What the heart does in one beat, and how much blood it pumps in a minute. How the electrical signal of the heart is drawn as an ECG, how nerves and hormones change the heart rate, and what goes wrong in high blood pressure and heart disease.
3 lessons, about 1 h 30 min6 simulations10 problems3 practice questionsPython in every lesson
Created by StemPy LabThe heart beats about 72 times a minute, and each beat is one cardiac cycle of about 0.8 s. In each cycle the atria contract, then the ventricles contract, and then the whole heart relaxes. The valves open and shut by the pressure of the blood. Each ventricle pumps about 70 mL in a beat, so the cardiac output is about 5 L in a minute.
An ECG is a record of the electrical activity of the heart. The P wave is the excitation of the atria. The QRS complex is the excitation of the ventricles, and the contraction starts soon after Q. The T wave is the return of the ventricles to normal. The rate of the heart is changed by the nervous system and by hormones, but the beat itself starts in the nodal tissue.
Blood pressure above 140/90 mm Hg is hypertension. In coronary artery disease, deposits narrow the arteries that feed the heart muscle. Angina is the chest pain that comes when the heart muscle gets too little oxygen. Heart failure is a heart that cannot pump enough blood. It is not the same as a heart attack or a cardiac arrest.
Log in to join the discussion.
Loading…