Lecture 14 - Cardiac Output • Starling's Law

Question 1

What is cardiac output

Answer 1

The volume of blood pumped by each ventricle per minute

Question 2

What is cardiac output the product of

Answer 2

The heart rate and the stroke volume

Question 3

What is the stroke volume

Answer 3

The volume of blood ejected per contraction

Question 4

What is cardiac output controlled according to

Answer 4

Physiological requirements via control of the heart rate and stroke volume

Question 5

What does intrinsic control of SV depend on

Answer 5

The direct correlation between end diastolic volume (EDV) and SV

Question 6

What does intrinsic control depend on

Answer 6

The length-tension relationship of cardiac muscle

Question 7

What causes the difference in length of muscle fibres before contraction

Answer 7

The degree of diastolic filling

Question 8

What does an increased EDV cause

Answer 8

The heart to be stretched more

Question 9

What does an increase in length of the muscle fibres cause

Answer 9

A greater force on the subsequence cardiac contraction, and thus in a greater stroke volume

Question 10

What is the intrinsic relationship between EDV and SV known as

Answer 10

The Frank-Starling Law of the heart

Question 11

What is the extent of filling known as

Answer 11

Preload

Question 12

What is preload

Answer 12

The workload imposed on the heart before contraction begins

Question 13

What is the arterial blood pressure known as

Answer 13

The afterload

Question 14

What is afterload

Answer 14

The workload imposed on the heart after contraction has begun

Question 15

How can the heart compensate an increased afterload

Answer 15

By enlarging

Question 16

What may cause a heart to not be able to compensate with an increased afterload

Answer 16

A diseased or weakened heart

Question 17

Why is the contractile state of the myocardium important

Answer 17

For determining the severity or progress of valve dysfunction

Question 18

What is the simplest measurement of myocardial contractility

Answer 18

To use the analysis of the pressure waveform during the isometric contraction phase

Question 19

What is the advantage of using the analysis of the pressure waveform during the isometric contraction phase for myocardial contractility

Answer 19

It is independent of afterload

Question 20

What it is used as a global assessment of myocardial contractility

Answer 20

Max dP/dT (the maximum rate of rise of pressure)

Question 21

What is the cellular basis of the Frank-Starling mechanism

Answer 21

Greater initial length increases the sensitivity of the contractile proteins to Ca2+

Question 22

What may increased initial length also cause

Answer 22

The increase of Ca2+ release from the sarcoplasmic reticulum

Question 23

What effect does sympathetic stimulation have on the heart

Answer 23

It increases contractility

Question 24

What extrinsic control occurs on the SV

Answer 24

Sympathetic stimulation and adrenaline

Question 25

What triggers increased Ca2+ entry

Answer 25

Noradrenaline and adrenaline

Question 26

What does an increase in Ca2+ during the plateau phase of the action potential cause

Answer 26

It enhances the intracellular calcium store

Question 27

What is Ca2+ required for

Answer 27

Excitation-contraction coupling in cardiac muscle cells

Question 28

How is the rate of relaxation increased in cardiac cells

Answer 28

By stimulating Ca2+ pumps

Question 29

What are the positive conotropic actions of noradrenalline

Answer 29

The duration of systole is decreased, the ventricular pressure wave rises faster, it has a higher peak tension, the end diastolic pressure is decreased and there is a decrease in the duration of the wave.