Description: Segment 1 The male narrator explains that arterial hypertension remains a great unsolved problem. He explains that blood pressure consists of two types of pressure, systolic pressure and diastolic pressure. Some conditions that either cause or result in hypertension are shown. The narrator points out that autopsies of people who died of diseases relating to hypertension found changes in the kidneys. Some examples of experiments on animals' kidneys are detailed. They result in a rise in blood pressure. An examperiment is carried out on a dog. Its femoral artery is exposed and extra fluid is infused into the dog. Its blood pressure rises. A large amount of blood is withdrawn and its blood pressure drops. Time start: 00:00:00:00 Time end: 00:07:10:21 Length: 00:07:10:21 Segment 2 An animated illustration shows the anatomy of regulatory aspects of the cardiovascular system, including the nerves and adrenal glands. A diagram is shown of what happens when blood pressure rises in the skull. An experiment is carried out on an animal where the carotid artery is clamped. Blood pressure drops in the skull and rises in the body. The external and internal carotid arteries are clamped and blood pressure drops in the head but general blood pressure remains unchanged. The results of the experiment are discussed. Further experiments are carried out on the nerve fibres in the neck, including squeezing the carotid sinus. Changes in blood pressure are monitored. Time start: 00:07:10:21 Time end: 00:15:01:15 Length: 00:07:50:19 Segment 3 The changes in blood pressure in the previous experiments are explained. An oscillograph is shown and heard, which demonstrates blood pressure optically and acoustically. Normal blood pressure is shown. Various changes are made and the oscillograph shows the change in blood pressure. A further experiment is carried out to show the relationship between respiration and blood pressure. Time start: 00:15:01:15 Time end: 00:21:55:05 Length: 00:06:53:15 Segment 4 An experiment is carried out using a dog to show the relationship between respiration and blood pressure. The narrator explains how blood pressure is maintained by receptors in the cardiovascular and nervous systems. In an experiment, the vagus nerves of a dog are cut and injected with adrenalin. The results are explained by the narrator. The renal arteries of the dog are compressed, making the blood pressure rise. Adrenalin is injected into the carotid sinus wall and the blood pressure falls. The various agents that affect blood pressure are explained. An animated diagram shows how nerves and blood vessels work together to regulate blood pressure. The regulatory agents of blood pressure, including drugs, are discussed. The narrator warns that these drugs can have side effects and that contemporary medicine is not in a position to treat the real causes of hypertension. Time start: 00:21:55:05 Time end: 00:29:01:21 Length: 00:07:06:16