Term
| Name the 2 types of muscles cells in the heart. |
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Definition
| 1) Contractile 2) Conducting cells |
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Term
| What do contractile cells do? Where are they located? |
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Definition
| Generate contractions, in most of the atrial and vent. tissues |
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Term
| What do the conducting cells do? |
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Definition
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Term
| Where are the conducting cells located? |
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Definition
| SA node, atrial internodal tracts, AV node, Bundle of His, Purkinje system |
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Term
| Explain the pacemaking ability of the the different heart regions. |
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Definition
| All capable of autorhythmicity - able to generate APs on their own |
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Term
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Definition
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Term
| Why is the spread of AP slower through the AV node than other cardiac tissues? |
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Definition
| Ensures vent. fill before contraction |
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Term
| What are the 3 criteria of NSR? |
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Definition
| 1) AP originate in SA node 2) 60-100bpm 3) Myocardium activation in correct sequence with timing and delays |
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Term
| What occurs during upstroke (0)ventricles? |
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Definition
| Rapid depolarization, transient increase in Na+ conductance (inward Na+ current) |
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Term
| What occurs during initial repolarization (1)in the ventricles? |
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Definition
| Na+ channels inactivate, outward K+ current |
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Term
| What occurs during plateau (2) in the ventricles? |
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Definition
| Sustained depolasrization, balance of outward K+ current and slow inward Ca++ current |
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Term
| What are the Ca++ channels that open during the plateau phase called? Why? |
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Definition
| L-type Ca++ channels - cause Ca++ induced Ca++ release - the release of Ca++ causes more Ca++ to be released from intracellular stores |
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Term
| What occurs during repolarization (3)in the ventricles? |
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Definition
| Decline in Ca++ conductance, increase K+ conductance |
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Term
| What occurs during Resting potential (4) in the ventricles? |
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Definition
| Potential returns to -85mV, high K conductance |
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Term
| What occurs during the upstroke phase in the SA node? |
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Definition
| Ca+ influx, Transient increase in Ca++ conductance - T type Ca+ channels (transient type) |
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Term
| What occurs during phases 1 and 2 in the SA node? |
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Definition
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Term
| What occurs during repolarization (3) in the SA node? |
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Definition
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Term
| What occurs during spontaneous depolarization (4) ? |
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Definition
| inward "funny" Na+ current (If) - slow leak of Na+ into the cells during repolarization and cause depolarization |
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Term
| Why is dV/dT is lower for the SA node AP? |
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Definition
| T-type Ca++ channels become inactively causing a slower rise |
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Term
| If the latent pacemaker cells have to take over, which one controls HR? |
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Definition
| The pacemaker w/ the fastest rate of phase 4 depolarization |
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