CDS (I) 2023 General Knowledge · Question 5 of 120

Correct — A, ventricular contraction and ventricular relaxation, respectively. A blood-pressure reading is taken from a systemic artery, usually the brachial artery in the upper arm, and it records the pressure in that artery through one cardiac cycle. The higher figure, 120 mmHg, is the systolic pressure — the peak reached while the ventricles contract and drive blood into the aorta. The lower figure, 80 mmHg, is the diastolic pressure — what is still left in the elastic arteries while the ventricles relax and refill. Both numbers therefore belong to the ventricles, and they are written in that order, contraction first.

• (b)ventricular relaxation and ventricular contraction, respectively — Right chambers, wrong order. Pressure is at its highest when the ventricle squeezes, so the larger number has to be the contraction. Writing 120 as relaxation would make the artery more stretched at rest than during ejection.
• (c)auricular contraction and auricular relaxation, respectively — The atria, or auricles, are low-pressure chambers that merely top up the ventricles; their contraction produces only a few millimetres of mercury and nothing a cuff on the arm could detect.
• (d)ventricular contraction and auricular contraction, respectively — Gets the first number right and then jumps chambers for the second. The two readings come from a single cardiac cycle in the same artery, so both must refer to the same pumping chamber.

The heart works in a repeating cycle of systole and diastole. During ventricular systole the left ventricle contracts and ejects blood into the aorta, and arterial pressure peaks — that peak is the systolic reading. During diastole the ventricles relax and refill from the atria; arterial pressure falls but does not reach zero, because the elastic walls of the large arteries recoil and keep pushing blood forward. That residual pressure is the diastolic reading. Written as a fraction, the two are quoted systolic over diastolic, so 120 over 80.

The item is really testing whether a student attaches the two numbers to the right chambers and in the right order, and the options are laid out to punish each half-memory separately. A quick internal check settles it: the pressure has to be higher while a chamber is squeezing than while it is resting, so the bigger number is the contraction; and only the ventricles generate enough force to register in an arm artery at all. Note that 120 over 80 is a textbook reference value rather than a clinical cut-off. The World Health Organization diagnoses hypertension when readings taken on two different days are at or above 140 systolic and/or at or above 90 diastolic, so the gap between the paper's normal and a diagnosis is wide.

• The higher figure, 120 mmHg, is systolic pressure — arterial pressure during ventricular contraction.
• The lower figure, 80 mmHg, is diastolic pressure — the pressure remaining while the ventricles relax and refill.
• Blood pressure is measured with a sphygmomanometer over the brachial artery of the upper arm.
• Atrial contraction generates only a few millimetres of mercury and is not what the cuff records.
• The World Health Organization defines hypertension as systolic readings of 140 mmHg or more and/or diastolic readings of 90 mmHg or more on two different days.

• Reversing the pair and calling 120 the relaxation figure.
• Assigning either number to the atria, which never generate arterial pressure.
• Treating 120 over 80 as a diagnostic threshold rather than a reference value.

As this two-number identification, or as an item on which chamber generates arterial pressure, or on what instrument and artery are used.

• practice — not a real PYQ

  In a blood-pressure reading written as 120/80 mmHg, the figure 80 represents the

  • (a)systolic pressure
  • (b)diastolic pressure
  • (c)pulse pressure
  • (d)mean arterial pressure

  Answer(b) diastolic pressure — the pressure remaining in the arteries while the ventricles are relaxed and refilling.

• practice — not a real PYQ

  Which chamber of the human heart pumps blood into the aorta?

  • (a)Right atrium
  • (b)Left atrium
  • (c)Right ventricle
  • (d)Left ventricle

  Answer(d) Left ventricle — it drives oxygenated blood into the aorta, which is why it carries the thickest muscular wall of the four chambers.