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Grade 12 Biology > Nerve Signaling > Flashcards

Nerve Signaling Flashcards

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1
Q

biology voltage definition

A
  • the difference in electrical potential (charge separation)
  • the difference in the amount of energy in charged ions between two points
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2
Q

membrane potential

A

the voltage across a membrane

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3
Q

What is the charge state outside the nerve cell in a membrane potential?

A

there is an excess of cations so positive

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4
Q

What is the charge state inside the nerve cell in a membrane potential?

A

there is an excess of anions so negative

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5
Q

what do you use to measure a membrane potential?

A

a voltmeter

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6
Q

what is resting potential and its value

A

membrane potential of a neuron at rest usually - 70mV

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7
Q

how do you calculate membrane potential?

A

Vm = Vin - Vout

membrane potential = potential inside of cell - potential outside of cell

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8
Q

which cells have a membrane potential?

A

ALL

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9
Q

which cells can generate a large enough change in membrane potential?

A

neurons and muscle cells

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10
Q

what factors maintain the resting potential neurons?

A
  • the ion distribution
  • membrane permeability
  • Na+/K+ pumps
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11
Q

what is the ion distribution in the maintenance of resting potential of neurons?

A

a large pool of negatively charge molecules inside the neuron

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12
Q

what is the membrane permeability in the maintenance of resting potential of neurons?

A
  • there are only Na+ and K+ leak channels
  • more permeable to K+ (efflux) than Na+ (influx
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13
Q

what is the Na+/K+ exchange rate in the maintenance of resting potential of neurons?

A

moves 3 Na+ out for every 2 K+ in

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14
Q

what types of molecules make up the large internal pool that is negatively charged in the ion distribution?

A
  • proteins
  • amino acids
  • sulfate
  • phosphate
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15
Q

Describe the molecules that make up the large internal pool that is negatively charged.

A

large molecules that cannot cross the membrane via diffusion

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16
Q

What regulates the movement of ions?

A

transmembrane proteins (leak channels)

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17
Q

How do the transmembrane transport proteins work?

A
  • facilitated diffusion (passive transport)
  • does not determine the direction or rate of flow
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18
Q

Which has more leak channels? K+ or Na+

A

K+

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19
Q

what is equilibrium potential?

A

potential at which there is no net movement of an ion at equilibrium

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20
Q

What causes the equilibrium potential?

A

passive movement of ions that is dependent on electrochemical gradient

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21
Q

what is the electrochemical gradient composed of?

A

the chemical gradient and electrical gradient

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22
Q

describe the chemical gradient

A
  • concentration gradient
  • chemical force
  • movement from high to low ion concentration
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23
Q

describe the electrical gradient

A
  • ion gradient
  • electrical force
  • movement of positive ion to area of negative ion concentration and vice versa
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24
Q

what type of movement does the K+ channel have with the chemical gradient?

A

passive movement OUT of the cell

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25
Q

what type of movement does the na+ channel have with the chemical gradient?

A

poassive moment INTO the cell

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26
Q

what type of movement does the Cl- channel have with the chemical gradient?

A

passive movement INTO the cell

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27
Q

what type of movement does the K+ channel have with the electrical gradient?

A

passive movement INTO cell

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28
Q

what type of movement does the Na+ channel have with the electrical gradient?

A

passive movement INTO the cell

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29
Q

what type of movement does the Cl- channel have with the electrical gradient?

A

passive movement OUT of cell

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30
Q

what is the net movement of the K+ with the electrochemical gradient?

A

out of the cell

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31
Q

what is the net movement of the Na+ with the electrochemical gradient?

A

into the cell

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32
Q

how does K+ establish equilibrium?

A
  • a chemical force causes K+ diffusion out of the cell making the inside of the cell more negative

the electrical force will pull the K+ back into the cell

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33
Q

When does equilibrium with chemical and electrical forces happen?

A

when chemical and electrical forces are in opposite directions and equal in magnitude

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34
Q

what happens with the cell is left unchecked?

A
  • influx of Na+ makes cell less negative
  • drives steady efflux of K+
  • concentration gradient dissipates
    YOU DIE
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35
Q

What drives the Na+/K+ pump ?

A

uses ATP to drive active transport to maintain ionic gradients

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36
Q

How many Na+ vs K+ get transported by the Na+/K+ pump?

A

3 Na+ out of cell
2 K+ into the cell

more positive ions leaving cell than entering contributing to the -70 mV resting potential

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37
Q

what is hyperpolarization?

A

an increase in voltage across the membrane

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38
Q

how does the Na+/K+ pump work?

