Blood Pressure

BLOOD PRESSURE

Q. 1

Which of the following statements regarding stroke volume is TRUE?

 A

Decreases by increase in heart rate

 B

Determined by pre-diastolic volume

 C

Determined by afterload

 D

Is equal to cardiac output

Q. 1

Which of the following statements regarding stroke volume is TRUE?

 A

Decreases by increase in heart rate

 B

Determined by pre-diastolic volume

 C

Determined by afterload

 D

Is equal to cardiac output

Ans. A

Explanation:

Stroke volume = cardiac output/heart rate, i.e it is inversely proportional to heart rate. As a result when heart rate increases the stroke volume decreases. This reduction in stroke volume at high heart rates is due to a decrease in the length of time the heart spends in diastole and thus a reduction in time available to the heart for filling.

Stroke volume refers to quantity of blood ejected with each heart stroke. According to Starling’s law of heart, stroke volume is determined primarily by the preload. As the preload increases, stroke volume also increases until it reaches a plateau. Stroke volume can also be increased by sympathetic stimulation of the heart.

Ref: Physiology Secrets By Hershel Raff, 2nd edn, page 74


Q. 2

Blood pressure is defined as the product of:

 A

Systolic pressure x pulse

 B

Diastolic pressure x pulse rate

 C

Pulse pressure x pulse rate

 D

Cardiac output x peripheral resistance

Q. 2

Blood pressure is defined as the product of:

 A

Systolic pressure x pulse

 B

Diastolic pressure x pulse rate

 C

Pulse pressure x pulse rate

 D

Cardiac output x peripheral resistance

Ans. D

Explanation:

D i.e. Peripheral resistance x cardiac output

The overall blood flow in circulation of adult at rest is about 5 liter/min which equals to cardiac output because it is the amount of blood pumped by heart per unit time. So

Blood pressure =

Cardiac output x peripheral resistanceQ or Blood flow (Q) x resistance (R)

 

Venous returnQ =

MSFP — RAP                       MSFP = Mean systemic filling pressure

 

 

 

 

= Right

RAP                                                 atrial pressure

RVR                                          RVR    = Resistance to venous return

 

Q. 3

SI unit for measuring Blood Pressure is :

 A

Torr

 B

mmHg

 C

kPa

 D

Barr

Q. 3

SI unit for measuring Blood Pressure is :

 A

Torr

 B

mmHg

 C

kPa

 D

Barr

Ans. C

Explanation:

C i.e. KPa


Q. 4

Blood pressure is defined as the product of.

 A

Systolic pressure x pulse

 B

Diastolic pressure x pulse rate

 C

Pulse pressure x pulse rate

 D

Cardiac output x peripheral resistance

Q. 4

Blood pressure is defined as the product of.

 A

Systolic pressure x pulse

 B

Diastolic pressure x pulse rate

 C

Pulse pressure x pulse rate

 D

Cardiac output x peripheral resistance

Ans. D

Explanation:

D i.e. Peripheral resistance x cardiac output:

Blood pressure is defined as the product of cardiac output and peripheral resistance.

Blood pressure =  Cardiac output x peripheral resistance or Blood flow (Q) x resistance (R)


Q. 5

SI unit for measuring Blood Pressure is:

 A

Torr

 B

mmHg

 C

kPa

 D

Barr

Q. 5

SI unit for measuring Blood Pressure is:

 A

Torr

 B

mmHg

 C

kPa

 D

Barr

Ans. C

Explanation:

Answer is C (kPa)

Pressure in SI units is measured in Pascal

Pal Blood pressure in SI units is measured in kPa


Q. 6

Mean BP is ‑

 A

CO x TPR

 B

CO x heart rate

 C

Heart rate x TPR

 D

Stroke volume x TPR

Q. 6

Mean BP is ‑

 A

CO x TPR

 B

CO x heart rate

 C

Heart rate x TPR

 D

Stroke volume x TPR

Ans. A

Explanation:

Ans. is ‘a’ i.e., CO x TPR

  • Arterial blood pressure is the product of the cardiac output and the total peripheral vascular resistance (TPR). Mean blood pressure is the major determinant of adequate blood flow through the tissues.

Mean BP = Cardiac output x Total peripheral resistance

  • If cardiac output is expressed as a product of stroke volume and heart rate, the formula blood pressure can be expressed as the product of three variables (the triple product) : –

Mean BP = Stroke volume x Heart rate x TPR

  • Blood pressure is therefore affected by conditions that affect any of these factors. Changes in cardiac output (or stroke volume) affect mainly the systolic pressure while changes in peripheral resistance affect mainly the diastolic pressure.


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