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(OCR A) - A-level Biology > 5.1.3 Neuronal communication > Flashcards

5.1.3 Neuronal communication Flashcards

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1
Q

What is a stimulus?

A

Change in the internal or external environment of an organism

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2
Q

What are the structures within a neurone?

A
  • Cell body
  • Dendrons
  • Dendrites
  • Axons
  • Myelin sheath
  • Schwann cells
  • Node of Ranvier
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3
Q

What is the cell body?

A

Contains the nucleus and organelles to produce neurotransmitters

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4
Q

What is the dendron?

A

Short extensions from cell body

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5
Q

What are dendrites?

A

Branches of dendrons

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6
Q

What is the axon?

A

Singular extension from cell body

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7
Q

What is the myelin sheath?

A

Fatty layers of insulation produced by Schwann cells that surround axon multiple times

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8
Q

Why is the myelin sheath needed?

A

Provides insulation for the electrical impulse to allow for a faster transmission of impulse

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9
Q

What are Schwann cells?

A

Cells that produce layers of membrane making up myelin sheath

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10
Q

What are the Nodes of Ranvier?

A

Unmyleinted gap between myelin sheath

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11
Q

Electrical impulse can _______ from one node to the next in a myelinated neurone

A

Jump

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12
Q

What does sensory neurone do?

A

Transmit impulse from sensory receptor cells to CNS

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13
Q

Is sensory neurone afferent or efferent neurone?

A

Afferent neurone

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14
Q

Where is the cell body located on a sensory neurone?

A

In the middle of the neurone

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15
Q

What does relay neurone do?

A

Transmit impulse between neurones e.g. between sensory and motor neurones

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16
Q

Which neurones are myelinated and which are unmyelinated?

A

Myelinated - sensory & motor
Unmyelinated - relay

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17
Q

What type of neurone makes up the brain and spinal cord?

A

Relay neurone

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18
Q

What does motor neurone do?

A

Transmit impulses from CNS to effector cells

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19
Q

Is motor neurone afferent or efferent neurone?

A

Efferent neurone

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20
Q

Where is the cell body found on motor neurone?

A

At the start of the neurone

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21
Q

What is the direction of impulse?

A

Dendrites to axon

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22
Q

What is the electrical impulse pathway?

A

Sensory receptor -> sensory neurone -> relay neurone -> motor neuorne -> effector

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23
Q

What are the features of sensory receptor?

A
  • Specific to a single type of stimulus
  • Act as a transducer
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24
Q

What does a transducer do?

A

Coverts stimulus (light, heat, sound or pressure) into nerve impulse called the generator potential

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25
Q

What is a generator potential?

A

Nerve impulse created when detected by sensory receptor

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26
Q

Describe mechanoreceptor with example?

A
  • Stimulus: pressure and movement
  • Example: Pacinian corpuscle
  • Example of sense organ: skin
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27
Q

Describe chemoreceptor with example?

A
  • Stimulus: chemicals
  • Example: olfactory receptor
  • Example of sense organ: nose
28
Q

Describe thermoreceptor with example?

A
  • Stimulus: heat
  • Example: end-bulbs of Krause
  • Example of sense organ: tongue
29
Q

Describe photoreceptor with example?

A
  • Stimulus: light
  • Example: cone cell
  • Example of sense organ: eye
30
Q

What is the structure of the Pacinian corpuscle?

A

Nerve ending in centre surrounded by layers of connective tissue with gel in between layers

31
Q

What does the membrane of the neurone ending in a Pacinian corpuscle contain?

A

Stretch mediated sodium ion channels

32
Q

What is the function of the stretch mediated sodium ion channels?

A

Change in shape due to pressure and changes permeability to Na+

33
Q

Describe steps in Pacinian corpuscle to covert mechanical pressure to nerve impulse

A
  1. Resting potential - stretch mediated Na+ channel too narrow
  2. Pressure applied - corpuscle membrane stretches and changes shape
  3. Sodium ion channels widen - Na+ diffuses in
  4. Depolarised - influx of Na+ results in generator potential
  5. Generator potential creates action potential
  6. Action potential to CNS
34
Q

Describe the movement of Na+ and K+ ions during the RESTING POTENTIAL

A

3Na+ OUT
2K+ IN
Via Na+ and K+ ion pump (active transport)

35
Q

What is the potential difference at resting potential?