A
  1. binding of the cytoplasmic Na+ to the protein causes phsohorylation by ATP
  2. phosphorylation causes the protein to change its conformation
  3. the conformational change expels Na+ to the outside and extracellular K+ binds
  4. K+ binding triggers release of a phosphate group
  5. loss of phosphate restores original conformation
  6. K+ is released into the cell and Na+ sites are receptive again CYCLE REPEATS
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39
Q

what is depolarization?

A

reduction in voltage across the membrane

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40
Q

describe the ions in hyperpolarization

A

K+ outflow, Cl- inflow

more negative

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41
Q

describe the ions in depolarization

A

increase Na+ flow, less negative + more positive

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42
Q

what are the types of potentials?

A
  • graded potential
  • threshold potential
  • action potential
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43
Q

what is the graded potential?

A

all membrane potentials are below the threshold

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44
Q

What is the magnitude of a membrane potential affected by?

A
  • strength of stimulus
  • distance that stimulus travels
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45
Q

what happens with a stronger stimulus?

A
  • more channels open
  • increase cells permeability for the ion
  • producing a larger change in membrane potential
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46
Q

what does it mean to be decremental?

A

the magnitude decays/degenerates as it spreads

47
Q

what is the threshold potential?

A

the potential at which an action potential occurs

48
Q

what happens with the threshold is reached?

A

the graded potential becomes an action potential

stimulus intensity plays no role in the magnitude

49
Q

what is the action potential?

A

a large depolarization followed by repolarizing back to resting

50
Q

where is the action potential generated?

A

in the axon

51
Q

what is the axon hillock?

A

an anatomical description site where the axon begins

52
Q

what is the trigger zone?

A

a functional description that refers to the region on the axon in which the first action potential occurs - often the same place as the axon hillock

53
Q

what are the types of channels on neurons?

A
  • ungated, leak
  • voltage-gated
  • chemically-gated
54
Q

describe the state of the ungated, leak channels

A

open at all times

55
Q

describe the state of the voltage-gated channels

A

open or close in response to changes in membrane potential

56
Q

describe the state of the chemically-gated channels

A

open or close in response to chemicals

57
Q

where are chemically-gated channels located on a neuron?

A

at dendrites

58
Q

where are voltage-gated channels located on a neuron?

A
  • on the axon at the notes of ranvier
  • the synaptic terminal
59
Q

where are ungated, leak channels located on a neuron?

A

all over the cell

60
Q

what are examples of ungated, leak channels?

A

Na+ and k+ channels involved maintaining resting potential

61
Q

what are examples of voltage-gated channels?

A
  • Na+ and K+ channels involved in an action potential
  • Ca+ channels involved in a synapse
62
Q

what are examples of chemically-gated channels?

A

receptors open when neurotransmitters bind

63
Q

Describe the K+ Channel.
- resting position
- depolarization stimulus
- speed

A
  • resting position: closed
  • depolarization stimulus: opens
  • speed: slow
64
Q

Describe the Na+ activation Channel.
- resting position
- depolarization stimulus
- speed

A
  • resting position: closed
  • depolarization stimulus: opens
  • speed: rapid
65
Q

Describe the Na+ inactivation channel.
- resting position
- depolarization stimulus
- speed

A
  • resting position: open
  • depolarization stimulus: closes
  • speed: slow
66
Q

what are the phases of an action potential?

A
  1. rapid depolarization
  2. rapid repolarization
  3. undershoot
  4. return to resting
  5. threshold
67
Q

what happens during the resting state

A

nothing - only ungated leak channel open

68
Q

What happens during Step 2 - threshold?

A
  • depolarization stimulus open some Na gates
  • results in a graded potential that reaches threshold
69
Q

What happens during Step 3 - depolarization phase?

A
  • the depolarization opens NA gates resulting in more depolarization
  • stimulates other Na gates to open until all are open
  • positive feedback bc depolarization potential triggers a larger depolarization to action potential
70
Q

What happens during Step 4 - repolarizing phase?

A
  • closing sodium inactivationg gates so there nore entry of Na+
  • opening of potassium channels so K+ moves out of cell
  • cell becomes more negative
71
Q

What happens during Step 5 - the undershoot?

A
  • closing K+ gates means too many K+ can get out of the cell resulting in hyperpolarization
  • reestablish resting potential with the Na+ and K+ leak channels
72
Q

propagation

A

an action potential “travels” by repeated regeneration along the axon

73
Q

what direction does propagation occur in?

A

unidirectional

74
Q

what is the refractory period?

A

period when neuron is insensitive to depolarization

75
Q

what causes the refractory period?

A

a closed Na activation gate

76
Q

When does the refractory period happen?

A

during the repolarization and undershoot phases

77
Q

What is the purpose of the refractory period?

