Lecture 5: Cardiac Muscle Electro/Mechano Coupling Flashcards
How wide is the fuzzy space?
10-15nm
What is the gradient between the calcium in the SR and ECF compared to the cytosol?
10,000 fold
What are the features of pumps?
Need energy
Only go one way
What are the features of exchangers?
No energy
Reverse
What provides the potential energy for contraction initiation?
Calcium concentration differences
Why does the heart go into diastole?
Calcium reuptake by SR and release via SL pump
How does the Na/Ca exchanger work?
3 Na in, 1 Ca out - counterproductive as it makes cell more positive
What is the ratio of internal and external calcium cycling?
Internal calcium cycling = 4 x external calcium cycling
After sodium moves in via the Na/Ca pump, how is the excess removed?
Na/K pump - 3Na out, 2K in - makes internal more negative
What happens when there is more metabolic activity in the cell?
More H ion build up - more acidic cell - less affinity between the myofilaments and calcium - reduced contraction
How is excess hydrogen removed from the cell?
Na/H exchanger
When will the Na/Ca exchanger reverse?
If there is a high sodium concentration in that region, sodium will want to move out so the pump will reverse (happens after depolarisation)
Why does potassium move out via potassium channels?
To get rid of potassium brought in via Na/K pump and to repolarise the cell
What do foxglove leaves do?
Inhibit Na/K ATPase
What happens when the Na/K pump is inhibited?
Excess Na, more Ca moves in than out - increased contraction
