The best answer is D.
In active transport, molecules move against a concentration gradient from areas of lower concentration to areas of higher concentration. This happens a lot in neurons. The membrane proteins are constantly pumping ions in and out to get the membrane of the neuron ready to transmit electrical impulses.
In active transport , energy is required to move molecules across the cell membrane. Carrier proteins are needed for this e.g. proteins of the GLUT family which transport glucose molecules across the cell membrane. Carrier proteins are very specific. GLUT proteins will only move glucose molecules and not sodium or calcium. There are hundreds of types of carrier proteins.
Answer:
The correct answer is: Eccentric phase.
When talking about movement, we are talking about the activation of muscle fibers in order for this process to happen. In order for this to happen, motor neurons must activate the phases of muscle excitation, contraction and relaxation, so that the sarcomeres, and thus the fibers, can generate movement.
In essence, there are three stages, or phases, to complete muscle movement: the concentric phase, which is when the muscle fibers are excited and begin the process of contraction. This means the muscle fibers will contract and generate movement, generating a shortening. Then we have the isometric stage, a moment in which there is no longer any more shortening of the muscle fibers, so basically, the movement is held and there is no further contraction, but neither is there relaxation of the muscle fibers. Finally, we have the eccentric phase. This phase is characterized precisely because it is the moment when the muscles begin to return to their resting position.
