9143183
Description
Flashcards by Victoria Wright, updated more than 1 year ago
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Created by Victoria Wright
over 7 years ago
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| Question | Answer |
| Pacemaker action potential occurs in what nodes? | SA and AV nodes. |
| Describe Phase 0 | upstroke—opening of voltage-gated Ca2+ channels. Fast voltage-gated Na+ channels are permanently inactivated because of the less negative resting potential of these cells. Results in a slow conduction velocity that is used by the AV node to prolong transmission from the atria to ventricles. |
| Describe Phase 1 | Phase 1 is absent |
| Describe Phase 2 | Phase 2 is absent |
| Describe Phase 3 | inactivation of the Ca2+ channels and increased activation of K+ channels ---> increased K+ efflux. |
| Describe Phase 4 | slow spontaneous diastolic depolarization due to If (“funny current”). If channels responsible for a slow, mixed Na+/K+ inward current; different from INa in phase 0 of ventricular action potential. Accounts for automaticity of SA and AV nodes. The slope of phase 4 in the SA node determines HR. ACh/adenosine decreases the rate of diastolic depolarization and decreases HR, while catecholamines increases depolarization and increases HR. Sympathetic stimulation increases the chance that If channelsare open and thus increases HR. |
| In Phase 4, slow spontaneous ___________ ____________ due to If (“funny current”) | Slow spontaneous diastolic depolarization due to If (“funny current”) |
| In Phase 4, ___________ decreases the rate of diastolic depolarization and decreases HR, while ___________ increases depolarization and increases HR. | ACh/adenosine decreases the rate of diastolic depolarization and decreases HR, while catecholamines increases depolarization and increases HR. |
| In Phase 4, The________ of phase 4 in the SA node determines _________ | The slope of phase 4 in the SA node determines HR |
| In Phase 4, Sympathetic stimulation increases the chance that If channels are open and thus _________ _________ | Sympathetic stimulation increases the chance that If channels are open and thus increases HR. |
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