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Phpy 301 > Unit 1 > Flashcards

Unit 1 Flashcards

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1
Q

Action Potential

A

Transient depolarization triggered by a depolarization beyond threshold

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2
Q

Simple Diffusion

A

Movement from one location to another as a result of random thermal motion
-passive

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3
Q

Driving force

A

Determined by electrochemical gradient acting on the solute between two compartments

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4
Q

Electrochemical potential energy difference

A

Contribution from concentration gradient and from any difference in voltage that exists between two compartments

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5
Q

Equilibrium

A

No net driving force for X

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6
Q

Facilitated diffusion

A

Proteins enable ions to cross membranes by moving them downhill
-passive

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7
Q

Pores

A

Channels that are always open

-leak channels

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8
Q

Channels

A

Can be opened/closed by the action of specific mechanisms

-gated

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9
Q

Carriers

A

Conformational change needed to open gate

-“steps”

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10
Q

Active transport

A

Proteins enable ions to cross membranes by moving them across as energy-dependent fashion

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11
Q

Secondary active transport

A

Movement of solute using the gradient created by a pump

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12
Q

Cotransporters (symporters)

A

Use existing gradient to move an ion across the membrane down the gradient
-both in same direction

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13
Q

Exchangers (antiporters)

A

Use an existing gradient to move one ion to the side of membrane of lower concentration in exchange for another ion that is moving to opposite side of membrane where it is present in higher concentration

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14
Q

Membrane potential

A

Separation of positive and negative charges across the cell membrane

  • depolarization = more positive
  • hyperpolarization = more negative
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15
Q

Nernst Equation

A

Equilibrium potential for any ion

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16
Q

Ionic gradient

A

Net diffusion of ions towards compartment of lower concentration

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17
Q

Steady state condition

A

Neither Na or K is in equilibrium but the net flux of charge is null

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18
Q

Resting potential

A

Determined by the relative proportion of different types of ion channels that are open together with the value of their equilibrium potentials

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19
Q

Goldman equation

A

Shows that the resting membrane potential of a cell could be changed by either changing the gradient for a given ion (change Nernst potential) or by changing the relative permeability for an ion

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20
Q

Cations

A

Positive charge

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21
Q

Anion

A

Negative charge

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22
Q

Current (I)

A

Net flow of charge from one point to the other

-amperes (A)

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23
Q

Resistance (R)

A

Resistance to movement of current

-Ohms

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24
Q

Capacitance

A

Ability of a system to store an electric charge

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25
Current clamp
Measurement of cell voltage while controlling the applied current
26
Voltage clamp
Measurement of a cell current while controlling cell voltage
27
Capacitative current
Only flows while Vm is changing
28
Time constant
Time required for voltage to fall to 37% of its initial value
29
Feedback amplifier
Injects opposing current if there is a difference from intended voltage to maintain a constant Vm -equal but opposite in sign
30
Patch clamp technique
Resolves unitary currents through single-channel molecules
31
Cell-attached patch
Only measure single channel that is inside pipette. Cytoplasm remains intact -Pipette solution = extracellular
32
Whole cell patch
Recording of all currents on cel membrane. Direct access to cytoplasm -Pipette solution =intracellular
33
Outside out patch
Extracellular side of channel facing out into bath solution. Broken ends of membrane join. -Pipette solution = intercellular
34
Inside out patch
Cytoplasmic side of channel is facing into bath solution. | -Pipette solution = extracellular
35
Probability of channel opening
Fraction of total time that the channel is in the open state | -applied voltage favours open state
36
Rising phase
Depolarization phase (positive going) - rapid - from -Vm to max + value
37
Depolarization phase
Negative going
38
Afterhyperpolarization
Repolarization undershorts to a voltage min., more negative than Vrest
39
Overshoot
Part of AP that lies above 0 mV
40
Absolute Refractory Period
Impossible to fire another AP - initiation of spike to when repolarization almost complete - due to Na channel inactivation.
41
Relative refractory period
Minimal stimulus necessary for activation is stronger or longer than predicted by the first AP -due to high K conductance and min Na conductance
42
S4 Segment
Positively charged residue every 3rd amino acid | -voltage sensing
43
P region
Dips into membrane but doesn’t cross it - ion selectivity of channel - lines the pore of the channel
44
Selectivity filter
Narrow regions that act as molecular sieves | -must shed waters of hydration to traverse channel
45
Waters of hydration
Ions in solution are surrounded by a cloud of water molecules that are attracted by the next charge of the ion -smaller ions = more waters of hydration
46
Channelopathies
Neurological diseases caused by altered function of ion channel subunits or the proteins that regulate them
47
Delay Rectifiers (Kvs)
Delay in activation. Outward rectifiers - carry current preferentially in an outward direction Voltage gated
48
A-type
Currents that are low threshold, rapidly activating and inactivating K currents
49
BK channels
Calcium activated - large conductance - sensitive to voltage and Ca
50
SK channels
Calcium activated - small conductance - only sensitive to Ca (not voltage)
51
KIR Channels
Inward rectifying K channels - not voltage gated - open at rest (contribute to resting potential)
52
GIRKS
G protein coupled KIR channels - activated by G protein - Mg blocks channels at + values
53
K2P channels
Mediate “leak” k currents | -2 subunits only
54
HVA Ca Channels
High Voltage Activated - more + Vm - L type and PQNR type
55
LVA Ca Channel
Low Voltage Activated - more - Vm - T type
56
T-Type Ca Channel
Tiny Conductance Transient current LVA -fast acting
57
L Type Ca Channel
Large Conductance Long lasting current HVA -slow acting
58
N type Ca Channel
Found in Neurons Neurotransmitter release HVA -fast acting
59
P/Q type Ca Channel
``` Located in Cerebellun Very closely related Neurotransmitter release HVA -fast acting ```
60
Potential difference (V or E)
Potential to do work - moving charge from one place to the other - measured in volts (v)

Phpy 301 (1 decks)

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