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A Level Biology > Topic 8 > Flashcards

Topic 8 Flashcards

1
Q

What is the peripheral nervous system made up the

A

Sensory nerves

Motor nerves

Relay neurone

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2
Q

What is the peripheral nerves system divided into

A

Autonomic nervous system (involuntary)

Somatic nervous system
Voluntary stimulates skeletal muscles

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3
Q

What is the autonomic nervous system divided into

A

Sympathetic nervous system stimulated the body for fight or flight response ie increase heart rate

Parasympathetic nervous system
Prepares body for rest and digest

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4
Q

Distinguish between nerve and neurone

A

Neurone is single cell

Nerve is a group of neurones working together and

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5
Q

What are dendrites and axons

A

Dendrites- conduct impulses toward cell body

Axon transmit impulses away from cell body

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6
Q

What are the 3 types of neurone and state their function

A

Motor neurone they conduct impulses from the CNS to effectors

Sensory neurone- they carry impulses from sensory cells to CNS

Relay neurone- they are found in the CNS and they connect with other nerve cells

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7
Q

What the myelin sheath and what is it made from

A

They are around the axon and it’s a fatty insulating layer made up of Schwann cells

They enable the nerve impulses to happen faster

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8
Q

State the stages in the reflex arcs

A

A stimulus is detected by receptors and it generates a nerve impulse

Sensory neurones conducts a nerve impulse to the CNS

Sensory neurone enter the spinal cord through dorsal route

Synapse former between sensory and relay neurone

Relay neurone forms a synapse with motor neurone

Motor neurone carries impulses to an effector hormones which produces s response either bicep moving from flame

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9
Q

What controls the size of a pupil and state the two antagonistic muscles involved

A

Iris

Radial and circular muscles and these muscles are controlled autonomic nervous system

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10
Q

What controls the radial and circular muscles

A

Radial- sympathetic reflex

Circular muscles control parasympathetic reflex

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11
Q

State what each muscle is doing when the pupil constricts

A

Radial muscles relax

Circular muscles contract

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12
Q

State the role of each muscle when the pupil dilate

A

Radial muscles contract

Circular muscles relax

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13
Q

What is the resting potential of an axon and why is the membrane said to be polarised

A

-70mv

The inside of the axon is more negative than the outside

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14
Q

What is the role of the sodium potassium pump and how is it driven and what does it create

A

It’s role is to pump carry sodium out of the cell and potassium into the cell which creates polarisation

And it creates a concentration gradient and it driven by the energy from the hydrolysis of ATP

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15
Q

How was the resting potential of the an axon found

A

Experiments hodges placed two electrodes one in the bathing solution and one across the axon membrane and they found a potential difference of -70 mv

With the inside of the axon being more negative than the outside ( hence its polarised

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16
Q

Describe the process results in the resting potential of an axon to be -70 mv

A

The na/k pump creates a concentration gradient across the membrane

K plus diffuses out of the cell down the k concentration this action causes the outside of the memebrane to be more positive than the inside and it results in a potential difference being created as

The potential difference means some k ions willl be pulled back into the cell(some cl ions move out of the cell to balance the charge due to the pd )anions build up in the cell

When the pd across the membrane is around -70 mv the electrical and chemical gradient balance out and there no move movement of k

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17
Q

What is the chemical gradient and electrical gradient in resting potential

A

Chemical gradient is k going out via the pump

Electrical gradient- k being pulled in and cl going out

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18
Q

State the permeability of the membrane towards k and na ions

A

The membrane is permeable to potassium as it can go through a channel

It’s impregnable to sodium

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19
Q

What is depolarisation

A

This is when pd across the membrane is locally reversed with the outside of the axon now becoming negative and the inside being positive +40mv

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20
Q

What is repolarisation

A

When resting potential returns back to -70mv

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21
Q

What is action potential

A

The large change in voltage across the memebrane

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22
Q

What are the 3 stages in the generation of action potential

A

Depolarisation
Repolarisation
Restoring resting potential for

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23
Q

What are voltage dependant gated channels

A

They are channels that open as a result of changes in voltage across a membrane they block passage of na and k channels

