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Week 7 - 12 > Spread Of Nerve Impulse > Flashcards

Spread Of Nerve Impulse Flashcards

1
Q

What do nerves use to communicate electrically?

A

Ion fluxes

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2
Q

What’s involved with CNS?

A

Brain

Cranial nerve II and retina

Spinal cord

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3
Q

What’s involved with PNS?

A

Everything outside dura mater

Sensory receptors

Peripheral portions of spinal + cranial nerves

Peripheral options of autonomic nervous system

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4
Q

How does PNS send signals to CNS?

A

Sensory (afferent) nerves

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5
Q

How does CNS send signals to PNS?

A

Motor (efferent) nerves

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6
Q

What happens to electrical signal when transducer down length of axon?

A

Converted to chemical signal + passed to target cell via nerve terminals

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7
Q

What are the different types of neuron?

A

Unipolar

Pseudo-unipolar

Bipolar

Multipolar

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8
Q

What happens when signal arrives at dendrites?

A

If greater than threshold, action potential is generated + transducer along axon to nerve terminal

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9
Q

How do nerves transmit electrical signals?

A

Movement of ions

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10
Q

In what ways can electrical charge be conducted?

A

Passively and actively

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11
Q

What happens in active conduction?

A

Action potentials are generated due to opening of ion channels

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12
Q

What happens if axon has larger diameter?

A

Lower resistance

Faster passive current flow

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13
Q

What’s a capacitor?

A

2 conducting regions separated by an insulator

E.g. extracellular and intracellular fluid and cell membrane

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14
Q

What must happen for a current to pass along a nerve?

A

Must overcome membrane capacitance e.g. stored charge

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15
Q

What do ions require to cross plasma membranes?

A

Membrane proteins inc. ion channels

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16
Q

Passive ion channels:

A

Always open

Leak channels

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17
Q

Ligand-gated channels:

A

Require ligand binding to open

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18
Q

Voltage-gated channels:

A

Require specific membrane voltage to open

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19
Q

What generates electrochemical gradients across plasma membrane?

A

Asymmetrical distribution of ions

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20
Q

What do neurons exhibit?

A

Electrical excitability

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21
Q

What is resting membrane potential?

A

-60 to -70 mV

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22
Q

What happens if inside of cell becomes more positive?

A

Depolarisation (excitatory)

23
Q

What happens if inside of cell becomes more negative?

A

Hyperpolarisation (inhibitory)

24
Q

What are channels like in neuron at rest?

A

Voltage gated Na+ channels inactive

Leak K+ channels open

25
Q

What happens when signal arrives from another nerve terminal?

A

Some voltage gated Na+ channels open

Na+ enters cell body —> depolarisation

26
Q

What effects do small signals produce?

A

Small effects - graded potentials

27
Q

What are graded potentials like?

A

They decay (temporarily and spatially)

Na+ disperses in cytoplasm and pumped out by Na+/K+ ATPase

28
Q

What happens when a larger of multiple signals arrive at neuron?

A

Many voltage gated sodium channels open

Cell depolarises + membrane potential crosses threshold

29
Q

What happens once threshold is reached?

A

Rapid depolarisation occurs by voltage gated Na+ channels opening

30
Q

What causes repolarisation?

A

Voltage-gated Na+ channels inactive rapidly

Voltage-gated K+ channels open + allow K+ to exit cell

31
Q

What causes hyperpolarisation?

A

Voltage-gated K+ channels are slow to close

K+ continue to leave cell down electrochemical gradient

32
Q

What causes membrane potential to reach back to resting potential?

A

Voltage-gated K+ channels close

Resting potential is reached due to action of K+ leakage channels and Na+/K+ ATPase pumps

33
Q

What is initial depolarisation due to?

A

Rapid opening of voltage-gated Na+ channels

34
Q

What is repolarisation due to?

A

Closing of voltage-gated Na+ channels

Opening of voltage-gated K+ channels

K+ moving through K+ leakage channels

35
Q

Nature of action potentials:

A

All-or-none

Only fired when threshold is reached

Can only move away from stimulus due to refractory period

36
Q

Voltage-gated Na+ channels at rest:

A

Closed

37
Q

Voltage-gated Na+ channels at depolarisation:

A

Fully open

38
Q

Voltage-gated Na+ channels at repolarisation:

A

Second gate shuts (not fully closed nut non Na+ going through)

39
Q

Voltage-gated Na+ channels at hyperpolarisation:

A

Initial gate closes (fully shut)

40
Q

Voltage-gated K+ channels at rest:

A

Closed

41
Q

Voltage-gated K+ channels at depolarisation:

A

Closed

42
Q

Voltage-gated K+ channels at repolarisation:

A

Open

43
Q

Voltage-gated K+ channels at hyperpolarisation:

A

Open

44
Q

Why isn’t it possible to generate second action potential immediately after first?

A

Absolute refractory period due to inactivation of voltage-gated Na+ channels

Takes time for inactivated channels to return to closed state

45
Q

Why is it more difficult to elicit second action potential?

A

Due to relative refractory period (need much greater threshold to elicit action potential)

46
Q

What is the significance of refractory period?

A

Action potential only travels away from stimulus

47
Q

What can a sustained stimulus that crosses the threshold produce?

A

Continuous firing of action potentials

48
Q

What helps speed up neuronal transmission?

A

Myelin sheath

49
Q

What can demyelination get diseases cause?

A

Impaired conduction as peripheral or central axons affected

50
Q

What is multiple sclerosis?

A

Autoimmune disease affecting oligodendrocytes

51
Q

How much can myelination speed up propagation?

A

Up to 10 fold

52
Q

What are gaps between insulated sections called?

A

Nodes of Ranvier - where voltage-gated Na+ channels are found

53
Q

What is saltatory conduction?

A

When action potentials jump at high speed from one gap to the next

Week 7 - 12 (38 decks)

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