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Flashcards in Regulation of arteriolar resistance Deck (24):

What can be used to measure korotkoff sounds (blood flow sounds)?

Sphygmomanometer & Stethoscope


Example of korotkoff sounds?

- Silence
- Tapping
- Thumping
- Muffled
- repeat


What do elastic arteries act as?

They act as a pressure reservoir.
- Damps down pressure variations.


What is the pressure wave affected by?

- Stroke volume
- Velocity of ejection
- Elasticity of arteries
- Total peripheral resistance


What is normal arterial pressure?

120/80 mmHg

- Arterial pressure increases with age


When can arterial pressure spike/increase?

A stimulus such as getting punched and activities such as sexual intercourse can increase arterial pressure from e.g. 80 to 150 mmHg.


How does pressure change through the vascular tree?

It decreases


What is the pressure change through arteries?

Drop from 95 to 90 mmHg.

-Low resistance conduit


What is the pressure change through arterioles?

Drop from 90 to 40 mmHg.

- The resistance vessels


What is the pressure of blood when it reaches the capillaries?

Pressure is already low when blood gets to capillaries.
- because they are thin-walled
Around 30mmHg, then pressure decreases as it travels back to the heart.


What is the systemic filling pressure?

Pressure created by ventricles and transmitted through vascular tree to the veins.

- The value of SFP in animal experimental models is approximately 7 mm Hg.


Where is the velocity of blood fastest and slowest?

Blood is fastest in the aorta and vena cava, and slowest in capillaries.


How does blood flow velocity change with cross-sectional area?

An increase in cross-sectional area causes a decrease in velocity of blood flow


How does standing up/gravity affect blood pressure?

- Increases pressure in legs and feet.
- Does not affect driving pressure from arteries to veins
- Causes venous distension in legs
- Causes venous collapse in neck


What can height of jugular collapse be used to estimate?

It can be used to estimate CVP (central venous pressure)

-CVP is the blood pressure in the vena cava, it reflects the amount of blood returning back to the heart.


What is the skeletal muscle pump?

It is a collection of skeletal muscles that aid the heart in the circulation of blood.

- It is especially important in increasing venous return to the heart!!!, but may also play a role in arterial blood flow.


What is the skeletal muscle pump significant in?

- Rhythmic vs Static exercise
- Hot guardsmen
- Deep vein thrombosis
- Varicose veins


What is the respiratory pump?

Respiratory activity influences venous return to the heart.

Briefly, increasing the rate and depth of respiration promotes venous return and therefore enhances cardiac output.

Non-typical respiratory activity such as being on positive pressure ventilation or doing a forced expiration against a closed glottis (Valsalva manoeuover) impedes and therefore reduces venous return and cardiac output


What is venous return?

It is the flow of blood from the periphery back to the heart's right atrium


How does the respiratory pump work (basic)?

During inspiration, expansion of the lungs and pulmonary tissues causes pulmonary blood volume to increase, which transiently decreases the flow of blood from the lungs to the left atrium.
Aiding venous return.


What is venomotor tone?

The state of contraction of the smooth muscle surrounding the venules and veins.

- It mobilises capacitance


What does clotting involve in the endothelium?

Clotting involves
- Formation of a platelet plug
- Formation of a fibrin clot


How is Fibrinogen converted to Fibrin

Via the enzyme Thrombin


What are anti-clotting mechanisms of the endothelium?

-Stops blood contacting collagen,
no platelet aggregation
- Produces prostacyclin and NO,
both inhibit platelet aggregation
- Produces tissue factor pathway inhibitor (TFPI),
stops thrombin production
- Expresses thrombomodulin,
binds thrombin & inactivates it
- Expresses heparin,
also inactivates thrombin
- Secretes tissue plasminogen activator (t-PA),
plasminogen > plasmin & digests clot