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24
Q

What occurs in depolarisation

A

Due to stimulation The shape of the sodium gate changes shape due to change in PD across the membrane this opens some voltage dependant sodium ions channels

This causes na ions to flow inside the axon,meaning depolarisation increases which causes positive feed back meaning more sodium channel gates to open once a certain pd threshold is reached

This eventually leads to reverse in polarity meaning the PD across the memebrane reached +40 mv

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25
Q

What is meant by all or nothing

A

It means that actions potential either occur or not

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26
Q

What occurs in repolarisation

A

After 0.5ms the voltage dependant na channels close spontaneously

The voltage dependant k channels open meaning potassium ions move out of the axon by diffusion down an electrochemical gradient

As they flow outside of the cell the inside again becomes negative

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27
Q

How is resting potential restored

A

The voltage dependant k channels close and k ions begin to diffuse into the axon and it aids in restavlishing the rest potential

Furthermore the sodium potassium Pumps aids in restoring the original ion concentration across the CSM

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28
Q

What is hyperpolarisation

A

It is when the potential difference is more negative than the normal resting potential in a membrane

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29
Q

Describe each stage in transmission of action potential known as propagation

A

When stimulated the voltage dependant na+ channels open and this causes Na* ions to flow into the axon causing depolarisation of the memebrane and it causes localised electric currents to be generated
This in turn causes na+ ions to move to the adjacent polarised region and PD to changes across that part of the memebrane

The change in the potential difference in the membrane adjacent to the first action potential initates a second action potential at the site the first action potential the membrane because depolarised

The second action potential Iniates a 3rd action potential(electric currents cause nerve impulse move along the axon

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30
Q

What is meant by refractory period and what does this mean

A

A period after stimulation in which nerve impulse is unresponsive to further stimulation means action
Potential can’t be propagated backwards

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31
Q

What does refractory period mean for action potential direction

A

It means that it only goes in one direction as action potential can’t be generated in the same section

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32
Q

How long does refractory period last

A

Until resting potential is restored and na and k channels have returned ri their normal resting states

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33
Q

Where are the nodes of ranvier and what happens there

A

They occur at intervals in the myelin sheath and it’s where depolarisation takes place

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34
Q

What is the role of the myelin sheath

A

It acts as an electrical insulator and it prevents ions moving across the membrane

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35
Q

Describe the process of saltatory conduction

A

In depolarisation ions flow across the memebrane at one node,this sets up a circuit which reduces PD at the next node triggering an action potential

This result in a faster wave of depolarisation

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36
Q

What is meant by a synapse and synaptic cleft

A

Synapse is when two neurone meant

Synaptic cleft is the gap between them

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37
Q

Name the 3 main stages in synaptic action

A

Neurotransmitter release

Stimulation of post synaptic memebrane

Inactivation of neurotransmitters

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38
Q

Describe the process of neurotransmitter releases

A

An action potential depolarises a pre synaptic membrane and it increases its permeability to ca ions

There is a greater concentration outside the cell of ca ions and so Thei diffuse into the cytoplasm across the membrane

The increased ca ions cause the synaptic vesicles which contain acetylcholine to fuse with the pre synaptic membrane this causes them to release their contents by exocytosis into the synaptic cleft

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39
Q

Why are ca ions important in the release of a neurotransmitter

A

When they increase in concentration they cause synaptic vesicles to fuse and it results in them releasing their contents by exocytosis

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40
Q

Describe the process in stimulation of a post synaptic membrane

A

Acetylcholine molecule binds to a protein receptor on the post synaptic membrane causeing it to change shape

This makes it more permeable na ions the flow of na ions across the postsynaptic memebrane causes depolarisation and if it’s sufficient an action potential is produced which is propagated

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41
Q

Where are the nodes of ranvier and what happens there

A

They occur at intervals in the myelin sheath and it’s where depolarisation takes place

