Term
| What is potential energy? |
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Definition
| the separation of positive and negative charges which results in stored energy which is referred to as voltage |
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Term
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Definition
| when the potential energy is released and work is done; allowing the separated charges to move freely will create a current |
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Term
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Definition
| the force which slows down the current flow |
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Term
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Definition
| substance which inhibits current flow |
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Term
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Definition
| substance with promotes current flow |
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Term
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Definition
basic equation that states that:
-current=voltage/resistance
-current varies as the voltage varies |
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Term
| What is the ion flow in a living system equivalent to? |
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Definition
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Term
| What creates the potential energy situation in living systems? |
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Definition
| the charge separation across a membrane |
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Term
| What is the equivalent of an insulator in a living system? |
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Definition
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Term
| What is the equivalent of a conductor in a living system? |
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Definition
| the proteins embedded in the plasma membrane |
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Term
| What are passive channels? |
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Definition
| (AKA leakage channels) typically always open and allow specific ions to flow through them |
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Term
| What are active channels? |
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Definition
| (AKA gated channels) only open when they are stimulated; chemically gated channels and voltage gated channels |
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Term
| What are chemically gated channels? |
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Definition
| opens when something binds to the particular transmembrane protein; after it opens, it provides a pathway for ions to flow in or out |
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Term
| What are voltage gated channels? |
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Definition
| opened by a change in potential energy; opens because there is a change in ion distribution at or about the membrane |
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Term
| What are the two factors that influence current flow? |
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Definition
-electrical charge movement
-chemical diffusion |
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Term
| What is electrical charge movement? |
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Definition
| ions that are charged will move to an area that contains an opposite charge |
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Term
| What is chemical diffusion? |
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Definition
| diffusing from an area of high concentration to low concentration |
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Term
| What do both electrical charge movement and chemical diffusion do? |
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Definition
| together they create an electrochemical gradient |
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Term
| What is the resting membrane potential? |
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Definition
| created by unequal concentrations of ions of both charges that exist in a narrow band around each side of the cytoplasmic and extracellular sides of the plasma membrane |
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Term
| What is the composition of a resting membrane potential? |
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Definition
| potential energy is created by separation of charges and a concetration gradient; it is created due to the chemical and electrical forces that develop by separating these ions |
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Term
| What are the charges on either side of the membrane? |
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Definition
| inside the cell is slightly negative and outside is slightly positive |
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Term
| What is polarization of the membrane? |
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Definition
| basis of electrical conductivity of cells that are capable of conducting action potentials |
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Term
| What is the resting membrane potential of the typical cell? |
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Definition
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Term
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Definition
| specific ions are separated at different concentrations immediately around the membrane |
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Term
| What generates concentration differences? |
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Definition
| Na+/K+ pump and # of passive potassium channels vs # of passive sodium channels |
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Term
| How does the presence of Na+/K+ pumps in the plasma membrane generate concentration differences? |
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Definition
-pump requires ATP because moves ions agains concentration gradient
-pumping prevents equilibrium from being reached
-maintains an unequal distribution of ions and therefore creates an electrochemical gradient |
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Term
| How does the # of passive potassium channels vs # of passive sodium channels generate concentration differences? |
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Definition
-# of K+ passive channels is greater
-K+ is able to move more freely than sodium, from in to out
-Na+ has been pumped out of cell but wants to go back in but can't because there isn't as many channels
-this leaves an unequal concentration gradient where plasma membrane is slightly - on inside and slightly + on outside |
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Term
| Why are some cells capable of altering their plasma membrane potential? |
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Definition
| they are either carrying a message of going to do a specific type of work; have gated channels |
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Term
| What are characteristics of a polarized cell? |
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Definition
-charge is separated across membrane
-any cell at RMP is polarized because cell has different concentrations of ions across membrane
-RMP= -70 mV |
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Term
| What are characteristics of a depolarized cell? |
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Definition
-charges have been allowed to flow across membrane
-0 mV |
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Term
| What are characteristics of a hyperpolarized cell? |
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Definition
-cell that is more polarized than it would normally be
-potential energy is greater
-separated more ions than normally would have been |
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Term
| What are characteristics of a repolarized cell? |
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Definition
| -membrane has returned to normal from having been somewhere else |
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Term
| What are mechanisms of change in plasma membrane potential? |
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Definition
-graded potential
-action potential |
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Term
| What are characteristics of graded potential cell membranes? |
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Definition
-chemically gated channels
-channels open and few ions move across
-no voltage gated channels
-change in potential is relatively small
-can be depolarized (move in -> out) or hyperpolarized (move out -> in) |
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Term
| What are characteristics of action potential cell membranes? |
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Definition
-voltage gated channels
-specific for single ion
-at least two types of channels (Na+ and K+ are necessary)
-different ions move in opposite directions
-has to be initiated by change in voltage |
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Term
| What are the 4 phases of an action potential? |
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Definition
1. resting phase
2. active phase: depolarization
3. active phase: repolarization
4. active phase: hyperpolarization |
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Term
| What happens in the resting phase of an action potential? |
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Definition
| cell is at rest, meaning that it is at its resting membrane potential and all of the gated channels are closed |
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Term
| What happens in the active phase: depolarization of an action potential? |
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Definition
| chemically gated channels have opened and Na+ enters which then depolarizes the membrane and causes the Na+ voltage gated channels to open |
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Term
| What happens in the active phase: repolarization of an action potential? |
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Definition
| Na+ channels close and the K+ voltage channels open |
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Term
| What happens in the active phase: hyperpolarization of an action potential? |
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Definition
| K+ ions continue to flow out of voltage gated channels, which stay open a while; have more polarization than would be necessary to return to baseline |
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Term
| What is action potential propogation? |
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Definition
| in the case of skeletal muscle, action potential will travel down both sides while others will just go in one direction and go around |
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Term
| What is the action potential threshold? |
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Definition
| must have enough of the stimulus in order to open the voltage gated channels |
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Term
| What is the all or none rule? |
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Definition
| once the voltage gated channels have opened, the action potential will proceed, no matter what |
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Term
| What is the refractory period? |
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Definition
-period of time where we have just completed an action potential and we have hyperpolarized or repolarized
-period of time when Na+ and K+ ATPases are working and restoring membrane back to its original concentration |
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Term
| What is the absolute refractory period? |
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Definition
| immediate period directly after the action potential stimulus has passed through and because the ions are on the wrong side of the membrane, that particular membrane is capable of generating an action potential |
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Term
| What is the relative refraactory period? |
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Definition
| a little later than absolute period; period where Na+ and K+ ATPase have had a little chance to work to restore the ion concentrations to where it's supposed to be; large stimulus can then generate and action potential |
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