Term
Is the outside or inside of the cell more positively charged?
Is there more potassium outside or inside of the cell? |
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Definition
outside is positively charged (Na+ and Cl-)
Potassium inside (and negatively charged proteins) |
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Term
| What is it called when there is a potential difference/electrical difference between the inside (- charged) of the cell and outside (+ charged) of the cell due to difference charges? |
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Definition
| resting membrane potention |
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Term
What equation determines the voltage at which the electrical and chemical forces for an ion (X) are balanced?
What does this mean in terms of net movement? |
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Definition
Nernst equation
NO net movement of ions |
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Term
| in excitable cells the RMP is primarily determined by ___ ions |
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Definition
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Term
If we changed the extracellular K concentration from 10 to 1, what would happen to the resting membrane potential of the cell?
What would happen if extracellular K increased instead of decreased? |
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Definition
hyperpolarized (RMP more negative because K more likely to move outside)
depolarized |
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Term
| Is the cell membrane uniformly permeable to all ion? |
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Definition
| No (different ions have different distributions, relative permeability of an ion determines its contribution to the RMP, small permeability to Na and Cl offsets some of the potential set up by K) |
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Term
True or False:
The rest in membrane potential of the cell is at Nernst potential or the equilibrium potential. |
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Definition
False
The resting membrane potential of the cell due to these ions and their limited permeability, the resting potential is not at the Nernst potential or the equilibrium potential, it is actually a little bit depolarized |
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Term
| What is the permeability of potassium, sodium, and chloride? |
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Definition
| The permeability of potassium is relatively high, sodium and chloride relatively low. |
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Term
| Where does the membrane potential lie in relation to ion equilibrium potentials? |
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Definition
Somewhere in between ion equilibrium potentials (-60 to -70)
Na= +67
Cl = -90
K= -98 |
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Term
| What happens if you artificially manipulate the membrane potential? |
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Definition
| reverse direction of current flow (hence reversal potential, ions move) |
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Term
| What faithfully transmit information along the membrane (axon) of excitable cells and allow rapid communication between distant parts of a neuron |
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Definition
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Term
| What are the 3 phase of the action potential? |
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Definition
Resting
Depolarization
Repolarization |
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Term
What phase of the action potential is there an "overshoot" (goes past 0mv and becomes +)
What phase of the action potential is there an "undershoot" (goes beyond resting membrane potential)? |
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Definition
depolarization (reversal of membrane potential)
repolarization |
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Term
True or False:
if the membrane becomes more permeable to one ion over other ions then the membrane potential will move towards the equilibrium potential for that ion (basis of AP) |
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Definition
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Term
| During the action potential, the permeability of ______ changes dramatically, increasing the resting equilibrium of the cell. |
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Definition
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Term
| In depolarization, once threshold is reached, there is a rapid opening of ___-selective channels to allow that ion to go down it's electrochemical gradient. |
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Definition
| Na (membrane more permeable to Na than K, so membrane potential moves toward Na equilibrium (+), overshooting zero) |
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Term
| At the peak of the action potential, ____ is the primary ion determine the membrane potential. |
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Definition
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Term
| In repolarization, what channel is inactivated and what channel is slowly opened? |
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Definition
closure (inactivation) of Na-selective channels
slower opening of K-selective channel |
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Term
Na and K channels:
Which one is fast (activation and inactivation gates open and close right away) and which one is slow? |
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Definition
Na- fast
K - slow (delayed rectifiers - why we get hyper polarization) |
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Term
True or False:
Action potential are graded potentials. |
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Definition
False
all-or-none
AP are NOT graded potentials |
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Term
In order for an AP to occur the membrane must be depolarized beyond a __________.
inward ____ overcomes resting outward ___ movement |
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Definition
in order for an AP to occur the membrane must be depolarized beyond a threshold level
inward Na overcomes resting outward K movement |
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Term
| What are 2 ways you can trigger an action potential? |
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Definition
electrical stimulation
synaptic activation |
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Term
True or False:
activation of Na channels is cyclical |
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Definition
True
APs are regenerative
initial depolarization
opening of Na channels
Na entry |
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Term
| the transmembrane potential difference exists within a narrow band just across the membrane ___________ (insulator-seperates/stores charge). |
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Definition
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Term
What must you do to change a membrane potential?
What slows this down? |
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Definition
must add or remove charge
capacitors (membrane) |
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Term
True or false:
Changing the membrane potential is instantaneous. |
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Definition
False
changing the membrane potential takes time
charging a capacitor is not instantaneous (more like an exponential slope) |
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Term
| What is the time it takes for a voltage to reach its peak (how fast or how slow the membrane responds) |
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Definition
| time constant of the membrane |
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Term
Which constant across neurons and which is not constant across neurons?
time constant of the membrane
membrane capacitance |
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Definition
time constant of the membrane is not constant (resistance changes-small cells have high resistance, big cells have low)
membrane capacitance is constant |
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Term
What is how far something travels before it decays?
What does it depend on? |
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Definition
length constant
depend upon membrane resistance and internal resistance of the axon |
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Term
Which will have a longer length constant: big axon or small axon?
Which will conduct faster: big or small axon? |
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Definition
big
big
(fat axons- big,myelinated-axons are the fastest!) |
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Term
True or False:
APs are conducted along excitable cell membranes away from their point of origin |
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Definition
True
down the axon from cell soma to terminal |
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Term
True or false:
depolarization of the membrane during the AP is restricted to a single spot |
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Definition
False
depolarization of the membrane during the AP is not restricted to a single spot (propagating down axon) |
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Term
| the inward current carried by ___ ions during the AP depolarizes adjacent portions of the membrane beyond threshold and the regenerative AP travels along the membrane |
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Definition
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Term
| What is following a single AP a second AP cannot be generated at the same site for some time? |
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Definition
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Term
| What is when you have two APs occurring very close in time, or two stimuli occurring very close in time, and the second one is ineffective (sodium channels have not recovered from the initial activation, and the potassium channels are open) |
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Definition
| absolute refractory period |
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Term
| Where is when you have two APs occurring and as sodium channels recover, the potassium channels are inactive so if the 2nd stimulus is a little bit later and larger, it can be activated? |
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Definition
| relative refractory period |
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Term
Local circuit propagation is (fast or slow)
In motor neurons, propagation is (fast or slow) |
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Definition
slow (<2 m/s)
fast (100 m/s) |
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Term
What cells envelop axons/provide a layer of insulation?
Does it (increase or decrease) resistance?
Does it (increase or decrease) capacitance? |
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Definition
schwann cell
increase resistance (rm)
decrease capacitance |
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Term
What is the a discontinuity in myelin sheath?
What does this site have a high density of? |
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Definition
Nodes of Ranvier
Na and K channels |
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Term
| What is it when APs are only generated at Nodes of Ranvier, current flows rapidly between nodes (little current leakage between nodes), and the AP “jumps” down fiber as successive nodal membrane capacitances are discharged? |
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Definition
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