The normal systolic pressure in human beings is:

Correct — C, 120 mm of Hg. Blood pressure is written as one number over another, and the standard healthy adult reading is 120 over 80 mm Hg. The upper figure is the systolic pressure: the peak pressure in the arteries during systole, the phase in which the ventricles contract and drive blood into the aorta and the pulmonary artery. The lower figure is the diastolic pressure, the pressure that remains during diastole, when the ventricles relax and refill and the arteries are held under tension only by their own elastic recoil. That recoil is why the pressure never falls to zero between beats and why blood keeps flowing forward while the heart is resting. So of the four figures offered, 80 is the normal diastolic value and 120 the normal systolic; they are the two halves of the same familiar reading, and the question is testing which belongs to which. The remaining numbers mark the edges of the normal range rather than its centre: around 100 systolic is on the low side of normal for an adult, and a sustained systolic reading of 140 mm Hg or more, or a diastolic of 90 or more, is the conventional threshold for diagnosing hypertension.

• (a)80 mm of Hg — The normal DIASTOLIC pressure — the lower number of the 120/80 pair, measured while the ventricles relax. Choosing it means reading the fraction the wrong way up.
• (b)100 mm of Hg — On the low side of the adult systolic range rather than its normal value. It is not the figure the textbook reading quotes.
• (d)140 mm of Hg — The conventional threshold at which a sustained systolic reading is treated as hypertension, not a normal value.

The heart works as a two-stage pump, and arterial pressure rises and falls with it. During systole the ventricles contract and eject blood, and pressure in the large arteries peaks at about 120 mm Hg in a healthy adult. During diastole the ventricles relax and fill from the atria; the aortic valve closes, and the elastic walls of the arteries, stretched by the previous ejection, recoil and keep the blood moving, so pressure falls only to about 80 mm Hg rather than to nothing. The difference between the two, about 40 mm Hg, is the pulse pressure, and it is the pulse you feel at the wrist. The unit, millimetres of mercury, survives from the mercury column of the original manometer.

The item is testing an ordering rather than a fact: nearly every candidate knows the pair 120 and 80, and the whole question is which of them is systolic. The reliable hook is that systole is the contraction, and a contraction is a push, so the systolic number has to be the larger. A second hook comes from how the reading is taken, which is the subject of Q71 of this same paper — as the cuff deflates, the first sound is heard when blood first breaks through against the highest arterial pressure, so the first, higher reading is systolic. Two honest qualifications belong on a card like this. First, 120 over 80 is a textbook value, not a fixed constant: pressure varies with age, activity, posture and emotion, and a single reading taken after climbing stairs proves nothing, which is why repeat readings are taken. Second, the thresholds themselves are conventions that guidelines revise; the widely used definition of hypertension in India remains 140 over 90 mm Hg or above on repeated measurement, while some international guidelines have moved to lower cut-offs. The physiology in this card does not change with those revisions.

• The standard healthy adult blood pressure reading is 120 over 80 mm Hg.
• The systolic pressure, 120 mm Hg, is the peak reached while the ventricles contract; the diastolic pressure, 80 mm Hg, is the trough while they relax and refill.
• The systolic figure is always the larger and is written first.
• The difference between the two, about 40 mm Hg, is the pulse pressure.
• Arterial pressure does not fall to zero in diastole because the elastic recoil of the arterial walls keeps blood moving forward.
• A sustained reading of 140 over 90 mm Hg or above is the conventional threshold for hypertension in Indian practice.
• Pressure is quoted in millimetres of mercury because the original instrument used a mercury column.

• Inverting the pair and giving 80 as the systolic value; systole is the contraction, so it carries the higher number.
• Treating 140 as normal because it is a familiar number. It is familiar as a threshold for hypertension, not as a healthy reading.
• Reading a single high measurement as a diagnosis; pressure varies with posture, exertion and anxiety, so repeat readings are needed.

As a value-recall item like this one, as a question on which phase of the cardiac cycle each number belongs to, or through the instrument used to take the reading.

• practice — not a real PYQ

  In a blood pressure reading of 120/80 mm Hg, the lower figure represents which one of the following?

  • (a)Pressure during ventricular contraction
  • (b)Pressure during ventricular relaxation
  • (c)Pressure in the pulmonary vein
  • (d)Mean pressure over the whole cycle

  Answer(b) Pressure during ventricular relaxation — the diastolic pressure, held up by the elastic recoil of the arterial walls while the ventricles refill.

• practice — not a real PYQ

  The difference between systolic and diastolic pressure is known as which one of the following?

  • (a)Mean arterial pressure
  • (b)Pulse pressure
  • (c)Venous pressure
  • (d)Osmotic pressure

  Answer(b) Pulse pressure — about 40 mm Hg in a healthy adult with a reading of 120 over 80, and what you feel as the pulse at the wrist.