A

-70mV

36
Q

Which channel is closed at resting potential?

A

Voltage gated Na+ ion channel

37
Q

Which channel is open at resting potential?

A

Non voltage gated K+ ion channel

38
Q

The outside of the membrane is ______ positive than the inside at RESTING POTENTIAL

A

More

39
Q

Why do the K+ ions leave the polarised membrane at RESTING POTENTIAL?

A

High concentration inside axon so leave via facilitated diffusion

40
Q

Describe the INITIAL movement of Na+ at DEPOLARISATION?

A

Synapse sends impulse which causes a few voltage gated Na+ to open and some Na+ ions enter via facilitated diffusion

41
Q

Describe the positive feedback involved in DEPOLARISATION?

A

Na+ concentration increases until the threshold potential is reached (-55mV) this causes MORE voltage gated Na+ ion channels to open and INLFUX of Na+ ions enter

42
Q

What is the threshold potential?

A

-55mV

43
Q

What is the potential difference at DEPOLARISATION?

A

+40mV

44
Q

What happens to the Na+ and K+ ion pump at REPOLARISATION?

A

Re opens and 3Na+ OUT 2K+ IN

45
Q

What happens to the voltage gated Na+ channel when potential difference is +40mV?

A

Closes

46
Q

What opens at +40mV during REPOLARISATION?

A

Voltage gated K+ channels open so MORE K+ can leave

47
Q

What happens to the potential difference inside the axon during REPOLARISATION?

A

Becomes less positive

48
Q

Why does HYPERPOLARISATION occur?

A

When voltage gated K+ channel opens, initially many K+ ions leave so the potential difference becomes slightly more negative than resting potential

49
Q

What is the refactory period?

A

Short period of time after action potential where axon cannot be excited again

50
Q

What occurs during the refactory period?

A

Voltage gated Na+ channels remain closed

51
Q

Why is the refactory period important?

A

Ensures action potential only travels in one direction

52
Q

What is saltatory conduction?

A

Action potential jumping from one node to another

53
Q

Where does depolarisation occur and why?

A

Nodes of Ranvier as there is no myelin sheath so Na+ ions can pass through protein channels in membrane

54
Q

Why is saltatory conduction beneficial?

A
  • Faster nerve transmission
  • Reduces amount of repolarisation needed (which uses energy)
55
Q

What affects the speed of an action potential?

A
  • Axon diameter: bigger = faster impulse as less resistance to flow of ions
  • Temperature: higher (to an extent as proteins can get denatured)= faster impulse as ions diffuse faster
56
Q

What is the all or nothing principle?

A

Only the threshold value will tigger an action potential

57
Q

What happens to the action potential when a larger stimulus is present?

A

Action potential same size, but occurs more frequently

58
Q

What is an excitatory neurotransmitter?

A
  • Result in depolarisation of post synaptic membrane
  • Action potential is triggered (if threshold reached)
  • E.g. Acetylcholine
59
Q

What is an inhibitory neurotransmitter?

A
  • Result in hyperpolarisation of post synaptic membrane
  • Prevents action potential being triggered
  • E.g. GABA
60
Q

What is the cholinergic synapse?

A

Synapses that use the neurotransmitter acetylcholine

61
Q

Where are cholinergic synapses commonly found?

A

CNS and neuromuscular junctions

62
Q

Which enzyme breaks down (hydrolyses) acetylcholine and where is it found?

A

Acetylcholinesterase on the post synaptic membrane

63
Q

What products is acetylcholine hydrolysed into?

A
  • Acetyl (ethanoic acid)
  • Choline
64
Q

How do synapses ensure impulses are unidirectional?

A

Neurotransmitter receptors only found on the post synaptic membrane

65
Q

What is spatial summation?

A

Multiple presynaptic neurones connect to one post synaptic neurone

66
Q

What is temporal summation?

A

Single presynaptic neurone releases neurotransmitter several times over a short period

67
Q

What is summation?

A

Amount of neurotransmitter builds up enough to reach threshold and trigger action potential

(OCR A) - A-level Biology (26 decks)

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