L6 Heart- Cardiac Conduction Flashcards
Describe the structure of intercalated disc.
Specialized region of intercellular connections between cardiac cells with 3 types of adhering jxns:
- Fascia adherens- actin anchoring sites
- Macula adherens (desmosomes)- binds intermediate filaments
- Gap junctions- connections that allow current to conduct between cardiac cells
Describe the function of intercalated disc and the role of gap jxns in cardiac conduction.
Connect cardiac cells together mechanically and electrically
- Gap jxns couple cells together for conduction
- Gap jxns are sensitive to intracellular Ca and pH
Describe the structure-fxn relationship of SA node and AV node
Fxn: pacemaker activity
Few gap jxn connections= slow conduction
Few myofibrils= weak contraction
Explain how the space constant and AP upstroke determine electrical conduction between cardiac cells.
1
Define the relationship between resting Vm and the Na channel availability.
More negative Vm= more Na channel availability
How does the relationship between resting Em and Na channel availability affect conduction in the heart.
As the Vm becomes more positive (depolarizes), less Na channels are available and the fast response AP upstroke decreases and conduction slows.
Define the PR interval.
1
Define the QRS complex.
1
How can the PR interval and QRS complex be used to evaluate conduction through the AV node?
1
How can the PR interval and QRS complex be used to evaluate conduction through the ventricular muscle?
1
Explain the cellular mechanisms by which PS (ACh) activity affects conduction through AV node.
1
Explain the cellular mechanisms by which Symp (NE) nerve activity affects conduction through the AV node.
1
Explain how autonomically- induced changes in AV conduction manifest on EKG.
1
Define 1st, 2nd and 3rd degree AV block.
1
Define supraventricular tachycardia
1
Define ventricular tachycardia
1
Define atrial fibrillation
1
Define ventricular fibrillation
1
Compare SVT, VT, AFib, VT’s effects on cardiac fxn/output.
1
What is healing over?
Increase in internal resistance due to a decrease in number of open gap jxns, caused by increase in intracellular Ca and H ions (decrease pH).
-Cells close gap jxns and disconnect dead from living cells
Describe the structure-fxn relationship of atrial and ventricular muscle.
Fxn: conduction/contraction
Many gap jxn connections= rapid conduction
Many myofibrils= strong contraction
Describe the structure-fxn relationship of His bundle, bundle branches and Purkinje fibers.
Fxn: very rapid conduction
Many gap jxn connections= rapid conduction
Few myofibrils= weak contraction