A

prevents the action potential from moving backwards

it limits the maximum frequency with which action potential can be generated

78
Q

What factors affect the speed of conduction?

A
  • axon diameter
  • myelination
79
Q

How does a larger axon diameter affect the speed of conduction? Why?

A

larger makes it faster as there is less resistance

80
Q

what is saltatory conduction?

A

when the current generated by action potential at a node “leaps” to next node to stimulate new action potential

81
Q

An action potential is All-or-Nothin. What does this mean?

A

magnitude of action independent of stimulus strength once threshold is reached

82
Q

How is stimulus strength translated into an action potential if the stimulus strength can’t change the magnitude?

A

Frequency coding

83
Q

what is frequency coding?

A

stimulus strength & duration correlates to frequency of action potential

84
Q

what is a synapse

A

a cell junction that controls communication between a neuron and another cell

85
Q

describe an electrical synapse

A

current from presynaptic cell flows directly to the postsynaptic cell through gap junctions - direct communication through physical connection

86
Q

What types of species have electrical synapses?

A
  • found in giant axons in crustaceans
  • not common in vertebrates
87
Q

what is the advantage of an electrical synapse?

A

rapid transmission of action potential from cell to cell

88
Q

what is the disadvantage of an electrical synapse?

A

more difficult to regulate

89
Q

what is a synaptic cleft?

A

a narrow gap separating pre and postsynaptic cell

90
Q

what are the steps of a chemical synapse?

A
  1. presynaptic membrane depolarized by action potential
  2. voltage-gated Ca2+ channels open
  3. Ca2+ enters cell
  4. stimulates exocytosis of synaptic vesicles
91
Q

what is a synaptic vesicles?

A

sacs at the synaptic terminal that contains neurotransmitters

92
Q

what is a neurotransmitter?

A

substance released by presynaptic cell as an intercellular messenger into synaptic cleft

93
Q

each neuron usually secretes only one type of neurotransmitter

A
94
Q

What is the effect of changing the Ca levels in the chemical synapse? Steps

A
  • Voltage-gated Ca2+ channels close soon after opening
  • Ca2+ actively transported out of axon terminal bringing it back to resting level
  • but if another action potential arrives soon after previous, then Ca2+ levels continue to increase
  • frequency of AP -> [Ca] -> [NT]
95
Q

What happens when a neurotransmittter (NT) binds to a receptor?

A

gates open allowing in a specific ion (I.i. Na, K, Cl)

96
Q

what are the receptors a part of?

A

a gated ion channel

97
Q

Each type of receptor on the post-synaptic membrane specifically recognize one neurotransmitter

A
98
Q

what are postsynaptic potentials? (PSP)

A

graded potentials that start at the dendrites and progress to the axon hillock on the post-synaptic neuron

are decremental

99
Q

what are the two types of PSP?

A
  • excitatory (EPSP)
  • inhibitory (IPSP)
100
Q

what’s an excitatory synapse?

A
  • an increased chance of generating an action potential
  • depolarization
  • net flow of positive charge into cell
101
Q

What is an inhibitory synapse?

A
  • a decrease in the chance of generating an AP
  • hyperpolarization
  • net flow of negative charge into the cell
102
Q

what is an example of an excitatory synapse?

A

neurotransmitter binding to receptor which open the gated Na+ channels causing Na+ to enter

103
Q

What is an example of an inhibitory synapse?

A

neurotransmitters binding to receptor that open gated K+ and Cl- channels and the diffusion down electrochemical gradients K+ leaves and Cl- enters

104
Q

What is summation?

A

the additive effects of postsynaptic potentials

105
Q

How/Why does summation work?

A

a single EPSP is usually not strong enough to trigger an action potential so you needed several EPSPs working together on the same postsynaptic cell to have a cumulative impact

106
Q

Where does summation occur?

A

at the axon hillock

107
Q

What are the different types of summation?

A
  • spatial summation
  • temporal summation
108
Q

what is spatial summation?

A

when several different synaptic terminals (usually from different presynaptic cells) stimulate the same postsynaptic cell at the same time

109
Q

What is temporal summation?

A

a chemical transmission form one or more synaptic terminal occuring close together in time affecting membrane on postsynaptic membrane before the voltage can return to resting potential

110
Q

how are neutrotransmitter’s removed?

A

enzymatic degradation

111
Q

What is the consequence of removing a neurotransmitter?

A
  • ensuring the effect of NT is bried and precise
  • allows transmission of the next action potential
112
Q

what are other possible fates for the neurotransmitter?

A
  • reuptake into the presynaptic cell
  • diffusion out of the synaptic cleft
113
Q
A

Grade 12 Biology (30 decks)

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