Diffen âº Science âº Biology âº Microbiology. Fraternal twins are âdizygotic,â meaning that they developed from two different eggs fertilized by two different sperm cells, while identical twins are âmonozygoticâ i.e., they developed from a single fertilized egg that split.
A T-tubule (or transverse tubule) is a deep invagination of the sarcolemma, which is the plasma membrane of skeletal muscle and cardiac muscle cells.These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the cell.ransverse tubules are invaginations of the sarcolemma. Though the invaginations are normally perpendicular to the length of the fiber, many T-tubules can lie axial to the long-axis of the fiber, both wrapping around and running alongside myofilament bundles.
Basically, acetylcholine is the neurotransmitter or chemical messenger that the nerve cell uses to communicate with the muscle cell. The result of this communication is electrical excitation of the muscle cell, what we call an action potential.The action potential of the muscle cell activates that muscle and causes the muscle cell to contract or shorten.he result of this communication is electrical excitation of the muscle cell, what we call an action potential. The action potential of the muscle cell activates that muscle and causes the muscle cell to contract or shorten.