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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
What happens when signal arrives from another nerve terminal?
Some voltage gated Na+ channels open Na+ enters cell body —> depolarisation
26
What effects do small signals produce?
Small effects - graded potentials
27
What are graded potentials like?
They decay (temporarily and spatially) Na+ disperses in cytoplasm and pumped out by Na+/K+ ATPase
28
What happens when a larger of multiple signals arrive at neuron?
Many voltage gated sodium channels open Cell depolarises + membrane potential crosses threshold
29
What happens once threshold is reached?
Rapid depolarisation occurs by voltage gated Na+ channels opening
30
What causes repolarisation?
Voltage-gated Na+ channels inactive rapidly Voltage-gated K+ channels open + allow K+ to exit cell
31
What causes hyperpolarisation?
Voltage-gated K+ channels are slow to close K+ continue to leave cell down electrochemical gradient
32
What causes membrane potential to reach back to resting potential?
Voltage-gated K+ channels close Resting potential is reached due to action of K+ leakage channels and Na+/K+ ATPase pumps
33
What is initial depolarisation due to?
Rapid opening of voltage-gated Na+ channels
34
What is repolarisation due to?
Closing of voltage-gated Na+ channels Opening of voltage-gated K+ channels K+ moving through K+ leakage channels
35
Nature of action potentials:
All-or-none Only fired when threshold is reached Can only move away from stimulus due to refractory period
36
Voltage-gated Na+ channels at rest:
Closed
37
Voltage-gated Na+ channels at depolarisation:
Fully open
38
Voltage-gated Na+ channels at repolarisation:
Second gate shuts (not fully closed nut non Na+ going through)
39
Voltage-gated Na+ channels at hyperpolarisation:
Initial gate closes (fully shut)
40
Voltage-gated K+ channels at rest:
Closed
41
Voltage-gated K+ channels at depolarisation:
Closed
42
Voltage-gated K+ channels at repolarisation:
Open
43
Voltage-gated K+ channels at hyperpolarisation:
Open
44
Why isn’t it possible to generate second action potential immediately after first?
Absolute refractory period due to inactivation of voltage-gated Na+ channels Takes time for inactivated channels to return to closed state
45
Why is it more difficult to elicit second action potential?
Due to relative refractory period (need much greater threshold to elicit action potential)
46
What is the significance of refractory period?
Action potential only travels away from stimulus
47
What can a sustained stimulus that crosses the threshold produce?
Continuous firing of action potentials
48
What helps speed up neuronal transmission?
Myelin sheath
49
What can demyelination get diseases cause?
Impaired conduction as peripheral or central axons affected
50
What is multiple sclerosis?
Autoimmune disease affecting oligodendrocytes
51
How much can myelination speed up propagation?
Up to 10 fold
52
What are gaps between insulated sections called?
Nodes of Ranvier - where voltage-gated Na+ channels are found
53
What is saltatory conduction?
When action potentials jump at high speed from one gap to the next

Week 7 - 12 (38 decks)

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