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42
Q

What is the role of the myelin sheath

A

It acts as an electrical insulator and it prevents ions moving across the membrane

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43
Q

What factors affect depolarisation of the post synaptic membrane

A

Depends on the amount of acetylcholine that reaches the post synaptic membrane

Functioning receptors on the post synaptic membrane

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44
Q

Why are na ions important in stimulation of the post synaptic membrane

A

It’s causes depolarisation of the post synaptic membrane meaning an action potential can occur

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45
Q

How does neurotransmitter become inactived

A

Acetylcholinesterase breaks down the acetylcholine so it can’t bind to receptors

Some of the broken down products are reabosred by the pre synaptic membrane to be reused

46
Q

State the role of acetyl cholinesterase in inactivation of the postsynaptic neurone

A

It breaks down acetylcholine meaning it can’t bind to receptors

47
Q

State the two types of synapses

A

Excitatory and inhibitory

48
Q

What do excitatory synapses do

A

They make the post synaptic memebrane more permeable to sodium ions

As a result of summation

49
Q

What is summation and state the two types and what they are

A

Summation is the adding up of the effect of impulses

Spatial summation - this is when lots of different neurones are producing impulses

Temporal summation- when several impulses arrive at a synapse after travelling along one neurone one after the other

50
Q

What is meant by an inhibitory synapse

A

These synapses mean it’s less likely that an action potential will result in the post synaptic membrane

51
Q

Describe how inhibitory synapses work

A

A neurotransmitter from these synapse causes chloride channels in psm to open which enables cl ions and k + ions to move down their diffusion gradient with cl going into the cell and k going out

These cause hyperpolarisation of membrane in which theirs a greater pd with the membrane being more negative inside

This means depolarisation is less likely to occur

52
Q

In inhibitory synapse what does the movement of cl and k ions result in and what effect does this have

A

They cause hyperpolarisation of the membrane in which the inside of the membrane is more negative meaning depolarisation in that membrane is less likely to occur

53
Q

Describe how pupil size is controlled

A

When light strikes photo receptors in the retina it causes nerve impulses to pass along the optic nerve to sites in the CNS , group of co ordinating cells

These cells send impulses along the pns via motor neurotransmitter they go to the circular muscles of the iris which causes them to contract and at the same time radial muscles relax

Thus action causes the pupil to construct

54
Q

Compare the differences in nervous and hormonal co ordination

A

Nervous control:electrical transmissions by nerve impulses and chemical transmission

Fast acting

Short term muscle contraction

Responses are local

Neurones carry action potentials with connections to specific cells

Hormonal control

Chemical transmission via blood

Slower acting

Longer term changes

Responses tend to be widespread

Blood carries hormone to all cells

55
Q

What is IAA and state it’s function

A

Indoleacetic acid and it’s an auxin, it stimulates growth which results in cell elongation

56
Q

Where are auxins produced in a plant

A

The meristem tissue in the tip

57
Q

Why in the face of unilateral light will the shoot bend towards the light

A

In The shaded area of the plant more auxin passed down that side and the increase in concentration on that side results cell elongation in the shaded area

Cell elongation is inhibited in the unshaded side of the plant due to sunlight and so there’s a reduced amount of auxin concentration

This results in shooting bending towards the light

58
Q

Why when the tip of the shoot is discarded cell elongation is inhibited

A

The tip contains meristem tissue that produces IAA which causes cell elongation

59
Q

What is phototropism

A

Growth of a plant in response to light

60
Q

What is tropism

A

It’s the response of a plant to a direct stimulus

61
Q

What is the difference between positive and negative tropism

A

Positive is growth towards the stimulus

Negative is growth away from the stimulus

62
Q

In propagation of a nerve impulse what causes the sodium ions to move to the adajecent membrane

A

The localised currents that are generated

63
Q

In an action potential why do the voltage-dependant potassium channel gates open

A

Due to the depolarisation of the membrane

64
Q

When the membrane is hyperpolarised give ways as to which the normal potential difference is restored

