Cardiovascular System Flashcards
Who described the heart as the seat of intelligence? What year?
Aristotle
4th century BC
What was Aristotle’s contribution to the cardiovascular system
In the 4th century BC, Aristotle described the heart as the most important organ of the body and as the seat of intelligence, motion & sensation.
Who described the heart as the organ most closely related to the soul? When?
Galen, 2nd century AD in his treatise “Usefulness of the parts of the body”
What was Galen’s contribution to the cardiovascular system?
In the 2nd century AD, Galen reaffirmed in his treatise, Usefulness of the parts of the body that the heart was the source of the body’s innate heat and the organ most closely related to the soul.
What’s the contribution of Avicenna?
11th century AD, in his book Canon of medicine, he integrated Aristotle’s ideas with his largely galenic physiology saying “The heart is the root of all faculties and gives the faculties of nutrition, life, apprehension and movement to several other members”
Whose treatise gave a viable alternative to Galenic physiology?
William Harvey’s treatise “On the circulation of blood” in 1628 17th century AD
How are chemicals or other substances carried by the blood exchanged?
By diffusion
Define cardiac cycle
Cardiac cycle refers to the sequence of events that take place within the heart from the beginning of one heartbeat to the other.
It embraces the repeated patterns of contractions and relaxations of the cardiac chambers.
What is heart rate?
Frequency of cardiac cycles.
Mention the electromechanical events in cardiac cycle
- Electrical changes: Depolarization or Repolarization
- Volume changes: Increase or decrease
- Pressure changes: Increase or decrease
- Myocardial wall changes (atria & ventricles): Contraction or relaxation
- Valvular changes: Open or close
- Blood flow
- Heart sounds
What is the ventricular diastole?
Refers to the ventricular relaxation phase
What marks the beginning of ventricular systole?
Closing of atrioventricular valves
What is ventricular systole?
This refers to the phase of ventricular contraction
Events occurring during ventricular systole include?
- Isovolumetric contraction
- Rapid ventricular ejection
- Slow ventricular ejection
What are the semilunar valves?
Collective name for the outflow valves in the heart i.e aortic valve & pulmonary valve
What marks the end of the ventricular systole?
The closing of the semilunar valves
Explain the events that take place in the ventricular systole
- Isovolumetric contraction
In IVC, the volume of the ventricle remains the same. All the valves are closed. Contraction of the ventricle raises the intraventricular pressure (the contraction of the ventricle is triggered by the closing of the atrioventricular valves).
When the intraventricular pressure is higher than the pressure of the great vessels, the aorta & pulmonary trunk for the left and right ventricles respectively, the semilunar valves open, starting the phase of ventricular ejection.
Rapid ventricular ejection
When the intraventricular pressure is higher than that of the aorta & pulmonary trunk, the semilunar valves open. This leads to the rapid ejection of blood.
Slow ventricular ejection
As the pressure of the ventricles starts to equal the pressure of the great vessels, ejection rate slows down. There’s also a fall in intraventricular pressure (protodiastole). As the intraventricular pressure almost falls below the pressure of the great vessels, the semilunar valves close, marking the end of the ventricular systole. The closing of the valve is associated with the second heart sound.
Note: The semilunar valves close inorder to prevent backflow of blood into the ventricle. Also, during ventricular systole, atrioventricular valves are tightly shut due to the contraction of the ventricle.
What is ventricular diastole?
This refers to the phase of ventricular relaxation
What marks the start of the ventricular diastole?
Closure of the semilunar valves
What marks the end of the ventricular diastole?
The closing of the atrioventricular valves
What is a normal diastolic function?
This is clinically described as the capacity of the left ventricle to receive a filling volume and its ability to guarantee adequate stroke volume without elevating the pressure.
Stroke volume?
Volume of blood pumped out of left ventricle of the heart during each systolic cardiac contraction
Mention all the phases and subphases of cardiac cycle
Ventricular systole
- Isovolumetric contraction
- Rapid ventricular ejection
*Slow ventricular ejection
Ventricular diastole
- Isovolumetric relaxation
- Rapid passive filling
- Diastasis (slow filling)
- Rapid active filling (atrial contraction)
Events that occur during the ventricular diastole
Isovolumetric relaxation
All valves are closed
Volume doesn’t change
Ventricles relax
No blood flow
Intraventricular pressure reduces (it already started dropping since the ventricular systolic phase)
But when the intraventricular pressure falls below atrial pressure (meaning atrial pressure is more than ventricular pressure, duh), atrioventricular valves open to pave way for the next phase—rapid passive filling
Rapid passive filling
The mitrial valve on the left side opens as well as the tricuspid valve on the right side opens. Blood rapidly flows from atria to ventricle due to diff in pressure gradient (duh).
