Ans. is 'b' i.e., Cardiac output & peripheral resistanceo Mean BP = Cardiac output total peripheral resistance.Blood pressureo Blood pressure is the lateral pressure exerted by the column of blood on the walls of the arteries.o Most commonly used unit of BP is mm Hg.o But recently there is a trend towards adopting the system International 'd' units (SI units).o In SI units, the basic unit for pressure is newton per square meter, and is called pascal (Pa)Q.o Blood pressure, if expressed in SI units, is expressed in Kilopascals (kPa).o Kilopascals may be converted into mm Hg by multiplying them by 7.5. Thus BP in mm Hg= BP in kPa x 7.5 or 1 mm Hg = 0.133 kPa.o The blood pressure is not steady, it fluctuates during cardiac cycle,o During ventricular systole, BP is higher than during diastole.o The maximum arterial pressure attained during systole is called the systolic BP (SBP) and the minimum pressure recorded during diastole is called diastolic BP (DBP).o When recorded from the brachial artery of a young adult in the sitting or supine position, the SBP is about 120 mm Hg and the DBP is about 80 mm Hg.o The difference between the systolic and diastolic pressure is called the pulse pressureQ,o It is normally about 40 mm Hg (120 minus 80 mm Hg).o The mean blood pressure is the average pressure throughout the cardiac cycle.o However, it is worth noting that mean BP is not the arithmetic mean or average of the systolic or diastolic BP.o This is because systole is much shorter than diastole.o Therefore arterial pressure is near the diastolic pressure for a longer part of cardiac cycle than it is near the systolic pressure; hence, greater weight is given to the diastolic BP in the calculation of mean BP.o Thus, mean BP is slightly less than the simple average of the systolic and diastolic BP.o As an approximation, the mean BP is weighted 2 : 1 in favour of diastolic BP.Mean blood pressure = 2/3 diastolic pressure (DBP) + 1/3 rd systolic pressure (SBP)o Normally, mean BP is about 93 mm Hg Q (2 x 80 +120)/3.