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A LEVEL BIOLOGY > Topic 6A and 6B > Flashcards

Topic 6A and 6B Flashcards

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1
Q

What is an Axon?

A

A single long fibre that carries nerve impulses away from the cell body.

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2
Q

What are dendrons and dendrites

A

Extensions of the cell body that carry nerve impulses

Dendrites are smaller divisions of dendrons

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3
Q

What is a neurone?

A

A specialised cell adapted to rapidly carrying nerve impulses.

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4
Q

What is a cell body?

A

Associated with production of proteins and neurotransmitters

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5
Q

What are Schwann cells used for?

A

protecting the axon and providing electrical insulation. they also carry out phagocytosis + help nerve regeneration

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6
Q

What are the two main forms of coordination in animals?

A

The nervous system

The hormonal system

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7
Q

What is a myelin sheath for?

A

covers the axon, made up of membranes of Schwann cells.

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8
Q

What are nodes of Ranvier ?

A

constrictions between adjacent schwann cells where there’s no myelin sheath.

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9
Q

Name 3 classifications of neurone

A

Sensory neurones
Motor neurones
Intermediate/ relay neurones

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10
Q

Neurones are adapted to carry electrochemical charges called…

A

Nerve impulses

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11
Q

Each neurone comprises a cell body that contains a ….. and large amounts of ………. …… ……

A

Each neurone comprises a cell body that contains a nucleus and large amounts of rough endoplasmic reticulum.

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12
Q

Axons are surrounded by ……… cells which protect and provide ……. because their membranes are rich in a lipid known as ……

A

Axons are surrounded by Schwann cells which protect and provide insulation because their membranes are rich in a lipid known as Myelin.

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13
Q

3 types of neurone. Those that carry nerve impulses to an effector are called ……. neurones. Those that carry impulses from a receptor are called ……. neurones and those that link the other two types are called …… neurones.

A

3 types of neurone. Those that carry nerve impulses to an effector are called motor neurones. Those that carry impulses from a receptor are called sensory neurones and those that link the other two types are called relay neurones.

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14
Q

List three ways in which a response to a hormone differs from a response to a nerve impulse

A

Hormone response is slow, widespread and long-lasting. Nervous response is rapid, localised and short-lived.

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15
Q

What do synapses do?

A

Transmit information, from one neurone to another or an effector.

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16
Q

What separates neurones?

A

Synaptic Cleft

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17
Q

Which neurone releases the neurotransmitter?

A

Presynaptic neurone

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18
Q

Axon of presynaptic neurone ends in a swollen portion called ……

A

Synaptic knob

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19
Q

Where is the neurotransmitter stored?

A

In the synaptic vesicles

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20
Q

What is the general path for a reflex arc?

A

Stimulus -> Receptor -> Sensory Neuron -> Relay Neuron -> Motor Neuron -> Effector -> Response

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21
Q

What are the extensions of neurones called?

A

dendrites (towards cell body)

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22
Q

How are nerve cells polarised in their resting state?

A

Imbalance between sodium ions and potassium ions, resulting in more negative inside of axon tha outside

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23
Q

As a result of polarisation there is a difference in the ……. across the axon membrane with a value of …. known as resting potential

A

As a result of polarisation there is a difference in the voltage across the axon membrane with a value of -70mV

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24
Q

The resting potential is generated as well as maintained by the help of the ………-……. ……..

A

The resting potential is generated as well as maintained by the help of the sodium-potassium pump

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25
Q

For ever …. sodium ions that are pumped out of the axon …. potassium ions are pumped in.

A

For every 3 sodium out

2 potassium in

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26
Q

Resting potential is maintained by…

A

Active transport and passive diffusion

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27
Q

During resting potential the plasma membrane of the axon is more permeable to …. ions

A

Membrane more permeable to K+ ions

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28
Q

The process where a neurone is depolarised and returns to resting potential is called….

A

an action potential

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29
Q

Where do motor neurones carry impulses?

A

From the CNS —> effector organs

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30
Q

Where do sensory neurons carry impulses?

A

From receptors –> CNS

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31
Q

Where do relay neurones carry impulses?

A

From sensory neurones –> motor neurone

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32
Q

What do receptors do?

A

Detect stimuli

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33
Q

What do effectors do?

A

Produce a response

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34
Q

Give some examples of receptors

A

cells/proteins on cell membranes

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35
Q

Give some examples of effectors

A

muscle cells and cells found in glands

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36
Q

What does the autonomic nervous system control?

