Cardiac Cycle And Output Flashcards

1
Q

Automaticity

A

Heart muscle is stimulated by nerves and is self excitable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How long is the Cardiac cycle?

A

0.8 seconds (75bpm)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the cardiac cycle?

A

Period between the start of one heart beat to the beginning of the next. Systole and diastole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Systole

A

Contraction of heart muscle, blood is pumped into the arteries, approx. 0.1 seconds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Diastole

A

Relaxation of heart muscle, heart filling with blood, approx. 0.7 seconds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the phases of the cardiac cycle?

A

Atrial systole > isovolumetric ventricular contraction > ejection > isovolumetric ventricular relaxation > passive ventricular filling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Atrial systole

A

Heart blood pressure is low as blood enters the atria from the pulmonary and systemic circulations and then flows into the ventricles. Approx. 80%, atrial kick forces the remaining 20% (AV valves open, semilunar valves closed)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Ventricular systole

A

Atria relaxes, ventricular pressures rise resulting in AV valves closing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Isovolumetric ventricular contraction

A

The ventricles are completely closed chambers, and pressure in the ventricles increase until the pressure is more than in the aorta/pulmonary trunks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Ventricular ejection

A

Opens semilunar valves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Isovolumetric ventricular relaxation

A

Ventricles relax, ventricular pressure drops. Backflow of blood in aorta and pulmonary trunk closes semilunar valves (dicrotic notch)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Dicrotic notch

A

Brief rise in aortic pressure caused by backflow of blood rebounding off semilunar valves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Passive ventricular filling

A

Blood has accumulated in the atria behind the closed atrioventricular valves passes rapidly into the ventricles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the cardiac cycle pressures?

A

Right atrium: 0-4 mmHg, right ventricle: 25 systolic mmHg, pulmonary arteries: 25 systolic mmHg, left atrium: 8-10mmHg, left ventricle: 120 systolic mmHg, aorta: 120 systolic mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is cardiac output (CO)?

A

The amount of blood pumped by each ventricle in one minute, it is the best indicator of adequate blood flow to the peripheral tissues. Product of heart rate (HR) and stroke volume (SV)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Heart rate

A

Number of beats per minute

17
Q

Stroke volume

A

Amount of blood pumped out by a ventricle with each beat

18
Q

Cardiac reserve

A

Difference between resting and maximal cardiac output

19
Q

The pump at work cardiac output conversion

20
Q

Ejection fraction

A

The percentage of blood pumped out of a ventricle with each contraction. Used as a measure of ventricular function.

21
Q

What is the normal ejection fraction?

A

Between 50% and 65%

22
Q

Regulation of stroke volume

A

SV- end diastolic volume (EDV) minus end systolic volume (ESV)

23
Q

End diastolic volume

A

Amount of blood collected in a ventricle during diastole

24
Q

End systolic volume

A

Amount of blood remaining in a ventricle after contraction

25
What are the 4 factors affecting stroke volume?
Venous return, preload, contractility, afterload
26
Venous return
Amount of venous blood returned to the heart
27
Preload
Amount ventricles are stretched by contained blood
28
Contractility
Cardiac cell contractile force due to factors other than EDV
29
Afterload
Back pressure exerted by blood in the large arteries leaving the heart
30
Critical factor controlling stroke volume?
Preload or degree of stretch of the cardiac muscle cells before they contract
31
What increases stroke volume?
Slow heart beat and exercise increase venous return to the heart
32
What decreases stroke volume?
Blood loss and extremely rapid heart beat
33
Frank-Starling Law
More blood in more blood out. The greater the volume of blood in the ventricle, the stronger the contraction. Both increased filling time and increase blood volume = increased SV
34
What are the Extrinsic factors influencing stroke volume that increase contractility?
Increased sympathetic stimuli, certain hormones, Ca2+ and some drugs
35
What are the extrinsic factors influencing stroke volume that decrease contractility?
Acidosis, increased extra cellular K+, beta blockers and calcium channel blockers
36
Signs and symptoms of decreased cardiac output?
Acute changes in BP, acute changes in mental status, cold/clammy skin, colour changes in the skin and mucous membranes, crackles (rales), dyspnea, dysrhythmias, fatigue, orthopnea, restlessness