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Cardiovascular System > Session 6 - Responses of the whole system > Flashcards

Session 6 - Responses of the whole system Flashcards

1
Q

At a constant CO, falls in TPR do what to venous and arterial pressure?

A
  • Decrease arterial pressure

- Increase venous pressure

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2
Q

At a constant TPR, increasing CO has what effect on venous and arterial pressure?

A
  • Increases arterial pressure

- Decreases venous pressure

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3
Q

Increasing venous pressure increases…

A

-CO

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4
Q

Decreasing arterial pressure increases…

A

…CO

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5
Q

How do falls in arterial pressure effect the bloodflow to the gut and skin, and the veins? What is the benefit of this?

A
  • Increases the flow resistance to divert blood from non-important tissues
  • Venoconstriction
  • Short-term defence to a decrease in AP as will counteract it
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6
Q

What happens if HR increases with no other change?

A

-Increased HR = increased CO -> increased AP and decreased VP -> SV falls (diastole shorter and VP decreased) -> CO decreased

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7
Q

How is it ensured that the left and right stroke volumes match?

A

-Starlings law, if the right pumps more the left fills more

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8
Q

What is the consequence of right heart stroke volume being greater than the left?

A

-Pulmonary oedema as blood becomes congested in the lungs increasing hydrostatic pressure -> forces fluid out into interstitial space =oedema

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9
Q

In what situation would the right heart SV be higher then the left?

A

-Anything which comprimises LV filling or ejection eg LHF

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10
Q

How is an extremely high VP and thus overfilling of the RH avoided during exercise?

A

-Increase in HR before VP starts to rise as this shortens the length of diastole and avoids overfilling

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11
Q

What transient problem is faced during standing up?

A

-Both venous pressure and arterial pressure decrease

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12
Q

What causes both venous pressure and arterial pressure to decrease transiently when standing up?

A

-Blood pools in the superficial veins of the legs -> reduction in central venous pressure -> reduced filling of RV -> decrease CO-> TPR remains the same so decrease in AP

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13
Q

What is the normal control mechanism of decreased AP?

A

-Increase CO through baroreceptors

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14
Q

Why would increasing CO to counteract the decreasing AP when standing not work?

A

-Venous pressure is already low -> would exacerbate the problem

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15
Q

How is the decrease in VP and AP on standing controlled?

A

-Bloodflow to the gut and skin shut down for a transient time to increase TPR which counteracts the decrease in CO and increases AP

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16
Q

Why does bloodflow to the gut and skin only need to be shut down temporarily on standing and not throughout the duration?

A

-When standing muscle pumping aids venous return to the heart so no need for decreased bloodflow to gut and skin

17
Q

What is postural hypotension?

A

-A transient fall in blood pressure associated with moving to a vertical position

18
Q

What can cause postural hypotension?

A
  • Reflex of shutting down bloodflow to gut and skin dont work
  • If VP is already low
  • Fluid imbalance
  • Problems with ANS adjusting TPR
19
Q

What occurs to the volumes, pressures, CO and TPR during haemorrhage?

A

Less blood in veins -> decreased VP -> decreases end diastolic volume -> decreased SV -> decreased CO whilst TPR is the same -> decreased AP-> detected by baroreceptors -> increases HR -> more blood removed from veins -> VP drops more-> heart fills less -> signals to increase CO but heart filing inadequately so low force of contraction -> increase in TPR and blood diverted from skin and gut -> helps AP a little but lowers VP -> cycles

20
Q

How can the CVS remain uncomprimised when loosing upto 1-1.5L of blood?

A
  • Venoconstriction -> smooth muscle in veins normally relaxed -> contracts and helps venous ret5urn, increasing venous pressure
  • Autotransfusion
21
Q

What is autotransfusion?

A

-Tissue fluid moves from the interstitial space into the vessels due to low pressure in vessels

22
Q

What is the first line of treatment in haemorrhage?

A

-Infusion of fluids (doesnt have to be RBCs at this stage just water salts and protein -> need to increase volume!!)

23
Q

What controls blood volume in the long term?

A

-The kidneys through controlling Na/water reabsorption

24
Q

What is the result of long term increase in blood volume on pressures, CO and TPR?

A

-Increased venous pressure -> increases CO (TPR unchanged as bodys need for blood unchanged)-> Increases arterial pressure -> Increased bloodflow to tissues -> vasodilator metabolites washed away-> TPR increases -> AP rises further (self-sustaining system)

25
Q

What is average arterial pressure related to?

A

-Blood volume

26
Q

What is the consequence of prolonged increased TPR in hypertension?

A

-Hypertrophy of smooth muscle in vessels leading to further vasoconstriction

27
Q

TPR is inversely proportional to…

A

…the body’s need for blood

Cardiovascular System (19 decks)

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