Blood Pressure

Question 1

What are the 4 stages in Blood Pressure measurement?

Answer 1

1. Pressure in the cuff is greater than systolic pressure (peak internal pressure): artery is completely pinched closed throughout the entire cardiac cycle and no turbulent blood flow occurs, therefore there is no sound.
2. Air in the cuff is slowly released to gradually reduce the pressure in the cuff to just below the systolic pressure: Blood escapes through the partially occluded artery. Turbulent blood flow present, therefore first sound can be heard at peak systolic pressure
3. Cuff pressure continues to fall: Intermittent sounds are produced by turbulent spurts of flow as blood pressure exceeds cuff pressure
4. Cuff pressure falls below diastolic pressure: Brachial artery is no longer pinched and blood flows without interruption. The minimum diastolic pressure is where the last sound can be heard.

Question 2

How to calculate pulse pressure?

Answer 2

Difference between systolic and diastolic pressure

Question 3

How to calculate mean arterial pressure?

Answer 3

Diastolic pressure + ⅓ pulse pressure

Question 4

What is the pulse pressure indicative of?

Answer 4

Stroke volume

Question 5

What factors affect the rate of blood flow?

Answer 5

1. Cardiac output
2. Vessel Diameter and resistance to blood flow

Question 6

What 2 factors affect flow rate and how?

Answer 6

1. Pressure gradient: The larger the pressure gradient, the faster the flow rate (Directly proportional)
2. Vascular resistance: As resistance increases, flow rate decreases (Indirectly proportional)

Question 7

How to measure pressure gradient in the entire circulatory system?

Answer 7

Mean arterial pressure - Central venous pressure

Question 8

Define resistance

Answer 8

Measure of hindrance or opposition to blood flow through the vessel, caused by friction between the moving fluid and the stationary vascular wall.

Question 9

Explain how resistance affects flow rate

Answer 9

• As resistance to flow increases, it is harder for blood to pass through the vessel, therefore, flow rate decreases (if pressure gradient stays the same)
• When resistance increases, the pressure gradient must increase in order to maintain the same flow rate
• Increased resistance=heart work harder to maintain adequate circulation

Question 10

What factors affect resistance and how?

Answer 10

1. Viscosity of blood: The more viscous the blood is, the greater the resistance to blood flow
2. Vessel length: The larger the length of the vessel, the greater the resistance to blood flow
3. Vessel radius: The smaller the vessel radius, the larger the resistance to blood flow

Question 11

What are arteries?

Answer 11

• Rapid-transit passageway for blood from the heart to the organs: They have large radius and little resistance to blood flow
• Act as pressure reservoir to provide the driving force for blood when heart is relaxing: Arteries are highly elastic and expand to temporarily hold the excess volume of ejected blood, storing some of the pressure energy imparted by cardiac contraction in their stretched walls.

Question 12

What factors affect Mean Arterial Pressure?

Answer 12

1. Cardiac Output
2. Total peripheral resistance

Question 13

What factors affect Cardiac Output?

Answer 13

1. Heart rate
2. Stroke Volume

Question 14

What are the short term and long term influences of blood volume on venous return?

Answer 14

1. Short term: Passive blood flow shifts between plasma and interstitial fluid
2. Long term: Salt and water balance that are hormonally controlled by the RAAA system and vasopressin

Question 15

What is Total Peripheral Resistance dependent on?

Answer 15

1. Arteriolar radius
2. Blood viscosity

Question 16

What factors influence arteriolar radius?

Answer 16

1. Local metabolic controls: For example, arteriolar vasodilation occurs in active skeletal muscle, increasing blood flow to the muscles
2. Extrinsic vasoconstrictor controls: Sympathetic activity and Vasopressin and Angiotensin II that are potent vasoconstrictors

Question 17

What mechanism is important in blood pressure regulation?

Answer 17

Baroreceptor Reflex

Question 18

How does the BARORECEPTOR REFLEX regulate blood pressure?

Answer 18

Influences heart and blood vessels to adjust cardiac output and total peripheral resistance

Question 19

What type of receptors are Baroreceptors?

Answer 19

Mechanoreceptors

Question 20

Where can Baroreceptors be found?

Answer 20

1. Aortic arch
2. Carotid Sinuses

Question 21

How does the Baroreceptor Reflex respond to an ELEVATION in blood pressure?

Answer 21

Elevation of blood pressure above normal

⇣

Increase in receptor potentials in carotid sinus and aortic arch (due to stretch)

⇣

Increase in rate of firing in afferent nerves

⇣

Cardiovascular system responds by:

INCREASED PARASYMPATHETIC activity and DECREASED SYMPATHETIC ACTIVITY of cardiac and vasoconstrictor nerve

⇣

Decreased heart rate and stroke volume

Arteriolar and venous vasodilation

⇣

Decreased cardiac output and total peripheral resistance

Question 22

How does the Baroreceptor Reflex respond to a DROP in blood pressure?

Answer 22

Drop in blood pressure below normal

⇣

Decrease in receptor potentials in carotid sinus and aortic arch (less stretch)

⇣

Decrease in rate of firing in afferent nerves

⇣

Cardiovascular system responds by:

INCREASED SYMPATHETIC activity, DECREASED PARASYMPATHETIC activity

⇣

Increased heart rate and stroke volume

Arteriolar and venous vasoconstriction

⇣

Increase in cardiac output and total peripheral resistance