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Neuroscience > Neurophysiology: Neural Signals and Transmission > Flashcards

Neurophysiology: Neural Signals and Transmission Flashcards

1
Q

Is the electrical potential negative or positive in cells?

A

Negative

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2
Q

What is the resting membrane potential?

A

Within excitable cells there is the capacity to change and become more and less negative

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3
Q

What is concentration gradient?

A

Difference in concentration of a dissolved substance in a solution between a region of high density and one of lower density

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4
Q

What is the resting membrane potential in most neurones?

A

-70mV

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5
Q

What generates an electrical current?

A

The difference in the electric potential

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6
Q

What happens when the neurone is inhibited?

A

Hyperpolarisation, the inside of the membrane is more negative than typically

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7
Q

What is depolarisation?

A

When the neurone is stimulated and moves closer towards 0

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8
Q

What are the phases during action potential?

A

Resting potential, rising phase, overshoot (depolarisation), the falling phase, the undershoot (hyperpolarisation), repolarisation

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9
Q

What is passive diffusion

A

Movement of particles in a fluid from regions of high conc to low until equilibrium is reached

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10
Q

What happens when the molecules are evenly distributed across a fluid?

A

No net diffusion

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11
Q

What causes the resting membrane potential?

A

The movement of potassium ions out of the cell

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12
Q

What is the reversal potential?

A

The point at which direction the net current flow reverses which is the same as the membrane potential

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13
Q

What is the driving force

A

The rate of net current flow for a particular ion being proportional to the difference between the membrane potential and the equilibrium potential

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14
Q

What is the graded potential?

A

The local depolarisation of the cell membrane in response to a stimulus

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15
Q

What causes the action potential?

A

The movement of sodium ions into the cell

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16
Q

What creates an electrostatic gradient?

A

Charged particles that generate electrostatic forced due to oppositely charged ions being attracted to each other

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17
Q

What is the ratio of the sodium gradient?

A

10:1, sodium is higher outside the cell

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18
Q

What is the ratio of the potassium gradient?

A

40:1, potassium is higher inside the cell

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19
Q

What does the sodium-potassium pump do?

A

Maintains the sodium and potassium gradients of the cell, 3 NA out of the cell and 2 K into the cell

20
Q

How much energy does the sodium potassium pump consume?

A

A single ATP molecule

21
Q

What ion is the neuronal membrane mainly permeable to?

A

Potassium

22
Q

What occurs when the potassium diffuses out of the cell?

A

The inside of the cell builds up a slight excess of negative charge

23
Q

What occurs at equilibrium in the resting membrane potential?

A

No net flow of potassium

24
Q

What will occur if sodium enters the cell?

A

The inside of the membrane will build up a slight excess of positive charge

25
Q

What is the action potential dependent on?

A

Voltage-gated ion channels

26
Q

What are the two gated channels?

A

Ligand-gated and voltage-gated ion

27
Q

What is a ligand-gated channel

A

A channel that opens in the presence of a signalling molecule that acts as a binding site on the extracellular area of the channel

28
Q

What is a voltage gated ion channel?

A

Channels that open and close in response to changes in the membrane potential

29
Q

What is the structure of the voltage gated ion channel?

A

Integal membrane proteins, pore loops for a selective filter and a charged domain as a voltage sensor

30
Q

What is the structure of the VG sodium channel?

A

Single large protein with 4 repeating motifs

31
Q

What is the structure of the VG potassium channel?

A

4 subunits and a characteristic motif

32
Q

What happens to VG ion channels at rest compared to depolarisation?

A

Rest= closed. Depolarisation= open

33
Q

Why do the VG ion channels ion in depolarisation?

A

Due to the voltage sensors (S4)

34
Q

What happens to the voltage gated sodium and potassium channels in depolarisation?

A

NA= open very quickly
K= open after a delay of 1 millisecond

35
Q

How is an action potential triggered?

A

By the neuronal cell body being depolarised by 15mV to reach the threshold value of -55mV

36
Q

What occurs at the threshold depolarisation?

A

A positive feedback loop so NA+ flows into the neuron so more VG NA channels open so NA+ can enter the cell

37
Q

When will the action potential be propagated?

A

During depolarisation to the threshold, in a series of action potentials

38
Q

What does the inactivation gate on the VG NA channels do?

A

Closes at the peak of action potential and will not re-open until repolarisation

39
Q

What is the refractory period?

A

When an action potential cannot be triggered until the sodium channel inactivation gate has reopened during repolarisation

40
Q

What is an electrotonic wave?

A

When the action potential is triggered in a certain part of the axon so a localised current of sodium is generated

41
Q

How does the electrotonic wave spread?

A

Along the axon in both directions and then decays when the positive charge goes across the neuronal membrane

42
Q

What occurs to the electrotonic wave in an unmyelinated axon?

A

Action potentials are close together as the electrotonic wave reaches a short diatance to trigger the next action potential

43
Q

How does bigger axon diameters effect nerve impulses?

A

Speed them up as there is less electrical resistance to the current flow so the electrotonic wave moves further as action potentials are not close together

44
Q

What does myelin sheath do?

A

Insulates axons and prevents current leakage

45
Q

What is myelin sheath made of?

A

300 layers of lipid rich cell membrane

46
Q

What are nodes of Ranvier?

A

Gaps between myelinated segments on an axon

Neuroscience (10 decks)

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