Regulation of arteriolar resistance

Question 1

How is arterial pressure measured?

Answer 1

• auscultation of Korotkoff sounds using sphygmomanometer + stethoscope

Question 2

Pressure - elastic arteries

Answer 2

• elastic arteries act as a pressure reservoir ( helps reduce pressure)

Question 3

What affects the pressure wave?

Answer 3

• SV
• Velocity of ejaculation
• elasticity of arteries
• TPR

Question 4

What is the normal arterial pressure

Answer 4

120/80mmHg

-increases with age(esp pule pressure)

Question 5

Describe the pressure + BF from arteries to veins

Answer 5

Pressure falls throughpit vascular tree;
Arteries-High but then small drop ( resistance conduit) [9-90mmHg]
Arterioles - large drop=low [90-40mmHg] (resistance vessels)
Capillaries-already low

In turn, this leaves a small pressure difference pushing blood back into veins (20-5mmHg)

Question 6

Fraction of pul.circulation pressure ( systemic)

Answer 6

1/5th of systemic pressure

Question 7

Pressure + flow in veins

Answer 7

Pressure is low
- There is a small pressure gradient driving blood from veins back into the RA which is why it’s imperative that this pressure gradient is maintained

Question 8

What external factors affect BF+BP?

Answer 8

Gravity, skeletal muscle pump, respiratory pump, venomotor tone, systemic filling pressure

Question 9

The effect of Gravity on BF+BP

Answer 9

• doesn’t affect driving pressure from arteries>veins but causes venous distension in legs
• > low EDV, preload, SV, CO, MAP
• > orthostatic (postural) hypotension
• causes venous collapse in neck
• can be used to estimate central venous pressure

Question 10

What can be used to estimate CVP?

Answer 10

Height of jugular colappse

Question 11

The effect of skeletal muscle pump on BP+BF

Answer 11

-rythmic vs static excercise

Failure in this can lead to :

• deep vein thrombosis
• varicose veins

Question 12

The effect of venomotor tone on BP + BF

Answer 12

• this is the state of contraction fo the smooth muscle surroudning venules and veins
• it mobilises capacitance

Question 13

What is the systemic filling pressure?

Answer 13

-pressure is created by ventricles + transmitted through vascular tree > veins

Question 14

What does clotting involve?

Answer 14

Clotting involves;

• formation of a platelet plug
• formation of a fibrin clot
• blood in capillaries move so slow that it predisposes clotting, so endothelium operates to prevent this.

Question 15

Anti-clotting mechanisms of endothelium

Answer 15

Inhibition of Platelet aggregation

• Stops blood contacting collagen
• production of prostacyclin + NO

Inhibition of thrombin production

• production of tissue factor pathway inhibitor
• Expresses thrombomodulin ( binds thrombin + inactivates it)
• Expresses heparin (inactivates thrombin)
• Secretes tissue plasminogen activator( aka t-PA, converts plasminogen into plasmin + digests clot)