CVS Session 6 (Lecture 6.2)

Question 1

A fall in AP causes what to occur in non-essential tissues?

Answer 1

Increase flow resistance (ie decrease flow) to skin and gut via veno-constriction

Question 2

Describe what occurs to blood flow after eating a meal?

Answer 2

1) Increased activity/metabolism of the gut leads to local vasodilation.
2) TPR decreases
3) VP rises
4) AP falls

Question 3

Describe how after a meal is eaten, the CVS returns to normal

Answer 3

1) Rise in VP causes rise in CO
2) Fall in AP triggers rise in HR and CO
3) VP reduced by extra pumping of heart
4) AP raised
5) Demand met

Question 4

What occurs when the HR alone rises?

Answer 4

1) HR rises
2) Initially CO rise but TPR is same
3) CO increase decreases VP
4) SV falls (less blood returning to heart)
5) CO back to original

Question 5

What is the main problem with exercise on the CVS?

Answer 5

TPR falls so VP increases and AP decreases with no other changes this would be too big to cope with.

Overfilling of heart would occur which would push the ventricles onto flat part of Starling curve.

This would increase the hydrostatic pressure possibly causing pulmonary oedema as RV and LV not matched

Question 6

How does the CVS correct problems in exercise?

Answer 6

LV and RV beat at same rate
Overfilling of ventricles prevented by rise in HR occuring as exercise begins by the brain (in readiness for increasing VP) so SV is kept down

Question 7

What happens to CVP as we stand?

Answer 7

Falls due to gravity as superficial veins blood pools in legs

Question 8

What occurs to CO, AP and VP as we stand?

Answer 8

CO falls as less filling due to decreased CVP
AP falls
VP falls

Question 9

How is standing up dealt with by the CVS?

Answer 9

Baroreceptors detect fall in AP
Raise HR
TPR increased to defend AP

Question 10

What occurs in a haemorrhage? How do baroreceptors react? What does this cause?

Answer 10

Reduced blood vol. lowers VP (70% of blood in Veins)
CO falls
AP falls

Baroreceptors detect fall in AP so increase HR
TPR increased. Causes lowering of VP further making problem worse, only corrects AP by TPR increased

Question 11

How is haemorrhage dealt with to correct it?

Answer 11

Increase VP by veno-constriction via SMCs
Auto-transfusion - decreased VP increases ECF to flow into veins by hydrostatic pressure increasing fluid loss

If fluid loss is too much, saline solution can be given to boost volume

Question 12

What occurs to VP if in the long term, BP rises?

Answer 12

Kidney controls blood volume
If increased Na+, increased blood volume to dilute Na+.
VP increases

Question 13

What happens to CO and AP as BP rises long term? What does this lead to?

Answer 13

CO and AP increases
Forces more blood through tissues
Autoregulate and increase TPR
AP rises and is maintained = hypertension