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42 Cards in this Set

  • Front
  • Back
Heart beat is caused by what current?

How does this current work?
Resting Na current that can occur between - 70 and -40 mV

Na channels open spontaneously and slowly depolarize pacemaker cell resting potential until it reaches threshold
These channels open at threshold and create action potential
Voltage gated Ca channels
_ returns membrane to resting potential
Slower opening of slower voltage gated K channels
"resets" (inactivates) Na channels
Hyperpolarization
What is a typical non-pacemaker cell potential
-90--> -110
Damage (e.g MI) that depolarizes non-pacemaker cells can activate Na channels and cause these cells to act as pacemaker cells - this is called _
ABNORMAL AUTOMATICITY
Increase the rate of opening of funny channel (Na channel)
Cyclic nucleotides
Increased opening of Na channels increases heart rate - this is effect of which agonists>
Dopamine/adrenergic
Decreased channel opening decreases heart rate - this is the effect of which agonists
Muscarinic
What happens when Purkinje cells are depolarized (as in hypoxia)
Many Na channels move from resting to closed state, where they cannot be activated. Further depolarization of these cells can activate " funny Na channels" and cause them to act like pacemaker cells
Creates NORMAL SINUS RHYTHM
SA node
Creates NODAL RHYTHM if SA node fails
AV node
Causes P and QRS waves
Na entry
Ca enters atria and ventricles during _
PR and ST segments
Exits in the T wave
K
T wave height is proportional to _
Plasma K
This condition can invert T wave
Hypokalemia
This ion blocks Ca channel
Mg
Ca and Na depolarize during which phases
0,1,2
Repolarization occurs when Ca current ceases while K current persists - which phase
3
Factors that decrease K currents increase or decrease AP duration?
Increase
These cells are most susceptible to increased AP duration
Midwall cells ( M cells)
This condition can cause EAD's if the cardiac AP exceeds effective refractory period
Long Q-T syndrome
Describe conditions that can cause long Q-T syndrome
- Unintended side effect of drugs that inhibit K channels (sotalol) or with congenital K channels defects
- Can also occur in bradycardia due to decreased lusitropic state
Tosade de Pointes is usually preceded by _
Several periods of EAD's
These are thought to cause Tosade de Pointes
EAD's + dispersion of repolarization
What is often given for Tosade de Pointes and why
Mg - blocks Ca channels and since K channels are already open, the cell repolarizes earlier
Thought to cause Premature Ventricular Contractions (PVC)
DAD- Delayed After Depolarizations
What comes first EKG or mechanical events
EKG events PRECEDE mechanical events
Systole starts with _

Ends with _
Ventricular contraction and closure of AV valve

Closure of semilunar valve
Ventricular relaxation extending from semilunar valve closure to ventricular contraction and AV valve closure
Diastole
4 phases of systole in cardiac cycle
1. Isovolumic contraction-no change in LV blood volume (end diastolic volume)
2.Rapid ejection-aortic valve opens followed by rapid ejection of blood from LV into aorta.
3. Reduced ejection-slowing of blood from ventricle to aorta
4. Aortic valve closure(incisura or dicrotic notch-rebound of blood back into closed Aortic valve cusps
Brief period just prior to aortic valve closure (actually part of systole)
Ventricles are relaxing with semilunar valves still open; reversal of flow in aorta
Protodiastole
3 parts of ventricular filling
1.Rapid filling-early rapid filling from atria
2.Reduced filling (Diastasis)-slowing of filling as pressures equalize
3.Atrial Systole-atrial contraction (“Atrial kick”)
a wave is due to _
atrial contraction
c wave is due to _
ventricular contraction (bulging of AV valves back into atria)
v wave is due to _
venous return (pulmonary blood flow into atria with AV valves closed)
Fall in atrial pressure following the c-wave. Base of ventricle pulls away from atria during contraction creating fall in pressure.
X descent = systolic collapse
Fall in atrial pressure following the v-wave- rapid outflow of blood from atria to ventricles causing pressure drop.
Y descent = diastolic collapse
Major contributor to “afterload”, the resistance the left ventricle has to pump against to eject blood
Aortic pressure
1st heart sound starts with _ and extends to _
Closure of AV valves to the opening of semilunar valve
2nd heart sound is associated with _
Semilunar valve closure