A

The closing of the voltage dependant k channels

And potassium ion diffusion into the axon

The work of the sodium potassium pump with na+ pumped out of membrane and k into it

65
Q

In a nerve impulse state the role of the localised electrical current

A

They cause a wave of depolarisation to occur as they cause Na+ ions to move into the adajecent resting region stimulating depolarisation to occur their this imitating an action potential

66
Q

In synaptic transmission describe the role of acetylcholine

A

It binds onto specfic receptor proteins and causes it to change shape which allows cation channels to open making it more permeable to sodium ions

This leads to depolarisation

67
Q

Where are auxins like IAA synthesised

A

In growing root and root tips(meristems

68
Q

How is IAA transported

A

In the phloem for long distances and via specific carried proteins in the cell membrane for short distances

69
Q

Explain how auxins work in changes in the target cells

A

They bind on to protein receptors in the target cells

This action activates second messenger signal molecules which activate the transcription of auxin regulated genes

These genes produce proteins that bring about metabolic changes in the cells

70
Q

What must happen to a cell wall before it can expand and describe this process up to expansins

A

It must first loosen its thought that the auxin causes acidification of the cell wall

As they stimulated the activity of proton pump that move H+ ions out of the cytoplasm into the cell wall it creates a low ph which activates proteins called expansins

71
Q

State what expansins do and how it leads to expansion of the cell wall

A

They disrupt the bonds that hold cellulose microfibrils and hemicelluloses together this causes loosening of the cell wall

There’s a slippage of polysaccharides resulting in bonds reforming in new locations this enables expansion of the cell

72
Q

How does cell elongation occur

A

The potential difference across the membrane increases due to acidification of the cell wall

This results in osmosis as the uptake of ions into the cell causes water uptake to take place this cause the cell to swell causing cell elongation

73
Q

How does cell wall acidification take place

A

Auxin stimulates the proton pump to move h ions out of the cytoplasm into the cell wall causing a low ph

74
Q

What are the two types of photoreceptors in the human retina

A

Rods and cones that are both sensitive to light

75
Q

What is the difference between rods and cones

A

Cones allow colour vision in bright light

Rods only give black and white vision but they work in both dim and bright light

76
Q

What is rhodopsin

A

It’s a photochemical pigment that absorbs light which results in chemical changes it can be found in the outer segment in vesicles

77
Q

State the parts of the eye and their function

A

Choroid-black layer prevents internal reflection of light

Vitreous humour-transparent jelly

Retina-contains light sensitive light

Lens-focuses light on the retina

Iris-controls the amount of light that enters the eye

Clilairy muscles-they alter the thickness of the lens

Blind spot-no light sensitive cells are here

78
Q

What are the 3 layers of cells that make up the retina and state their arrangement

A

Bipolar neurone cells,ganglion neurones,rod cell

Ganglion cell-bipolar cell-rod They form synapses with them

79
Q

What axons make up the optic nerve

A

Biopolar neurone which in synapses with ganglion neurones

80
Q

Describe what happens to rod cells in the dark

A

Sodium ions flow into the outer segment through non specific cation channels

They move down a concentration gradient into the inner segment where they are pumped out it of the cell

This pumping out of Na causes depolarisation of the cell which triggers the release of a ns called glutamate from rod cells

This happens continousley in the rod cells and it binds to the bipolar cells which stops it depolarising

81
Q

Describe the process that happens in the rod cells in the presence of light

A

Light falls on rhodopsin causing it to break down into retinal and Opsin

Opsin causes a range of reactions to happen which results in the hydrolysis of a molecule which binds to the cation channel that’s attached in the outer segment

The breakdown of molecule causes the cation channels to close

This means less sodium ions enter the rod cells but the inner segment continues to pump Na out this results in hyperpolarisation and glutamate isn’t released

This means the bipolar cell can depolarise and it results in an action potential being produced in the optic neurones

