GMS6530 FINAL EXAM PT. 2 QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
How to convert a concentration gradient to an electrical potential?
make the membrane permeable to one ion
What is the Nernst potential?
the outward "diffusive" force on K+ ions balances the inward electrical force on the K+
ions
What is the Nernst equation?
equilibrium between an ion concentration difference and the potential across a semi-
permeable membrane
How many human ion channel genes are known?
340
T/F: Na+ channel opening initiates the action potential
true
When do sodium channels activate to open?
~-70 mV
What maintains the plateau of the action potential?
Calcium channel opening and Na+/Ca+ exchanger
What terminates the action potential?
calcium channel closing and K+ channels opening
What are the five phases of contractile and conductile cells?
, 0 = Ina
1 = close Ina; open Ito
2 = calcium in and K out
3 = increase in K decrease in calcium
4 = ~-90mV
What are fast response myocardial cells?
found n cells designed to contract and cells designed to conduct; based on membrane
properties/ionic currents
Where are slow response cardiac cells?
found in nodal cells (SA and AV) and are based on ionic currents
T/F: Slow response cardiac cells have NO resting potential
true (-60 mV and decreasing)
What are the electrical properties of the heart?
excitability of myocardial cells, threshold values, depolarization, conduction velocity,
refractoriness, automaticity
What does conduction velocity depend on?
1. the amount of Na ions flowing through activated channels and the speed at which this
occurs determines the amplitude of upstroke and AP velocity
2. sodium channel blockers slow conduction by reducing inward sodium current
3. gap junction resistance increase impedes flow from cell to cell and slows conduction
When does gap junction resistance increase?
in late phase ischemia
T/F: Rate of rise depends on number of available sodium channels
COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
How to convert a concentration gradient to an electrical potential?
make the membrane permeable to one ion
What is the Nernst potential?
the outward "diffusive" force on K+ ions balances the inward electrical force on the K+
ions
What is the Nernst equation?
equilibrium between an ion concentration difference and the potential across a semi-
permeable membrane
How many human ion channel genes are known?
340
T/F: Na+ channel opening initiates the action potential
true
When do sodium channels activate to open?
~-70 mV
What maintains the plateau of the action potential?
Calcium channel opening and Na+/Ca+ exchanger
What terminates the action potential?
calcium channel closing and K+ channels opening
What are the five phases of contractile and conductile cells?
, 0 = Ina
1 = close Ina; open Ito
2 = calcium in and K out
3 = increase in K decrease in calcium
4 = ~-90mV
What are fast response myocardial cells?
found n cells designed to contract and cells designed to conduct; based on membrane
properties/ionic currents
Where are slow response cardiac cells?
found in nodal cells (SA and AV) and are based on ionic currents
T/F: Slow response cardiac cells have NO resting potential
true (-60 mV and decreasing)
What are the electrical properties of the heart?
excitability of myocardial cells, threshold values, depolarization, conduction velocity,
refractoriness, automaticity
What does conduction velocity depend on?
1. the amount of Na ions flowing through activated channels and the speed at which this
occurs determines the amplitude of upstroke and AP velocity
2. sodium channel blockers slow conduction by reducing inward sodium current
3. gap junction resistance increase impedes flow from cell to cell and slows conduction
When does gap junction resistance increase?
in late phase ischemia
T/F: Rate of rise depends on number of available sodium channels
