*Blood flow is regulated in all three types of blood vessels through constriction and dilation.
*Contraction of blood vessels slows blood flow, while relaxation of blood vessels, or dilation, allows free flow of blood.
*Muscle fibers control the constriction and dilation of vessels. In the capillaries, rings of muscle called capillary sphincters control blood flow.
*The directional flow of blood in the veins is controlled with valves , which prevent backward blood flow when closed, and allow blood to flow only toward the heart when open.
Vasoconstriction and vasodilatation allow blood vessels (arteries and veins) to control blood flow and thus control the blood pressure. This is possible because of the smooth muscle cells that surround the vessels. The contraction and dilatation of those muscles is controlled by chemical signals (e.g. norepinephrine constricts the vessels, while NO dilates them).
That would be active transport
Answer:
D.
Explanation:
the term natural selection is how evolution takes place
Answer:
1. Use a Rain Barrel. There are several options when it comes to water catchment systems, so if you don't love the look of rain barrels, there are other systems.
2. Plant Trees or Shrubs. A great choice for any landscape, trees and shrubbery serve several purposes.
Two daughter cells are created
