Fichas
Cardiac contraction
Fichas del conjunto (21)
- 11. An ______ _________ arrives at the __ __ node and causes _____________action potential,
AV,
depolarisation - 22. 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 - 33. Underneath the __ ______ is the _________ _________. Ca++ binds to _________ _________ on its surface and causes ______ __________ ________ _________.T tubules,
sarcoplasmic reticulum,
Ryanodine receptors,
Calcium-induced calcium release - 44. ___ ions bind to ________ on cardiac muscle fibres, exposing the _______ binding site and allowing _______ ______ to form and contraction to occur.Ca++,
troponin,
myosin,
cross bridges - 5At rest, myocytes do not fully ______, so that if needed, a higher influx of ___ will give stronger _________.contract,
Ca++,
contraction - 6Once the myocyte is _______, there is no more ___ influx and the __ __ __ __ are closed.repolarised,
Ca++,
VDCCs - 7During _________ _________: 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 mitochondriaisovolumetric relaxation,
CICR,
Ca++,
Ca++/Na+
Ca++,
ATPase,
Ca++ ATPase,
Ca++,
Ca++ - 8There is no longer any __ ions available for _______ so _______ occursCa++,
contraction,
relaxation - 9What are positive inotropes?Substances that increase the strength of contraction
- 10When might drugs be given which are positive inotropes?To increase contractility in heart failure patients
- 11Name 2 classes of positive inotropes?1. Sympathomimetics
2. Cardiac glycosides - 12Name 2 sympathomimetics1. Dobutamine
2. Dopamine - 13What do they do?Stimulate beta 1 receptors
- 14How 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
- 15Despite 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 - 16What does amrinone do?Inhibits phosphodiesterase so cAMP is not broken down. Only used in severe cases.
- 17Name a cardiac glycosideDigoxin (from the foxglove)
- 18How do they work?Stop Ca++ from being extruded from cells.
- 19How 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.
- 20What else can digoxin be used for?Atrial fibrillation - increases activity of vagus nerve = increased ACh = slower HR
- 21What is the disadvantage?Can have toxic side effects - LOW therapeutic index
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- Degree CVS1 Fichas sobre Cardiac contraction, creado por Hannah Tribe el 26/04/2014.
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- Hannah Tribe
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