794506
Description
Flashcards by Hannah Tribe, updated more than 1 year ago
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Created by Hannah Tribe
almost 10 years ago
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| Question | Answer |
| 1. An ______ _________ arrives at the __ __ node and causes _____________ | action potential, AV, depolarisation |
| 2. There is an influx of ____ ions, which causes ______ ________ ______ ______ to open slowly in the ___ _______ of cardiac myocyte membranes. This is called the _______ ________ | Na+, voltage gated calcium channels, T tubules, plateau phase |
| 3. Underneath the __ ______ is the _________ _________. Ca++ binds to _________ _________ on its surface and causes ______ __________ ________ _________. | T tubules, sarcoplasmic reticulum, Ryanodine receptors, Calcium-induced calcium release |
| 4. ___ ions bind to ________ on cardiac muscle fibres, exposing the _______ binding site and allowing _______ ______ to form and contraction to occur. | Ca++, troponin, myosin, cross bridges |
| At rest, myocytes do not fully ______, so that if needed, a higher influx of ___ will give stronger _________. | contract, Ca++, contraction |
| Once the myocyte is _______, there is no more ___ influx and the __ __ __ __ are closed. | repolarised, Ca++, VDCCs |
| During _________ _________: 1. __ __ __ __ from sarcoplasmic reticulum stops 2. __ ions leave the cell by __/__ exchanger 3. __ ions leave the cell via an ______ pump 4. _______ pumps __ back into sarcoplasmic reticulum 5. ___ ions enter mitochondria | isovolumetric relaxation, CICR, Ca++, Ca++/Na+ Ca++, ATPase, Ca++ ATPase, Ca++, Ca++ |
| There is no longer any __ ions available for _______ so _______ occurs | Ca++, contraction, relaxation |
| What are positive inotropes? | Substances that increase the strength of contraction |
| When might drugs be given which are positive inotropes? | To increase contractility in heart failure patients |
| Name 2 classes of positive inotropes? | 1. Sympathomimetics 2. Cardiac glycosides |
| Name 2 sympathomimetics | 1. Dobutamine 2. Dopamine |
| What do they do? | Stimulate beta 1 receptors |
| How does that increase contractility? | beta 1 receptors are linked to the Gs pathway which causes increased cAMP and PKA. PKA phosphorylates VDCCs so their activity increases = more Ca++ influx and higher contractility |
| Despite quicker APs, the time for _______ remains similar so __ __ is maintained. However if HR is excessively increased, ________ will be too short to sustain __ __. | diastole, SV, diastole, SV |
| What does amrinone do? | Inhibits phosphodiesterase so cAMP is not broken down. Only used in severe cases. |
| Name a cardiac glycoside | Digoxin (from the foxglove) |
| How do they work? | Stop Ca++ from being extruded from cells. |
| How do they do this? | Inhibit Na+/ K+ pump so intracellular Na+ builds up. This prevents the Na+/Ca++ exchanger from working (maybe even reversing it). More Ca++ is also stored in the SR for more CICR next time. |
| What else can digoxin be used for? | Atrial fibrillation - increases activity of vagus nerve = increased ACh = slower HR |
| What is the disadvantage? | Can have toxic side effects - LOW therapeutic index |
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