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;
26 Cards in this Set
- Front
- Back
|
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.
|
