C&b 057 & 059 Cardiodynamics And Cardiac Output In Normal & Failing Hearts I & Ii

Front 1

'The volume of blood pumped from one ventricle each minute' is known as the...

Back 1

Cardiac output

Front 2

What is cardiac output?

Back 2

The volume of blood pumped from one ventricle each minute

Front 3

Heart rate * stroke volume =

Back 3

Cardiac output

Front 4

How do you calculate cardiac output?

Back 4

Heart rate * Stroke volume

Front 5

What is the normal cardiac output in an adult human at rest?

Back 5

Between 4 and 7 l min^-1

Front 6

'The volume of blood returning to the heart from the vasculature *every minute*' defines...

Back 6

Venous return

Front 7

What is venous return?

Back 7

The volume of blood returning to the heart from the vasculature *every minute*

(Linked to cardiac output)

Front 8

Cardiac output and venous return are often, but not always, different. T/F

Back 8

False! Nearly always, and essential, that they are identical.

Front 9

Oxygen uptake (ml min^-1)/(CvO2 - CaO2) =

Back 9

Cardiac output (Q)

CvO2 --> Oxygen content of the blood in the pulmonary veins (same as that of normal arterial blood)

CaO2 --> The oxygen content of the blood in the pulmonary arteries (same as that of fully mixed venous blood)

Oxygen uptake AKA VO2?

Front 10

'The total uptake or release of a substance by an organ is equal to the blood flow through that organ multiplied by the difference between the arterial and venous concentrations of the substance ' Describes what principle?

Back 10

Fick's principle

Front 11

What is the most accurate method of measuring cardiac output in humans?

Back 11

The dy dilution method

Front 12

I (quantity of a dye) * 60/C (mean concentration in l) * t (time) =

Back 12

Cardiac output

Front 13

What is 'flow'?

Back 13

Volume, per unit of time

Front 14

'Volume, per unit of time' describes what measurement?

Back 14

Flow

Front 15

Give a dye that is can be used in the dye dilution method of calculating cardiac output.

Back 15

Indocyanine green

Front 16

What is a 'chronotropic effect'?

Back 16

Physiological changes in heart rate are known as 'chronotropic effects'

(i.e. a chronotropic effect is that which affects the heart rate)

Front 17

Physiological changes in heart rate are known as...

Back 17

'Chronotropic effects'

Front 18

The parasympathetic supply to the heart is the _____ nerve which, when activated, slows the heart (positive/negative chronotropy)

Back 18

Vagus nerve, negative chronotropy

Front 19

Stimulation of the sympathetic nerves increases the heart rate (positive/negative chronotropy)

Back 19

Positive chronotropy

Front 20

Definitions of bradycardia and tachycardia (wrt heart rate)

Back 20

Bradycardia < 60 bpm
Tachycardia > 100 bpm

Front 21

Do vagal nerve fibres (parasympathetic) synapse with postganglionic neurones just outside the heart, or in the heart itself?

Back 21

In the heart itself

Front 22

Which neurones secrete acetylcholine onto the cells of the SAN and AVN? What effect does this have?

Back 22

Postganglionic parasympathetic neurones do. Effect is to slow the heart rate

Vagal stimulation also reduces the rate of conduction of the cardiac impulse from the atria to the ventricles by decreasing the excitability of the AV bundle fibres

Front 23

The heart rate of a normal healthy adult at rest is about 70 bpm. A denervated heart beats around 100 times per minute. What does this indicate?

Back 23

It indicates that the vagus nerves exert a tonic inhibitory action on the SAN to slow the intrinsic heart rate

Important!

Front 24

Vagal stimulation increases the permeability of the nodal cells to potassium T/F

Back 24

T (important in realising why vagal stimulation lowers heart rate)

Front 25

Where do the sympathetic preganglionic nerves that supply the heart originate from?

Back 25

T1-T6 (mainly T1-T3)

Front 26

Which two factors regulate stroke volume?

Back 26

Intrinsic regulation [of force of contraction] (Determined by the degree of stretch of the myocardial fibres at the end of diastole)

Extrinsic regulation (determined by the activity of the autonomic nerves and circulating levels of the various hormones)

Front 27

What is 'preload' (wrt the heart)

Back 27

The tension in the heart muscle or chamber at the end of diastole, before the contraction.

Front 28

'The tension in the heart muscle or chamber at the end of diastole, before the contraction.' describes...

Back 28

Preload

Front 29

'The greater the volume of blood entering the heart during diastole (end-diastolic volume), the greater the volume of blood ejected during systolic contraction (stroke volume) and vice-versa' describes...

Back 29

The Frank-Starling law

Front 30

What does the Frank-Starling law state?

Back 30

'The greater the volume of blood entering the heart during diastole (end-diastolic volume), the greater the volume of blood ejected during systolic contraction (stroke volume) and vice-versa'

Front 31

The heart automatically adjusts its cardiac output to match its venous return

Back 31

Important point to understand!


0837250111

Front 32

Is the output of the left ventricle the same as the right ventricle?

Back 32

Yes, very important that they are. A 1% change can have a huge effect (pp280-281)

Front 33

The pressure in the aorta opposes the ejection of blood from the ventricles and represents the load against which the heart must pump the blood. This is known as the...

Back 33

Afterload

Front 34

What is 'afterload'?

Back 34

The pressure in the aorta opposes the ejection of blood from the ventricles and represents the load against which the heart must pump the blood. This is known as the afterload

Front 35

The pressure outside the heart is the _____________ pressure and is altered by breathing. During inspiration, intrathoracic pressure decreases and abdominal cavity pressure increases. This favours blood flow from abdominal veins to thoracic veins and so enhances the filling of the _____ _________

Back 35

Intrathoracic pressure

Right ventricle

Front 36

The pressure inside the right ventricle at the end of diastole is equal to the pressure in the superior *and* inferior vena cavae as they enter the heart T/F

Back 36

T (this is central venous pressure)

Front 37

What is 'central venous pressure'?

Back 37

The pressure of blood in the thoracic vena cava, near the right atrium of the heart (Same pressure as RV diastole)

Front 38

The pressure of blood in the thoracic vena cava, near the right atrium of the heart

Back 38

Central venous pressure

Front 39

Central venous pressure is an important factor in determining cardiac output T/F

Back 39

T (pp 280, fig 15.18)

Front 40

What does a change in the 'inotropic state' of the myocardium mean? I.e. What is an inotrope?

Back 40

An agent that alters the force or energy of muscular contractions.

Negatively inotropic agents weaken the force of muscular contractions. Positively inotropic agents increase the strength of muscular contraction.

Most commonly, the inotropic state is used in reference to various drugs that affect the strength of contraction of heart muscle (myocardial contractility). However, it can also refer to pathological conditions. For example, enlarged heart muscle (ventricular hypertrophy) can increase inotropic state, while dead heart muscle (myocardial infarction) can decrease it.

NB This is *independent* of the initial resting length of heart fibres

Front 41

'An agent that alters the force or energy of muscular contractions.'

Back 41

An inotrope

Front 42

Give an example of a bodily drug that has a positive inotropic effect on the heart

Back 42

Epinephrine
Norepinephrine (less so)