Lecture 8 Flashcards
What is the design of the mammalian cardiovascular system?
Four chambered heart, blood flows in one direction, arterial blood flows away while venous blood flows towards.
What is the function of the hearts right pump?
Receive deoxygenated blood from the body and send it to the lungs
What is the function of the hearts left pump?
Receive oxygenated blood from the lungs and send it to the rest of the body
What is the relative flow through the pulmonary and systemic circuits?
Must be equal
Do the left and right ventricles contract at the same time or in sequence?
At the same time
Do the atria and ventricles contract at the same time or in sequence?
In sequence, atria first then ventricles second
What controls the flow of blood between the atria and ventricles?
The atrioventricular (AV) valve
What controls the flow of blood between the ventricles and the circulatory vessels?
Aortic and pulmonary valves
What is the name for the contractile units of cardiomyocytes?
Sarcomeres
What is the thin filament of a cardiomyocyte sarcomere?
Actin
What is the thick filament of a cardiomyocyte sarcomere?
Myosin
What is the function of the actin and myosin?
To create cross bridges for contraction
What must be released into a muscle cell to facilitate sarcomere cross bridging and contraction?
Calcium
What is the basic process of cardiomyocyte contraction?
Ca2+ released into cell by sarcoplasmic reticulum, myosin head binds to actin forming cross bridges that pull on sarcomeres to shorten them and generate force.
How does cardiomyocyte recruitment increase the force of cardiac contraction?
It doesn’t - all cardiomyocytes are activated during every heart beat, so there are no more to be recruited
How is the force of cardiac contraction increased?
Increased cytosol Ca2+ release in cardiomyocytes facilitates the formation of more cross bridges, allowing individual cells to contract more strongly.
What is the cellular mechanism of cardiac relaxation?
Ca2+ pumped into sarcoplasmic reticulum, cross bridges released as ATP binds to myosin
What are the 2 states that the heart alternates between?
Diastole and systole
What is diastole associated with in the heart?
Relaxation and falling pressure
What is systole associated with in the heart?
Contraction and rising pressure
What are 5 main phases of the cardiac cycle?
Atrial systole, atrial diastole, isovolumetric ventricular contraction, ventricular ejection, isovolumetric ventricular diastole, passive filling
What occurs during atrial systole?
Contraction of atria’s, rise in pressure, AV valves open to allow filling on ventricles
What is the ‘lubb’ sound?
The closing of the AV valves, after atrial systole
What occurs during isovolumetric ventricular contraction?
Ventricles begin to contract however all valves are closed therefore there is a rapid increase in pressure
What occurs during ventricular ejection?
Pressure builds to a point where semilunar valves open, blood flows out of heart
What is the ‘dubb’ sound?
Closing of the semilunar valves, after ventricular ejection
What occurs during isovolumetric ventricular relaxation?
A small amount of leftover trapped blood remains in the ventricles. Ventricles relax and pressure decreases significantly.
What occurs during the passive filling phase?
When pressure is low enough the AV valves will open, allowing the atria’s to fill and then the ventricles
What is longer, diastole or systole?
Diastole
Where is arterial pressure highest, systemic or pulmonary?
Systemic
What is the pulsatile change in pressure in the major arteries linked to?
Ejection of blood
What is systolic pressure on a blood pressure trace?
The highest point
What is diastolic pressure on a blood pressure trace?
The lowest point
What is pulse pressure?
The difference between the highest and lowest points
What is mean pressure?
The average pressure across one cycle
What is hypertension?
High blood pressure
What is hypotension?
Low blood pressure
