Blood Pressure Regulation

Question 1

Factors affecting blood pressure

Answer 1

Total peripheral resistance
Cardiac output
Blood volume
Elasticity

Question 2

What are resistance vessels?

Answer 2

Arterioles

Question 3

What are muscular arterioles?

Answer 3

Resistance vessels

Question 4

What is systolic blood pressure?

Answer 4

Maximum pressure in arteries

When blood is ejected into them during systole

Question 5

What is diastolic pressure?

Answer 5

Minimum pressure in arteries

Blood draining into remaining vessels in diastole

Question 6

Pulse pressure

Answer 6

Difference between systolic and diastolic pressure

Question 7

Mean arterial pressure

Answer 7

Average pressure responsible for driving blood forward through vessels into tissues throughout cardiac cycle

Question 8

How many cm of water does 1mmHg equal?

Answer 8

1.36 cmH2O

Question 9

Different pressures in circulatory system
1)
2)
3)

Answer 9

1) Driving pressure
2) Transmural pressure
3) Hydrostatic pressure

Question 10

Driving pressure

Answer 10

Difference in blood pressure between different parts of the vasculature

EG: Diff between arteries and veins

Vector parallel and in the same direction as blood flow

Question 11

Transmural pressure

Answer 11

Pressure inside vessel vs pressure outside vessel

Runs perpendicular to driving pressure

Question 12

Effect if transmural pressure is negative

Answer 12

No blood flow

Pressure outside vessel is greater than inside

Question 13

Hydrostatic pressure

Answer 13

Difference in pressure form height of blood

Function of potential energy

Question 14

Difference in blood pressure between heart and head

Answer 14

~85mmHg (if head is 50cm higher than heart)

Question 15

Factors contributing to pressure in circulation
1)
2)
3)
4)

Answer 15

1) Gravity
2) Compliance of vessel
3) Viscous resistance
4) Intertia

Question 16

Effect of gravity on blood pressure

Answer 16

Causes hydrostatic pressure when there is a change in height

Doesn’t affect driving pressure

Rho G H

Question 17

Vascular compliance

Answer 17

Increase in volume/Increase in pressure

Question 18

Factors determining viscous resistance of blood
1)
2)
3)
4)
5)

Answer 18

1) Fibrinogen concentration
2) Haematocrit
3) Vessel radius
4) Linear velocity
5) Temperature

Question 19

Velocity of blood at vessel wall

Answer 19

Zero

Question 20

Area where blood velocity is maximum

Answer 20

Centre of vessel

Question 21

Effect of increased blood velocity

Answer 21

Decreased pressure

Question 22

Why does blood pressure decrease when velocity increases?

Answer 22

Law of conservation of energy

As kinetic energy (velocity) rises, potential energy (pressure) must decrease

Question 23

Delta P (pressure)

Answer 23

Flow x resistance

Question 24

Issues for Poiseuille’s law in the human body

Answer 24

1) Rule is only true for an incompressible liquid
2) Constant velocity
3) Straight, rigid, unbranched tube
4) Steady, not pulsatile flow
5) Uniform flow in a tube

Question 25

What is conductance in a blood vessel?

Answer 25

Measure of blood flow through a vessel for a given pressure difference

Question 26

Ways to calculate conductance

Answer 26

1/Resistance Flow/Change in pressure

Question 27

What happens to resistance if tubes are in series?

Answer 27

Increases

Question 28

What happens to resistance if tubes are in parallel?

Answer 28

Decreases

Question 29

Is total resistance higher in arterioles or capillaries?

Answer 29

Arterioles

Question 30

Why do arterioles have higher total resistance than capillaries?

Answer 30

Capillaries have a narrower aperture BUT Capillaries have more vessels in parallel

Question 31

Role of elasticity in blood pressure

Answer 31

Maintains a steady pressure and flow despite pulsatile heartbeat

Question 32

Does the heart spend more time in systole or diastole?

Answer 32

Diastole

Question 33

Why is vasoconstriction so effective in increasing blood pressure?

Answer 33

Poisuille's equation (radius^4) 60% of blood is in systemic veins --> pushes extra blood into arteries

Question 34

What determines mean arterial pressure?

