Cardiac AP Flashcards
(147 cards)
How is cardiac muscle like skeletal muscle? (3)
contains actin and myosin myofilaments
capable of contraction
T-tubule system and the SR work to maintain Ca++ homeostasis for contraction and relaxation
How is cardiac muscle NOT like skeletal muscle? (2)
Tight junctions serve as low resistance pathways that help spread the cardiac action potential throughout the myocardium.
(Tight junctions are also called gap junctions or nexi)
cardiac myocytes contain more mitochondria than skeletal muscle cells.
How is cardiac muscle like neural tissue? (3)
It generates resting membrane potential
It can initiate an action potential.
It can propagate an action potential
What is automaticity?
The ability to spontaneously generate an action potential
What is excitability?
The ability to respond to an electrical stimulus by depolarizing and firing an action potential.
What is conductance?
Ions require an open channel to cross from one side of the membrane to the other. An open ion channel increases the conductance of that ion, while a closed channel reduces conductance of that ion.
What equation can be used to predict an ion’s equilibrium potential?
Nernst equation
When is equilibrium of the cardiac cells reached?
Equilibrium is achieved when there is no concentration gradient and therefore no net flow of ion across the cell membrane. The charge inside the membrane balance the charges on the outside of the membrane.
What is the Nernst equation?
E Ion = -61.5 log ( [Ion] inside / [Ion] outside )
What is RMP?
The difference in electrical potential between the inside and outside of the cell. The inside of the cell is negative relative to the outside.
RMP is established by three mechanisms?
chemical force
electrostatic counterforce
sodium/potassium ATPase
Is the inside or outside of the cardiac cell relatively negative?
Inside
What is threshold potential?
The initial voltage at which the cell depolarizes.
Can depolarization be stopped?
Depolarization is an all or none phenomenon - once it begins, it cannot be stopped.
When is the cell easier to depolarize?
When RMP is closer to threshold potential.
When is the cell harder to depolarize?
When RMP is further from threshold potential.
When does depolarization take place?
When there is a reduced polarity across the membrane. This means there is less of a charge difference between the inside and outside of the cell.
In excitable tissue, depolarization results in what?
action potential
Negative to positive is known as?
depolarization
Positive to negative is known as?
repolarization
What is hyperpolarization?
Hyperpolarization takes place when there is an increased polarity across a membrane, there is a large charge difference between the inside and the outside of the cell.
What is repolarization?
The restoration of membrane potential towards resting membrane potential following depolarization.
Why is the cardiac cell relatively positive on the outside and negative on the inside?
The cell continuously leaks potassium, thus losing positive charge from the inside of the cell.
What electrolyte is the MYOCYTE permeable to?
potassium