Mechanical properties of the heart, starlings’ law: Flashcards
Elements of contraction: What are the element of contraction
- CC (contractile elements)
- SEC (serial elastic component)
- PEC (parallel elastic component)
- Col (collagen fiber system)
- Isometric phase
- Isotonic phase
- The collagen fibers
Elements of contraction: CC name and example
contractile component: Actin and myosin
Elements of contraction: SEC name
serial elastic component:
Elements of contraction: SEC explain
serial elastic component: Attached to CC, relaxes during diastole and is expanded during systole.
Elements of contraction: PEC name
parallel elastic component
Elements of contraction: PEC explain
parallel elastic component: Attached to CC and to the SEC. Stretched by the blood filling heart during diastole
Elements of contraction: Col name
collagen fiber system:
Elements of contraction: Col explain
collagen fiber system: Overexpansion and rupture of the tissue is prevented by the rich collagen fiber system.
Elements of contraction: Isometric phase explain
At the beginning of the contraction the weight stretches the SEC elements only.
Elements of contraction: Isotonic phase:
When the stretch in the SEC gets into balance with the weight, the weight begins to move.
Collagen fibre explain
collagen fibers are
expanded and display maximal resistance to prevent rupture.
When do low performances occur in single working fibre
at short sarcomeric lengths which then
increases when the sarcomeric length is increased
Optimal position for both heart and skeletal muscle in single working fibre
1,9-2,5 micrometer sarcomeric lengths.
Entry of Calcium to sarcomeric space …..
( in single working fibre)
The entry of the calcium into the sarcomeric space is length dependent in the heart muscle.
Properties of the total working musculature: What is the law of the heart by Starling and Frank
The heart muscle can adapt itself to higher requirements automatically, without the intervention of the nervous system.
Properties of the total working musculature: Volume fraction ( total working musculature)
During contraction and relaxation the heart empties a part of its blood content towards the circulatory bed and then takes up blood from the periphery. The emptying is not complete: the remaining fraction is of big importance in the adaption.
Properties of the total working musculature:
The amount of blood found in the heart by the end of diastole is called
end diastolic volume (EDV)
Properties of the total working musculature: end diastolic volume (EDV)
The amount of blood found in the heart by the end of diastole is called
Properties of the total working musculature: The amount of blood remaining in the heart by the end of systole is called
end systolic volume (ESV)
Properties of the total working musculature: end systolic volume (ESV)
The amount of blood remaining in the heart by the end of systole is called
Properties of the total working musculature: The difference between ESV and EDV is called
stroke volume (SV), this volume fraction passes into the aorta at each cycle.
Properties of the total working musculature: What is cardiac output
Cardiac output = volume of blood forwarded by the left ventricle into the aorta per unit time.
Properties of the total working musculature: Cardiac output equation:
CO = SV (stroke volume) x FR (frequency)
Properties of the total working musculature: SV=
SV=EDV-ESV
Properties of the total working musculature: Measuring cardiac output:
Cardiac output is equal to the total oxygen consumption divided by the arterio-venous oxygen concentration difference.
Properties of the total working musculature: what does the Fick’s principle measure
Measuring cardiac output
Starlings experiment: what is it and what did it prove?
First he increased the venous return, then he changed the peripheral resistance. Proved that the heart can adapt to the increased load.
Starlings experiment: what does it explain
By increased venous return= the cardiac output and stroke volume increased.
By changing the peripheral resistance= the stroke volume and cardiac output stay the same (because EDV and ESV increases proportionally)
Starlings experiment: Physiological importance
The heart can increase its diastolic reserves so that it can perform better:
the work of the heart: The total work of the heart is composed
The total work of the heart is composed of outer work (mechanical work) and inner work (heat production):
the work of the heart: The total work of the heart equation
Wt= Wo + Wi
the work of the heart: outer work of the heart equation word
the product of the stroke volume times the pressure difference between the aorta and the vena cava (∆P)
the work of the heart: outer work of the heart equation letter
Wo = SV x ∆P
the work of the heart: how does the heart gain its energy
heart gains its energy purely from the oxidative processes
the work of the heart: the total work of the heart can be determined by equation word
measuring the total oxygen consumption of the tissue
the work of the heart: the total work of the heart can be determined by equation letter
Wt = oxygen consumption x energy equivalent of O2.
the work of the heart: How to calculate the efficiency of the heart
Knowing Wo and Wt the efficiency (E) of the heart can also be calculated: E = Wo/Wt
Rushmer diagram: what is it?
Analyses the work of the heart in the pressure-volume coordinate system.
Rushmer diagram: 1
Mitral valve close, isovolumetric contraction
Rushmer diagram: 2
Aortic valves open, ejection phase
Rushmer diagram: 3
Semilunar valves close, isovolumetric relaxation
Rushmer diagram: 4
Mitral valves open, filling.
Performance of the heart: equation words
Performance = work/time
Performance of the heart: equation letter
W/t = PxV/t
Performance of the heart: equation explain
Since the heart maintains a close to constant peripheral pressure (constant P), the performance (W/t) is mainly determined by the volume flow.
