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Electrophysiology ((Afterload: (Resistance against which left ventricle…
Electrophysiology
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Lapalce's law: Press sphere = 2*wall tension/radius
AS EDV increases, efficiecy of heart decreases
- Eventually increase in preload will cause overstretching of heart and lead to reduced force of contraction
Darcy's Law: Flow= diff in pressure at either end of tube/resistance
- Resistance due to friction and determined by viscosity of fluid and diameter of tube
- Combined with Poiseulle's law, shows small changes in radius and large effect on flow
Coronary arteries
- Bottom of aorta: diastolic phase: Heart relaxes, it opnes, blood goes through
- Circumflex artery
- Left anterior descending artery
- right coronary artery
Aorta
LCA
(Left ventricle, left atrium, anterosuperior two thirds of interventricular septum)
Anterior IV artery
( RV, LV, IV septum)
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RCA
(Right ventricle, Right atrium, Inferior third of interventricular septum)
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Posterior IV artery
(RV, LV, IV septum)
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AV nodal artery
(Atrioventricular node, surrounding myocardium)
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Electrophysiology
- K+ move out: Chemical gradient
- K+ move in: Electrical gradient
- Until equilibrium is reached
- Membrane potential: equilibrium potential: Nernst equation Membrane potential at which no net movement for give ion
All myocytes
- Phase 4: resting
- Phase 0: Depolarisation
- Phase 3: Repolarisation
Ventricular myocytes
- Phase 1: transient K+ efflux
- Phase 2: Plateau
SA node
Funny current:
Sodium enters cell through hyperpolarisation - activated cyclic nucloetide- gated (HCN) channels
REgulate blood pressure
- Baro, chemo and cardiopulmonary recpetors
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Atrial natriuretic peptide:
- Atrial myosites to kidneys
- Increased GFR, Reduce Na reabsorption inhibit angiotensin 2, aldosterone and endothelin and lower BP
Diastole
Ventricles
Relaxed, filling with blood
Atria
Contracting, pushing blood to ventricles
Systole
Ventricles
Contracting, pushing blood to body
Atria
Relaxed, filling with blood
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Conducting system
- Specialised cardiac myocytes (not nerves)
- Impulse conducted between SA node and AV node by internodal tracts (Bachmann's)
- 0.1 second delay AV node: Allow atria to contract before ventricles depolarise and contract
- Ventricular impulse down septum towards apex and up
MAP
((Systolic BP) + (2* Diastolic VP))/3
- Determined by total preipheral resistance and cardiac output
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