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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
How do mechanically-gated channels work
Regulated by a physical change (pressure, stretch, etc.)
26
What are graded potentials
Changes in the membrane potential that cause an electric signal
27
Graded potentials vary in __ and depend on __
Vary in magnitude and depend on the strength of the stimulus
28
Graded potentials an lead to what
Depolarizations or hyperpolarizations of the membrane potential depending on stimulatory or inhibitory stimuli, respectively
29
What do ligand-gated ion channels cause
Graded potential changes in the membrane potential within the dendrites and cell body
30
What is conduction with decrement
Graded potentials decrease in strength as they get farther away from the opened ion channel
31
When will an action potential fire
When the membrane depolarization caused by graded potentials is large enough at the axon hillock
32
What is spatial summation
When signals arrive at the same time at different locations on the cell membrane and are intergated
33
What part of the neuron integrates/summates graded potentials in space and time
Dendrites and the cell body
34
What is temporal summation
Integration of signals arriving at different times at the same location on the cell membrane
35
What are two neurotransmitters that cause excitatory depolarizations
Glutamine & Acetylcholine
36
What is a neurotransmitter that causes inhibitory hyperpolarizations
Gamma amino butyric acid - GABA
37
What is the action potential
A small stimulus that generates a small depolarizations that is restored quickly
38
How is the action potential generated
A large enough stimulus that can bring the membrane potential to the threshold potential
39
What is the threshold potential
The potential at -55mV at which an action potential will then fire
40
How high does the action potential reach
+40mV
41
List the phases of the action potential
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
What does depolarization of the membrane to threshold potential activate
Voltage-sensitive Na+ channels. Voltage-sensitive K+ channels also open, but with slower kinetics than the Na+ channels
43
How is the action potential triggered
By the gated opening of voltage-gated Na+ channels
44
When do the voltage-gated Na+ channels become unstable and close
At the peak of the action potential. They have an intrinsic capacity for inactivation at +30mV
45
What happens in the action potential's first step - "Resting State"
Voltage-gated channels are closed
46
What happens in the action potential's second step - "Threshold"
In response to a stimulus, voltage-gated Na+ channels open rapidly leading to depolarization->threshold potential is reached->Action potential
47
What happens in the action potential's third step- "Depolarization"
Depolarization of the action potential
48
What happens in the action potential's fourth step - "Repolarization Phase"
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
What happens in the action potential's fifth stop - "Undershot"
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
What is the refractory period
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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