RAK_Physio of Conductive System PDF

The conducting system & cardiac electrophysiology Prof. Tarig Hakim Merghani RAKCOMS- RAKMHSU Intended Learning Outcomes Interpret cardiac action potential, its propagation, excitability and refractory period. Illustrate the normal and abnormal ECG and explain the phys...

The conducting system & cardiac electrophysiology Prof. Tarig Hakim Merghani RAKCOMS- RAKMHSU Intended Learning Outcomes Interpret cardiac action potential, its propagation, excitability and refractory period. Illustrate the normal and abnormal ECG and explain the physiological basis of PR, and QT intervals; QRS complex, PR and ST segments; P,T and U waves; and J-point. The SA Node The SA Node or Can discharge action potential spontaneously The pacemaker pacemaker St can discharge action  SA Node The SA Node suppliedby sympatTPasymath increase decrease Supplied by the: the rate of discharge the rate of discharge –sympathetic (increases the rate of discharge) –parasympathetic (decreases the a rate of discharge) Action potential of the SA Node The AP of SA Is characterized by: is characterized by the Eventsface –The prepotential (unstable resting membrane resting membrane potential)) resting membrane happened due potassium efflux catenthar ae through different type ppym of channel  efflux 7 I m 1st eat EEE  AP out in re esht palate Ii mind  decreasethrough leak channel Efflux Cate_through T channels Action potential of the SA Node efflux of Causes of the prepotential: Phase me It –Decreased K+ efflux (through leak a channels) because these channel not fully developed.TT fully developed –Ca++ influx (through T channels) –Funny current caused by Na+ & K+ influx through funny channels 00 um Funny current through influx of K and Wat  fums chanted Efflux Insux of care thing Decrease isthough T channels through leakcheme Action potential of the SA Node icrease the rate of dischang Effect of sympathetic stimulation –Makes prepotential more verical more verical regarding the effect of pre potential on the heart sympathetic receptor Beta 1 Decurens kt esteem 2911518 Rmore verical  Action potential of the SA Node Effect of parasympathetic –Makes prepotential more horizontal The SA Node Mention other factors that affect the discharge rate of the SAN. Mention the 2 Nerotal factor  The AV Node Found above the Fibrous ring Node connect to AS through bundle of His  The AV Node Have the slowest conduction to reach the ventricle velocity (0.02 to 0.05 m/sec) due to gab junction Delays conduction (for about 0.1 sec)  The AV Node AVR The AV nodal delay protects the ventricles from very fast supraventricular rhythm (e.g., ygfapmypmgggygg.gg atrial fibrillation) contraction roughly can reach 500 per min to ventical but due  fibrillation result Death Bundle of His (AV bundle) Cross the Fibrous them into The Bundle branches because it the Fibrone Paes ring  Purkinje fibers Highest conduction velocity (4-5 m/s) Spread of cardiac excitation The interventiular Septum From left to right name the lead The Electrocardiogram It is a record of the electrical activity of the heart The sum of all action potentials that occur in the heart The Electrocardiogram Recording requires: –Ten electrodes Nine active (to chest & limbs) One inactive (to right leg)  The device used is the electrocardiograph which is a modified voltmeter.  Recording Two types: –Unipolar –Bipolar  Recording Unipolar recording: –By one active electrode + an inactive electrode –Gives nine unipolar leads  Recording Bipolar recording: –Two active electrodes + inactive electrode –Gives three bipolar leads Remember The standard ECG consists of 12 leads: 3 bipolar limb leads, 3 augmented limb leads and 6 chest leads.