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BMS Neuroscience > The Excitable Cell > Flashcards

The Excitable Cell Flashcards

1
Q

Neurones must..?

A
  • Collect
  • Integrate
  • Output
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2
Q

What does the nervous system do?

A

System of communication that allows an organism to react rapidly and modifiably to changes in its environment

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3
Q

Electrical activity provides a ____, _____, and _____ means for neurons to receive, integrate and transmit signals

A
  • Rapid
  • Reliable
  • Flexible
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4
Q

Electrical signals may be divided into…

A
  • Action potentials

- Graded potentials

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5
Q

Action potential

A
  • Fixed size
  • All-or-nothing
  • Propagate the axon
  • Can pass both ways but tend to go only one way
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6
Q

Graded potential

A
  • Variable size
  • Local signals not propagated over long distances
  • Pass both ways along neuronal membrane
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7
Q

Action potentials are coded by…

A

Frequency

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8
Q

Graded potentials are coded by…

A

Size

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9
Q

Why do neurons have a resting potential?

A

Consequence of..

  • Selectively permeable membrane
  • Unequal distribution of charged molecules/ions
  • Physical forces
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10
Q

Channels….

A

Confer selectivity

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11
Q

Pumps assist…

A

Unequal charge distribution

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12
Q

What is the resting potential of a membrane?

A

Between -65mV and -90mV

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13
Q

What is an absolute requirement for a functioning nervous system?

A

A negative Vm

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14
Q

Important ion pumps

A
  • Na+/K+ ATPase

- Ca2+ pumps

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15
Q

Na+/K+ ATPase

A
  • Exchanges extracellular K+ for intracellular Na+
  • Against concentration gradient - uses ATP
  • Uses about 70% brain ATP
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16
Q

Ca2+ pump

A
  • Transports Ca2+ out of neurons
  • Maintains low intracellular Ca2+
  • Ca2+ is toxic at high intracellular levels
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17
Q

Intracellular K+

A

100 mM

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18
Q

Extracellular K+

A

5 mM

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19
Q

Intracellular Na+

A

15 mM

20
Q

Extracellular Na+

A

150 mM

21
Q

Intracellular Ca2+

A

0.0002 mM

22
Q

Extracellular Ca2+

A

2 mM

23
Q

Intracellular Cl-

A

13

24
Q

Extracellular Cl-

A

150

25
Q

Increasing extracellular K+ causes the membrane to become…

A

Depolarised (more positive)

26
Q

The Nernst Equation

A

Used to calculate the equilibrium potential (Eion) for an ion

27
Q

The Goldman Equation

A

Used to estimate real Vm (combined potentials)

28
Q

Properties of the action potential

A
  • Transient, rapid and reversible change to membrane potential
  • -ve to +ve
  • Different types of excitable cell have different types of AP
  • Neuron AP triggered by Na+ permeability increase
  • All same size and duration
  • Don’t decrease down the axon
29
Q

Factors influencing conduction velocity of an axon

A
  • Diameter (larger diameter = faster)
  • Permeability of membrane (leaky)
  • Insulation (myelin vs non-myelin)
30
Q

Why does diameter affect Cv?

A

Resistance to current flow is inversely proportional to cross-sectional area of the axon

31
Q

Why does myelination affect Cv?

A

It prevents current loss along the axon by increasing membrane resistance (Rm) and the Space Constant

32
Q

Why do we have so many unmyelinated, small axons?

A
  • Benefit of high membrane resistance is reduced by the high internal resistance
  • Metabolic and volume costs of myelination
33
Q

The Space Constant

A

The distance from the site of depolarisation where it has fallen to 37%

34
Q

Cv of smallest unmyelinated axons? (0.2 - 1.5 micrometers)

A

0.5 - 2 m/s

35
Q

Cv of most axons > 1.0 micrometers?

A

5 - 120 m/s

36
Q

Cv of squid giant axon?

A

25 m/s

37
Q

What does lidocaine act on?

A

Poisons Na+ channels

38
Q

What does tetraethylammonium (TEA) act on?

A

K+ channels

39
Q

What does tetrodotoxin (TTX) act on?

A

Na+ channels

40
Q

What do saxitoxins (STX) act on?

A

Na+ channels

41
Q

What do dinoflagellates act on?

A

Na+ channels

42
Q

What type of conduction does myelination result in?

A

Saltatory conduction

43
Q

Absolute refractory period

A

Neuron is incapable of generating another action potential no matter what

44
Q

Relative refractory period

A

A stronger stimulus is able to cause an action potential as the threshold is raised

45
Q

Graded potentials can be ____ or _____

A

Excitatory

Inhibitory

46
Q

What are graded potentials caused by?

A

Opening of neurotransmitter-gated ion channels
OR
Opening/closing of K+ channels

47
Q

Electrical synapses

A
  • Retinal neuronal
  • Cardiac muscle
  • Smooth muscle
  • Rapid
  • Two way?

BMS Neuroscience (23 decks)

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