In skeletal muscle a muscle fiber is a single cell. There is therefore no need for gap junctions or other transmission mechanism. However, skeletal muscle is weird in the fact that the muscle fiber cell has multiple nuclei. IIRC, at some point in development they were separate cells each with one nucleus whose membranes fused together to make a single multinuclear cell.biophysics said:I know that smooth and cardiac muscle cells (myofibers) are connected to each other by gap junctions.
How are skeletal muscle cells connected to each other (to transmit the AP)?
Thanks, any responses appreciated
The action potential travels along skeletal muscle cells through a process called excitation-contraction coupling. This involves the AP causing the release of calcium ions from the sarcoplasmic reticulum, which then bind to the protein complex troponin, leading to the exposure of binding sites on actin filaments. This allows the myosin heads to bind to the actin and initiate muscle contraction.
T-tubules, also known as transverse tubules, are invaginations of the muscle cell membrane that help to transmit the AP deep into the muscle fiber. This allows for a simultaneous and coordinated contraction of the entire muscle cell, as the AP is able to reach all areas of the cell quickly through the T-tubules.
Skeletal muscle cells maintain a resting membrane potential through the activity of ion channels in the cell membrane. These channels allow for the movement of ions such as sodium, potassium, and calcium, which are crucial for generating and maintaining the resting membrane potential. Additionally, the Na+/K+ ATPase pump also plays a role in maintaining the resting membrane potential by actively pumping sodium and potassium ions against their concentration gradients.
The neuromuscular junction is the site where the motor neuron connects to the skeletal muscle cell. It is responsible for transmitting the AP from the motor neuron to the muscle cell, leading to muscle contraction. This junction also allows for a precise and coordinated control of muscle movement, as each motor neuron is connected to only a few muscle fibers.
In conditions like muscular dystrophy, there is a disruption in the proteins involved in the excitation-contraction coupling process, which can lead to decreased AP transmission and muscle weakness. Additionally, the loss of muscle cells in these conditions can also affect the ability of the muscle to generate and transmit APs, further contributing to muscle weakness.