This section is from the book "The Human Body: An Elementary Text-Book Of Anatomy, Physiology, And Hygiene", by H. Newell Martin. Also available from Amazon: The Human Body.
When the left ventricle of the heart contracts it forces on about six ounces of blood into the aorta, which, with its branches, is already quite full of blood. The elastic arteries are consequently stretched by the extra blood, and the finger laid on one feels it dilating; this dilatation of an artery following each beat of the heart is called the pulse; it is easiest felt on arteries which lie near the surface of the body, as the radial artery, near the wrist, and the temporal artery, on the brow.
The arteries at their ends furthest from the heart lead into capillaries; before the next heart-beat occurs they pass on into these minute vessels as much blood as the aorta received during the preceding ventricular systole; consequently they shrink again during the pause, just as a piece of rubber tubing with a small hole in it, when overfilled with water, would gradually collapse as the water flowed out of it. The next beat of the heart again overfills and expands the arteries, and so on; at each heart-beat there is a dilatation of the arteries due to the blood sent into them from the ventricle, and between each beat there is a partial collapse of the arteries, due to their emptying blood into the capillaries.
How much both ventricles together?
How high would a man have to climb in order to do as much work by the muscles of his legs as the heart does in a day?
How may we account for the fact that the heart does not become fatigued and unable to work?
What happens when the left ventricle of the heart contracts? What results in the arteries? What is the pulse? Name arteries on which the pulse is easily felt.
The pulse being dependent on the heart's systole, "feeling the pulse" of course primarily gives a convenient means of counting the rate of beat of that organ. To the skilled touch, however, it may tell a great deal more; as, for example, whether it is a readily compressible or "soft pulse," showing that the heart is not keeping the arteries properly filled up with blood, or tense and rigid ("a hard pulse"), indicating that the heart is keeping the arteries excessively filled, and is working too violently, and so on. In healthy adults the pulse rate may vary from sixty-five to seventy-five a minute, the most common rate being seventy-two. In the same individual it is faster when standing than when sitting, and when sitting than when lying down. Any exercise increases its rate temporarily and so does excitement; a sick person's pulse should not therefore be felt when he is nervous or excited (as the physician knows when he tries first to get his patient calm and confident). In children the pulse is quicker than in adults, and in old age slower than in middle life.
Into what do the final arterial branches open? How much blood is sent into the capillaries during a cardiac period? What change takes place in the bulk of the arteries during the interval between two ventricular contractions? Illustrate. What happens in the arteries during each heart-beat? Why? What during each heart pause? Why?
How may we conveniently count the rate of heart-beat? What does a soft pulse indicate? A hard pulse? What is the most common pulse rate in health ? Within what limits may it vary? How is it influenced by the position of the body?