CV - Quiz 2 resting membrane potentials, electrical activity of heart, excitation-contrtaction coupling Flashcards
Relative to the outside of a cell is the inside positive or negative in charge?
-Negative
Is potassium higher in concentration inside or outside of a cardiac muscle cell?
-Potassium is higher inside the cell
Is sodium higher in concentration inside or outside of a cell?
-Sodium concentration is higher outside the cell.
What prevents potassium from leaking out of a cell until the concentration is the same on the outside and inside of the cell?
-As the K+ leaves cell, negativity increases on the inside of the cell membrane and electrostatically attracts K+. This electrostatic force prevents K+ from leaving cell.
What does the Nernst Equation calculate?
-When chemical driving force (-) electrostatic driving force, NO net movement of K+ = equilibrium.
What ion makes the major contribution to the resting membrane of the cardiac muscle cell?
-Potassium is the major determinant of the Resting Membrane Potential.
What ion makes a small contribution to the resting membrane potential?
-Sodium
What ion pump returns ion concentrations back to baseline?
-The Na+-K+-ATPase Pump
How does the Na+-K+ - ATPase pump contribute to the resting membrane potential?
-For every 3 Na+ going OUT of the cell 2 K+ would be going INTO the cell.
What ion moves rapidly into a cell during depolarization?
- Na+
What ion exits the cell to restore the baseline electrical charge in a cell during repolarization?
- +K
What restores ion concentrations back to their baseline levels?
- Na+-K+- ATPase Pump
In what part of the heart are Fast-Response Action Potentials (non-pacemaker action potentials) found?
- Atrial myocardial fibers, Ventricular myocardial fibers, Purkinje fibers
In what part of the heart are Slow-Response Action Potentials (pacemaker action potentials) typically found?
- Sinoatrial node and atioventricular node
What are some of the differences between Non-pacemaker and Pacemaker action potentials?
- (Fast response = non-pacemaker) and (Slow-response = pacemaker)
- RMP = Slow > Fast; Slope of upstroke = Fast > Slow; Amplitude of action potential = Fast >Slow; Overshoot of action potential = Fast > Slow
What are the 5 phases of the Non-pacemaker (Fast-Response) action potential?
- Phase 0 = Depolarization
- Phase 1 = Partial Repolarization
- Phase 2 = Plateau
- Phase 3 = Repolarizaiton
- Phase 4 = Resting Membrane Potential
Which ions contribute to the various phases?
- Phase 0 = Na+
-Phase 1 = Inactivation of Na+ channels ends transient outward K+ current
-Phase 2 = Slow inward Ca++ currents ( L-type calcium channels) Outward K+ currents.
-Phase 3 = Outward K+ (repolarization) Na+ channel recovery begins during relative refractory period.
-Phase 4 = Na+, K+-ATPase Na+-Ca++ exchanger
ATP-driven Ca++ Pump
What is another name for Phase 2 in a Non-pacemaker cell?
- Plateau
Release of a large amount of calcium from the Sarcoplasmic Reticulum is triggered by entry of which ion?
small amounts of Calcium
What is the function of the Sarcoplasmic Reticulum within a cardiac muscle cell?
regulate intracellular calcium concentration
Which ion is the major determinant of the Resting Membrane Potential in Cardiac cells?
Potassium
What are the various phases found in Pacemaker (Slow Response) Action Potentials?
0,(no phase 1), 2 (very brief),3,4
Which ions contribute to the various phases in the Pacemaker Action Potential?
Zero - calcium influx
Three - Potassium influx (repolarized), low Ca
Four - Na, lower K+ and elevated Ca
What are the different refractory periods associated with the cardiac action potentials?
- Effective or Absolute (ERP) - no action potential can happen
- Relative (RRP)
What is automaticity?
Ability of focal area of heart to generate pacemaking stimuli
What is diastolic depolarization?
slow iinward leakage of Na+ through funny channels, Ca++ influx, K+ efflux
What effects on aspects of diastolic depolarization will cause changes in heart rate?
-Increasing
sympathetic stimulation
Muscarinic receptor antagonist
B-Adrenoceptor agonists
Circulating catecholamines
Hypokalemia
Hyperthyrodism
Hyperthermia
-Decreasing
Parasympathetic stimulation
Muscarinic receptor agonists
B-blockers
Ischemia/hypoxia
Hyperkalemia
Sodium and calcium channel blocker
HypothermiaWhich pacemaker region of the heart is typically dominant?
SA node
What is Overdrive Suppression?
2ndary pacemeakers are hyperpolarized when driven beyond their set rate
What is a sarcomere?
the basic contractile unit of myocite, between two Z-lines
Cardiac cells are arranged in a branching network that is known as what?
functional syncytium
What are T-tubules in a cardiac muscle cell?
openings from sarcolemma that run deep. Let ions (Na+, Ca++) exchange between extra and intracellular compartments
What is the Sarcoplasmic Reticulum?
extensive branching tubular netwrok to regulate intracellular calcium, storage and realease of calcium
What is Excitation-Contraction coupling? pg 43 in book
coupling between myocyte action potentials and contraction
What is the trigger for release of large amounts of calcium from the Sarcoplasmic Reticulum?
small amounts of calcium influx causes release of large amount of calcium from sarcoplasmic reticulum
What is this process called whereby large amounts of calcium are released from the Sarcoplasmic Reticulum into the cell?
Calcium-Induced Calcium Release
The presence of what ion allows binding between actin and myosin?
Calcium
What is the function of Troponin in the binding between actin and myosin?
To inhibit actin and myosin from binding
What is the Sliding Filament Model ?
ratcheting of myosin heads along the actin filaments
Is ATP required for cardiac muscle relaxation?
Yes