82
Q

State the role of Opsin

A

It causes a series of membrane bound reactions that results in the breakdown of a molecule that attaches to and closes cation channels that

83
Q

In the presence of light how does hyperpolarisation occur

A

The closing of the cation channels makes the inside of the inner segment more negative as more Na is pumped out but no Na is coming in

84
Q

What is the outer layer of the brain called and what is it made up of

A

It’s called grey matter it’s mainly made of nerve cell bodies,synapses and dendrites

85
Q

Why is white matter white and what does it contain

A

It’s contains nerve axons that connect neurones in different parts of the brain

It’s white because of the axons myelin sheath

86
Q

What are the four lobes in the brain

A

Frontal
Parietal
Occipital
Temporal

87
Q

What is the function of the thalamus

A

It routes all incoming Sensory information to the correct part of the brain via axons of the white matter

88
Q

What is the function of the frontal lobe and what does it contain

A

It’s concerned with higher brain functions like descion making,reasoning and consciousness of emotions

The motor cortex

89
Q

State the function of the motor cortex

A

It sends info to the body via motor neurones to carry our movements

90
Q

What is the function of parietal lobe

A

It’s concerned with sensation(pain)as well as orientation

91
Q

What is the role of the occipital lobe and what does it contain

A

It contains the visual cortex and so is associated with processing visual info

92
Q

What is the role of the temporal lobe

A

It’s concerned with processing auditory information

93
Q

Where is the hypothalamus and what does it contain and describe some of its features

A

It lies below the thalamus and it’s contain the thermoregulatory centre

It also acts as an endocrine gland as it secretes hormones

94
Q

What is the function of the hippocampus

A

It’s involved in long term memory

95
Q

What is the basal ganglia responsible for

A

They are responsible for selecting and initiating stored programmes for movement

96
Q

Explain how the right and left hemisphere are able to communicate with one another

A

White matter known as the corpus callosum enables them to communicate with each other

97
Q

What is the cerebellum responsible

A

It’s responsible for balance

Coordinates movements as they are being carried out as it receives info from the primary motor cortex

98
Q

State where the brain stem extends from

A

The midbrain to the medulla oblongata

99
Q

What is the function of the midbrain.

A

It relays info to the cerebral hemispheres ie auditory info

100
Q

What is the role of the medulla oblongata

A

It regulates bodily processes that we don’t control consciously ie heart rate,breathing and blood pressure

101
Q

What is neural plasticity

A

That as a result of experience or damage the brain is able to change in structure and function

102
Q

Give the 4 types brain imaging research

A

FMRI
PET
MRI
CT

103
Q

What is a phytochrome

A

It’s a light absorbing pigment molecule that has a protein component bonded to non protein

104
Q

What are the two non protein components had two forms

A

Pr-which absorb red light

Pfr-they absorb far red light

105
Q

State how CT scans are performed

A

It uses lots of narrow beam of X-rays that are rotated around an individual so it passes through tissues at different angles

The X-rays are detected and they at used to produce an image of thin brain structure

106
Q

How are CT scans performed

A

They can be used to diagnose medical issues like damaged areas of the brain

Ie the location of bleeding on the brain
Blood has different density so appears lighter

107
Q

Give some issues with CT scans

A

They have a limited resolution

Only look at structures not function

X-rate create issue of cancer

108
Q

How do MRI work

A

The magnetic field is placed on a person as they pass through a tube

Another magnetic field is superimposed by the radio waves

The two combined fields cause the direction and frequency of the hydrogen nuclei to spin and change as they absorb energy from the radio waves

They release the energy once the radio waves are turned of and this energy release is detected and a signal sent to a computer and an image is produced

109
Q

What is dark adaptation

A

This is when the rhodopsin rebuilds its self after being broken down by light

110
Q

Compare the structures of the neurones ie describe

A

Motor neurone and relay neurones have many short dendrites carry

Motor neurone have long axons the others don’t

Sensory neurone have long dendron,relay neurones Have short dendrites

A Level Biology (9 decks)

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