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30 Cards in this Set
- Front
- Back
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Coordinated contraction of heart chambers by... |
- rhythmic depolarization along cardiac muscle fibers and a specialized conduction system (bundle of His & Purkinje fibers |
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Fast response cells |
cardiomyocytes Perkinje fibers |
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Slow response cells |
SA node AV node |
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Basic properties of cell membranes |
- selectively permeable: permitting specific substances to pass between the cell and its environment - ion gradient: maintains differences in ion concentrations between the cell's interior and exterior; important in the electrical activity of cells. Roles of Na+/ K+ ATPase, Ca+2 ATPase... - sensitive to changing physical conditions: temperature, pH, voltage, mechanical stimulations - sensitive to extracellular signals: receptor- ligand, anagonits and agonists for ion channel pumps, transporters, exchanger... |
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Gibbs- Donnan Equilibrium across semipermeable membrane |
- phenomenon of solution that contributes to the formation of an electrical potential across a cell membrane --> diffusible ions have affinity for non- diffusible substances distributed unequally |
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Nerst- Goldman equation and membrane potential |
- relationship between the energy or electrochemical potential at a cell membrane to the outside and inside concentrations of a particular ion - the movement of any ion down its own electrochemical gradient will tend to drive the membrane potential toward the equilibrium potential for that ion |
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Donnan equilibrium |
ion imbalance driven by affinity of ions for non-diffusible substances |
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Electrochemical Equilibrium potential |
sum of chemical and electrical potentials. Net ion flow is 0 in resting cell |
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Equilbrium potential |
estimated by Nerst equation |
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Goldman- Hodkin- Katz equation |
determines equilibrium potential across a cell's membrane taking into account concentrations and permeabilites of ALL ions that can pass through the membrane |
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Membrane conditions in cell: |
-permeable to K+ and Cl- -relatively impermeable to Na+ - non- permeable to most anions |
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Membrane potential results from... |
charge separation between inside and outside the cell due to the semipermeable nature of the cell membrane |
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Membrane potential depends on... |
ionic concentration gradients and permeabilities. The membrane permeability is a measure of the ease with when any substance penetrates the membrane when driven by a concentration gradient across the membrane |
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How is the magnitude of the membrane potential determined? |
by the ion with the greater permeability and ionic concentration gradient |
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During resting state what is the charge of the inside of the cell? |
normally negative relative to outside In cardiomyocytes, the resting membrane poetntial is close to Eeq K+ |
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What is the difference between the Nerst and Goldman equation? |
Nernst equation can be used to estimate the elctrochemical equilibrium potential of a single ion while the Goldman equation is used to determine the resting membrane potentials in real cells by taking into account the concentrations and permeabilities pf ALL ions that can pass through the membrane (K+, Na+, Cl-) |
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Compare Action potentials |
draw the difference |
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Resting membrane potential (RMP) |
the difference in potential across the membrane of a cardiomyocyte when it is at rest |
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Threshold potential (TP) |
the level of membrane potential at which sufficient depolarization has occured to initiate an an action potential |
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Depolarization |
the cell membrane potential becomes less polarized (less negative) |
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Repolarization |
the cell membrane becomes polarized (more negative) |
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Hyperpolarization |
the cell membrane becomes more polarized then originial RMP |
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Action potential (AP) |
short-lasting even in which the eelctrical membrane potential of cardiomyocytes rapidly rises and relative slowly falls, following a consistent trajectory |
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Inward currents (negative) |
positive charge (Na+, Ca+2) flowing INTO the cell, or negative charge flowing OUT of the cell |
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Outward currents (positive) |
positive charge (K+) flowing OUT of the cell, or negative charge flowing INTO the cell |
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Refractory period (RP) |
amount of time it takes for an excitable membrane to be ready for a second stimulus once it return to its RMP following excitation |
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What are the two types of sodium channel gating? |
1. voltage gated (electrical-activated) channels 2. Ligand gated (chemically-activated) channels |
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Voltage gated channels |
- open and close with specific changes in the membrane potential o slow channels: rate of opening when voltage changes o fast channels: L type Ca+2 o so variables are membrane voltage and time
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Ligand gated channels |
depend on activation by chemical transmitter |
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What are the 3 conformational states of an ion channel? Draw them |
1. Resting (deactivated)- channel is closed but is avaliable for opening if chemical/voltage stimulus comes 2. Activated state (open)- channel is open and permits the passage of ionic current 3. Inactivated state- channel is closed and unavaliable for activation cell refractory (cell refractory) |
