The Heart Channels Electrophysiology of Pacemaker Cells Contracting

The Heart Channels Electrophysiology of Pacemaker Cells Contracting Myocytes Marieb 18

Channels Selectivity Voltage. Gating Inactivation

Currents Flow of ions that change the membrane potential Usually named after ion that moves

Electrophysiology of Pacemaker Cells Resting membrane potential Thresholds Depolarization Repolarization

Pacemaker Cell Currents: ICa 20 m. V -20 m. V -40 m. V -60 m. V

Pacemaker Cell Currents: IK 20 m. V -20 m. V -40 m. V -60 m. V

Pacemaker Cell Currents: If 20 m. V -20 m. V -40 m. V -60 m. V

Slowing the Heart Rate Parasympathetic Vagus Nerve ACh Muscarinic Receptors

Increasing Heart Rate Sympathetic Cardiac Ganglion NE Adrenergic Receptors

Conducting Network Contractile Myocardium Threshold RMP Pacemaker 20 m. V -20 m. V -40 m. V -60 m. V Conducting Contractile

Depolarizing Skeletal Muscle ACh Ligand Gated Channels Voltage Gated Na+ Channels

Zipper Proteins Dihydropyrid ine Receptor (DHP) Ryanodine receptor

Cardiac Muscle Contraction Voltage Gated Na Channel Voltage Gated Ca Channel Voltage gated K Channel

Cardiac Muscle Contraction Voltage Gated Calcium Channels DHP Receptor

Ca++ Mediated Ca++ Release Most Calcium causing contraction is released from SR Ryanodine Receptor

Contractility [Ca++] Force of Contraction

NE and Epinephrine increase Contractility Voltage-gated Ca++ channel Ryanodine SERCA pump

Contractility Positive Inotropic Agents (More Ca++) Negative Inotropic Agents (Less Ca++)