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NRSC2000 > Electrical Properties of Nerve Cells Part 1 > Flashcards

Electrical Properties of Nerve Cells Part 1 Flashcards

1
Q

What causes receptor potential?

A

Due to the activation of
sensory neurons by external stimuli

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2
Q

How do neurons respond to external stimuli (receptor potential)?

A

These neurons respond to the external stimuli (ex: touch) with a receptor
potential that changes the resting potential for a fraction of a second

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3
Q

What is synpatic potenital reocrded throuhg?

A

Synpatic contacts

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4
Q

When does an action potential occur?

A

Occurs when a neuron sends information down an axon, away from the cell body

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5
Q

Action Potential Function

A

Responsible for long range transmission of information within the nervous system and allow the nervous system to transmit information
to its target organs, such as muscle

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6
Q

Effects of current on membrane potential?

A

injection of small amounts of current result in small shifts of membrane potential

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7
Q

Effects of stopping current injection on membrane potential

A

When current injection stops, the membrane potential recovers to the resting potential

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8
Q

Hyperpolarized

A

A change in a cell’s membrane potential that makes it more negative

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9
Q

Depolarization

A

Change in cell’s membrane potential that makes it more positive

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10
Q

Graded Potential

A

A change in the electrical potential on the membrane of an nerve cell in response to a stimulus, and where the magnitude of change is proportional to the strength of the stimulus

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11
Q

Electrochemical Equilbrium

A

when the movement of ions down their electrical gradient is equal and opposite in direction to the movement of ions down their concentration (chemical) gradient.

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12
Q

Equilibrium Potential

A

Refers to the membrane potential at which there is no net movement of an ion across the plasma membrane into or out of the cell

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13
Q

Three types of neuronal signals

A

1)Receptor potential
2) synaptic potential
3) Action potential

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14
Q

Steps of Action Potential

A

1) Rest: Leaky K+ channel and Na+/K+ pump are in action.
2) Rising Phase: Initial depolarization brings to threshold. Once reached, voltage gated Na+ channels open.
3) Falling Phase: K+ voltage gated channels open and Na+ channels inactivate.
4) Undershoot (Refractory): K+ voltage channels remain open, Na+ still inactivated.
5) “Return to rest”: Both voltage gated channels begin to close.

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15
Q

Synaptic Potential

A

The electrical signal associated with communication between neurons at synaptic contacts.

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16
Q

Action Potential

A

Responsible for long-range transmission of information within the nervous system or to target organs

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17
Q

Passive electrical responses:

A

Does not require a unique property of the neuron

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18
Q

Active electrical response:

A

Action potentials and requiring a fundamental change in how proteins will respond

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19
Q

What is the difference in electric potential between the interior and the exterior of a biological cell?

A

Membrane potential, measured in mv

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20
Q

The amplitude of the action potential is INDEPENDENT of the magnitude of the current used to evoke it. What is this principle?

A

all-or-none response,

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21
Q

What property is DEPENDENT on the magnitude of the current?

A

frequency of action potentials

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22
Q

If a current-passing electrode produces a current that yields a(n) ______ change in membrane potential as shown in Fig. C, then the magnitude of the resulting potential change will ______ with increasing distance from the site of current injection (B). This is known as ______ conduction.

A

subthreshold, decay, passive

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23
Q

If a current-passing electrode produces a current that yields a(n) ______ change in membrane potential as shown in Fig. C, then the magnitude of the resulting potential change will remain ______ with increasing distance from the site of current injection (B). This is known as ______ conduction.

A

suprathreshold, constant, active

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24
Q

Why does passive conduction decay over time? How can this be prevented?

A

ion dissipation, myelin which helps to speed up action potential conduction by acting as an electrical insulator

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25
Q

Active Transporters

A

Membrane proteins are responsible for actively moving selected ions against their concentration gradient and creating ion concentration gradients?

