Question

1. Skeletal muscle fibers do not have gap junctions, but heart muscle cells do. Why do you think there is this difference? In other words: Why would it be bad to connect skeletal muscle fibers with gap junctions?

2. What is the benefit of having gap junctions in the heart?

Answer 1

Gap junctions in cardiac muscle allow for the synchronized contraction of heart cells, which is vital for the heart's function as a pump. Skeletal muscles do not have gap junctions because they require precise individual control to perform nuanced movements. The presence of gap junctions in skeletal muscles would lead to uncoordinated contractions and a loss of fine motor control.

Step-by-step explanation:

The presence of gap junctions in cardiac muscle and their absence in skeletal muscle has significant functional implications. Gap junctions are structures that develop when six proteins, called connexins, are arranged in a connexon formation. These junctions allow for the passage of ions and the efficient transmission of electrical signals between the heart muscle cells, enabling the cardiomyocytes to contract in tandem or synchronously. This synchronization is crucial for the heart's function as a pump, ensuring that each heartbeat is a coordinated effort circulating blood throughout the body.

On the other hand, skeletal muscles are controlled voluntarily and require precise and individual activation. The lack of gap junctions means each muscle fiber in a skeletal muscle can be individually stimulated by nerve impulses via neuromuscular junctions. This setup allows for more nuanced and controlled movements. If gap junctions were present, it would result in a loss of fine motor control, as muscle fibers would contract indiscriminately whenever one fiber receives a signal, leading to uncoordinated muscle contractions.

While intercalated discs in cardiac muscle contain gap junctions for this coordinated contraction, the skeletal muscles rely on the formation of motor end-plates and neuromuscular junctions (NMJs) for targeted action potential transmission and muscle fiber stimulation. This allows skeletal muscles to specialize into slow and fast fibers based on the distribution of electrical signals from the nervous system. Gap junctions in cardiac muscle cells support the physiological need of the heart to act as a single functional unit, a syncytium, to pump blood effectively.

Answer 2

Gap junctions

Step-by-step explanation:

• Skeletal muscle also called as voluntary muscle, is anchored to bone by tendons and is used to effect skeletal movement in activities such as locomotion and maintaining posture
• Muscle associated with heart is called cardiac muscle is also an involuntary muscle but is more akin in structure to skeletal muscle
• Both cardiac and skeletal muscles are striated, they contain sarcomeres and are packed into highly regular, repeating arrangements of bundles
• Skeletal muscle do no have gap junctions because they are not single cells
• The gap junctions, which are protein-lined tunnels, allow direct transmission of the depolarizing current from cell to cell, across the chambers of the heart, so that the cells contract in unison
• Because of the way these gap junctions function, the cardiac muscle cells are said to be electrically coupled