What happens when a person is having a heroin overdose?

Heroin Overdose: Airways and lungs no breathing!shallow breathing, slow and difficult breathing, eyes, ears, nose, and throatdry mouth, extremely small pupils, sometimes as small as the head of a pin ("pinpoint pupils"), tongue discoloration, heart and blood, low blood pressure, weak pulse, skin, bluish-colored nails and lips, stomach and intestines, constipation, spasms of the stomach and intestinal tract, nervous, coma.