Feb 3 - Introduction to Cardiac Physiology Flashcards
What does the heart provide (in a general sense)?
The heart provides energy (potential energy or pressure) to maintain homeostasis
What is the role of blood?
It moves oxygen, electrolytes, hormones to meet metabolic requirements.
Removal of waste (nitrogenous waste and carbon dioxide) that are the by-products of oxidation
What is heart failure?
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
What is the incidence of heart disease?
Very high. Complications after the onset of heart failure remains a primary cause of death in Canada and in other developed nations
What are symptoms of heart failure?
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
What does heart failure cause breathlessness?
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)
What is an MI?
Myocardial infarction. It is the loss of heart muscle due to the stoppage of blood flow
What are common risk factors for heart failure?
Genetics, smoking, gender, diet, personality, stress, social stratum, alcoholism, etc.
What are other causes of heart failure?
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)
The heart is an endocrine organ. Explain
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.
Name the three basic components of the cardiovascular system
The heart
The blood vessels
The blood
Describe the heart
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
Describe the blood vessels
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)
Name the two circulatory systems of the body
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)
Where does the heart sit? Why is there a misconception about where the heart sits?
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
Name the four chambers of the heart
The left and right atria (upper chambers)
The left and right ventricles (lower chambers)
What is the role of the atria?
The atria are the receiving chambers of the heart (they receive blood from the pulmonary and circulatory circulation
What is the role of the ventricles?
They pump the blood into the pulmonary and systemic circulation
What separates the two halves of the heart?
The ventricular septum
Describe systemic return
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.
Describe pulmonary return
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
Which side of the heart pumps more blood per beat, the right or the left?
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)
What are cardiac valves?
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)
How many valves are there?
4 different valves within the heart (2 atrioventricular valves, 2 semilunar valves)
Name all four valves and what they separate
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
What makes up the heart wall?
The heart wall is composed of spirally arranged cardiac myocytes (muscle fibres). They form an electrical syncytium
Describe the cardiac ultrastructure
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)
How are electrical signals spread?
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
What are some additional features unique to the heart?
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)
What was the old dogma regarding cardiac cells?
No new heart cells are generated after birth (recently changed). Increase in heart size occurs due to increase in cell size
What is the pericardial sac?
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
What does hemorrhage in the pericardial sac mean?
Hemorrhage into this space may compress the heart and lead to dysfunction due to insufficient filling
