Unit 1 - CV System The Heart PART F

Question 1

What are the 2 stages of the cardiac cycle?

Answer 1

1. Diastole

2. Systole

Question 2

Diastole

Answer 2

period of relaxation and filling.

Question 3

Systole

Answer 3

period of contraction and emptying.

Question 4

Cardiac Cycle

Answer 4

a single contraction-relaxation cycle

Question 5

What does 1 cardiac cycle involve?

Answer 5

systole + diastole of the atria and systole + diastole of the ventricles.

Question 6

Events (phases) of the cardiac cycle

Answer 6

1. The heart is at rest and filling – period of both atrial
   and ventricular diastole
2. Atrial contraction (atrial systole, end of ventricular diastole)
3. Isovolumetric contraction of ventricles (start of ventricular systole)
4. Ventricular ejection (ventricular systole, atrial diastole))
5. Isovolumetric relaxation of ventricles (start of ventricular diastole)

Question 7

1. The heart is at rest and filling – period of both atrial

and ventricular diastole

Answer 7

• Pressure in ventricles is LOWER than in atria, so AV valves are open and PASSIVE VENTRICULAR FILLING OCCURS – blood entering relaxed atria passes into the relaxed ventricles under its own pressure. (BF from atria –> ventricles)
• Ventricular volume INCREASES. (to accommodate the blood that’s entering)

Question 8

2. Atrial contraction (atrial systole, end of ventricular diastole)

Answer 8

• Contraction of the atria drives the last ~20% of atrial blood volume into the ventricles.
• The volume of blood now in each VENTRICLE is called the END- DIASTOLIC VOLUME (EDV)
• contains the LARGEST volume they will hold during the cycle
• maximal volume occurring @ the end of ventricular relaxation (diastole)

Question 9

The volume of blood now (phase 2) in each ventricle (contains the LARGEST volume they will hold during the cycle) is called the…

Answer 9

End-diastolic volume (EDV)

- maximal volume occurring @ the end of ventricular relaxation (diastole)

Question 10

3. Isovolumetric contraction of ventricles (start of ventricular systole)

Answer 10

• early ventricular contraction that occurs prior to a change in ventricular blood volume
• ventricular pressure quickly increases causing AV valves to CLOSE
• Turbulent blood flow caused by closure of the AV valves causes 1st HEART SOUND (“LUB”)
• but pressure is not yet high enough to causes ejection, so blood is unable to enter or exit the ventricles
• At the same time, atria are in diastole and filling.

Question 11

Isovolumetric contraction of ventricles meaning

Answer 11

• volume in the ventricle is not changing
• analogy: squeezing the tube with the cap on: HIGH pressure develops within the tube, but the toothpaste has nowhere to go

Question 12

Describe the left ventricular pressure-volume changes during 1 cardiac cycle

Answer 12

Represents pressure & volume changes in the left ventricle, which sends blood into the systemic circulation
- left side of the heart creates higher pressures than the right side, which sends blood to the shorter pulmonary circuit

Question 13

When heart contracts, the pressure _______ & blood flows ___ of the heart into areas of ______ pressure

Answer 13

CONTRACTS

OUT

LOWER

Question 14

4. Ventricular ejection (ventricular systole, atrial diastole))

Answer 14

• increasing pressure in ventricles forces semilunar valves open
• ~ 1⁄2 of ventricular blood volume enters aorta (and pulmonary arteries via the right ventricle).
• Volume of blood ejected from each ventricle = STROKE VOLUME
• Volume of blood left in each ventricle at the end of ejection = END SYSTOLIC VOLUME.

Question 15

Volume of blood ejected from each ventricle =

Answer 15

stroke volume

Question 16

Volume of blood left in each ventricle at the end of ejection =

Answer 16

End Systolic Volume

Question 17

5. Isovolumetric relaxation of ventricles (start of ventricular diastole)

Answer 17

• once ventricular pressure declines below aortic pressure, the semilunar valves close
• Turbulent blood flow caused by semilunar valve closure results in second heart sound (“dup”)
• ventricular tension decreases, and pressure falls, but still too high for AV valves to open, so no blood enters ventricles.

Question 18

Isovolumetric relaxation of ventricles meaning

Answer 18

called this b/c the volume of blood in the ventricles is not changing