Electrical Activity of the Heart Flashcards
What is a functional syncytium?
A system in which the cells are connected by gap junctions to act functionaly as one cell
How are cardiac muscle cells connected both physically and electrically?
Physically via desmosomes
Electrically via gap junctions
Why does cardiac muscle has a significantly longer refractory period compared to skeletal muscle?
To prevent tetanic contraction
Why do certain cells in the hear have unstable resting membrane potentials?
These cells called pacemaker cells allow the heart to still beat even if there is no stimulation from the brain
How is the resting membrane potential maintained in a non-pacemaker cell?
Resting membrane potential maintained by high resting PK+
What causes the initial depolarization in non-pacemaker cells?
Increase in PNa+
What causes repolarization in non-pacemaker cells
Decrease in PCa+2
Increase in PK+
What causes an action potential in a pacemaker cell
Increase in PCa2+ (L-type)
What causes the pacemaker potential?
Gradual decrease in PK+
Early increase in PNa+
Late increase in PCa2+
What is hyperkalemia and how does it affect the heart?
High plasma K+
Fibrilation and heart block
What is hypokalemia and how does it affect the heart?
Low plasma K+
FIbrilation and heart block
What is hypercalcemia and how does it affect the heart?
High plasma Ca2+
Increased heart rate and force of contraction
What is hypocalcemia and how does it affect the heart?
Decreased heart rate and force of contraction
