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

5.1.3 Neuronal communication Flashcards

(67 cards)

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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
What is a generator potential?
Nerve impulse created when detected by sensory receptor
26
Describe mechanoreceptor with example?
- Stimulus: pressure and movement - Example: Pacinian corpuscle - Example of sense organ: skin
27
Describe chemoreceptor with example?
- Stimulus: chemicals - Example: olfactory receptor - Example of sense organ: nose
28
Describe thermoreceptor with example?
- Stimulus: heat - Example: end-bulbs of Krause - Example of sense organ: tongue
29
Describe photoreceptor with example?
- Stimulus: light - Example: cone cell - Example of sense organ: eye
30
What is the structure of the Pacinian corpuscle?
Nerve ending in centre surrounded by layers of connective tissue with gel in between layers
31
What does the membrane of the neurone ending in a Pacinian corpuscle contain?
Stretch mediated sodium ion channels
32
What is the function of the stretch mediated sodium ion channels?
Change in shape due to pressure and changes permeability to Na+
33
Describe steps in Pacinian corpuscle to covert mechanical pressure to nerve impulse
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
Describe the movement of Na+ and K+ ions during the RESTING POTENTIAL
3Na+ OUT 2K+ IN Via Na+ and K+ ion pump (active transport)
35
What is the potential difference at resting potential?
-70mV
36
Which channel is closed at resting potential?
**Voltage** gated Na+ ion channel
37
Which channel is open at resting potential?
**Non voltage** gated K+ ion channel
38
The outside of the membrane is ______ positive than the inside at RESTING POTENTIAL
More
39
Why do the K+ ions leave the polarised membrane at RESTING POTENTIAL?
High concentration inside axon so leave via facilitated diffusion
40
Describe the INITIAL movement of Na+ at DEPOLARISATION?
Synapse sends impulse which causes a few **voltage** gated Na+ to open and some Na+ ions enter via facilitated diffusion
41
Describe the positive feedback involved in DEPOLARISATION?
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
What is the threshold potential?
-55mV
43
What is the potential difference at DEPOLARISATION?
+40mV
44
What happens to the Na+ and K+ ion pump at REPOLARISATION?
Re opens and 3Na+ OUT 2K+ IN
45
What happens to the voltage gated Na+ channel when potential difference is +40mV?
Closes
46
What opens at +40mV during REPOLARISATION?
**Voltage** gated K+ channels open so MORE K+ can leave
47
What happens to the potential difference inside the axon during REPOLARISATION?
Becomes less positive
48
Why does HYPERPOLARISATION occur?
When voltage gated K+ channel opens, initially many K+ ions leave so the potential difference becomes slightly more negative than resting potential
49
What is the refactory period?
Short period of time after action potential where axon cannot be excited again
50
What occurs during the refactory period?
Voltage gated Na+ channels remain closed
51
Why is the refactory period important?
Ensures action potential only travels in one direction
52
What is saltatory conduction?
Action potential jumping from one node to another
53
Where does depolarisation occur and why?
Nodes of Ranvier as there is no myelin sheath so Na+ ions can pass through protein channels in membrane
54
Why is saltatory conduction beneficial?
- Faster nerve transmission - Reduces amount of repolarisation needed (which uses energy)
55
What affects the speed of an action potential?
- 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
What is the all or nothing principle?
Only the threshold value will tigger an action potential
57
What happens to the action potential when a larger stimulus is present?
Action potential same size, but occurs more frequently
58
What is an excitatory neurotransmitter?
- Result in **depolarisation** of post synaptic membrane - Action potential is triggered (if threshold reached) - E.g. Acetylcholine
59
What is an inhibitory neurotransmitter?
- Result in **hyperpolarisation** of post synaptic membrane - Prevents action potential being triggered - E.g. GABA
60
What is the cholinergic synapse?
Synapses that use the neurotransmitter acetylcholine
61
Where are cholinergic synapses commonly found?
CNS and neuromuscular junctions
62
Which enzyme breaks down (hydrolyses) acetylcholine and where is it found?
Acetylcholinesterase on the post synaptic membrane
63
What products is acetylcholine hydrolysed into?
- Acetyl (ethanoic acid) - Choline
64
How do synapses ensure impulses are unidirectional?
Neurotransmitter receptors only found on the post synaptic membrane
65
What is spatial summation?
**Multiple presynaptic** neurones connect to one post synaptic neurone
66
What is temporal summation?
Single presynaptic neurone releases neurotransmitter **several times** over a short period
67
What is summation?
Amount of neurotransmitter builds up enough to reach threshold and trigger action potential

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

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