Lecture 25 Mechanical events of the cardiac cycle

Question 1

Describe the events of the cardiac cycle, including pressure and volume changes in the left ventricle correlated to EKG during systole and diastole

Question 2

Define measures of cardiac function, including cardiac output, end - diastolic volume, end systolic volume, ejection fraction and stroke volume

Answer 2

cardiac output- is how much blood is being pushed forward after a filling phase in the ventricles

End Diastolic volume(EDV)- is how much volume is at the end of the ventricular diastole, so after the atria pumps blood down into the ventricle

End Systolic Volume (EDS)- is the volume of blood at the end of systole, so after the ventricles have pumped blood into the arteries.

Ejection fraction(EF) - is the proportion of blood volume ejected by each ventricle with each contraction.
EF=Stroke volume(SV)/EDV

Stroke Volume(SV)- blood ejected by each ventricle with each contraction.
SV=EDV-ESV

Question 3

Describe two valve defects that can lead to abnormal heart sounds

Answer 3

-Stenotic valve
- Does not open completely due to stiffness and narrowing
- When blood is forced through a stenotic valve, there is turbulence which results in an abnormal sound resembling whistling

-Insufficient valves
- Is scarred, resulting in poor apposition of the leaflets and preventing complete closure of the valve
- allows blood to flow backward (regurgitation)
-Blood flowing backward collides with forward moving blood, producing a swishing sound

Question 4

What are the key roles of the Circulatory system?

Answer 4

1.To transport nutrients to tissues (O2 & glucose, lipids, amino acids)
2. To remove metabolic by-products from tissue (CO2 & Hydrogen ions)
3. To transport hormones so they can exert their effects on target tissues

Question 5

What are the main components of the Circulatory system?

Answer 5

1.Carrier for transport of nutrients/waste/hormone, i.e. blood
2. A system of pipes for the carrier to efficiently move through, i.e. the blood vessels
3. A pump to drive the movement of the carrier through the pipes i.e. the heart

Question 6

What are the key design criteria of the circulatory system?

Answer 6

1. Each region of the body must be adequately perfused to meet its specific demands
2. the system must be able to rapidly adapt to changes in demand both globally (i.e. throughout the body) and locally (i.e. in specific tissues)
3. The system must be able to repair itself, or failing that, to adapt to impairments in order to allow the organism to survive

Question 7

What is the systole phase in the cardiac cycle?

Answer 7

-Contraction of the heart and ejection of the blood
-occurs due to depolarization of the cardiac muscle

Question 8

What is the Diastole phase in the cardiac cycle?

Answer 8

-Relaxation of the heart and refilling of the blood
-occurs due to repolarization of the cardiac muscle

Question 9

revise the Wiggers diagram on the slides.

Question 10

What do the P wave, QRS complex and T wave represent on the EKG

Answer 10

P wave- Atria become depolarized
QRS complex- Ventricles become depolarized
T wave- Ventricles become repolarized