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Phpy 301 > Unit 1 > Flashcards

Unit 1 Flashcards

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
Q

Current clamp

A

Measurement of cell voltage while controlling the applied current

26
Q

Voltage clamp

A

Measurement of a cell current while controlling cell voltage

27
Q

Capacitative current

A

Only flows while Vm is changing

28
Q

Time constant

A

Time required for voltage to fall to 37% of its initial value

29
Q

Feedback amplifier

A

Injects opposing current if there is a difference from intended voltage to maintain a constant Vm
-equal but opposite in sign

30
Q

Patch clamp technique

A

Resolves unitary currents through single-channel molecules

31
Q

Cell-attached patch

A

Only measure single channel that is inside pipette. Cytoplasm remains intact
-Pipette solution = extracellular

32
Q

Whole cell patch

A

Recording of all currents on cel membrane. Direct access to cytoplasm
-Pipette solution =intracellular

33
Q

Outside out patch

A

Extracellular side of channel facing out into bath solution. Broken ends of membrane join.
-Pipette solution = intercellular

34
Q

Inside out patch

A

Cytoplasmic side of channel is facing into bath solution.

-Pipette solution = extracellular

35
Q

Probability of channel opening

A

Fraction of total time that the channel is in the open state

-applied voltage favours open state

36
Q

Rising phase

A

Depolarization phase (positive going)

  • rapid
  • from -Vm to max + value
37
Q

Depolarization phase

A

Negative going

38
Q

Afterhyperpolarization

A

Repolarization undershorts to a voltage min., more negative than Vrest

39
Q

Overshoot

A

Part of AP that lies above 0 mV

40
Q

Absolute Refractory Period

A

Impossible to fire another AP

  • initiation of spike to when repolarization almost complete
  • due to Na channel inactivation.
41
Q

Relative refractory period

A

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
Q

S4 Segment

A

Positively charged residue every 3rd amino acid

-voltage sensing

43
Q

P region

A

Dips into membrane but doesn’t cross it

  • ion selectivity of channel
  • lines the pore of the channel
44
Q

Selectivity filter

A

Narrow regions that act as molecular sieves

-must shed waters of hydration to traverse channel

45
Q

Waters of hydration

A

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
Q

Channelopathies

A

Neurological diseases caused by altered function of ion channel subunits or the proteins that regulate them

47
Q

Delay Rectifiers (Kvs)

A

Delay in activation.
Outward rectifiers - carry current preferentially in an outward direction
Voltage gated

48
Q

A-type

A

Currents that are low threshold, rapidly activating and inactivating K currents

49
Q

BK channels

A

Calcium activated

  • large conductance
  • sensitive to voltage and Ca
50
Q

SK channels

A

Calcium activated

  • small conductance
  • only sensitive to Ca (not voltage)
51
Q

KIR Channels

A

Inward rectifying K channels

  • not voltage gated
  • open at rest (contribute to resting potential)
52
Q

GIRKS

A

G protein coupled KIR channels

  • activated by G protein
  • Mg blocks channels at + values
53
Q

K2P channels

A

Mediate “leak” k currents

-2 subunits only

54
Q

HVA Ca Channels

A

High Voltage Activated

  • more + Vm
  • L type and PQNR type
55
Q

LVA Ca Channel

A

Low Voltage Activated

  • more - Vm
  • T type
56
Q

T-Type Ca Channel

A

Tiny Conductance
Transient current
LVA
-fast acting

57
Q

L Type Ca Channel

A

Large Conductance
Long lasting current
HVA
-slow acting

58
Q

N type Ca Channel

A

Found in Neurons
Neurotransmitter release
HVA
-fast acting

59
Q

P/Q type Ca Channel

A 
Located in Cerebellun
Very closely related
Neurotransmitter release
HVA
-fast acting
60
Q

Potential difference (V or E)

A

Potential to do work

  • moving charge from one place to the other
  • measured in volts (v)

Phpy 301 (1 decks)

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