Answer:
regulation of the diameter of blood vessels and control of blood pressure
Explanation:
Skeletal muscles are the multinucleated muscles with striations and are attached to the bones (skeleton). The main function of skeletal muscles is to generate the voluntary movement of the body or body parts. The skeletal muscles of face, rectum, and urinary bladder generate their voluntary movement as per the will of the organism. On the other hand, blood vessels are lined with smooth muscles with spindle-shaped cells.
For example, the muscles present in the subcutaneous layer of the skin of the face are responsible for various facial expressions. Contraction of these facial muscles brings about the movement of skin of the face to generate a wide variety of emotions. Smooth muscles of blood vessels are involuntary in nature.
Vasodilation and vasoconstriction as brought about by smooth muscles of blood vessels are regulated by the autonomic nervous system. Under the conditions of lower blood pressure, contraction of smooth muscles of blood vessels restore the reduced blood pressure. On the other hand, when the blood pressure rises above the normal range, the smooth muscles of blood vessels relax to dilate them and to lower down the blood pressure.
The four factors are availability of food, water, shelter and space. The effect they have on the population includes: lower birth rates, increasing death rates or leading to emigration
