pressure and flow in arteries and veins

Question 1

define venomotor tone:

Answer 1

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

This is regulated by sympathetic system which mobilises capacitance and increases end-diastolic volume

Question 2

define systolic and diastolic pressure in reference to korotkoff sounds:

Answer 2

systolic pressure - pressure at which a Korotkoff sound is first heard is the highest pressure in the artery and is recorded

diastolic pressure - the point at which the Korotkoff sounds disappear is the lowest pressure in the artery and is recorded.

Question 3

state the 5 external influences that affect the venous pressure and venous return/flow:

Answer 3

[1] Gravity

[2] Skeletal muscle pump

[3] Respiratory pump

[4] Venomotor tone

[5] Systemic filling pressure

Question 4

Describe the mechanics behind orthostatic (postural) hypotension:

Answer 4

Gravity causes venous distension (blood pooling) in the legs and that leads to:

→ a decrease in EDV & preload & SV & CO & MAP

Question 5

describe the relationship between blood flow velocity and total cross-sectional area:

Answer 5

The velocity of blood flow depends on the total cross-sectional area, they are inversely proportional.

Question 6

define the skeletal muscle pump:

Answer 6

it’s a rhythmic contraction that increases venous return and therefore EDV.

Significant in:

rhythmic vs. static exercise

deep vein thrombosis

Question 7

define the respiratory pump:

Answer 7

it’s the increased respiratory rate and depth which increases venous return and therefore EDV

Question 8

define the systemic filling phase:

Answer 8

it’s the pressure (20 - 5 mmHg) created by ventricles and transmitted through the vascular tree to the veins.

→ The major factor pushing the blood back to the right heart.

Question 9

describe the clotting process:

Answer 9

Fibrinogen becomes Fibrin via Thrombin enzyme

platelet plug forms and a fibrin clot.