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19 Cards in this Set
- Front
- Back
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Modified myocytes |
-SA node -more rapid rate of phase 4 depolarization |
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Ventricular myocytes |
-contractile -Fast response action potential |
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Ions |
Na+- 150mM out 15mM in = depolarize Ca2+ - 2mM out .0001mM in = depolarize K+ - 5mM out 150mM in =Repolarize
-Potential depends on permeability to each ion |
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SA node Slow response |
Phase 0: Upstroke - opening of L-type Ca2+ and influx of Ca2+ Phase 3: Repolarization - Above 0, opening of delayed rectifier K+ channels - efflux of K+ Phase 4: Pacemaker - K+ close ; Funny (IF) open, Na+ influx and depolarize -At -55 mV T type Ca2+ open to depolarize to -40 where L type open |
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Ventricle / Atrial Fast response |
Phase 0: depolarizing - opening of Na+ channels Phase 1: Early repolarization- close of Na+ and open of transient K+ Phase 2: Plateau- Open Of L type Ca2+ channels and the open rectifier K+ (equal) Phase 3: Rapid Repolarization - efflux of K+ dominates; L type Ca2+ closure Phase 4: Resting potential - inward K+ rectifier open - maintain -90mV |
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Overdrive suppression |
-SA node dictates firing frequencies of AV and Purkinje (tertiary pacemaker) SA-60-100 AV-40-60 Purkinje-20-40 |
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Conduction pathway |
SA node---> AV node----> Bundle of HIS ---> Bundle Branches ----> Purkinje fibers |
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Action potential |
Starts by going down T tubules (wider than skeletal)---> depolarizes ----> L type calcium channels (DHPR) in t tubules open ----> Ca2+ entry---> bind to Ryanodine receptor----> increase in opening SR Ca2+ release channels (RYR)
-DHPR and RYR not physically connected like in skeletal
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Amplifier |
-Calcium Induced Calcium release (CICR) -30% calcium outside -70% from SR |
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Diastole |
-relaxation -Calcium taken out |
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Mechanisms that take calcium out |
-Back into SR via ATP-Ca2+ pumps -3 Na+ ---> 1 Ca2+ exchanger (NCX) -Sarcolemmal Ca2+ ATPase
The same that entered must leave |
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Troponin complex |
-Tropomyosin bound to actin -Troponin T bound to Tropomyosin and Troponin I -Troponin I bound to actin in absence of Ca2+ (covers actin- myosin binding site) -Troponin C weakly bound to Troponin I |
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Troponin complex (Continued) |
1 Calcium binds to Troponin C---> Troponin C binds more strongly to Troponin I ----> Troponin I no more binds to actin----> Troponin I binds to Troponin T ---> Troponin T binds to tropomyosin ---->Tropomyosin binds to actin---> Tropomyosin moves into groove of actin and Troponin swings out uncovering myosin binding site |
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Cross bridge |
1. Actin x Myosin x ADP x Pi 2. Actin x Myosin ( rigor mortis) 3. Actin x myosin x ATP 4. Actin x myosin x ADP x Pi |
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ATP |
-needed for every contraction -Aerobic metabolism and oxidative phosphorylation - Fatty and lactic acids
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Cardiac Contraction |
-One can not build on the other -Must have diastole for refill
-Absolute refractory period - Fast Na+ channels -Relative refractory period - Large stimulus required |
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Cardiac tension |
-During diastole = passive tension -Diastolic volume is equivalent to muscle length -Preload =EDV |
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Preload |
-Rest length -normal working range but not optimal length - the more preload the more contraction |
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Afterload |
-Pressure in aorta that must be overcome to open aortic valve -Diastolic Pressure
-For a given afterword, as you increase preload you increase shortening velocity (shift to the right) |