A

Unconscious activities e.g. digestion

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37
Q

What 2 parts is the autonomic nervous system split into?

A

Sympathetic- ready for response, fight/flight

Parasympathetic- calms body down

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38
Q

What does the somatic nervous system control?

A

Conscious activities e.g. running

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39
Q

What is a reflex?

A

An involuntary response to a stimulus

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40
Q

What is a tropism?

A

the growth of a plant in response to a directional stimulus.

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41
Q

What is the difference between positive and negative tropisms?

A 
Positive = growth towards stimulus
Negative = growth away from stimulus
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42
Q

What is phototropism?

A

The growth of a plant in response to light

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43
Q

….. are positively phototropic and grow ….. light

A

Shoots are positively phototropic and grow towards light

44
Q

…. are negatively phototropic and grow ……. light

A

Roots are negatively phototropic and grow away from light

45
Q

What is gravitrotropism?

A

The growth of a plant in response to gravity.

46
Q

Shoots are …… gravitropic and grow ……..

A

shoots are negatively gravitropic and grow upwards

47
Q

Roots are ……. gravitropic and grow …….

A

Roots are positively gravitropic and grow downwards

48
Q

What is auxin?

A

a growth factor that stimulates the growth of shoots by elongation

49
Q

What is cell elongation?

A

cell walls becoming loose and stretchy, so the cells get longer

50
Q

Name an important auxin that’s produced in the tips of shoots in flowering plants

A

Indoleacetic acid (IAA)

51
Q

In phototropism IAA moves to the more….. parts of the shoots and roots resulting in …..

A

During phototropism IAA moves to the more shaded parts of the shoots and roots resulting in uneven growth

52
Q

In gravitrotropism IAA moves to the ……… of shoots and roots so there’s ……

A

In gravitrotropism IAA moves to the underside of shoots and roots so there’s uneven growth

53
Q

Receptors only detect one particular stimulus so they are…

A

specific

54
Q

What happens if a stimulus is too weak?

A

The generator potential won’t reach the threshold so there’s no action potential

55
Q

Why do organisms respond to changes in environment?

A

To increase their chance of survival

56
Q

What do Pacinian corpuscles detect?

A

mechanical stimuli e.g. pressure and vibrations

57
Q

Photoreceptors convert light into what?

A

An electrical impulse

58
Q

Neurone cell membranes become …….. when they’re stimulated.

A

depolarised

59
Q

What is the value for the threshold?

A

-55mV

60
Q

Describe what happens during depolarisation

A

If potential difference reaches the threshold (-55mV) then more sodium ion channels open and more sodium ions rapidly diffuse into neurone

61
Q

Describe what happens during repolarisation

A

At a potential difference of around +30mV the sodium ion channels close and K+ channels open. The membrane is more permeable to potassium so potassium diffuses out down the conc grad to regain resting potential.

62
Q

Describe what happens during hyperpolarisation

A

Potassium ion channels are slow to close so there’s an overshoot as too many potassium ions diffuse out of neurone. Potential difference becomes more negative than resting potential (less than 70mV)

63
Q

Describe resting potential

A

The ion channels are reset. The sodium-potassium pump returns the membrane to its resting potential and maintains until another stimulus excites the membrane.

64
Q

why don’t action potentials overlap or move in more than one direction?

A

During the refractory period ion channels can’t be opened. Therefore it acts as a time delay

65
Q

Why are action potentials described as all or nothing responses?

A

As once the threshold is reached an action potential will always fire with the same change in voltage no matter how big the stimulus

66
Q

A bigger stimulus won’t cause a bigger action potential but it causes …..

A

them to fire more frequently

67
Q

What is the gap between neurons called?

A

Synaptic Cleft

68
Q

Where are neurotransmitters stored?

A

Synaptic vesicles

69
Q

What is a synapse?

A

The point where one neuron communicates with another or an effector

70
Q

What is the neurone called that releases the neurotransmitters?

A

Presynaptic neurone

71
Q

What is the synaptic knob? What does it contain lots of?

A

Swollen portion at the end of an axon.

Mitochondria and Endoplasmic reticulum

72
Q

What are Pacinian Corpuscles

A

Pressure receptors in your skin

73
Q

Pacinian corpuscles contain the end of ….. …..

A

a sensory neurone surrounded by lamellae

74
Q

What happens when pressure is applied to a Pacinian corpuscle?

A

The tissue is deformed and pressues the sensory nerve ending causing the membrane of neurone to stretch, deforming the stretch mediated Na+ channels which opens them so Na+ ions diffuse in and a generator potential is made.

