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Neural communication Flashcards

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1
Q

A healthy neuron has a resting membrane potential (or voltage) of

A

between -60 and -80 mV

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2
Q

Neuronal communication is chemical

A

sodium Na+ and potassium K+ move in and out of the membrane

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3
Q

Neuronal communication is electrical

A

Ions are charged positively Na+ K+

as they move in and out of the cell, they change the potential of the membrane. It is relative!

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4
Q

Electrical and chemical gradients

A

charge/ions wants to flow from high concentrations to low

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5
Q

Equilibrium between electrical and chemical gradients

A

When they are at odds, one against each other. = 0mV

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6
Q

Membrane potential

A

Electrical gradient pushing one way and chemical pushing other

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7
Q

The cell membrane

Phospholipid bilayer

A

Hydrophilic heads and hydrophobic tails

Lipid bilayer is tightly packed

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8
Q

Passive transport through bilayer

A

Very very small molecules can pass the layer without channels or pumps

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9
Q

Channels

A

Facilitates passive diffusion (along chemical gradient) for bigger molecules

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10
Q

Pumps

A

Active transport.
They push ions against their chemical gradient: requires ATP.
Slower than channels

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11
Q

Consumes 2/3rds of all neuronal energy

A

The sodium potassium pump

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12
Q

The sodium potassium pump

A

Pushes 3 Na+ out and 2 K+ in
(more Na+ out of cell than K+ into)
Inside gets negative

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13
Q

Conformation of protein

A

When a protein changes shape so that only one ion can bind

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14
Q

Potassium leak channel

A

Constantly open, K+ can move freely via this channel
K+ moves more to outside
Builds up potential - makes cell more negative

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15
Q

After the cell pumps K+ to the inside

K+….

A

Gets out of the cell, according to the chemical gradient, through leak
cell gets more and more negative

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16
Q

Electrical force starts trying to push K+ back into the cell through channel BUT…

A

electrical force (pushing K+ in) is as high as chemical gradient (pushing K+ out) = equilibrium

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17
Q

When electrical gradient (pushing k into cell) equals force of chemical gradient (pushing k out of cell)…

A

resting membrane potential of -70mV

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18
Q

Postsynaptic Potentials

A

When a neurotransmitter molecule binds to a postsynaptic receptor. It can have two localized effects: Depolarize or hyperpolarize the membrane

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19
Q

Excitatory postsynaptic potential (EPSP)

A

Depolarizes membrane!
The membrane potential goes from -70 to -67 mV.
Increases the likelihood that the postsynaptic neuron will fire an action potential (AP).

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20
Q

Inhibitory postsynaptic potential (IPSP)

A

Hyperpolarizes membrane!
The membrane potential goes from -70 to -72mV.
Decreases the likelihood that the postsynaptic neuron will fire an action potential (AP)

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21
Q

The transmission of postsynaptic potentials (PSPs) is

Graded means…

A

The more NTs are binding to more receptors the stronger the voltage change will be

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22
Q

The transmission of postsynaptic potentials (PSPs) is

Rapid means…

A

PSPs travel like an electrical signal along an uninsulated wire (dendrite)

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23
Q

The transmission of postsynaptic potentials (PSPs) is

Decremental means…

A

It decays along the dendrite

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24
Q

Temporal summation of postsynaptic potentials

A

EPSPs and IPSPs voltages sum over time until threshold of excitation is reached (-55)

25
Q

Spatial summation

A

If 1 EPSP and 1 IPSP are released into one axon, the voltages are neutralized. They are summed.

26
Q

Threshold of excitation (-55) is reached when…

A

the sum of PSP’s reaches the axon initial segment and is sufficient to depolarize the membrane above -55

27
Q

What is an action potential?

A

Massive momentary reversal of the membrane potential - from -70 to +55 mV (reversal of the polarity at the membrane from negative to positive)

28
Q

Action potential steps

A

Resting potential -> depolarization -> repolarization -> hyperpolarization phase

29
Q

Voltage gated (or activated) ion (mostly sodium) channels are responsible for..

