Arrhythmia 1 Flashcards
What is an arrhythmia?
Problem with heart rate
What is bradycardia?
Decrease in blood rate
What is tachycardia?
Increase in blood rate
Where is location of damage normally for an arrhythmia?
- Atrial
- Junctional
- Ventricular
Explain how the heart beat conducts?
- The Sino-atrial node sends a signal to the left atrium
- The atrial ventricular node receives this
- Goes through Atrioventricular bundle
- Intraventricular septum through the right and left fibres
- The purkinje fibres cause the heart to contract
What are the cardiac action potential phases?
- Phase 0: Rapid depolarisation
- Phase 1: Initial repolarisation
- Phase 2: Plateaux
- Phase 3: Repolarisation
- Phase 4 : Baseline
Describe how the depolarisation phase 0 goes from phase 1 in the cardiac action potential?
- Certain ion channels open up in the cell to allow ions to flow down the concentration gradient (sodium channels)
- Sodium concentration is much higher outside the cell compared to inside the cell
- Positive charge in the cell creates the potential difference (increased to +10 mv)
(depolarisation)
How does the +10 mv in phase 1 go back to phase 3 to -90mv?
- When pottasium channels open, pottasium will flow outside the cell so it’ll cause a decrease in charge
(hyperpolarisation) - Repolarisation is back to -90mV
- All depends on the opening and closing of ion channels
Explain how each phase the cardiac action potential works?
Phase 0: Na+, voltage dependent sodium channels,
Phase 1: initial repolarisation causes some pottasium to leave the cell, some negative charge comes into the cell via chloride ions
Phase 2: Influx in calcium keeps membrane potential the same, contraction is entirely dependent on calcium (need increase to cause contraction) (cardiac contracts)
Phase 3: Potassium currents take over which leads to a efflux of pottasium
Phase 4: Largely maintained by sodium, pottasium, ATPase (creates net negative charge to keep membrane potential pinned. Phase 0: Na+, voltage dependent sodium channels,
Describe how the sodium channels work in terms of depolarisation in phase 0?
- -90mv they’re closed and once the threshold is activated, sodium enters
- Inactivation gate inactives itself after some time of the channel being open
- Activation gate is open but closes it’s pore to block itself (inactivation state from phase 1,2)
- Sodium channels only begin to repolarise when it’s from resting state
What is the relative refractory period?
- 200 millisecond heart beats, heart cannot beat faster than this during this period
- Limits the possible maximum contraction
What is the absolute refractory period?
Cannot evoke a heart beat
Explain what the pacemaker potential is?
When the resting membrane potential is unstable
Describe how the pacemaker action potential works?
- Phase 0: L type calcium channel entry
- Phase 3: K+ efflux
- Phase 4: Lf (sodium channel opening)
What is the right vagus controlled by which nervous system?
Parasympathetic
