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Neuroscience > Neurophysiology > Flashcards

Neurophysiology Flashcards

1
Q

Neuronal communication occurs through…

A

Electrical signaling (action potentials)

Chemical signaling (release of neurotransmitters)

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2
Q

What is an action potential?

A

A propagated electrical message of a neuron that travels along the axon to the presynaptic axon terminal

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3
Q

All living cells possess an electrical charge which means…

A

It is more negative inside the cell than outside

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4
Q

What is polarization?

A

The reversal of the electrical charges inside/outside of the cell

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5
Q

By inducing a change in polarization…

A

an action potential is initiated and propagated

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6
Q

Changes caused by the action potential help …

A

initiate release of neurotransmitters

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7
Q

What causes a change in polarization?

A

Movement of specific ions into or out of the neuron

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8
Q

What is a neuron’s resting state?

A

State in which the neuron is inactive - not receiving or sending information

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9
Q

What is a neuron’s resting membrane potential?

A

The difference in voltage between the inside and outside of a neuron.

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10
Q

What is the range for a neuron’s resting membrane potential?

A

-50 to -90 mV

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11
Q

A neuron’s resting state is dependent on..?

A
  • Distribution of different ions (what is the concentration of ions in and out of the neuron?)
  • Membrane selectivity (how easily can ions cross the membrane?)
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12
Q

Ion channels are selectively permeable to…

A

Potassium (K+)

Other ions cannot easily travel across the membrane

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13
Q

What forces act on ions to maintain a resting state?

A

-Forces that drive K+ ions in or out of the neuron
(Diffusion and electrostatic pressure)

-Ion transporters
(Sodium-potassium pump)

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14
Q

What is diffusion?

A

Ions want to travel from an area of high concentration to an area of low concentration

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15
Q

Where do K+ molecules want to go based on diffusion?

A

Inside the cell

less ions inside the cell than outside

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16
Q

Where do K+ molecules want to go based on electrostatic forces?

A

Inside the cell

Potassium is positive and the inside of the cell is more negative

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17
Q

What are the key components of ion transporters?

A
  • Actively move ions against concentration gradient

- Create ion concentration gradients

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18
Q

What are the steps involved in ion transporters?

A
  1. Ion binds

2. Ion transported across membrane

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19
Q

What are the key characteristics of ion channels?

A
  • Allow ions to diffuse down concentration gradients

- Cause selective permeability to certain ions

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20
Q

Is the sodium-potassium pump an ion transporter or an ion channel?

A

Ion transporter

Active transport - requires energy (ATP!)

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21
Q

What ions are pumped into and out of the neuron in a sodium-potassium pump?

A

3,2,1 NOKIA

  • 3 Na+ ions pumped out of neuron
  • 2 K+ ions pumped into neuron
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22
Q

What maintains the resting membrane potential in a sodium-potassium pump?

A
  • Sodium-potassium pump brings K+ into the neuron
  • K+ leaves the neuron through ion channels (diffusion)
  • As negative charge builds up in neuron, electrostatic pressure pulls K+ ions back inside neuron
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23
Q

What is equilibrium?

A

The point at which movement of ions across the cell membrane is balanced

Corresponds to the resting membrane potential (-50 to -90 mV)

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24
Q

What forces act on ions to initiate an AP?

A

EPSPs and IPSPs

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25
Q

What is an excitatory postsynaptic potential (EPSPs)?

A

Message from neuron causes the membrane potential to become less negative (depolarization)

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26
Q

What is an example of an EPSP?

A

Opens Na+ ion channels

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27
Q

Where do Na+ molecules want to go based on electrostatic forces?

A

Inside the cell

Sodium is positive and the inside of the cell is more negative

28
Q

Where do Na+ molecules want to go based on diffusion?

A

Inside the cell

There are less molecules inside the cell than outside

29
Q

What are inhibitory postsynaptic potentials (IPSPs)?

A

Message from neuron causes the membrane potential to become more negative (hyper polarization)

30
Q

What is an example of an IPSP?

A

Opens Cl- ion channels

31
Q

If combination of inputs drives membrane potential to ______ mV, an action potential is triggered.

A

-40 mV

32
Q

True or False:

An action potential is an all-or-none property

A

True.

33
Q

What is special about -40 mV?

A

Na+ voltage-gated ion channels open when the membrane potential depolarizes to -40 mV (threshold)

34
Q

What are voltage-gated ion channels?

