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Bio 225 > Neurobiology 2 > Flashcards

Neurobiology 2 Flashcards

1
Q

Define membrane potential

A

The difference in electrical charge between the outside and inside of the cell measured in millivolts (mV)

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2
Q

Where do electrical charges that influence membrane potential come from

A

Ions

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3
Q

At rest, what are the concentrations of ions inside the neuron

A

Potassium - High.

Sodium & Chlorine - Low.

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4
Q

What can be said about organic anions (A-) and their concentrations with respect to neurons

A

High inside concentration and does not leave the cell.

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5
Q

When does the membrane potential change

A

When an ion is selectively allowed to move down its concentration gradient

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6
Q

Ion flux across a membrane depends on:

A
  1. Concentration gradient

2. Electrical difference (membrane potential)

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7
Q

Greatest electrochemical difference is greatest in which type of cells

A

Neurons

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8
Q

How does a neuron generate a resting membrane potential

A

By the movement of potassium (K+) down its concentration gradient out of the cell

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9
Q

What type of K+ channels are open at rest in the neuron

A

Non-gate K+ channels

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10
Q

What direction is the net flux of potassium in the neuron

A

Out of the cell

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11
Q

What channels determine the net flux of potassium in the neuron

A
  1. Non-gated (leaky) potassium channels

2. Na+/K+ ATPase

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12
Q

How is the resting membrane potential generated

A

Movement of K+ down its concentration gradient

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13
Q

How is the resting membrane potential maintained

A

Na+/K+ ATPase

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14
Q

How do you calculate the equilibrium potential (E-ion) for a particular ion

A

Nernst Equation

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15
Q

How do you calculate the membrane potential based on the concentrations, valences, and relative permeabilities of a series of ions

A

Goldman Equation

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16
Q

The membrane at rest is slightly leaky to what ions

A

Na+ and K+

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17
Q

Why is the neuron’s resting potential -70mV when potassium’s equilibrium potential is -90mV

A

Because of leaky Na+ channels making it more positive

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18
Q

If you selectively open a particular type of ion channel, what will the neuron try to do

A

Cause the membrane potential to approach the equilibrium potential for that ion

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19
Q

How can a neuron rapidly change its membrane potential

A

By changing its permeability to specific ions

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20
Q

What are gated ion channels

A

An ion channel where something causes them to open and close

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21
Q

What are three types of gated ion channels

A
  1. Ligand-gated channels
  2. Voltage-gated channels
  3. Mechanically-gated channels
22
Q

How do ligand-gated channels work

A

A signal (ligand) binds to the channel and regulate the opening/closing of the gate

23
Q

What is an example of a ligand-gated channel

A

Acetycholine regulatin the entry of Na+ into muscle cells

24
Q

How do voltage-gated channels work

A

Regulated by the electrical state of the cell

25
Q

How do mechanically-gated channels work

A

Regulated by a physical change (pressure, stretch, etc.)

26
Q

What are graded potentials

A

Changes in the membrane potential that cause an electric signal

27
Q

Graded potentials vary in __ and depend on __

A

Vary in magnitude and depend on the strength of the stimulus

28
Q

Graded potentials an lead to what

A

Depolarizations or hyperpolarizations of the membrane potential depending on stimulatory or inhibitory stimuli, respectively

29
Q

What do ligand-gated ion channels cause

A

Graded potential changes in the membrane potential within the dendrites and cell body

30
Q

What is conduction with decrement

A

Graded potentials decrease in strength as they get farther away from the opened ion channel

31
Q

When will an action potential fire

A

When the membrane depolarization caused by graded potentials is large enough at the axon hillock

32
Q

What is spatial summation

A

When signals arrive at the same time at different locations on the cell membrane and are intergated

33
Q

What part of the neuron integrates/summates graded potentials in space and time

A

Dendrites and the cell body

34
Q

What is temporal summation

A

Integration of signals arriving at different times at the same location on the cell membrane

35
Q

What are two neurotransmitters that cause excitatory depolarizations

A

Glutamine & Acetylcholine

36
Q

What is a neurotransmitter that causes inhibitory hyperpolarizations

A

Gamma amino butyric acid - GABA

37
Q

What is the action potential

A

A small stimulus that generates a small depolarizations that is restored quickly

38
Q

How is the action potential generated

A

A large enough stimulus that can bring the membrane potential to the threshold potential

39
Q

What is the threshold potential

A

The potential at -55mV at which an action potential will then fire

40
Q

How high does the action potential reach

A

+40mV

41
Q

List the phases of the action potential

A
  1. Depolarizing graded potential
  2. Depolarization phase of action potential
  3. Absolute refractory period
  4. Relative refractory period
  5. Repolarization phase of action potential
  6. After-hyperpolarization (the dip phase)
42
Q

What does depolarization of the membrane to threshold potential activate

A

Voltage-sensitive Na+ channels. Voltage-sensitive K+ channels also open, but with slower kinetics than the Na+ channels

43
Q

How is the action potential triggered

A

By the gated opening of voltage-gated Na+ channels

44
Q

When do the voltage-gated Na+ channels become unstable and close

A

At the peak of the action potential. They have an intrinsic capacity for inactivation at +30mV

45
Q

What happens in the action potential’s first step - “Resting State”

A

Voltage-gated channels are closed

46
Q

What happens in the action potential’s second step - “Threshold”

A

In response to a stimulus, voltage-gated Na+ channels open rapidly leading to depolarization->threshold potential is reached->Action potential

47
Q

What happens in the action potential’s third step- “Depolarization”

A

Depolarization of the action potential

48
Q

What happens in the action potential’s fourth step - “Repolarization Phase”

A

Na+ channels become unstable and the inactivation gates close rapidly. Voltage-gated K+ channels open and K+ moves out of the cell. Closing of Na+ channels and opening of K+ leads to a repolarization

49
Q

What happens in the action potential’s fifth stop - “Undershot”

A

After depolarization, the membrane potential goes all the way down to -90mV because both the Na+ channels activation and inactivation gates are closed. K+ channels are still open, but slowly

50
Q

What is the refractory period

A

During the undershoot phase of the action potential, the neuron cannot depolarize in response to another stimulus

Bio 225 (11 decks)

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