chapter 13 Flashcards
What is the electrical signaling of the heart?
- Sinoatrial node (SA node)
- Atrioventricular node (AV node)
- Bundle of His
- Right and Left bundle branches
- Purkinjie fibers
Why don’t we have erratic action potentials throughout the heart?
The SA node has the highest frequency therefore setting the pace, faster rate than others
Why is there a .1 delay in the signaling of the SA node and AV node?
To allow enough time for the ventricles to fill up
What are the first 3 steps of the cAMP 2nd messenger system?
- Ligand binds to G- Proteinreceptor
- G- proteins are activated, GDP is swapped for GTP
- Alpha subunit and GTP dissociate from beta and gamma units and bind with Adenylate cyclase
What are the steps 4 and 5?
- Adenylate cyclase is activated, catalyzes ATP into cAMP
5. cAMP activates PKA (Protein Kinease A)
Which enzyme is activated?
Adenylate Cyclase
Which second messenger is increased?
cAMP
What does that second messenger do?
Activates PKA (Protein Kinase A)
What does PKA do in cardiac muscle?
Phosphorylates the protein phospholammban increasing activation of CA2+ ATPase pump in sarcoplasmic reticulum of cardiac muscle
How does phospholamban affect cardiac contractions?
Makes stronger contractions
What are the differences between the action potentials in autorhythmic cells vs. cardiac myocytes?
- Autorhythmic cells DO NOT need an external stimulus to fire, steady resting potentials
- Cardiac Myocytes DO need a stimulus to fire, steady resting potential
What ion is important in Phase 0 (depolarization) during the action potentials for cardiac myocytes?
Sodium
What ion is important in Phase 1 (early repolarization) during the action potential for cardiac myocytes?
potassium
What ion is important in Phase 2 (Plaeau) during the action potential for cardiac myocytes?
potassium and calcium
What ion is important in Phase 3 (Repolarization) during the action potential for cardiac myocytes?
potassium
