Cardiac Physiology Flashcards
What is the conduction system?
specialized muscle cells (myocytes) produce and transmit electrical impulses to create contraction and relaxation
What are myocytes?
specialized muscle cells
What are the components of the conduction system?
SA node, AV node, bundle of HIS, Purkinjie fibers
What is the SA node?
aka sinoatrial node
located at border of SVC and RA
‘Pacemaker of heart’
beats 60-100bpm
causes atria to contract
P wave on EKG
What is the AV node?
aka atrioventricular node
receives impulse from SA node
‘back up pacemaker’
lets ventricles fill
What is the bundle of HIS?
located at base of IVS
receives impulse from AV node
divided AV bundle branches
What are the Purkinjie fibers?
located at apex of heart
curves with each ventricle
carries impulse through ventricle walls
continuation of bundle branches
What causes depolarization?
stimulation of cardiac muscle cells
Where does contraction of the heart start?
starts from inside to outside, starts at apex and moves to base
What does the SNS do?
increases HR and contraction
fibers attach to SA and AV nodes via Vagus nerve
What does the PNS do?
decreases HR and force of contraction
attached to SA node
derived from vagal cardiac nerves
What is an EKG?
recording of electrical activity of the heart, consists of P, QRS, T waves
What does the P wave represent?
depolarization of atria, atrial systole
What does the T wave represent?
repolarization of ventricles, ventricular diastole
What does the QRS complex represent?
depolarization of ventricles, ventricular systole
What is the cardiac cycle?
the timing from beginning of one heart beat to the next
What are the components of pulmonary circulation?
RV, PA and branches, pulmonary capillaries, pulmonary veins
What are the components of systemic circulation?
LV, aorta, systemic capillaries, cerebral, abdominal and peripheral veins, SVC, IVC
What is sinus bradycardia?
slow HR, less than 60 bpm, occurs during sleep or in trained athletes
What is sinus tachycardia?
regular but rapid HR, 100-140 bpm, occurs with exercise
What are premature atrial contractions (PAC)?
when the atria beat early, often felt as palpitations, QRS waves are close together and loss of P wave
What are premature ventricular contractions (PVC)?
when the heart beat originates in ventricles, very common, results in wide QRS complexes, felt as palpitations
What is ventricular tachycardia (V-Tach)?
when several ventricular beats occur in a row, ventricles are not able to fill completely with blood, results in wide QRS complexes
What is ventricular fibrillation?
rapid, chaotic beating of ventricles that can disrupt hearts pumping action, no QRS complexes, LETHAL rhythm
What is asystole?
without systolic beat, ventricular standstill, occurs when heart stops beating
What is a pacemaker?
pulse generator consisting of electronic circuitry and battery, releases impulse when it does not sense intrinsic heart beat
