The Heart as a Pump Flashcards
What are the functions of circulation?
Transport nutrients to body tissues
Waste away from the body
Hormones throughout the body
Homeostasis
What is the difference between syncytium and gap junctions?
Syncytium cells joining electrical gap junctions-cytosol is continuous Gap junctions (intercalated discs) specially fused cell membranes
What is the purpose of the transmission of electrical signals by gap junctions and syncytium?
Forming a coordinated contraction of the ventricular tissue
What are the two major difference between cardiac muscle and skeletal muscle?
Cardiac t-tubules have a diameter 5x that of muscle (increased volume)
Cardiac SR less developed than skeletal muscle
Are gap junctions located between the atria and ventricles?
No, otherwise they would contract at the same time
What is the importance of the chorda tendineae and papillary muscles?
Prevent bulging backwards during ventricular systole
What is a benefit of the cardiac muscle’s ability to use Lactate as an energy source?
During brief ischemic conditions, the cardiac muscle can use lactate for energy
When are the coronary arteries best perfused?
During diastole, the arteries can become compressed during systole
How does the SNS affect the coronary arteries?
B2 outweighs A1 resulting in vasodilation (remember local responses can overrule neural responses)
Why do we give CV patients B1 specific beta blockers?
If its non selective it can affect B2 (vasodilation thus alpha would win out and the vessels would constrict) B1 prolongs diastole thus perfusing the coronary arteries longer
The period of time when the pressure is rising in the ventricle yet no volume is exiting
Isovolumic contraction, tension is increasing but little or no shortening of the muscle fibers is occurring
There is no change in the volume of blood in the ventricle but there is a decrease in pressure
Isovolumic relaxation, eventually the pressure in the ventricle is less than that in the atria and thus AV valves open
What causes the aortic valve to open?
The pressure in the ventricle exceeds the pressure in the aorta (90ish)
What is the difference between isometric and isotonic muscles?
Isometric means the muscle length remains constant
Isotonic means the muscle tension remains constant
Why does kinetic work increase in stenosis?
The cross sectional area through the aorta decreases meaning the velocity of ejection with be much higher for a given flow rate
In a cardiac function curve what do lines I, II, III and IV indicate?
I: ventricular filling
II: isovolumic contration
III: ejection of blood from the ventricle to the aorta
IV: isvolumic relaxation
The work required to move blood from veins to arteries?
External work (volume-pressure work)
The work required to accelerate blood to the velocity of ejection
Kinetic energy
What is the difference between skeletal muscle and cardiac muscle in the length/tension relationship?
There is a finite limit to the cardiac muscle, if you stretch the myocytes too much you will get diminished ventricular pressure (fibrous tissue of the pericardium)
How do you calculate ejection fraction?
stroke volume/preload
What does the area inside the cardiac function curves represent?
External work, the product of volume moved against a given pressure
Define the Frank Starling mechanism.
Length/tension relationship, if preload increased the heart is able to pump the extra blood out (with greater cross bridge formation) and return to the same end systolic blood volume. There is however a limit to this mechanism
Why is more oxygen used when systolic b/p is elevated?
O2 consumption is nearly proportional to the tension that occurs in the heart muscles during contraction
