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A2 Biology - Unit 5 > Unit 3.5.2 - Coordination may be chemical or electrical in nature > Flashcards

Unit 3.5.2 - Coordination may be chemical or electrical in nature Flashcards

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1
Q

During depolariation is the membrane more permeable to sodium or potassium ions?

A

Sodium

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2
Q

Draw a graph that represents the potential differnce when an action potential is triggered.

A
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3
Q

Why isn’t an action potential always fired in the post synaptic knob?

A

If the stimulus is too weak then only a small amount of neurotransmitter will be released

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4
Q

Draw a diagram of a synapse.

A
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5
Q

What is salutatory conduction?

A

When the impulse jumps between the nodes of ranvier

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6
Q

Name two classification for neurotransmitters.

A

Excitatory or inhibitory

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7
Q

Is the membrane of a neurone permeable or impermeable to sodium ions when at rest?

A

Impermeable

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8
Q

Do larger or small diameters of the axon increase the speed of conduction? And why?

A

Larger- there is less resistance to the flow of ions than in a cytoplasm of a small axon

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9
Q

Name an important auxin produced in the root and shoots of flowering plants.

A

IAA - Indoleacetic acid

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10
Q

What is summation?

A

Where the effect of the neurotransmitter released from many neurones is added together

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11
Q

Where is histamine stored? And when is is released?

A

Stored in mast cells, in response to the body being injured or infected

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12
Q

What do excitatory neurotransmitters do?

A

They depolarise the postsynaptic knob making it fire go an action potential

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13
Q

What is a gland?

A

A group of cells that are specialised to secrete a useful substance such as a hormone

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14
Q

Do neurotransmitters have a localised or widespread effect? And why?

A

Localised - they are secrete directly onto cells so only have a localised effect

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15
Q

Do hormones provide a fast or slow response compared to the nervous system?

A

Slow - the hormones aren’t released straight onto the target cells like neurotransmitter and must travel around the body first making the response slower than nerves

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16
Q

What is the general name for the chemical that takes the nerve impulse across a synapse?

A

Neurotransmitter

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17
Q

Give two purposes of the refractory period.

A

1.) Makes sure the potentials don’t overlap and so pass as discrete impulses 2.) Makes sure impulses can only pass in one direction

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18
Q

What is meant by resting potential?

A

The electrical potential across the neurone when it is not conducting an impulse

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19
Q

Describe how the resting potential is maintained, in two steps.

A

1.) 3 Na⁺are actively transported out of the axon and 2K⁺ are actively transported inside the axon by the sodium potassium pump 2.) They creates an electrochemical gradient as outside the neurone is more positively charged and so the membrane is polarised

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20
Q

What does the all-or-nothing principle prevent?

A

The brain from getting over stimulated by not responding to very small stimuli

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21
Q

During the resting potential what are the relative charges instead and outside of the neurone? And why?

A

The outside of the membrane is relatively positively charged because there are more positive ions outside than inside

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22
Q

What two ways can a gland be stimulated?

A

1.) Change in concentration of a specific substance 2.) By an electrical impulse

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23
Q

What is the refractory period?

A

The time delay between the conduction of one action potential and the next

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24
Q

Why does increasing the temperature increased the speed of conduction but only up to a point?

A

Any higher than 40ºC proteins start to become denatured

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25
Q

What is hyperpolarisation and what is it caused by?

A

When the potential difference becomes less than the resting potential - potassium ion channels are slow to close so there is a slight dip when too many potassium ions diffuse out of the neurone

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26
Q

Draw a myelinated motor neurone.

A
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27
Q

What is spatial summation?

A

Where two or more presynaptic knobs release neurotransmitter at the same time onto the postsynaptic knob

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28
Q

What is a chemical mediator?

A

A chemical messenger that acts locally

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29
Q

What breaks down acetylcholine when it is binded to receptors?

A

Acetylcholinesterase

30
Q

What is the exact voltage across the membrane of a neurone during the resting state?

A

-70mV

31
Q

What is a neuromuscular junction?

A

A specialised cholinergic synapse between a motor neurone and a muscle cell

32
Q

What causes the waves of depolarisation?

A

During an action potential some of the sodium ions that enter the neurone diffuse sideways, is its creates a potential difference past the threshold in the next part of the cell then more sodium ion channels open and more sodium diffuses into that part of the cell This process is repeated and causes a wave of depolarisation to travel along the neurone

33
Q

Why does myelination increase the speed of conduction?

A

Depolarisation only happens are the nodes of ranvier as the neurones cytoplasm conducts enough electrical charge to depolarise the next node so the impulse can jump from one node to the next, this means the whole axon doesn’t have to be depolarised and so the impulse travels faster

34
Q

Why do spatial and temporal summation increase the chance of an action potential being fired in the post synaptic knob?

A

There is more neurotransmitter being released so there is a higher chance the threshold level is reached

35
Q

Is the effect of hormones long lasting or short lived and why?

A

Long lasting - they aren’t broken down very easily so the effect lasts longer

36
Q

What happens when a neurone is stimulated for it to become depolarised during an action potential?

A

Sodium channels open and sodium ions diffuse into the axon down the sodium ion electrochemical gradient, when the membrane reaches a potential difference of -55mV then more sodium ions rapidly changing the potential difference until it is depolarised

37
Q

What effect does histamine have?