Answer 34

Cardiac output x total peripheral resistance

Question 35

Equation for MAP

Answer 35

Diastolic pressure + 1/3(Systolic - Diastolic)

Question 36

Preload

Answer 36

What's in the heart before contraction

Question 37

Frank-Starling law

Answer 37

Relationship between stretch and force Force increases as stretch increases, until a point where it plateaus (sarcomeres stretched too much, heart begins to fail)

Question 38

Cardiac output

Answer 38

Heart rate x stroke volume

Question 39

Average cardiac output

Answer 39

5L/min

Question 40

Stroke volume

Answer 40

End diastolic volume - end systolic volume

Question 41

Average stroke volume at rest

Answer 41

70mL

Question 42

Inotropy

Answer 42

Force of ventricular contaction

Question 43

Factors affecting stroke volume

Answer 43

Inotropy

Question 44

Factors affecting inotropy

Answer 44

Preload Contractility Afterload

Question 45

What determines end diastolic volume (afterload)

Answer 45

Venous return - Skeletal muscle pump, thoracic pump - Varying degrees of vasoconstriction

Question 46

Increasing afterload increases what?

Answer 46

Resistance Harder to get blood into the heart Decrease stroke volume, increase end systolic pressure

Question 47

Effect of increasing preload

Answer 47

Increase stroke volume | Increase end diastolic volume

Question 48

Effect of increasing inotropy

Answer 48

Increase stroke volume | Decrease end systolic volume

Question 49

How is the heartrate modulated?

Answer 49

By autonomic nervous system

Question 50

``` Effect of sympathetic stimulation on heart 1) 2) 3) 4) 5) ```

Answer 50

1) Changes ion permeability 2) Depolarises 3) Reaches threshold sooner 4) Beta1 noradrenaline receptors 5) Enhances rate of transmission of AP through AV node

Question 51

``` Effect of parasympathetic stimulation of the heart 1) 2) 3) 4) 5) ```

Answer 51

1) Changes ion permeability 2) Hyperpolarises 3) Harder to reach threshold 4) ACh muscarinic receptors 5) Slows conduction of AP through AV node

Question 52

Short term blood pressure regulation

Answer 52

Barroreflex | Neural

Question 53

Where are baroreceptors located?

Answer 53

Carotid sinus | Aortic arch

Question 54

What do baroreceptors in the carotid sinus and aortic arch do?

Answer 54

1) Fire constantly 2) Respond rapidly to changing blood pressure, within 1 - 2 cycles 3) Synapse in medullary cardiovascular control centre

Question 55

Short-term blood pressure homeostais 1) 2) 3)

Answer 55

1) Change in BP detected by baroreceptors in aortic arch, carotid sinus 2) Medullary cardiovascular control centre 3) Either sympathetic or parasympatheitc activation of vasculature

Question 56

``` Result of activating sympathetic nervous system 1) 2) 3) 4) 5) ```

Answer 56

1) Increase heart rate 2) Increase contractility 3) Increase total peripheral resistance 4) Increase venous tone 5) Decrease AV conduction time

Question 57

Result of activating parasympathetic nervous system 1) 2)

Answer 57

1) Decrease heart rate | 2) Increase AV conduction time

Question 58

``` Homeostatic mechanisms for blood pressure when you stand up 1) 2) 3) 4) 5) ```

Answer 58

1) Decrease in MAP 2) Decrease in baroreceptor stretch 3) Decrease in nerve firing to cardiovascular medullary center 4) Increase sympathetic response --> Increase HR, contractility, TPR of arteries 5) Decrease parasympathetic response

Question 59

Homeostatic mechanisms for blood pressure when you lie down

Answer 59

1) Increase in MAP 2) Increase baroreceptor stretch 3) Increase in nerve firing to cardiovascular medullary center 4) Reduce sympathetic response --> decrease TPR of arteries, vascular resistance 5) Increase parasympathetic response --> Decrease heart rate

Question 60

Long-term blood pressure regulation

Answer 60

Chemoreceptors Detect pH, [O2], [CO2] Increase respiration

Question 61

Hormonal ways to increase cardiac output

Answer 61

Increase extracellular fluid | Decrease renal salt excretion

Question 62

Hormonal ways to increase TPR

Answer 62

Thicken arterial wall (hypertrophy) | Vasoconstrictive hormones

Question 63

Where are low pressure receptors located?

Answer 63

Atrial baroreceptors

Question 64

Factors determining MAP

Answer 64

1) Blood volume 2) Cardiac output 3) Resistance 4) Distribution of blood between arterial and venous blood vessels

Question 65

What determines resistance to blood flow?

Answer 65

Diameter of arterioles

Question 66

What determines the distribution of blood between arterial and venous systems?

Answer 66

Diameter of veins