Cardiac Cycle

Question 1

How are cardiomyocytes different than skeletal muscle?

Answer 1

• Branched cells
• Lots of Mitochondria
• Electrically connected

Question 2

How does a cardiomyocyte action potential that stimulates muscle contraction work?

Answer 2

• Sodium enters, causing very rapid depolarization
• Potassium gates open to start initial repolarization
• Calcium gates open to cause the plateau and to cause contraction of muscle due to calcium induced calcium release in SR
• longer contraction of muscle due to Ca gate staying open (plateau)
• Calcium gates close, and repolarization occurs

Question 3

What are the Cardiac Cycle phases?

Answer 3

1) Atrial systole
2) Isovolumetric ventricular systole - no blood ejection, ventricular pressure increasing but valves closed
3) Ventricular systole - blood ejected from ventricles
4) Isovolumetric ventricular diastole - contraction of ventricles stopped, AV valves still closed
5) Late ventricular diastole - AV valves open, volume increasing

Question 4

What is the average number of APs and the average heart rate of a human?

Answer 4

AP - 100 per minute
Heart Rate
- 70/min for male
- 80/min for female