G1 + G2 electric and anatomy Flashcards
Give 5 differences anatomically between the RV and LV
Functionally what are the main differences between RV and LV 5
Draw how an RV and LV pressure volume curve looks Different
What feature of the ANS is unique with respect to the heart?
The only site where PSNS tone is tonically active at the SA node instead of the SNS being the tonically active agent
What receptors does acetycholine interact with at the SA node
M2
- Speed of conduction through specialised Purkinje fibres
1-4m/sec
AP duration in ventricular cells
- Action potentials lasting 300msec in ventricular cells
Phase 4 of the myocardial action potential - features 2
- Stable Resting membrane potential = -85 to -95mV
- Maintained by I (kI) inward rectifying potassium current balancing the sodium and calcium entering the cell leading to equal inward and outward current
At what point is the depolarisation thewshold reached in cardiac muscle cells
-65mV
How fast is depolarisation in cardiac myocytes? In seconds and in V/sec
By how much amplitude?
What triggers to do so?
What electrolytes move
- Na channels opening at -65mV voltage gated
- Rapid depolarisation over 1-5 10 thousands of a second through fast voltage gated sodium channels increasing sodium permeability and entrance into the cell
- Simultaneous reduction in potassium conductance (potassium leaving cell) - iK1
- Depolarisation by 105mV - high amplitude
- VMax 200-800 V/sec
Describe phase 0 of the cardiac action potential
- Na channels opening at -65mV voltage gated
- Rapid depolarisation over 1-5 10 thousands of a second through fast voltage gated sodium channels increasing sodium permeability and entrance into the cell
- Simultaneous reduction in potassium conductance (potassium leaving cell) - iK1
- Depolarisation by 105mV - high amplitude
- VMax 200-800 V/sec
Phase 1 of the cardiac action potential
- Rapid repolarisation through voltage sensitive transient outward potassium currents (I to) triggered through voltage changes and decreases in sodium permeability (inactivation of fast sodium channels)
- Drop in membrane potential to 0-10mV relative to intercellular fluid
Phase 2 of the cardac action potential features 3
- Prolonged plateau ~0mV
- Lasting 100-200msec
- Mediated by L type calcium channels with calcium inflow, and simultaneous potassium outflow balancing electrical potentials
Phase 3 of the cardiac action potential
- Rapid repolarisation through closure of L type calcium channels and potassium efflux through delayed rectifier K current (I kr), I (ks) and I(k1) potassium currents- resting membrane potential again reached at the end of phase 3 as the membrane potential is closer to the equilibrium potential of K
- Refractory periods
◦ Absolute 200msec
◦ Relative 50msec
How long are the 2 main refractory periods
- Rapid repolarisation through closure of L type calcium channels and potassium efflux through delayed rectifier K current (I kr), I (ks) and I(k1) potassium currents- resting membrane potential again reached at the end of phase 3 as the membrane potential is closer to the equilibrium potential of K
- Refractory periods
◦ Absolute 200msec
◦ Relative 5mm sec
Relate action potential and tension
Phase 0 of the action potential relates to what 2
- Phase 0 —> beginning of the Q wave and QRS complex
◦ Initially corresponding to beginning of systole and isovolumetric contraction
Phase 1 and 2 correspond to what part fo the ECG and cardiac cycle
- Phase 1/2 correspond to the QRS + ST interval
◦ Corresponds to systole
◦ Phase 1 - isovolumetric contraction