3 - Mechanical Properties of the Heart 2

Question 1

What are the 2 main phases of the cardiac cycle/heart beat?

How may subphrases do they involve?

Answer 1

DIASTOLE - ventricular relaxation during which the ventricles fill with blood
(4 subphases)
SYSTOLE - ventricular contraction
(2 subphases)

Question 2

How is stroke volume calculated?

Answer 2

EDV-ESV

Question 3

What is end diastolic volume(EDV)?

Answer 3

the volume of the blood in the ventricles at the end of relaxation, when the volume of blood in the ventricles is at maximum capacity (just before systole)

Question 4

What is end systolic volume(ESV)?

Answer 4

the residual volume that remains in the ventricles after a complete contraction (and as much blood has been ejected as possible)

Question 5

What is diastole?

Answer 5

‘relaxation’, but also the filling of the ventricles

Question 6

What is the purpose of atrial systole?

Answer 6

to top off the volume of blood in the ventricles

Question 7

What are the two main features of isovolumic contraction?

Answer 7

• AV valves close

- ventricular pressure increases

Question 8

Between what point does isovolumic contraction take place ?

Answer 8

between the closing of the AV valves and the spending of the semi lunar valves

Question 9

When does isovolumic contraction end?

Answer 9

When the SL valves open and blood starts to be ejected from the heart

Question 10

What does the QRS wave on an ECG represent?

Answer 10

ventricular excitation/depolarisation

Question 11

What does the T wave represent on an ECG?

Answer 11

ventricular repolarisation (during reduced ejection phase)

Question 12

What is isovolumic relaxation?

Answer 12

(represents the beginning of diastole)
the pressure in the ventricles fall
SL valves close and the AV valves remain closed
atrial pressure increases as blood begins to fill them

Question 13

What does and ECG and a heart sound monitor look like during isovolumic relaxation?

Answer 13

ECG - no excitation

heart sounds - the 2nd heart sound (‘dub’) can be heard when the aortic and pulmonary valves close

Question 14

What changes to cause rapid ventricular filling?

Answer 14

AV valves open and blood flows from the atria to the ventricles
NOTE: this is a passive process

Question 15

What abnormal heart sound can be heard at rapid ventricular filling and what is it usually referred to?

Answer 15

S3 - referred to as ventricular gallop

Question 16

What is another name for the slow filling of the ventricles during reduced ventricular filling?

Answer 16

diastasis

Question 17

overall, when are the sound detected by a stethoscope made?

Answer 17

when the valves close during isovolumic contraction and relaxation

Question 18

What is the average heart rate?

Answer 18

70-72

60-100

Question 19

Clinically, what are pressure-volume loops useful for?

Answer 19

for cardiac transplants - to assess how ‘good’ the heart is functionally

Question 20

What changes occur during exercise?

Answer 20

• contractility increases due to an increase in sympathetic activity
  THIS MEANS THAT POINT 3 AND 4 ARE PUSHED FURTHER TO THE LEFT
• EDV increases (ESV decreases, thus ejection fraction increases) - changes in peripheral circulation (e.g. venoconstriction and muscle pump) means that more blood is returned to the heart
  THIS MEANS THAT POINT 1 AND 2 ARE PUSHED FURTHER RIGHT

this means there is an overall increase in stroke volume