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26
Q

Ion channels

A

Membrane proteins are selectively permeable to certain ions and allow these ions to move passively down their concentration gradients

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27
Q

Both hyperpolarizing and depolarizing electrical stimulation result

A

Graded Potential

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28
Q

Some _______ channels types (non-gated) in the plasma membrane are “leaky” allowing a _______ diffusion of K+ out of the cell

A

potassium, slow facilitated

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29
Q

Why do all cells in the body have a negative-inside resting potential compared to the outside?

A

1)The membrane of the
resting neuron is more permeable to K+ than any other ion so the resting potential is closer to the equilibrium potential
2)more K+ inside than outside due to transporter activity so more cations are leaving than entering the cell

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30
Q

Why are squid axons larger than the standard mamallian axon?

A

Giant neurons evidently evolved in squid because they enhanced the animal’s survival. These neurons helped produce a jet propulsion effect that
allows the squid to move away from
predators at a remarkably fast speed.

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31
Q

Increasing the external K⁺ concentration makes the resting membrane potential more (POSITIVE / NEGATIVE).

A

POSITIVE since increasing the external K+ concentration causes depolarization

32
Q

What did Hodkin and Katz find about Na+ concentration and rate or rise of action potential?

A

External Na+ concentration reduces both the rate of rise of the action potential and its peak amplitude

33
Q

Hodgkin and Katz found that lowering the Na⁺ concentration had very little effect on what variable

A

Resting membrane potential

34
Q

Capacitive Current

A

The redistribution of charge that occurs across the membrane when the membrane potential is set to a given command voltage

35
Q

The action potential arises from the coordinated activation of two conductance

A

1) A sodium conductance (transient inward current) that activates rapidly and drives the rising phase of the action potential
2) A a potassium conductance (delayed outward current) that activates more slowly and contributes to the falling phase of the action potential and the undershoot.

36
Q

What happens as the membrane becomes more depolarized?

A

The inward current decreases and outward current increases

37
Q

Relationship between current and sodium

A

Removal of external Na⁺ causes this initial inward current to become outward, an effect that is reversed by restoration of external Na⁺. (sodium moved out of the cell)

38
Q

What is the relationship between both peak Na+and K+ conductance and membrane potential?

A

Both peak Na⁺ conductance and steady-state K⁺ conductance increase as the membrane potential becomes more positive.

39
Q

Refractory Period

A

Refers to the period of time immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation

40
Q

Feedback cycles

A

responsible for membrane potential changes during an action potential.

41
Q

Membrane depolarization activates a (POSITIVE / NEGATIVE) feedback cycle fueled by the voltage-dependent activation of Na+ conductance. This phenomenon is followed by the slower activation of a (POSITIVE / NEGATIVE) feedback loop as depolarization activates a K+ conductance, which helps to (DEPOLARIZE / REPOLARIZE) the membrane potential and terminate the action potential.

A

positive, negative, repolarize

42
Q

Action potential propagation requires the coordinated action of two forms of current flow:

A

Passive and active currents flowing through voltage dependent ion channels

43
Q

Where are voltage gated sodium and potassium channels located?

A

Nodes of Ranvier

44
Q

Function of Myelin

A

Acts as an insulator to close leaky membranes and speed up propagation of relatively slow action potentials.

45
Q

saltatory conduction

A

Describes the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials

46
Q

Myelin

A

Insulating layer, or sheath that forms around nerve

47
Q

myelin sheath

A

allows electrical impulses to transmit quickly and efficiently along the nerve cells

48
Q

What type of cells form myelin sheth and where is myelin formed?

A

PNS, Schwan cells

49
Q

In the CNS what is myelin formed by?

A

myelin is formed by oligodendrocytes

50
Q

Difference between schwan and oliogendrocytes

A

1) Location
2) scwhann cells in the PNS form a 1:1 relationship with an axon and oligodenfrocytes in the CNS can wrap around myelin, making contact with many axons

51
Q

What happens if you lose the ability to form compact myelin?

A

The nerve/neuron doesn’t send the signal and action potential to the muscle at the right speed, causing muscle degeneration

52
Q

Voltage Clamp

A

Allows for the macroscopic current of the cell, meaning it measures the current flowing through thousands of voltage gated channels

53
Q

Patch Clamp

A

Specialized type of voltage clamp method and allows for the microscopic current of the cell, meaning it measures the current flowing through an individual channel.

