deck_624681 Flashcards Preview

2 - CVS > deck_624681 > Flashcards

Flashcards in deck_624681 Deck (33):
1

At rest, what are the relative venous and arterial pressures?

Venous pressure = lowerArterial pressure = higher

2

What happens when TPR falls?

arterial pressure will fallvenous pressure will rise

3

What happens when TPR rises?

arterial pressure will risevenous pressure will fall

4

What happens when cardiac output rises?

arterial pressure will risevenous pressure will fall

5

What happens when cardiac output falls?

arterial pressure will fallvenous pressure will rise

6

What is demand-led pumping?

When the body needs more blood, it causes the heart to beat more in order to facilitate the need

7

What is stroke volume?

The difference between the end diastolic volume and the end systolic volume-- the amount of blood ejected by the heart

8

Describe ventricular filling

In diastole, the ventricles are connected to the veins so blood can enter. The ventricle fills until the walls stretch enough to produce an intra-ventricular pressure equal to venous pressure, due to the stretchiness of the walls.

9

What does the degree of ventricular filling depend on?

Venous Pressure (higher venous pressure, the more the heart fills in diastole)Stretchiness of the wallsIntraventricular pressure

10

What is the ventricular compliance curve?

The relationship between venous pressure and ventricular volume

11

What does Starlings Law of the Heart state?

If the myocardium is stretched before contracting it contracts harder-- the more the heart fills up, the more it contracts-- the harder the heart contracts the bigger the stroke volumeIncreased venous pressure causes an increase in the stroke volume

12

What is "pre-load"?

End diastolic stretch

13

What is "after-load"?

The force necessary to expel blood into the arteries

14

Define contractility

The slope of the curve showing the relationship between venous pressure and stroke volume

15

What is the force on contraction determined by?

End diastolic volumeContractility

16

What can have an effect on contractility?

Sympathetic activityNeurotransmittersHormonesDrugs which act on the myocardium

17

What affect does increasing the venous pressure have on the stroke volume?

Increases stroke volume -- more blood is entering the ventricles

18

What happens when it is easy to eject blood from the heart?

The volume output increases and there will be a small pressure increase in the arteries

19

What happens when it is difficult to eject blood from the heart?

The volume output decreases and the arterial pressure will increase

20

What will a fall in the TPR do to the stroke volume?

It will increase the stroke volume

21

How is the heart rate controlled?

Autonomic outflow is determined by signals from baroreceptors

22

Where are baroreceptors situated in the heart and what do they do?

Carotid sinus at the bifurcation of the common carotid artery and in the walls of the aorta. They detect changes in the arterial pressure

23

What section of the brain controls the heart?

Medulla oblongata

24

What is the effect on sympathetic and parasympathetic activity when the arterial pressure falls?

Increases heart rate by:-- reducing parasympathetic activity-- increasing sympathetic activityIncreases contractility by:-- increasing sympathetic activity

25

What does a rise in venous pressure do?

CARDIAC OUTPUT RISES-- increase stroke volume (Starlings Law) -- increase heart rate

26

What does a fall in arterial pressure do?

CARDIAC OUTPUT RISES-- increase stroke volume (sympathetic activity and direct effect)-- increase heart rate

27

What do baroreceptors ensure?

If arterial pressure falls, heart rate and stroke volume will both rise

28

How does the ANS affect cardiac output?

By changing heart rateBy changing contractility

29

What is the mean filling pressure?

The mean pressure in the arteries and veins when the heart stops

30

What happens to the arterial and venous pressure when the heart stops?

Arterial pressure fallsVenous pressure rises

31

Why at the top end of a starling curve, does the stroke volume fall with increasing pressure?

The elastic fibres in teh myocardium have been stretched past a certain point where they do not return to their original shape

32

What factors/illnesses increase the central venous pressure?

hypervolaemia, heart failure, tension pneumothorax, cardiac tamponade

33

What factors/illnesses decrease the central venous pressure?

hypovolaemia, shock