Rapid passive filling is responsible for 75-80% of the ventricular filling
The third heart sound (S3) occurs during this phase
Diastasis (slow filling)
This refers to the slow ventricular filling following rapid passive filling. This phase occurs when atria & ventricular pressure are almost equal.
This period is not always constant, it may be absent in a very rapid heart rate
Rapid active filling
This phase refers to the period of atrial systole. It contributes to 20-25% of the ventricular filling. The fourth heart sound (S4) occurs in this phase.
It ends at the closure of the atrioventricular valves (S1 sound occurs here) paving way for the ventricular systole phase.
The rapid active filling phase depends on?
- Ventricular compliance
- Pericardial resistance
- Atrial force
- Atrioventricular synchronicity
Duration of cardiac cycle?
0.8s
Which of the ventricular phases is longer?
Ventricular diastole because the ventricle is larger than the atrium, thus takes longer to fill. It takes about ⅔ the cycle duration
Average duration of ventricular diastole of the cardiac cycle?
≈0.5s
Average duration of ventricular systole of the cardiac cycle?
≈0.3s
What’s the relationship between the heart rate and the duration of diastole?
Duration of diastole is inversely proportional to the heart rate.
The cardiovascular system in humans is an open circulatory system. T/F?
F
Closed circulatory system
What does the vascular network consist of?
Aorta, arteries, arterioles, capillaries, venules, veins & vena cavae
What’s the major division of the CVS?
Systemic circulation
How many divisions does the CVS have?
- Major & Minor division
What’s the minor division of the CVS?
Pulmonary circulation
Define systemic circulation
Systemic circulation involves the transport of blood and its constituents from the left side of the heart to the body tissues and then back to the right side of the heart.
What is the pump for the systemic circulation?
Left ventricle
What is the feeding venous system to the systemic lupus?
The pulmonary venous system
Which of the division of the CVS is a high-pressure driven system?
Systemic circulation
Course of blood for systemic circulation
Left atrium —- left ventricle —- aorta —– arteries —- arterioles —– capillaries —- venules —- veins —- vena cavae —- right atrium
Define pulmonary circulation
This involves the transportation of blood and its constituents from the right side of the heart to the lungs and back to the left side of the heart
What is the pump for pulmonary circulation?
Right ventricle
The feeding venous system to the pulmonary circulation?
Systemic venous system
Course of blood in the pulmonary circulation
Right atrium —- right ventricle —- pulmonary trunk —- pulmonary arteries —- lung capillaries —- pulmonary veins —- left atrium
Categories of the function of CVS
1) Electrical function
2) Mechanical function
Mechanical function of CVS
- CVS serves as the vehicle for the delivery of blood and its constituents across the body
- CVS generates the blood pressure needed to transport and redistribute blood and its constituents
Substances transported by the CVS
- Blood cells é.g erythrocyte, leucocyte, etc.
- Gases é.g CO2, O2
- Hormones é.g Steroid hormone, thyroid hormone
- Food nutrients é.g Glucose, lipid, amino acid, vitamins, minerals
- Fluid é.g Water
- Electrolytes é.g Na, K
- Waste products é.g Urea
- Cytokines
- Energy & heat
Mention the electrical functions of the CVS
- The CVS generates and propagates the electrical impulses that give the body life
- The electrical activity initiates mechanical activities. Without the electrical activity there’d be no mechanical activities.
Functions of the components of the CVS
- Heart: Central pump & generates and propagates the cardiac electrical impulses
- Arteries: Transport blood under high pressure and maintains blood flow at high velocities
- Arterioles: Maintains blood flow in response to tissue demand
- Capillaries: exchange water, cytokines, gases, nutrients, etc. between vascular system and interstitium
- Venules: Transports blood from capillaries to veins
- Veins: Transport blood under low pressure from venules to the heart and can also serve as controllable blood reservoir.
- Vascular endothelium: Barrier, blood flow modulator, endocrine function & haemostatis