75
Q

Photoreceptors convert …… into an ……… …….

A

light into an electrical impulse

76
Q

Spatial Summation

A

many different neurones collectively trigger a new action potential by combining the neurotransmitter they release to exceed the threshold value.

77
Q

Temporal summation:

A

One neurone releases neurotransmitter repeatedly over a short period of time to add up to enough to exceed the threshold value.

78
Q

Name the two types of photoreceptors found in your eye

A

rods and cones

79
Q

List features of Rods

A 
Rods =                                        
black and white
low intensity light
many rods to 1 bipolar cell
pigment = rhodopsin
low visual acuity
80
Q

List features of Cones

A 
Cones=
Colour
high intensity
1 cone to 1 bipolar
pigment= iodopsin
high visual acuity
81
Q

Explain the importance of reflex actions (3)

A
  • involuntary/automatic response
  • prevents damage to tissues/injury
  • Escape from predators
82
Q

What is a tactic response (taxes)

A

When an organism moves towards or away from a directional stimulus e.g light

83
Q

What is a kinetic response (kineses)

A

When the organisms movement is affected by non-directional stimulus e.g. humidity

84
Q

What is summation?

A

the effect of a neurotransmitter released from many neurones is added together.

85
Q

What is a neuromuscular junction?

A

a synapse between a motor neurone and a muscle cell

86
Q

Which neurotransmitter is found at neuromuscular junctions?

A

Acetylcholine

87
Q

What receptors does Acetylcholine bind to?

A

Cholinergic receptors

88
Q

Acetylcholine is always ……. at a muscular junction

A

Excitatory

89
Q

What enzyme breaks down Acetylcholine?

A

Acetylcholinesterase

90
Q

Rods can generate an action potential in ……. …… whereas cones require ….. …. to generate an action potential

A

Rods can generate an action potential in dim light whereas cones require brighter light to generate an action potential

91
Q

How is a generator potential established in a Pacinian Corpuscle?

A

Deformation of stretch-mediated sodium ion channels in a Pacinian corpuscle leads to the establishment of a generator potential.

92
Q

Function of SAN?

A

Acts as pacemaker, sends electrical activity to atria so they contract

93
Q

Function of Purkyne tissues

A

sends electrical activity through ventricle muscles so that they contract.

94
Q

Outline the Resting Cardiac cycle

A

SAN sends electrical activity. Atria contract. AVN receives electrical activity from SAN and slightly delays and then sends to bundle of His onto Purkyne tissue, into muscular ventricle walls for ventricular contraction.

95
Q

Why does the AVN delay passing on the waves of electrical activity?

A

So that the atria empty before ventricles contract

96
Q

What is the rate of the SAN controlled by?

A

The medulla oblongata UNCONSCIOUSLY controls rate

97
Q

Why do animals need to alter their heart rate?

A

To respond to internal stimuli i.e make sure heart rate is high enough to supply the body with enough oxygen

98
Q

What are the pressure receptors in the aorta and carotid arteries called?

A

Baroreceptors

99
Q

What are the pressure receptors in the aorta and carotid arteries called? What are they stimulated by?

A

Baroreceptors stimulated by high and low blood pressure

100
Q

What are the chemical receptors called that are found in aorta, medulla and carotid arteries? What are they stimulated by?

A

Chemoreceptors monitor oxygen levels in blood, and CO2 and pH (indicators of O2 level)

101
Q

Light inhibits … …….. in the tip so it is only produced on the ….. …..

A

IAA production

shaded side

102
Q

Why does Axon diameter affect speed of conduction?

A

The bigger the diameter the less resistance to flow of ions therefore depolarisation reaches other parts of neurone quicker.

103
Q

Why does temperature affect speed of conduction?

A

Ions diffuse faster at higher temperatures (after 40”c they denature)

104
Q

Name the cell membrane of muscle fibres

A

Sarcolemma

105
Q

Name the cytoplasm of muscle fibres

A

Sarcoplasm

106
Q

What is the network of internal membranes called in a muscle? What do they do

A

Sarcoplasmic reticulum (store and release calcium ions)

107
Q

Compare slow and fast twitch muscle fibres

A 
Slow = contract slowly, endurance, long time without tiring, aerobic resp, lots of mitochondria
Fast= contract quickly, tired v quickly, short bursts of speed and power, few mitochondria, anaerobic resp

A LEVEL BIOLOGY (19 decks)

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