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26 Cards in this Set

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What is the source on NO in the heart?
endothelial cells
What forms scar tissue in the heart?
collagen
What are the roles of troponin I and troponin C?
I=inhibits interaction between actin and myosin, C=binds Ca and thus allows interaction between actin and myosin
Detail the Ca++ cycle from AP--> SR release
AP--> depolarization --> small amount of Ca++ is released into the cell (trigger Ca) by Ca++ channel --> Ryaodine receptor (under cAMP-PKA control controls speed and strength of contraction) causes the mass release of Ca from SR -->
Detail the removal of Ca++ from the cytoplasm into the SR.
Ca is removed from troponin C by SR Ca ATPase and by Na/Ca exchanger and sarcolemma Ca ATPase pump
What is the relationship between Ryanodine and phospholambin?
In terms of the SR: ryanodine releases Ca, while phospholambin causes Ca uptake
What is the biochemical basis for the effects of digitalis?
It inhibits the Na/K ATPase pump, does this make more ATP available for Ca ATPase?
What controls the uptake of Ca by the SR Ca ATPase?
phospholamban, which when dephosphorylated inhibits Ca uptake, and when phosphorylated by a ß-adrenergic-cAMP mechanism it increases SR Ca ATPase uptake activity
What happens upon phosphorylation of troponin I?
It reduces the affinity of Ca to troponin C --> leading to muscle relaxation.
What are three examples of the effects of phosphorylation on muscle activity?
1) Ryanodine receptor (phosphorylation --> increases contraction speed and strength), 2) Phospholamban (phosphoryaltion it increases the SR Ca ATPase uptake of Ca), 3) Troponin I (phosphorylation reduces Ca's affinity for Troponin C and thus enhances relaxation)
What overall effect do ß-adrenergic mechanisms have on muscle?
They enhance contraction and facilitate relaxation… thus contractions are faster, stronger and relaxation is faster.
What percentage of myocardium is occupied by mitochondria?
30%.. Thus, there is a high demand for oxygen… there is not much capacity for oxygen debt… without O2, heart muscle dies.
How long can creatine phosphate maintain heart function?
seconds
What are the main substrates for producing energy for the heart?
fatty acids, glucose, lactate, pyruvate and ketones. … FATTY ACIDS are the #1 source for energy, especially in the fasting state.
What do ADP, NAD+, ß-adrenergic stimuli have in common?
they stimulate metabolic patways
What is the role of insulin?
uptake of glucose by cells.
In terms of metabolic substrates, what effect does an insulin deficiency, seen in diabetics, cause?
a reliance on FAs, which may cause some pathologies.
Why is a dependence on FAs, seen in diabetics a negative health factor?
FAs require more oxygen per energy produced. Thus, it puts a larger strain on the heart.
Can the heart use lactate as a metabolic substrate?
yes, it converts it to pyruvate, which then enter the mitochondria.
Does a small increase in ADP have a small effect on phosphorylation potential?
No, it has a large effect.
What two things regulate FA uptake?
carrier system (FAT/CD36) and peroxisome proliferation-activator receptors (PPARs, which activate genes that are responsible for FA uptake and oxidation)
Metabolically speaking, why is it FA metabolism is harder on the heart than glucose?
3 ATP/glucose… and 2 ATP/FA… thus, this puts a big strain on the heart function for diabetics
What effect does cholinergic stimulation through muscarinic receptors have on cardiac function? Inhibitory or stimulatory?
inhibitory
In terms of contraction, what does tension equate to?
tension = # of cross-bridges at any one time
What are the three fundemental characteristics used to describe muscle contraction vs. energy consumption?
Tension, velocity of contraction, and the extent of shortening during contraction… Each component has its own energy cost associated with it. Thus, in a diseased state, concerns would be to lower tension (BP), lower speed of contraction, increase shortening, and decrease BPM.
Which of the the three fundamental charactistics of muscle contraction have the most energy associated with it? (in fact it has a linear relationship with respect to energy)
Tension (shortening has very little energy associated with it.)… however, speed of contraction is also energetically costly.