Basic Heart Cards Flashcards
Semilunar Valves
Pulmonic and Aortic
Atrioventricular Valves
Tricuspid and Mitral
Have chordae tendinae and papillary muscles
Describe the Conduction System
- Sinoatrial node in right atrium, automaticity.
- Conducts through atria and then to AV node in intraventricular septum (fibrous rings of semilunar valves limits conduction to AV node only)
- Conduction slows in AV node/bundle of His due to lack of Na channel conduction (Calcium flux depolarizing)
- quickly moves through Purkinje fibers right and left BBBs (Left has anterior and posterior fascicles)
Which artery supplies the AV node?
Right Coronary Artery
Myocyte Resting Potential
-90mV
5 Phases of Cardiac Myocyte Action Potential (0 to 5)
Phase 0: voltage gated Na channels rapidly depolarize
Phase 1: Fast depolarization to roughly 0mV from transient K channels
Phase 2: Plateau phase where inward L-type Ca current = outward K current so that membrane potential is constant
Phase 3: slow and rapid delayed rectifying K currents overcome Ca current and cell repolarizes as more K channels open and Ca is re-sequestered/channels close.
Phase 4: Resting potential is maintained by inward rectifying K channels
Pacemaker Cell Action Potential
Funny current (If) of Na/K slowly depolarizes cells until L-type Ca channels open and cause AP, this provides automaticity. Na channels do not play a major role as the funny current and resting potential of -60mV keeps them in inactivated state
Absolute Refractory Peiod
When too many Na channels are inactivated to create AP
Relative Refractory Period
When Na channels are non longer inactivated but strong K current makes AP threshold much higher
Proteins involved in sarcomere contraction (5)
Myosin Actin Troponin (I, C, T) Titin Tropomyosin
Calcium-Induced Calcium Release
- T-Tubule invaginations contain L-type Ca channels
- Depolarization causes L-Ca to open, Ca enters and binds RyRs on sarcoplasmic reticulum cisternae
- RyRs open and Ca is released into cytoplasm to bind Troponin for sarcomere contraction
- SERCA, Na-Ca Exchanger, and Ca ATP-ase pumps remove Ca from cytoplasm and stops contraction cycles
What nerves/NTs increase cytosolic calcium?
Beta Adrenergic signaling through NE
Net affect is increased inotropy and lusitropy
How does NE signaling increase cytosolic Calcium?
NE binds Gs-coupled beta adrenergic Rs on myocytes. Gs activates AC which increases cAMP which phosphorylates PKAs
PKA phosphorylation increases L-type Ca Channel activity, increases RyR calcium sensitivity, inhibits Phospholamban (SERCA inhibitor), increases Calcium dissociation from troponin C through troponin I
What nerves/NTs decrease cytosolic calcium?
Cholinergic signaling through ACh activates Gi coupled channel which reduce cAMP
Myosin in Myocytes
Mostly beta isoform, slower ATPase activity than in skeletal muscle, prevents tetany
