<span>a positively charged ion
a is the answer
</span>
Answer:
Alpha-1
Explanation:
Adrenergic receptors are the integral proteins present in the postsynaptic plasma membranes. These receptors are activated when the neurotransmitter norepinephrine and the hormones norepinephrine and epinephrine bind to them. The alpha 1 adrenergic receptors are found in the smooth muscle fibers of blood vessels that serve the salivary glands, skin, and kidneys. These receptors are also found in the radial muscle of iris of the eye as well as in the sphincter muscles of the stomach and urinary bladder.
They exert excitatory effect and lead to contraction of smooth muscles of the blood vessels, dilation of pupil, and closure of sphincters of the bladder.
C human selection is the answer hope this helps
