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Bio 8: Grey Matter > Neurones > Flashcards

Neurones Flashcards

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Biology 101 flashcards
1
Q

What is resting potential?

A

When the membraae is not stimulated as it is polarised: the outside of the membrane is more positive than the inside

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2
Q

What value is resting potential at?

A

-70mv

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3
Q

What does mV stand for?

A

Milivolts

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4
Q

What 3 things in the neurone membrane work towards maintaining resting potential?

A
  • Sodium-potassium pump
  • Voltage gated sodium ion channels
  • Voltage gated potassium ion channels
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5
Q

In the maintenance of resting potential, what does the sodium potassium pump do? 3

A
  • Uses active transport and ATP
  • Pumps 3x Na+ out
  • Pumps 2x K+ ions in
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6
Q

In the maintenance of resting potential, is the voltage gated sodium ion channel open/closed?

A

Closed

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7
Q

Why are the voltage gated sodium ion channels closed in maintaining resting potential?

A
  • Membrane not permeable to sodium ions

- Can’t diffuse back in

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8
Q

Are the voltage gated potassium ion channels open/closed in maintaining resting potential?

A

Open

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9
Q

Why are the voltage gated potassium ion channels open in maintaining resting potential? 2

A
  • Allows facilitated diffusion of K+s out of membrane down the concentration gradient
  • Doesn’t reach equilibrium because of the positive charge outside
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10
Q

What do the sodium-potassium pumps, voltage gated sodium ion channels and voltage gated potassium ion channels all ensure in resting potential?

A

That there is an electrochemical gradient and therefore resting potential maintained by more positive ions being on the outside than inside

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11
Q

What are the steps in generating action potential?

A
  1. Resting potential
  2. Depolarisation
  3. Repolarisation
  4. Hyperpolarisation
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12
Q

Summarise resting potential 3

A
  • Sodium Potassium pumps Na+ out and K+ in
  • Using active transport with ATP against concentration gradient
  • Some K+ diffuses out the K+ channel
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13
Q

What happens in depolarisation? 4

A
  • Potential difference reaches threshold [-55mv]
  • More voltage gated Na+ channels open
  • More Na+ diffuse into axon
  • More positive on the inside
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14
Q

What is depolarisation an example of?

A

Positive feedback

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15
Q

What occurs in repolarisation? 4

A
  • Voltage gated K+ channels open
  • Membrane more permeable to K+
  • K+ diffuse out down concentration gradient
  • Voltage gated Na+ channels close
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16
Q

What occurs in hyperpolarisation? 4

A
  • Potential difference becomes more negative than resting potential
  • K+ channels are too slow to close
  • Too many potassium ions diffuse out of neurone
  • Too positive outside of membrane
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17
Q

Label the stages of action potential on a graph

A

See notes

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18
Q

When drawing action potential on a graph, what are the labels for the x and y axis?

A

x axis: time [per ms]

y axis: potential difference across membrane [mV]

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19
Q

What happens if there is a weak stimulus?

A
  • Some Na+ channels open
  • Some Na+ diffuses in
  • Does not reach threshold
  • Sodium potassium pump restores resting potential
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20
Q

What value is threshold?

A

-55mV

21
Q

What is the refractory period?

A

Period of time when another action potential cannot be generated

22
Q

What 2 things does the refractory period ensure?

A
  • Action potentials are discrete [don’t overlap]
  • Action potentials are unidirectional [one way] - can’t go backwards because neurone being in refractory period prevents action potential being triggered behind initial action potential
23
Q

How does the refractory period occur?

A

Ion channels are closed
Na+ channel was closed in repolarisation
K+ channel closed in hyperpolarisation

24
Q

What 2 stages of generating action potential make up the refractory period?

A
  • Repolarisation

- Hyperpolarisation

25
Q

How does action potential move along a neurone?

A

In a wave of depolarisation

26
Q

How does action potential move along in a wave of depolarisation?

A
  • Ahead of the action potential the neurone is in resting potential
  • In action potential some Na+ ions diffuse sideways along neurone
  • Causes sodium ion channels in the next region of neurone to open
  • Triggers threshold
27
Q

How does the refractory period affect the wave of depolarisation?

A
  • Wave moves away from parts of membrane in refractory period
  • Because these parts cannot fire action potential
28
Q

What is the all or nothing law? 2

A
  • If a generated potential/stimulus reaches threshold this triggers an action potential
  • No matter how big the stimulus the action potentials are the same size
29
Q

What does a strong stimulus generate compared to a weak stimulus?

A

More frequent action potentials

30
Q

Define an anaesthetic

A

Drug stopping pain in a localised area of the body

31
Q

How do anaesthetics work? 5

A
  • Binds to Na+ channels in neurone membrane
  • Stops Na+ moving in
  • Membrane doesn’t depolarise
  • Action potential not conducted along neurone
  • Information about pain doesn’t reach brain
32
Q

What is the myelin sheath?

A

Electrical insulator preventing depolarisation of neurone membrane

33
Q

How does myelin sheath prevent depolarisation?

A

Prevents movement of ions in and out the membrane

34
Q

What is the myelin sheath made up of?

A

Schwann cells

35
Q

What are the nodes of Ranvier? 3

A
  • Gaps in the myelin sheath where there is bare membrane
  • K+ and Na+ channels are concentrated at these nodes
  • Depolarisation only happens at these nodes
36
Q

What is saltatory conduction?

A
  • Action potential jumps between nodes of Ranvier

- Neurone’s cytoplasm conducts enough electrical charge to depolarise the threshold at the next node

37
Q

What are the advantages of saltatory conduction?

A
  • Speeds up transmission of nerve impulse

- As in a non myelinated neurone - the impulse travels as a wave along the whole length of axon membrane - slower

38
Q

What is conduction velocity?

A

The speed at which an impulse moves along a neurone

39
Q

The higher the conduction velocity…

A

…the more quickly the impulse is travelling along the neurone

40
Q

What are the 3 types of neurones?

A
  • Relay
  • Motor
  • Sensory
41
Q

What are the general structural features of the motor neurones? 3

A
  • Cell body
  • Many short dendrites
  • One long axon
42
Q

What are the general structural features of the relay neurones?

A
  • Cell body
  • Short dendrites
  • Many short axons
43
Q

What are the general structural features of the sensory neurones?

A
  • Single long dendron
  • Cell body in middle of neurone
  • Short axon
44
Q

What is the function of a motor neurone?

A

Conducts impulse from CNS to effector

45
Q

What is the function of a relay neurone?

A

Conducts impulses from sensory neurones to motor neurones in the CNS

46
Q

What is the function of a sensory neurone?

A

Conducts impulses from receptors to the CNS

47
Q

What makes up all neurones? 3

A
  • Dendrites
  • Cell body
  • Axons
48
Q

Label a neurone

A

See notes

Bio 8: Grey Matter (11 decks)

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