The Heart + Electro Flashcards
Where does the heart sit
Between the lungs, retrosternal against the 5th to 8th thoracic vertebrae
Functions of the heart
Generating blood pressure, pushing blood through pulmonary and systemic routes, ensuring one at blood valve, regulating blood supply to meet needs
Pericardium
Fibrous sac the surrounds and anchors the heart
Layers of the heart wall
Outer - epicardium
Middle - Myocardium
Inner - Endocardium
Left coronary artery
Divides into left anterior descending artery
Right coronary artery
Divides into right marginal artery, and Paterson interventricular artery
Left Circumflex artery supplies
Left atrium and left ventricle
Left anterior descending artery supplies
Right ventricle, left ventricle, septum
Left Marginal Artery supplies
Left ventricle
Right marginal artery supplies
Right ventricle and apex
Right coronary artery
Right atrium and right ventricle
What is secreted for SNS
Epi and norepi
What is secreted from PSNS
Acetylcholine
Properties of cardiac cells
Contractility
Automaticity
Rhythmicity
Conductivity
Refractory Period
Cardiac Output
Volume of blood ejected in one minute
Stroke Volume
Blood pumped out of the left ventricle during each contraction
Preload
Stretch of the ventricle at the end of diastole
After load
Amount of force the heart must pump against
Starlings Law
The more the muscle fibers are stretched, the greater the force of contraction
Main function of electrical conduction system
To create electrical impulse and transmit it to rest of myocardium
Pacemaker
Dictate the rate at which the heart will cycle through its pumping cycle
SA node acts as main pacemaker
Pacemaker settings
SA Node = 60-100
Atrial cells = 55-60
AV Node = 40-60
Bundle of HIS = 40-45
Bundle Branch = 40-45
Purkinje = 20-40
AV node
Controls heart rate, to atria to fully contract and ventricles to fully fill before contracting
Polarization
State of readiness
Na and C outside
K inside
Depolarization
Contraction
Na and C in cell
K outside
Repolarization
Recovery phase
K moves back
Absolute refractory
Brief period where cell will resist re-stimulation
Absolute - will not respond to any stimulus
Relative refractory
Few ms after absolute, the membrane will only respond to very strong stimuli
P wave
Represents atrial depolarization
QRS Complex
Ventricular depolarization
T wave
Represents ventricular repolarization
