CDS (I) 2024 General Knowledge · Question 64 of 120

Correct — C, aorta and main arteries. Each time the left ventricle empties, a slug of blood is driven into the aorta faster than it can drain away downstream. The aortic wall is loaded with elastic fibres, so it stretches to take the extra volume and then springs back, and that stretch-and-recoil travels outward along the large arteries as a pressure wave. What your fingertips register at the wrist is that wall movement, which is why the standard physiology description of the pulse is the expansion and recoiling of the elastic arteries. The pulse is therefore counted at any main artery running close to the surface — the radial artery at the wrist and the common carotid in the neck are the usual sites — and never over a vein or over the heart itself.

• (a)chambers of heart — The heart's chambers generate the wave, but they are not what you feel. Contraction of the ventricles is heard as the heartbeat over the chest; the pulse is the arterial wall movement it sets off further along the circuit.
• (b)valves present in veins — Vein valves are passive flaps that stop backflow in low-pressure vessels. By the time blood reaches the veins the pressure wave has been damped out in the capillary bed, so veins carry no pulse.
• (d)valves of heart — The heart valves snap shut to give the 'lub-dub' heart sounds, which is a different phenomenon heard with a stethoscope over the chest, not a wave felt in a peripheral artery.

Blood leaves the left ventricle in spurts, but it must reach the capillaries as a steady stream. The elastic walls of the aorta and the large arteries do that conversion: they balloon out during ventricular contraction, storing part of the ejected volume, then recoil during relaxation and push it onward. The pulse is that cycle made palpable, and it repeats once per heartbeat, so pulse rate and heart rate are the same number in a healthy person.

Two things make this item easy to get wrong. The first is that the heart is the obvious cause, so option (a) feels right — but the question says where the pulse is felt, and nobody takes a pulse over the ventricles. The second is the paper's own wording. Arteries do not truly 'contract and relax' the way a muscle does; they are stretched passively by the pressure wave and recoil elastically. Large arteries do carry smooth muscle in their walls, but its job is slow adjustment of vessel calibre, not the beat-by-beat expansion you feel. The stem is using everyday language for elastic expansion and recoil, and reading it that way still points only to the aorta and the main arteries.

• The pulse is the expansion and recoil of elastic arteries as blood is ejected from the heart.
• It is normally palpated at the radial artery in the wrist or the common carotid artery in the neck.
• Any superficial artery can be used; veins carry no pulse because the pressure wave is damped in the capillaries.
• Pulse rate equals heart rate in a healthy person, since one wave is generated per heartbeat.
• The elastic recoil of the aorta is also what keeps blood flowing forward during ventricular relaxation.

• Choosing the heart's chambers because they cause the pulse, when the question asks what is felt.
• Confusing the heart sounds made by closing valves with the pulse felt in an artery.
• Assuming veins pulse too, when the wave has already been damped out before the blood gets there.

Asked as a sentence-completion item where three options sit inside the heart and only one names a vessel.

• practice — not a real PYQ

  The pulse rate of a healthy adult at rest is normally closest to

  • (a)20 to 30 per minute
  • (b)40 to 50 per minute
  • (c)60 to 100 per minute
  • (d)120 to 150 per minute

  Answer(c) 60 to 100 per minute — one pulse wave is produced per heartbeat, so the resting pulse tracks the resting heart rate.

• practice — not a real PYQ

  Which one of the following vessels carries oxygenated blood away from the heart to the body?

  • (a)Pulmonary artery
  • (b)Aorta
  • (c)Vena cava
  • (d)Pulmonary vein

  Answer(b) Aorta — it takes oxygenated blood from the left ventricle to the body; the pulmonary artery is the one artery that carries deoxygenated blood.