54
Q

Cell-attached recording

A

Patch clamp configuration involves applying suction to a membrane, creating a seal between the fine-tipped glass electrode and a single membrane channel?

55
Q

Whole -Cell Recording

A

Patch clamp configuration involves applying strong suction such that the interior of the pipette becomes continuous with the cell cytoplasm?

56
Q

Outside-out recording?

A

Patch clamp configuration involves breaking the membrane such that the membrane will come back together with the extracellular domain exposed

57
Q

Inside-out Recording?

A

Patch clamp configuration involves breaking the membrane such that the cytoplasmic domain is accessible?

58
Q

At a positive membrane potential, the Na⁺ current is (POSITIVE / NEGATIVE) and (INWARD / OUTWARD).

A

positive, outward (neg potential current is negative nad inward)

59
Q

Does depolarization active/inactive Na and K+

A

While depolarization activates and then inactivates Na⁺, it does not inactivate K⁺, allowing it to flow outward for the entire depolarization phase.

60
Q

Describe the functional state of voltage-gated Na⁺ and K⁺ channels when the membrane potential is hyperpolarized.

A

The gates of both channels are closed when the membrane potential is hyperpolarized.

61
Q

Describe the functional state of voltage-gated Na⁺ and K⁺ channels when the membrane potential is depolarized.

A

When the potential is depolarized, voltage sensors (indicated by +) allow the channel gates to open—first the Na+ channels and then the K+ channels. Na+ channels also inactivate during prolonged depolarization, whereas many types of K+ channels do not

62
Q

Voltage Gated Channels

A

are selectively permeable to each of the major physiological ions: Na⁺, K⁺, Ca²⁺, and Cl⁻.

63
Q

Ligand gated channels

A

less selective and allow permeation of two or more types of ions through the channel pore

64
Q

Pore Loop -Voltage gated sodium channels

A

a filter for certain ions, providing ion selectivity for sodium ions

65
Q

Selectivity Filter

A

made of negatively charged amino acid residues, which attract the positive Na+ ion and keep out negatively charged ions such as chloride

66
Q

Voltage Sensors

A

enable movement within the membrane in response to changes in membrane potential.

67
Q

Structure mammalian voltage-gated K⁺ channel when it is hyperpolarized

A

Closed because the inside of the cell is more negatively charged. These negative charges attract the positively charged voltage sensors, such that the pore is closed

68
Q

Structure mammalian voltage-gated K⁺ channel when it is depolarized

A

Open (When the membrane is depolarized, the inside of the cell is more positively charged. These positive charges repel the positively charged voltage sensors, such that the pore is open.)

69
Q

Co-transpoters

A

Type of active transporters do not use ATP directly but instead carry multiple ions in the same direction?

70
Q

Three types of active transporters

A

1) ATPase pumps
2) Ion Exchangers
3)Co-transporters

71
Q

Ion exchangers

A

Do not use ATP directly but instead carry one or more ions up its electrochemical gradient while simultaneously taking another ion down its gradient?

72
Q

ATPase Pump

A

Acquired energy directly from the hydrolysis of ATP (examples depicted in figure)?

73
Q

What two factors does the efflux of radioactive Na⁺ from a squid giant axon depend on?

A

1) If extracellular K+ is removed, Na+ efflux is reduced
2) If ATP is blocked, the function of this channel is blocked

74
Q

Correctly order the sequence of events for the movement of ions by the Na⁺/K⁺ pump.

A

1) Na⁺ binding.
2) Phosphorylation.
b.) Dephosphorylation-induced conformation changes leads to K⁺ release.
d.) Phosphorylation-induced conformation changes leads to Na⁺ release and K⁺

75
Q

Correctly order the sequence of events for the movement of ions by the Ca²⁺ pump starting with Ca²⁺ binding.

A

1) ATP binding
2)Phosphorylation
c.) Ca2+ binding
d) Conformational change causes Ca²⁺ release

NRSC2000 (13 decks)

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