Cardiophysiology Winden Flashcards
Ionotropy
- The force of contraction
- positive or negative ionotropic
Chronotropy
- Rate
- Positive or negative
Dromotropy
- Conduction velocity
What are the 2 types of cardiac muscle cells?
- Condusting System
- Controls and coordinates heartbeat
- Contractile cells
- Produce contractions that propel blood
- Both are myocytes
Trachycardia
Bradycardia
Arrhythmia
Dysrhythmia
Conducting system cells function
- Controls and coordinates heartbeat
- Initiates and distributes electrical impulses that stimulate contraction
- Automaticity
Contractile cells function
- Produce contraction to propel blood
- Purkinje fibers distribute stimulus to contractile cells
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Cardiac contraction and calcium
- Contraction produced by calcium ion concentration around myofibrils
- 20% of Ca ions required are extracellular (cardiac muscle very sensitive to extracell Ca)
- enter plasma mebrane during plateau phase
- Arrival of extracell Ca triggers SR to release Ca reserves
- As calcium channels close Intracell ca is absorbed or pumped out
Where does the heart get aerobic energy from
- Mitochondrial breakdown of fatty acids and glucose
- Oxygen from circulating hemoglobin
- Cardiac muscles store oxygen in myoglobin
Components of conducting system
- SA node
- Internodal pathways
- AV nodes
- AV bindle
- Bundle branches
- Purkinje fibers
Prepotential
- AKA pacemaker potential
- Resting potential of conducting cells
- gradually depolarizes toward threshold
- SA node depolarizes first, establishing heart rate
SA Node location and features
- In posterior wall of right atrium
- Contains pacemaker cells
- Connected to AV node by internodal pathways
- Begins atrial activation
AV node
- In floor of right atrium
- Stimulus spreads across atrial surfaces and reaches AV node
AV bundle location and action
- In septum
- Carries impulse to left and right bundle branches
- which conduct to Purkinje fibers
- And to the moderator band
- Which conducts to papillary muscles
Purkinje fibers action
- Distribute impulse through ventricles
- Atrial contraction is completed
- Ventricular contraction begins
P Wave
Atria depolarize
QRS complex
Ventricles depolarize
T wave
Ventricles repolarize
P-R Interval
From start of atrial depolarization
Tostart of QRS complex
Q-T interval
From ventricular depolarization
To ventricular repolarization
Which portion of ECG is the only isoelectric period when the entire ventricle is depolarized?
S-T segment
Cardiac cycle is the period…
- Period between start of one heartbeat and beginning of the next
- Includes both contraction and relaxation
What are the 2 phases of cardiac cycle
- Within any one chamber (atrial or ventricular)
- Systole (contraction)
- Diastole (relaxation)
Atrial Systole steps
- Atrial systole
- Atrial contraction begins
- Right and left AV valves are open
- Atria eject blood into ventricles
- Filling ventricles
- Atrial systole ends
- AV valves close
- Ventricles contain max blood volume
- Known as end-diastolic volume
Ventricular Systole Steps
- Ventricles contract and build pressure
- AV valves close cause isovolumetric contraction
- Ventricular Ejection
- Ventricular pressure exceeds vessel pressure opening the semi-lunar valves allowing blood to leave
- Amount of blood ejected is called Stroke Volume
- Ventricular pressure falls
- Semi-lunar valves close
- Ventricles contain End-Systolic Volume, about 40% of end diastolic volume
Ventricular Diastole
- Ventricular pressure is higher than atrial pressure
- All heart valves are closed
- Ventricles relax (isovolumetric relaxation)
- Atrial pressure is higher than ventricular pressure
- AV valves open
- Passive atrial filling
- Passive ventricular filling
