SESSION 2 LECTURE 2: Control Of Cardiac Output

Question 1

Define the term afterload

Answer 1

The load the heart must eject blood against

Question 2

Define the term preload

Answer 2

The amount the ventricles are stretched (filled) in diastole

Question 3

Where does the biggest drop hence giving the greatest resistance in systemic pressure occur?

Answer 3

Arterioles

-constriction of the arterioles increases the resistance

Question 4

Effect of increasing the Total Peripheral Resistance(TPR) and Cardiac Output (CO)remains unchanged

Answer 4

• Arterial pressure will increase

- Venous pressure will fall

Question 5

Effect of decreasing the total peripheral resistance and CO remains unchanged

Answer 5

• Arterial pressure will fall

- Venous pressure will increase

Question 6

Effect of increasing the cardiac output and TPR remains unchanged

Answer 6

• Arterial pressure will increase

- Venous pressure will fall

Question 7

Effect of decreasing the cardiac output and TPR remains unchanged

Answer 7

• Arterial pressure will fall

- Venous pressure will increase

Question 8

2 ways in which the heart responds to changes in CVP (central venous pressure) and ABP(arterial blood pressure)

Answer 8

• Intrinsic factors (mechanical)

- Extrinsic factors (neurohumoral)

Question 9

State the intrinsic factors in which the heart responds to changes in CVP (central venous pressure) and ABP(arterial blood pressure)

Answer 9

• increased stroke volume due to a rise in venous pressure and fall in TPR
• Increased filling of the heart

Question 10

Define the term contractility

Answer 10

The force of contraction for a given fibre length

Question 11

State the extrinsic factors in which the heart responds to changes in CVP (central venous pressure) and ABP(arterial blood pressure)

Answer 11

• Sympathetic stimulation
• Circulating Adrenaline

both increases contractility

Question 12

Define cardiac output

Answer 12

The volume of blood ejected from the ventricles per min

Question 13

Factors determining cardiac output

Answer 13

-How hard it contracts
determined by the end-diastolic volume and contractility

-how hard it is to eject blood
determined by aortic impedance

Question 14

Explain the Frank-Starling Law of the Heart

Answer 14

• Intrinsic control mechanisms ensure that the output of the left and right ventricles match
• the more the heart fills, the harder it contracts up to a limit as it is stretched more
• the harder the heart contracts, the bigger the stroke volume
• an increase in venous pressure will fill the heart more