Cardiac Cycle and Cardiac Output

Question 1

Stimulated by nerves and is self excitable

Answer 1

Heart Muscle

Question 2

Self-excitable

Answer 2

Automaticity

Question 3

How long is the Cardiac Cycle on Average

Answer 3

0.8 seconds (assuming 75 bpm)

Question 4

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

Answer 4

Systole

Question 5

Relaxation of the heart muscle, heart is filling with blood, longest period of time, approx. 0.7 seconds

Answer 5

Diastole

Question 6

Explain Cardiac Cycle

Answer 6

1. Atrial Systole
2. Isovolumetric ventricular contraction
3. Ejection
4. Isovolumetric ventricular relaxation
5. Passive ventricular filling

Question 7

AV valves are open, semilunar valves closed

Answer 7

Atrial Systole

Question 8

• Atria relaxes
• Ventricular pressure rises resulting in closing AV valves

Answer 8

Ventricular Systole

Question 9

Ventricles are completely closed, pressure in the ventricles increases until the pressure is more than in the aorta/pulmonary trunks

Answer 9

Isovolumetric Ventricular Contraction Phase

Question 10

Opens semilunar valves

Answer 10

Ventricular Ejection Phase

Question 11

• Ventricles relax, ventricular pressure drops
• Back flow of blood in aorta and pulmonary trunk closes semilunar valves, dicrotic notch

Answer 11

Isovolumetric Ventricular Relaxation- Early Diastole

Question 12

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

Answer 12

Dicrotic Notch

Question 13

Cardiac Cycle Pressure of Right Atrium

Answer 13

0-4 mmHg

Question 14

Cardiac Cycle Pressure of Right Ventricle

Answer 14

25 systolic mmHg

Question 15

Cardiac Cycle Pressure of Pulmonary Arteries

Answer 15

25 systolic mmHg

Question 16

Cardiac Cycle Pressure of Left Atrium

Answer 16

8-10 mmHg

Question 17

Cardiac Cycle Pressure of Left Ventricle

Answer 17

120 systolic mmHg

Question 18

Cardiac Cycle Pressure of Aorta

Answer 18

120 systolic mmHg

Question 19

The amount of blood pumped by each ventricular in one minute, best indicator of adequate blood flow to the peripheral tissues

Answer 19

Cardiac Output

Question 20

Cardiac Output Equation

Answer 20

Stroke volume X Heart Rate

Question 21

The percentage of blood pumped out of a ventricle with each contraction (average = 50%-65%)

Answer 21

Ejection Fraction

Question 22

The volume of blood pumped out of the left ventricle of the heart during each systolic cardiac contraction

Answer 22

Stroke Volume

Question 23

Stroke Volume Equation

Answer 23

End diastolic volume (EDV) minus end systolic volume (ESV)

Question 24

Amount of blood collected in a ventricle during diastole

Answer 24

End Diastolic Volume (EDV)

Question 25

Amount of blood remaining in a ventricle after contraction

Answer 25

End Systolic Volume (ESV)

Question 26

Factors Affecting Stroke Volume

Answer 26

- Venous return - Preload - Afterload - Contractility

Question 27

Amount of venous blood returned to the heart

Answer 27

Venous Return

Question 28

Amount ventricles are stretched by contained blood

Answer 28

Preload

Question 29

Cardiac cell contractile force due to factors other than EDV

Answer 29

Contractility

Question 30

Back pressure exerted by blood in the large arteries leaving the heart

Answer 30

Afterload

Question 31

What increases Stroke Volume?

Answer 31

Slow heartbeat and exercise increases venous return, increasing SV

Question 32

What decreases Stroke Volume?

Answer 32

Blood loss and extremely rapid heart beat

Question 33

Frank Sterling Law

Answer 33

- "More blood in = more blood out" - The greater the volume of blood in the ventricle, the stronger the contraction - Both an increased filling time and increased blood volume = increased stroke volume

Question 34

Increase in Contractility come from:

Answer 34

- Increased sympathetic stimuli - Certain hormones - Ca2+ and some drugs

Question 35

Agents/factors that Decrease Contracility:

Answer 35

- Acidosis - Increased extracellular K+ - Beta blockers and calcium channel blockers (cardiac drugs)

Question 36

Signs and Symptoms of Decreased Cardiac Output

Answer 36

- Acute changes in BP - Acute changes in mental status - Cold, clammy skin - Colour changes in the skin and mucous membranes - Crackles (rales) - Dyspnea - Dysrhythmias - Orthopnea - Restlessness