Flashcards in Cardiovascular Deck (71):
What is the ability of a cell to respond to an external electrical stimulus, usually in the form of an action potential?
What is the ability for a cell or a group of cells to initiate an action potential?
What is the ability of a cell or region of cells to receive and transmit an action potential?
What is the **inability** of a cell to receive and transmit an action potential?
What is the ability of cells to alter the rate of electrical conduction?
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
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.
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?
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?
1. Activation gate closed
2. Gates opened
3. 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
What happens when the activation gate on Na channels open in response to depolarization?
Inactivation gate closes
What happens to Na channels when repolarization occurs?
First, activation gate closes, then inactivation gate opens
What happens when you block the opening of the activation gate? Relate this to the phases of depolarization.
Prolong Na intake, prolong phase 0
What happens when you block the inactivation state of Na channels?
What happens when there is an enhanced late I(Na)? Relate this to Ca levels.
prolonged depolarization of Na, causes more Na to enter. NCX transporter also causes increased intracellular Ca, leading to cellular instability/mechanical dysfunction
What are the 4 cardiovascular conditions that are caused by increased late I(Na) channel closing?
1. Ischemic heart disease (angina)
2. Heart failure
What are the two neurological disorders that are caused by increased late I(Na) channel closing?
Neuropathic pain/muscle paralysis
Draw out the SA/AV node depolarization curve vs the ventricular muscle fiber depolarization curve.
What is responsible for phase 0 depolarization of the SA node?
What is responsible for phase 0 depolarization in ventricular muscle fibers?
What is the main ion change that is occurring in phase 3 of the nodal depolarization curve?
What is the main ion change that is occurring in phase 4 of the nodal depolarization curve?
What is the main ion change that is occurring in phase 1 of the ventricular muscle depolarization curve?
What is the main ion change that is occurring in phase 2 of the ventricular muscle depolarization curve?
What is the main ion change that is occurring in phase 3 of the ventricular muscle depolarization curve?
What is the effect of blocking Ca influx on the nodal cell?
Decrease in automaticity
What is the effect of blocking Na on ventricular muscle fibers?
Decrease in phase 0 depolarization
What is the effective refractory period?
the period in which the tissue will not respond to any additional stimulus
What does the ERP/APD ratio determine?
the ability of abnormal impulses to depolarize the tissues
What is the relative refractory period?
time after the effective refractory period in which it is difficult, but not impossible, to generate an action potential
A lower ERP/APR ratio means what?
easier to depolarize
What does the SANS affect on cardiac function?
What does the PANS affect on the cardiac function?
What happens in sinus node tachycardia?
Increase in the depolarization of the sinus node and increased conduction velocity
What does SA node tachycardia look like on an EKG?
What is the pathophysiology of atrial tachycardia?
Ectopic foci in the atria cause depolarization,
How does atrial tachycardia present on an EKG?
P waves without QRS complex
What are early afterdepolarizations?
Depolarizations that occur before the total repolarization of the ventricular muscle.
What are "triggered activities"?
Abnormal upstrokes that occur after a normal upstroke
What metabolic disturbance can result in early after depolarizations?
EADs are induced more readily in what part of the heart?
What is torsades de pointes?
QRS complex occurs when a P wave is supposed to happen, triggering a ventricular fibrillation
What does a U wave represent?
Depolarization of papillary muscle
What are delayed after depolarizations?
Ca overload (secondary to some condition) causes a depolarization after the normal depolarization, which can generate aberrant beats if it reaches threshold
What is the EKG of a first degree block?
What is the EKG of a second degree AV block?
Not all P waves pass (followed by a QRS complex)
What is the EKG of a third degree block?
no P/QRS relationship
What is the cause of reentry?
Existence of conduction routes with different conduction velocities
What is AV node reentrant tachycardia?
Two different conduction pathways in the AV node with different conduction speeds. A premature beat causes circus motion between the loops
P waves that come after the QRS complex = ?
Accessory pathway mediated SVT
Atrial flutter is caused by what?
What does the EKG of a ventricular reentry look like?
Huge QRS complexes