A nursing instructor is explaining the role of vascular smooth muscle cells in relation to increases in the systemic circulation. During the discussion, which neurotransmitter is primarily responsible for contraction of the entire muscle cell layer, thus resulting in decreased vessel lumen radius?

Norepinephrine

Explanation:

Nerve cells and circulating hormones are the one responsible for vasoconstriction of the vessel walls, as they do not enter the tunica media of the blood vessel, the nerves do not synapse directly on the smooth muscle cells. Instead, they release the neurotransmitter, norepinephrine, which diffuses into the media and acts on the nearby smooth muscle cells, which result in contraction of the entire muscle cell layer and thus reducing the radius of the vessel lumen.