A

Ion channels that open when a specific membrane potential is reached

35
Q

True or False:

Many voltage-gated Na+ channels in the membrane are present in the membrane of the soma or the dendrites which is why many APs start here.

A

False

There are many voltage-gated Na+ channels at the axon hillock which is why APs start here

36
Q

Based on diffusion and electrostatic pressure…

A

Na+ rushes through voltage-gated channels

37
Q

When Na+ rushes through the voltage-gated channels, this opens additional channels, and Na+ continues to enter until the membrane potential of the neuron is _____ mV.

A

+ 40

38
Q

What is change in polarization that is characteristic of an AP?

A

The change from a membrane potential of -40 mV to +40 mV

39
Q

What happens after the membrane potential reaches +40 mV?

A
  • Na+ channels close
  • Voltage-gated K+ channels open, further increasing the permeability of the membrane to K+
  • Neuron becomes hyperpolarized
  • Resting membrane potential is restored
40
Q

What are the 5 steps of an AP?

A
  1. Resting state
  2. Depolarization
  3. Rising phase of the action potential
  4. Falling phase of the action potential
  5. Undershoot
41
Q

What is a refractory period?

A

A period where it is unlikely or impossible for another AP to be initiated

42
Q

What are the two forms of refractory periods?

A
  • Absolute refractory period

- Relative refractory period

43
Q

What is an absolute refractory period?

A

No AP can happen because voltage-gated Na+ channels are either open or unresponsive

44
Q

What is a relative refractory period?

A

AP is unlikely because K+ is still rushing out of the neuron and the neuron is hyperpolarized

45
Q

Why is a refractory period important?

A

Refractory periods help ensure that the axon potential is propagated in one direction down the axon

46
Q

How does the AP travel?

A

-AP is regenerated down the axon by an impulse within a neuron
(Voltage-gated channels are crucial for this process)

  • Depolarization of the far end of the axon leads to the opening of nearby voltage-gated Na+ channels
  • Entire process repeats itself down the axon
47
Q

Propagation speed of the AP is dependent on…

A
  • Diameter of the axon

- Whether the axon is myelinated

48
Q

Why do AP travel faster on a myelinated axon?

A

Because myelin prevents K+ leakage

Depolarization is maintained and spreads

49
Q

Where do voltage-gated Na+ channels open at?

A

Nodes of Ranvier

50
Q

What is saltatory conduction?

A

AP jumps from node to node

51
Q

What occurs at the end of the axon in the presynaptic terminal?

A

Depolarization

52
Q

True or False:

Most electrical messages (APs) cannot be sent between neurons.

A

True

Neurons are structurally independent

53
Q

AP causes release of neurotransmitters into the ______.

A

synaptic cleft

54
Q

A higher frequency of APs is related to a…

A

A higher amount of Ca2+ in the axon terminal

55
Q

True or False:

All neurotransmitters bind on the postsynaptic neuron dendrites.

A

False.

(Some bind to auto receptors on the presynaptic neuron to tell the neuron the concentration of the transmitter in the synaptic cleft)

56
Q

What determines the postsynaptic reaction?

A

Postsynaptic receptors

The same neurotransmitter may produce an EPSP or IPSP, depending on what type of receptor it binds to

57
Q

What is a ligand?

A

A substance that binds to receptor molecules

Ex: Acetylcholine

58
Q

What are the 2 different types of receptors?

A
  • Ionotropic

- Metabotropic

59
Q

What are the key characteristics of ionotropic receptors?

A
  • Directly control ion channel
  • ‘Ligand-gated ion channels’
  • Fast synapse
60
Q

What are key characteristics of metabotropic receptors?

A
  • Indirectly control ion channel
  • Neurotransmitter binds to a G protein-coupled receptor
  • Slow synapse
61
Q

What does the binding of the neurotransmitter to the G protein coupled receptor activate?

A

Alpha subunit of G protein

62
Q

What does the alpha subunit open?

A

The ion channel

63
Q

True or False:

The alpha subunit may activate a second messenger.

A

True

64
Q

What is degradation?

A

Enzymes break down the neurotransmitter

Specific enzymes for specific neurotransmitters

65
Q

What is reuptake?

A

Transporters (receptors for the transmitter) bring transmitter back into the presynaptic neuron

Neuroscience (5 decks)

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