Angiotensin ii stimulates vasoconstriction, whereas stimulates vasodilation.

The hormone responsible for stimulation of vasodilation is epinephrine or adrenalin.  

Widening of blood vessels is called vasodilation. It increases blood flow thorough blood vessels. Increase in the blood flow provides more oxygen and nutrients such as glucose and lipids to the body tissues in case of nutrient shortage or insuffient blood supply to the cells. Vasodilation occurs in response to hormones or the nervous system.  

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.