Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
25 Cards in this Set
- Front
- Back
|
What does lower compliance mean?
|
Greater stiffness. Cardiac muscle has lower compliance than skeletal.
|
|
|
What is cardiac preload?
|
Left ventricular end diastolic volume. How much blood is in left ventricle just before it contracts. It's putting tension on the L ventricle fibers.
|
|
|
What is cardiac afterload?
|
The aortic pressure. It must be overcome in order to push blood out of the L ventricle
|
|
|
What determines the difference in elasticity between cardiac and skeletal muscle?
|
The isoform of titin found within the sarcomere.
|
|
|
Which limb of the active length-tension curve does cardiac muscle operate on?
|
Ascending.
|
|
|
What are the factors responsible for the length-dependence of twitch tension? (why longer fibers can have more tension?)
|
a) Longer sarcomeres have more potential cross-bridges because tehre's just more stuff there.
b) Actomyosin complexes exhibit positive cooperativity, so the longer the fiber is and the more cross-bridges are formed, the easier it is for others to form. Generating some cross-bridges makes it easier to generate MORE of them. |
|
|
How does initial length/preload affect the amount of shortening?
|
Directly proportional. Greater preload causes greater shortening.
|
|
|
How does afterload affect the amount of shortening?
|
Indirectly proportional. Greater afterload causes less shortening.
|
|
|
How does contractility affect the amount of shortening?
|
Directly proportional. More contractility increases shortening.
|
|
|
Force-velocity relationship: what is it?
|
Initial velocity of muscle shortening depends on the load (force). Fastest velocity at zero load.
|
|
|
What does it mean to shift the force/velocity relationship to the right?
|
Means a greater afterload can be lifted/handled with the same velocity.
|
|
|
What things shift the force/velocity curve to right?
|
1) Increased initial length
2) Increased contractility 3) Increased heart rate |
|
|
Formula for <b>stroke volume</b>
|
SV = End diastolic volume - End systolic volume
|
|
|
End diastolic volume: defn
|
The volume of blood in the left ventricle directly before systole begins
|
|
|
End systolic volume: defn
|
The volume of blood in left ventricle when the aortic valve closes
|
|
|
Ejection fraction: formula and typical value
|
Ejection fraction EF = stroke volume / End diastolic volume
Typical value is .50-.55 |
|
|
What is the Law of Laplace?
|
Relates tension and pressure. For a thin walled sphere: P = 2HT/r
|
|
|
What is the ventricular diastolic pressure curve?
|
The relationship between diastolic pressure and diastolic volume
|
|
|
What must happen before the left ventricle can eject blood?
|
Intraventricular pressure must exceed aortic pressure for the aortic valve to open. This requires an isovolumetric contraction.
|
|
|
What is the Frank Starling relationship?
|
ability of the heart to change its force of contraction and therefore stroke volume in response to changes in venous return
|
|
|
How do these things affect stroke volume?
a) Incr Preload b) Incr Afterload c) Incr Contractility |
a) Incr SV
b) Decr SV c) Incr SV NOTE: reverse relationships are also true. |
|
|
How does the heart compensate for decreased contractility?
|
Decr. contractility means reduced SV. Reduced SV means venous blood pressure increases, leading to increase in pressure in Right Atrium, leading to increase in preload.
The increased preload compensates for reduced contractility. |
|
|
How does the heart compensate for increased afterload?
|
Pretty much same as decr. contractility.
Incr afterload means reduced SV. Reduced SV means venous blood pressure increases, leading to increase in pressure in Right Atrium, leading to increase in preload. The increased preload compensates for increased afterload. |
|
|
Is the compensation of Frank Starling mechanism complete?
|
NO, and it occurs over several beats
|
|
|
What does the cardiac function curve describe?
|
The relationship between a right heart parameter (RAP) (input) and left heart paramater (CO) (output).
|
