Cardiovascular Flashcards
What is the ability of a cell to respond to an external electrical stimulus, usually in the form of an action potential?
Excitability
What is the ability for a cell or a group of cells to initiate an action potential?
Automaticity
What is the ability of a cell or region of cells to receive and transmit an action potential?
Conductivity
What is the inability of a cell to receive and transmit an action potential?
Refractoriness
What is the ability of cells to alter the rate of electrical conduction?
Dromotropism
Why is it that the SA node is the pacemaker part of the heart, and not the AV node?
SA node is faster
Why is it that potassium channel blockers prolong the QRS complex?
Prevent the K channels from releasing K to balance out Ca that has rushed into the cell
True or false: the electrical activity always precedes the mechanical activity
True
What does the P wave represent?
Depolarization of the AV node
What does the Q wave represent?
What does the R wave represent?
What does the S wave represent?
What does the T wave represent?
Repolarization of the ventricles
Where is the EKG line of repolarization of the atria?
Hidden in the QRS complex
What allows for the spontaneous depolarization of phase 4 in the SA and AV nodes?
Funny channel If (Leaky Na channels)
What causes the initial depolarization of the AV node? (phase 0)
Opening of Na channels (influx)
What causes the prolonged phase 2 in the AV node?
influx of Ca and efflux of K
Draw the phases of the AV node AP.
Draw
What is responsible for the phase 3 repolarization of the AV node?
Ca channels close, K continues to leak out
What are the two types of Ca channels? When do they open?
L type (long) T type (transient)
Both open at beginning of phase 1
What is the ion exchange that is occurring in phase 2?
Ca goes in, K goes out
What happens with the ion exchange in phase 3 of the AP?
Ca stops
K continues to efflux to balance out charges
What is the channel that is responsible for the upward depolarization in phase 4?
Funny Na Channel
What are the three phases of the Na channels?
- Activation gate closed
- Gates opened
- Inactivation gate closed (repeat)
What happens in phase 3 of the cardiac myocytes?
Ca channels close
K continues to leak out
What is responsible for the phase 4 current in the AV/SA node?
If (funny Na channel)
True or false: the Na channels have two gates, which respond in the same way to depolarization
False–respond in opposite ways
What is the resting state of the Na channels? What happens when depolarization occurs?
Activation gate closed, inactivation gate open
Rapid opening of the activation gate