cardiac structure conducting and cycle part 2

Question 1

When is coronary blood flow at its highest

Answer 1

when the ventricle is relaxing

Question 2

why is blood flow into the coronary arteries not good

Answer 2

the coronary arteries originating at the base of two of the cusps of the aortic valve causes this

Question 3

10. How is heart muscle supplied with oxygenated blood

Answer 3

via the coronary arteries and their branches

Question 4

11. What 2 things does narrowing or bloackage of the coronary arteries or their branches with atheroma or thrombus lead to?

Answer 4

• cardiac ischaemia (angina)
• myocardial infarction (heart attack)

Question 5

13. What does the left coronary artery supply with blood?

Answer 5

supplies Left side of heart

Question 6

14. Where is the coronary sinus located?

Answer 6

found in the inferior portion of the left atrioventricular groove

Question 7

15. Where does the coronary sinus receive blood from?

Answer 7

many tributary veins

Question 8

16. Where does the coronary sinus empty into? (think position and then the actual place)

Answer 8

posteromedial right atrium

Question 9

17. What is the largest cardiac venous structure?

Answer 9

coronary sinus

Question 10

18. What are the three distinct layers of the heart wall?

Answer 10

1. epicardium
2. Myocardium
3. endocardium

Question 11

19. Describe 1 feature of the epicardium layer of the heart wall

Answer 11

• Thin, external membrane that covers the heart

Question 12

20. Describe the 4 features of the myocardium

Answer 12

1. middle layer composed of cardiac muscle
2. makes up bulk of heart
3. consists of interlacing bundles of cardiac muscle fibres
4. arranged spirally around circumference of heart

Question 13

21. Describe the 2 features of the endocardium

Answer 13

1. Thin, inner layer
2. lined by the endothelium

Question 14

what is the endothelium unique to

Answer 14

unique to the circulatory system

Question 15

23. How is striated muscle shortened?

Answer 15

the thick filaments pulling the thin filaments towards the centre of the sarcomere, thereby making the H zone and I bands shorter

Question 16

what does striated mean

Answer 16

composed of repeating sarcomeres

Question 17

24. What does the shortening of the striated cardiac muscle depend on?

Answer 17

the calcium ion

Question 18

25. How long are cardiac myocytes

Answer 18

25-100µm

Question 19

what is the range of the amount of nuclei cardiac myocytes can have

Answer 19

can have between 1 and 4

Question 20

27. What percentage of cell volume do mitochondria take up in cardiac myocytes

Answer 20

30-40%

Question 21

28. How are cardiac myocytes linked together

Answer 21

by intercalated disks

Question 22

31. What 2 things do intercalated discs contain

Answer 22

contain:

• demosomes
• gap junctions

Question 23

32. What do demosomes help with?

Answer 23

helps hold the cardiac cells together against mechanical stress

Question 24

33. What do gap junctions allow?