A

It increases the permeability of the capillaries nearby to allow more immune system cells to move out of the blood to the injected or injured area

38
Q

What is the neurotransmitter called in a neuromuscular junction?

A

Acetylcholine

39
Q

What are the two types of summation?

A

Spatial and temporal summation

40
Q

What is temporal summation?

A

Where two or more nerve impulses arrive in quick succession from the same presynaptic knob

41
Q

During repolarisation is the membrane more permeable to sodium or potassium ions?

A

Potassium

42
Q

What maintains the resting potential?

A

The sodium-potassium pump

43
Q

Name four things that prostaglandin is involved in.

A

Inflammation, fever, blood pressure regulation and blood clotting

44
Q

What is meant by some neurones are myelinated?

A

Some parts are covered in myelin sheath

45
Q

What three factors affect the speed of conduction of an action potential

A

Myelination, axon diameter and temperature

46
Q

Do hormones have a localised or widespread effect and why?

A

Widespread - they aren’t realised directly onto target cells so have to be transported around the body making the effect widespread

47
Q

Give three differences between chemical mediators and hormones?

A

1.) Secreted from cells all over the body not just from glands 2.) The target cells are right next to where they are produced so they have a localised response instead of widespread 3.) They only have to travel a short distance to their target cells so they have a quicker response than hormones

48
Q

What are the ten steps for how an action potential/impulse travels across a synaptic cleft?

A

1.) The action potential arrives at the presynaptic knob 2.) This causes calcium channels open 3.) Calcium ions diffuse into the knob 4.) This causes vesicles containing the neurotransmitter to move to the membrane 5.) The vesicles release the neurotransmitter into the synaptic cleft by exocytosis 6.) The neurotransmitter diffuses across the synapse 7.) It binds to receptors on the postsynaptic knob 8.) This causes sodium channels to open 9.) Sodium ions diffuse into the postsynaptic knob 10.) This sets up a new action potential

49
Q

What are synapses that use acetylcholine called?

A

Cholinergic synapses

50
Q

What is a hormone?

A

A chemical messenger that travel in the blood which are secreted once a gland is stimulated

51
Q

What is acetylcholine broken down into and where does it go after it is broken down?

A

Into acetyl and choline, it diffuses back across the synaptic cleft and is reabsorbed and formed back into acetylcholine inside a vesicle

52
Q

What happens if the potential difference across a neurone doesn’t reach the threshold level?

A

No action potential is generated

53
Q

What is meant by waves of depolarisation?

A

When the action potential/impulse moves down the neurone

54
Q

What do hormones diffuse into? And what carries that around the body?

A

They diffuse directly into the blood and are carried around by the circulatory system

55
Q

Name five ways drugs can affect synaptic transmission?

A

1.) Mimiking neurotransmitters in receptors 2.) Blocking receptors 3.) Inhibit the enzyme that breaks down the neurotransmitter 4.) Stimulate the release of neurotransmitter 5.) Inhibit the release of neurotransmitter

56
Q

Why does an increase in temperature increase the speed of conduction?

A

The ions move faster and so diffuse faster increases the speed of the depolarisation

57
Q

What do inhibitory neurotransmitters do?

A

They hyper polarise the postsynaptic knob preventing it from firing an action potential

58
Q

Are chemical mediators similar to hormones? And why?

A

Similar - the cells release chemicals that bind to receptors on target cells to cause a response

59
Q

Where is prostaglandin produced?

A

By most cells in the body

60
Q

What two systems do receptors communicate with effectors through?

A

The nervous system or the hormonal system

61
Q

What is the all-or-nothing principle?

A

Once the threshold is reached the action potential generated is always the same size no matter how big the stimuli

62
Q

What two things is the hormonal system made up of?

A

Glands and hormones

63
Q

After an action potential why can’t the neurone be stimulated straight away?

A

Time is needed for it to return to the resting potential - repolarisation and hyperpolarisation

64
Q

Why does myelin sheath act as?

A

An electrical insulator

65
Q

Name two examples of chemical mediators.

A

Histamine and prostaglandins

66
Q

What happens to a neurone after depolarisation during an action potential?

A

At around +30mV the sodium channels close and potassium channels open causing potassium ions to diffuse into the son down the potassium ion electrochemical gradient decreasing the potential difference and re polarising the membrane

67
Q

What about synapses ensures the impulse only travels in one direction?

A

The neurotransmitter is only released from the presynaptic knob and there are only receptors for it on the postsynaptic knob

68
Q

Name three difference between normal synapses and neuromuscular junctions?

A

1.) Has folds in the postsynaptic membrane which forms clefts, the clefts store acetylcholinesterase 2.) There are more receptor sites than usual 3.) When a motor neurone fires an action potential it will always trigger a response in muscle cells

69
Q

How does IAA move short and long distances?

A

Short - diffusion or active transport Long - through the phloem

70
Q

What are nodes of ranvier?

A

Gaps in the myelin sheath

71
Q

Why is the membrane of a neurone said to be polarised?

A

As there is a difference in charge between the outside and inside

72
Q

Is the effect of neurotransmitters long lasting or short lived and why?

A

Short lived - neurotransmitters are easily removed

A2 Biology - Unit 5 (8 decks)

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