Action potential of Cardiac Muscle and Pacemaker cells : CVS Physiology USMLE / Dr G Bhanu Prakash

📌𝗝𝗼𝗶𝗻 𝗢𝘂𝗿 𝗧𝗲𝗹𝗲𝗴𝗿𝗮𝗺 𝗖𝗵𝗮𝗻𝗻𝗲𝗹 𝗛𝗲𝗿𝗲:- https://t.me/bhanuprakashdr 📌 𝐅𝐨𝐥𝐥𝐨𝐰 𝐨𝐧 𝐈𝐧𝐬𝐭𝐚𝐠𝐫𝐚𝐦:-   / drgbhanuprakash   📌𝗦𝘂𝗯𝘀𝗰𝗿𝗶𝗯𝗲 𝗧𝗼 𝗠𝘆 𝗠𝗮𝗶𝗹𝗶𝗻𝗴 𝗟𝗶𝘀𝘁:- https://linktr.ee/DrGBhanuprakash Action Potential of Cardiac Muscle & Pacemaker Cells | CVS Physiology | USMLE Step 1 & Step 2 CK | Dr G Bhanu Prakash In this high-yield lecture on Cardiovascular Physiology, Dr G Bhanu Prakash explains the detailed action potential of cardiac muscle cells and pacemaker cells, a frequently tested topic in both USMLE Step 1 and Step 2 CK. Understanding the electrophysiological differences between ventricular myocytes and SA/AV nodal cells is crucial for mastering cardiac conduction, arrhythmia mechanisms, and the pharmacologic actions of antiarrhythmic drugs. We begin with the action potential of ventricular contractile cells (non-pacemaker cells), which follows five distinct phases: Phase 0 (Rapid Depolarization) ⚡ – Due to a fast influx of Na⁺ through voltage-gated sodium channels. Phase 1 (Initial Repolarization) 🧲 – Transient K⁺ efflux through Ito channels. Phase 2 (Plateau Phase) ➖ – Unique to cardiac muscle, maintained by a balance between Ca²⁺ influx (via L-type calcium channels) and K⁺ efflux, allowing sustained contraction necessary for effective blood ejection. Phase 3 (Repolarization) 🔋 – Closure of Ca²⁺ channels with continued K⁺ efflux, restoring resting membrane potential. Phase 4 (Resting Phase) 💤 – Maintained by inward rectifier K⁺ channels. We then compare this with the action potential of pacemaker cells (SA node and AV node), which display spontaneous depolarization and lack a true resting membrane potential: Phase 4 (Slow Depolarization) 🔁 – Driven by “funny” If Na⁺ channels, gradually bringing the membrane to threshold. Phase 0 (Depolarization) 📈 – Slower Ca²⁺ influx via L-type channels (no fast Na⁺ channels). Phase 3 (Repolarization) 🧲 – Due to K⁺ efflux. Key concepts covered include: _______________________________ Why the SA node is the dominant pacemaker due to its fastest phase 4 depolarization The role of the AV node in conduction delay How drugs like beta blockers, calcium channel blockers, and class I/III antiarrhythmics target specific phases of the action potential The basis of reentry circuits, ectopic pacemakers, and arrhythmogenesis #CardiacActionPotential #PacemakerCells #VentricularMyocytes #USMLEStep1 #USMLEStep2CK #CardiacElectrophysiology #DrGBhanuPrakash #CVSPhysiology #SA_Node #AV_Node #AntiarrhythmicDrugs #FunnyCurrent #LTypeCalciumChannel #PotassiumChannels #Phase0Phase3 #Repolarization #BetaBlockers #ECGConcepts #MedicalEducationUSA #WhiteboardMedicine #HighYieldPhysiology #USMLEBuzzwords #Step1Review #CardiologyBasics #USMLE2025 #medicalanimations #fmge #fmgevideos #rapidrevisionfmge #fmge2024 #mbbslectures #nationalexitexam #nationalexittest #neetpg #usmlepreparation #usmlestep1 #fmge #usmle #drgbhanuprakash #medicalstudents #medicalstudent #medicalcollege #neetpg2025 #usmleprep #usmlevideos #usmlestep1videos #medicalstudents #neetpgvideos #usmlestep2videos