, which utilize gap junctions to enable coordinated contraction and communication between cells, skeletal muscle fibers are formed from long, multinucleated cells that function independently. This independence is crucial for the precise control of voluntary movements, allowing each motor unit to contract individually when activated by the nervous system. In skeletal muscle, the communication is primarily achieved through neuromuscular junctions where motor neurons release neurotransmitters to stimulate muscle contraction. The lack of gap junctions means that the electrical signal does not propagate from one muscle fiber to another as it does in cardiac muscle, where the interconnectedness of cells through gap junctions facilitates synchronized contraction. Thus, the characterization of skeletal muscle cells as not having gap junctions is essential to understand their physiological role compared to other muscle types.