CS: Cardiac Cycle Flashcards Preview

Year 2: Human Anatomy and Physiology > CS: Cardiac Cycle > Flashcards

Flashcards in CS: Cardiac Cycle Deck (30)
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1
Q

Where is the heart located?

A

In the mediastinum in the thoracic cavity

2
Q

What is the mediastinum?

A

Space between the lungs

3
Q

How is the heart separated from the other structures in the mediastinum?

A

By a tough membrane known as the pericardium that sits in the pericardial cavity

4
Q

Where is the heart positioned in the lungs?

A

In the cardiac notch seen in the left lung

5
Q

What are the 4 valves that regulate the movement of blood through the heart?

A
  1. Right atrioventricular valve (tricuspid)
  2. Aortic semilunar valve
  3. Left atrioventricular valve (bicuspid)
  4. Pulmonary semilunar valve
6
Q

Describe the action of the right atrioventricular valve

A

Regulates the movement of blood between the right atrium and right ventricle. When the pressure in the right atrium is greater than the pressure in the right ventricle, the valve opens to allow the flow of blood into the ventricle.

7
Q

Describe the action of the aortic semilunar valve

A

Regulates the movement of blood between the right ventricle and the aorta for transport to the lungs. When the press in the right ventricle is greater than the pressure in the aorta, the valve opens to allow the flow of blood into the aorta.

8
Q

Describe the action of the left atrioventricular valve

A

Regulates the movement of blood between the left atrium and left ventricle. When the pressure in the left atrium is greater than the pressure in the left ventricle, the valve opens to allow the flow of blood into the ventricle.

9
Q

Describe the action of the pulmonary semilunar valve

A

Regulates the movement of blood between the left ventricle and the pulmonary artery for transport around the body. When the pressure in the left ventricle is greater than the pressure in pulmonary artery, the valve opens to allow the flow of blood into the pulmonary artery.

10
Q

What is a significant feature of valves that make them suited to their role?

A

They are unidirectional; they allow the flow of blood in one-direction through the heart to prevent back flow.

11
Q

How is blood flow controlled?

A

Blood flow is controlled by pressure changes which reflect the alternating contraction and relaxation of the heart. Blood moves along pressure gradients from high to low.

12
Q

What are the 7 stages of the cardiac cycle?

A
  1. Atrial systole
  2. Isovolumetric contraction
  3. Rapid ejection
  4. Reduced ejection
  5. Isovolumetric relaxation
  6. Rapid ventricular filling
  7. Reduced ventricular filling
13
Q

What happens during the atrial systole stage of the cardiac cycle?

A

Contraction of the atria follows depolarization, represented by the P wave of the ECG. As the atrial muscles contract from the superior portion of the atria toward the atrioventricular septum, atrial pressure rises (‘a’ wave) and blood is pumped into the ventricles through the open atrioventricular valves. Contraction of atria finishes before the ventricle contracts.

14
Q

What happens during the isovolumetric contraction stage of the cardiac cycle?

A

Interval between the atrioventricular valve closing and the opening of the semilunar valves. Atrioventricular valve closes when ventricular pressure exceeds atrial pressure; ventricle pressure increases, but volumes remains the same, to match the pressure in the aorta/pulmonary artery.
Ventricular systole follows the depolarization of the ventricles and is represented by the QRS complex in the ECG.

15
Q

What happens during the rapid ejection stage of the cardiac cycle?

A

Ventricle contraction causes the pressure in the ventricles to exceed the pressure in the aorta/ pulmonary artery, causing the semilunar valves to open.
Right ventricular contraction pushes atrioventricular valve into the atrium causing a ‘c’ wave.

16
Q

What happens during the reduced ejection phase of the cardiac cycle?

A

Ventricular pressure falls and blood flow decreases. Ventricular pressure less than aorta/ pulmonary artery pressure so blood begins to flow back, causing the semilunar valves to close.

17
Q

What happens during the isovolumetric relaxation stage of the cardiac cycle?

A

Ventricular pressure continues to fall and volume falls to minimum, ready to refill again with blood.

18
Q

What happens during the raid ventricular filling stage of the cardiac cycle?

A

Atria pressure exceeds ventricle pressure and the atrioventricular valves open. Ventricular volume increases rapidly as blood flows from atria.

19
Q

What happens during the reduced ventricular filling stage of the cardiac cycle?

A

Ventricular volume increases more slowly until nearly full

20
Q

What percentage of the ventricles are full at the start of atrial systole?

A

70-80% due to inflow during diastole

21
Q

What is the percentage contribution of the blood in the ventricles due to atrial contraction/ kick?

A

20-30%

22
Q

What is the pressure generated by the left ventricle greater than the pressure generated by the right ventricle?

A

Pressure generated by the left ventricle during ventricle systole (ie. rapid ejection) will be appreciably greater than the pressure generated by the right ventricle, as the blood needs to travel a greater distance from the pulmonary artery around the body. The volume of blood ejected will be the same, despite the differences in pressure, and this volume of blood is known as the stroke volume.

23
Q

What is stroke volume?

A

Volume of blood ejected by the ventricles each beat

24
Q

How is the heart supplied with oxygenated blood? How is deoxygenated blood removed from the heart?

A

The heart is supplied with oxygenated blood by the coronary arteries and deoxygenated blood is removed from the myocardium by coronary veins.

25
Q

What causes myocardial infarctions?

A

Myocardial infarctions are caused when there is a build up of plaque in the coronary arteries that repress the flow of blood to the heart cells. Macrophages ingest cholesterol and other lipids to form fatty streaks below the endothelial lining of coronary arteries, that eventually form a lipid core. Lipid core grows, with local smooth muscle cell division, to create a bulging plaque which develops hard calcified regions and fibrous collagen caps; if caps ruptures, it initiates a clot and causes a heart attack.

26
Q

What are heart muscle cells called?

A

Cardiomyocytes

27
Q

Describe the linkage of adjacent cardiomyocytes

A

The intercalated disc is a region where cardiomyocytes interlock and they contain desmosomes and gap junctionss. Desmosomes are anchors which prevent adjacent cells pulling apart during contractions. Gap junctions are ion permeable passages that allow stimulating impulses to move through cells.

28
Q

What are T-tubules?

A

Invagination of the sarcolemma that allow for the conduction of impulses to the deeper cell regions. T-tubules are only found at the Z discs.

29
Q

What is the sarcoplasmic reticulum?

A

Sarcoplasmic reticulum consists of a specialised SER that surrounds the myofibrils and stores calcium ions which are needed for muscle contractions.

30
Q

Describe the ‘sliding filament theory’

A

Cardiac myofibrils and contractile filaments (actin and myosin) slide past each other during contraction