A

Action Potential generation and conduction

30
Q

Na+ channels open and Na+ goes into cell when…

A

Potential reaches -55 mV -> threshold of excitation

31
Q

Na+ goes into the cell and it becomes positive.

After this, the activation gate…

A

Innactivated the channel. Automatic built in inactivation - ball and chain that blocks gate without closing

32
Q

What is the absolute refractory period?

A

it is when Na+ channels stay inactivated (after action potential) until membrane goes back to resting potential

33
Q

After threshold of excitation, sodium channels open, and after that…

A

Potassium channels open and finish opening at the peak of action potential. K+ flows to outside.

34
Q

At the peak of AP K+ channels finish openning and…

A

Sodium channels innactivate (ball and chain)

35
Q

At the end of AP curve, at the start of hyperpolarization…

A

K+ channels start closing

36
Q

The slow closing of voltage-gated K+ channels at the end of AP leads to

A

hyperpolarization phase and the relative refractory period

37
Q

Relative refractory period

A

Happens during hyperpolarization. The cell can fire but requires more EPSPs

38
Q

After AP Na+/ K+…..

A

Na+/ K+ pumps restores ion balance over time (slow) back to -70

39
Q

Potassium pumps don’t play a role in the firing of AP because…

A

They are too slow

40
Q

What is hyperpolarization (after AP)?

A

After AP, when K+ (potassium) channels start to close. cell is between -70 and -75

41
Q

What makes the AP an all of nothing event?

A

The voltage gated ion channels, that only open in a certain voltage

42
Q

Depolarization

A

When Na+ channels open and action potential happens. curve going up

43
Q

Repolarization

A

after K+ channels finish opening and sodium channels close. Curve going down.

44
Q

cascading signal of the axon, AP doesn’t spread in all directions

A

Channels are opened by the previous ones
Voltage spreads in all directions but the action potential goes straight due to the channels behind it being inactive (ball and chain blocks NA channels)

45
Q

myelinated axon - nodes of Ranvier

A

Na+ gated channels ONLY at the nodes of ranvier in a myelinated axon
These nodes are between the myelin sheaths

46
Q

myelin sheaths

A

located between nodes of ranvier

47
Q

Why do myelinated axons conduct action potentials faster?

A

Because of Saltatory conduction and because less Na+ gated channels need to open for the conduction to happen.

48
Q

Saltatory conduction

A

Channel in the node of ranvier is activated and the electricity generated is insulated inside the myelinated sheath, where the it spreads passively, and at almost the speed of light

49
Q

terminal buttons (boutons) have…

A

vesicles filled with neurotransmitters

50
Q

What does the action potential do to terminal boutons?

A

Action potential depolarizes bouton and causes NT to release

51
Q

How does an action potential depolarize a bouton?

A

AP Causes voltage-gated Ca++ channels to open

  • Ca++ causes vesicles to fuse with membrane
  • When the vesicle fuses -> Neurotransmitters released into synapse
52
Q

Receptors are often just closed channels

A

ligand-gated ion channels - that open when they bind with NTs

53
Q

When an NT binds to a receptor it can…

A

causes the flow of Na+ inside (depolarization = EPSP) or K+ outside (hyperpolarization = IPSP)

54
Q 
More chloride (Cl-) outside than inside of cell
IPSP causes Cl- ...
A

to flow into the cell

55
Q

Are action potentials graded?

A

No, APs always look the same

56
Q

PSPs (Postsynaptic potentials) strength is amplitude modulated, which means…

A

a stronger signal has stronger potential

57
Q

Action potentials strengths are frequency modulated, which means..

A

The stronger the signal, the more frequent APs fire

58
Q

Rapid: PSPs?

APs?

A

PSPs - yes

APs - less so

59
Q

Are APs decremental?

A

No

Psych 207 (9 decks)

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