*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).
Genes are a unit of heredity that is transferred from a parent to the offspring and is held determine some characteristics of the offspring. Some genes include: the color of the eyes (whether you have your mother's or father's eyes) the hair color, and skin color.
Inherited traits means you received something from your parents, grandparents or other family members.
Acquired traits means a characteristic or trait that produces a phenotype that is a result of an environmental influence.Acquired traits are not coded for in the DNA of an individual and therefore cannot passed down to offspring during reproduction. <span />
Answer:
they can fly , which requires alot of energy & keep their body warm with their feathers
Answer: A. virus strains multiplied in cell cultures
Answer:
Adaptive immune responses are triggered by activation of antigen-specific T cells that produce antibodies against foreign antigens such as, for example, harmful viruses. These immune responses are useful to eliminate dangerous molecules from the body. In a normal immune reaction, the antibodies produced by T-cells target antigen molecules in order to be subsequently absorbed by phagocytic macrophage cells.
Autoimmune diseases are triggered by the response of the adaptive immune system against self-antigen molecules. Since the immune system can not eliminate antigens from the own body, this immune reaction generates an excessive inflammatory response, and it may lead to the damage of tissues and organs.
