Term
| Membrane potential is dependent on what? |
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Definition
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Term
| Membrane potential is created primarily due to what ion? |
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Definition
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Term
| Contracting and conducting cardiac myocytes respond to what type of action potential? |
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Definition
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Term
| Pacemaker cells in the SA and AV node respond to what type of action potential? |
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Definition
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Term
| What is the resting membrane potential in fast-response cardiac myocytes? |
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Definition
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Term
| What is the resting membrane potential in slow-response pacemaker cells? |
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Definition
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Term
| What occurs during phase 0 of an action potential in ventricular cardiac myocytes? |
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Definition
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Term
What occurs during phase 1 of an action potential in ventricular cardiac myocytes?
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Definition
| Early partial repolarization |
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Term
What occurs during phase 2 of an action potential in ventricular cardiac myocytes?
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Definition
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Term
What occurs during phase 3 of an action potential in ventricular cardiac myocytes?
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Definition
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Term
What occurs during phase 4 of an action potential in ventricular cardiac myocytes?
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Definition
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Term
| What causes rapid depolarization during phase 0 in cardiac myocytes? |
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Definition
| Rapid Na+ influx through voltage gated channels |
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Term
| What causes early partial repolarization during phase 1 in cardiac myocytes? |
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Definition
| Efflux of K+ and the transient outward K+ current |
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Term
| What causes the plateau phase during phase 2 in cardiac myocytes? |
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Definition
| Increased Ca++ conductance |
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Term
| What causes final repolarization during phase 3 in cardiac myocytes? |
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Definition
| Efflux of K+ exceeds the influx of Ca++ |
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Term
| The resting potential during phase 4 in cardiac myocytes is determined chiefly by what? |
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Definition
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Term
| Which refractory period is absolute? |
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Definition
| Effective refractory period |
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Term
| When does the effective refractory period occur? |
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Definition
| During phases 0, 1, and part of 3 |
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Term
| What causes the effective refractory period? |
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Definition
| Inactivation of voltage gated Na+ channels |
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Term
| What is required to elicit an action potential during a relative refractory period? |
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Definition
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Term
| What causes a relative refractory period |
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Definition
| All Na+ have not been completely reactivated |
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Term
| Effective refractory periods protect the heart by preventing what? |
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Definition
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Term
| Voltage gated channels participating in phase 0 depolarization of non-pacemaker cardiac APs describes what? |
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Definition
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Term
| What maintains resting membrane potential in phase 4, and permits K+ outflow at highly negative potential in cardiac cells? |
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Definition
| Inward rectifier (Iir or Ikr) K+ channels |
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Term
| What contributes to phase 1 by transiently permiting K+ outflow at positive membrane potential? |
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Definition
| Transient outward (Ito) K+ channels |
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Term
| What contributes to phase 3 repolarization of cardiac action potentials and permits K+ outflow? |
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Definition
| Delayed rectifier (Ikr) K+ channels |
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Term
| What effect do acetycholine and adenosine have on cardiac myocyte action potentials? |
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Definition
| G-protein coupled receptors hyperpolarizes membrane during phase 4 and shortens phase 2 |
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Term
| What voltage-gated channels provide a slow inward, long lasting current, and are responsible for phase 2 non-pacemaker cardiac APs? |
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Definition
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Term
| The unstable resting potentials of autorhythmic pacemaker cells are called what? |
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Definition
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Term
| What do pacemaker cells use for the upstroke of the action potential during phase 0 |
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Definition
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Term
| When does the ionic current upstroke occur in pacemaker potentials? |
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Definition
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Term
When does the ionic current repolarization occur in pacemaker potentials?
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Definition
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Term
When does the ionic current slow (spontaneous) depolarization occur in pacemaker potentials?
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Definition
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Term
| Slow depolarization during phase 4 of paemaker potentials occurs due to the opening of what? |
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Definition
| Funny current (If) Na+ channels |
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Term
| When do funny current (If) Na+ channels open and close? |
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Definition
| During hyperpolarization (-60mV) and depolarization (-20mV) |
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Term
| As the pacemaker potential becomes more positive, what channels begin to open? |
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Definition
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Term
| What opens in the latter part of phase 4, casuing a small increase in Ca++ |
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Definition
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Term
| Inactivation of voltage gated Ca++ channels and opening of voltage gated delayed K+ channels occurs during what phase of a pacemaker potential? |
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Definition
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Term
| What term refers to the relative refractory period in pacemaker cells extending beyond phase 3? |
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Definition
| Post-repolarization refractoriness |
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Term
| What are the effects of post-repolarization refractoriness in pacemaker cells? |
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Definition
| Recovery of full excitability is much slower than in fast-response AP, leads to conduction blocks |
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Term
| Slow Na+ channels (If) acting in pacemaker potentials are also known as what? |
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Definition
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Term
| Delayed rectifier (Ikr) potassium channels are active during what phase of pacemaker potential? |
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Definition
| Phase 3 of reporlarization of cardiac action potentials |
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Term
| Are ATP-sensitive (Ik, ATP) open or closed during a pacemaker potential when ATP decreases? |
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Definition
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Term
| What effect do protein coupled, Ach-activaed potassium channels (Ik, Ach) have on pacemaker potentials? |
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Definition
| Slows pacemaker potential via hyperpolarization during phase 4 |
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Term
| How do L-type (ICa-L) calcium channels modulate pacemaker potentials? |
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Definition
| Creates slow, inward, long-lasting current important in vascular smooth muscle contraction |
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Term
What phase are L-type (ICa-L) calcium channels active during non-pacemaker cardiac action potentials?
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Definition
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Term
| What phase are L-type (ICa-L) calcium channels active during pacemaker potentials of SA and AV nodal cells? |
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Definition
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Term
| T-type (ICa-T) calcium channels are associated with what type of current in pacemaker potentials? |
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Definition
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Term
| In what phase areT-type (ICa-T) calcium channels active during pacemaker potentials in SA and AV nodal cells? |
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Definition
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Term
| What is the order of conduction of electrical impulses? |
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Definition
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Term
| A normal heart rate falls between what range? |
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Definition
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Term
| The vagus nerve has projections on what part of the heart? |
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Definition
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Term
| Sympathetic nerve fibers inenrvate what parts of the heart? |
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Definition
| Primarily cardiac muscle, very little pacemaker cells |
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Term
| Sympathetic (NE) neurons have what effect on the heart? |
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Definition
| Stimulation, positive chronotropic, dromotropic, and ionotropic effects |
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Term
| Parasympathetic (Ach) neurons have what effect on the heart contraction? |
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Definition
| Inhibition via negative chronotropic, dromotropic, and ionotropic effects |
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