Feb 3 - Introduction to Cardiac Physiology

Question 1

What does the heart provide (in a general sense)?

Answer 1

The heart provides energy (potential energy or pressure) to maintain homeostasis

Question 2

What is the role of blood?

Answer 2

It moves oxygen, electrolytes, hormones to meet metabolic requirements.
Removal of waste (nitrogenous waste and carbon dioxide) that are the by-products of oxidation

Question 3

What is heart failure?

Answer 3

The heart muscle is unable to contract optimally to pump blood at a rate sufficient to meet the requirements of metabolizing organs.
It occurs when the heart can no longer move blood into the systemic (and/or pulmonary) circulation at a rate commensurate to the needs of metabolizing cells

Question 4

What is the incidence of heart disease?

Answer 4

Very high. Complications after the onset of heart failure remains a primary cause of death in Canada and in other developed nations

Question 5

What are symptoms of heart failure?

Answer 5

Congestion in the lungs results in breathlessness, the main symptom of left-sided heart failure. Symptoms of heart failure also include fatigue, swelling of the ankles and legs, enlargement of the liver

Question 6

What does heart failure cause breathlessness?

Answer 6

Because the left side of the heart starts to fail and as it does, blood is damming up in the right side because it’s not being pushed forward as it should be. So the fluid in the blood starts to push through into the tissues and the first tissue to be affected is the lung tissue (RALES)

Question 7

What is an MI?

Answer 7

Myocardial infarction. It is the loss of heart muscle due to the stoppage of blood flow

Question 8

What are common risk factors for heart failure?

Answer 8

Genetics, smoking, gender, diet, personality, stress, social stratum, alcoholism, etc.

Question 9

What are other causes of heart failure?

Answer 9

Essential hypertension (high blood pressure, especially diastolic pressure)
Diabetes (diabetic cardiomyopathy)
Idiopathic primary cardiomyopathy (is independent of CAD)
Viral infection of the heart (myocarditis)
Cardiac valve diseases and associated abnormalities (volume overload)

Question 10

The heart is an endocrine organ. Explain

Answer 10

It generates a host of hormones and cytokines that may impact on cardiac wound healing and/or growth (myocytes and nonmyocytes). List includes angiotensin II, IL-6, cardiotropin-1, FGF-2, TNF-alpha, etc.

Question 11

Name the three basic components of the cardiovascular system

Answer 11

The heart
The blood vessels
The blood

Question 12

Describe the heart

Answer 12

The heart is a pump that serves to pressurize the arterial tree. Blood moves from area of high pressure (LV) to regions of lower pressure (capillary beds). A major loss of blood pressure occurs at points of restriction within the arterial tree e.g., the arterioles

Question 13

Describe the blood vessels

Answer 13

The blood vessels serve as the delivery mechanisms for blood as it moves from heart and for its return to the heart. Vessels that carry blood away from the heart are the arteries, those carrying blood to the heart are veins (their naming is independent of state of blood oxygenation)

Question 14

Name the two circulatory systems of the body

Answer 14

Pulmonary circulation (which carries blood between the heart and the lungs)
Systemic circulation (which carries blood from the heart to all the peripheral organ systsms, e.g., brain, liver, skeletal muscles, skin, etc)

Question 15

Where does the heart sit? Why is there a misconception about where the heart sits?

Answer 15

The heart is located in mid-chest between the sternum and the vertebrae. The left side myth exists because the heart’s apex thumps on the chest wall on the left of the sternum, and it is concluded that the whole heart is located there

Question 16

Name the four chambers of the heart

Answer 16

The left and right atria (upper chambers)

The left and right ventricles (lower chambers)

Question 17

What is the role of the atria?

Answer 17

The atria are the receiving chambers of the heart (they receive blood from the pulmonary and circulatory circulation

Question 18

What is the role of the ventricles?

Answer 18

They pump the blood into the pulmonary and systemic circulation

Question 19

What separates the two halves of the heart?

Answer 19

The ventricular septum

Question 20

Describe systemic return

Answer 20

Deoxygenated blood enters the right atrium via the vena cava. It flows into the right ventricle, which pumps it out via the pulmonary trunk to the lungs, where it become oxygenated.

Question 21

Describe pulmonary return

Answer 21

Oxygenated blood enters the left atrium via the pulmonary veins. It flows into the left ventricle, which pumps it out via the aorta to the systemic circulation

Question 22

Which side of the heart pumps more blood per beat, the right or the left?

Answer 22

Both sides of the heart pump equal volumes of blood per unit time, but the left does so a high pressure (120 mmHg max systolic pressure), whereas the right side is low pressure circulation (25-30 mmHg max systolic pressure)

Question 23

What are cardiac valves?

Answer 23

These structures allow unidirectional flow of the blood for efficient pump action (they behave like one-way doors, open in response to pressure; backwards pressure forces the valves closed)

Question 24

How many valves are there?

Answer 24

4 different valves within the heart (2 atrioventricular valves, 2 semilunar valves)

Question 25

Name all four valves and what they separate

Answer 25

The tricuspid valve separates the right atrium from the right ventricle
The pulmonary valve separates the right ventricle from the pulmonary trunk
The mitral valve separates the left atrium from the left ventricle
The aortic valve separates the left ventricle from the aorta

Question 26

What makes up the heart wall?

Answer 26

The heart wall is composed of spirally arranged cardiac myocytes (muscle fibres). They form an electrical syncytium

Question 27

Describe the cardiac ultrastructure

Answer 27

They myocytes are connected at specific junctions (intercalated discs) that feature porosity and electrical connectivity. Populated by gap junctions (low resistance regions) and desmosomes (structural anchoring). The heart is made up of endocardium (endothelial tissue), myocardium (muscle) and epicardium (thin external membrane)

Question 28

How are electrical signals spread?

Answer 28

Electrical signals spread from cell to cell as one. Atria and ventricles are electrically isolated, but share specialized connections or “wiring”; behave as separate syncytiums

Question 29

What are some additional features unique to the heart?

Answer 29

The atria and the ventricles are separated by a non-conductive fibrous skeleton
Spiral arrangements of myocytes allow the heart to wring the blood from the ventricular cavities with each contraction
Unlike skeletal muscle, cardiac contractions uses all-or-non recruitment of muscle cells
A great deal of mitochondria are present in cardiac myocytes (dependant upon oxphos for epsilon production)

Question 30

What was the old dogma regarding cardiac cells?

Answer 30

No new heart cells are generated after birth (recently changed). Increase in heart size occurs due to increase in cell size

Question 31

What is the pericardial sac?

Answer 31

The pericardial sac is a double walled membrane that hold the heart in position. It is removed during cardiac transplantation. Resistance to movement is reduced by pericardial fluid, secreted by the membrane

Question 32

What does hemorrhage in the pericardial sac mean?

Answer 32

Hemorrhage into this space may compress the heart and lead to dysfunction due to insufficient filling