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2 - Sarah's CVS > Control of Cardiac Output -- 6.1 > Flashcards

Control of Cardiac Output -- 6.1 Flashcards

1
Q

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

A

Venous pressure = lower

Arterial pressure = higher

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2
Q

What happens when TPR falls?

A

arterial pressure will fall

venous pressure will rise

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3
Q

What happens when TPR rises?

A

arterial pressure will rise

venous pressure will fall

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4
Q

What happens when cardiac output rises?

A

arterial pressure will rise

venous pressure will fall

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5
Q

What happens when cardiac output falls?

A

arterial pressure will fall

venous pressure will rise

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6
Q

What is demand-led pumping?

A

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

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7
Q

What is stroke volume?

A

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

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8
Q

Describe ventricular filling

A

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.

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9
Q

What does the degree of ventricular filling depend on?

A

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

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10
Q

What is the ventricular compliance curve?

A

The relationship between venous pressure and ventricular volume

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11
Q

What does Starlings Law of the Heart state?

A

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 volume

Increased venous pressure causes an increase in the stroke volume

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12
Q

What is “pre-load”?

A

End diastolic stretch

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13
Q

What is “after-load”?

A

The force necessary to expel blood into the arteries

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14
Q

Define contractility

A

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

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15
Q

What is the force on contraction determined by?

A

End diastolic volume

Contractility

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16
Q

What can have an effect on contractility?

A

Sympathetic activity
Neurotransmitters
Hormones
Drugs which act on the myocardium

17
Q

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

A

Increases stroke volume

– more blood is entering the ventricles

18
Q

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

A

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

19
Q

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

A

The volume output decreases and the arterial pressure will increase

20
Q

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

A

It will increase the stroke volume

21
Q

How is the heart rate controlled?

A

Autonomic outflow is determined by signals from baroreceptors

22
Q

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

A

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
Q

What section of the brain controls the heart?

A

Medulla oblongata

24
Q

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

A 
Increases heart rate by:
-- reducing parasympathetic activity
-- increasing sympathetic activity
Increases contractility by:
-- increasing sympathetic activity
25
Q

What does a rise in venous pressure do?

A

CARDIAC OUTPUT RISES

    • increase stroke volume (Starlings Law)
    • increase heart rate
26
Q

What does a fall in arterial pressure do?

A

CARDIAC OUTPUT RISES

    • increase stroke volume (sympathetic activity and direct effect)
    • increase heart rate
27
Q

What do baroreceptors ensure?

A

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

28
Q

How does the ANS affect cardiac output?

A

By changing heart rate

By changing contractility

29
Q

What is the mean filling pressure?

A

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

30
Q

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

A

Arterial pressure falls

Venous pressure rises

31
Q

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

A

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

32
Q

What factors/illnesses increase the central venous pressure?

A

hypervolaemia, heart failure, tension pneumothorax, cardiac tamponade

33
Q

What factors/illnesses decrease the central venous pressure?

A

hypovolaemia, shock

2 - Sarah's CVS (13 decks)

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