Topic 8 - Response Flashcards
(131 cards)
1
Q
Nature: genetic component
70% twins recognised
A
Identical twins agreement is greater - 41% more
Alleles are involved
Non-identical twins have genetic differences, identical twins are genetically the same
Because less than 100%, some other factor is involved
2
Q
Recognising handwriting vs. faces of twins
A
Less of a gap between the results
3
Q
fMRI during face identification: suggest why fMRI
A
Active areas have more oxygen/ oxygenated blood
Active areas involved in face recognition will be identified
Level of brain activity between identical twins and non-identical twins is compared: more areas showing activity in common in identical twins
To offer supportive evidence/improve validity of study
fMRI shows brain activity in real time
High resolution
Safer: fMRI does not use X-rays
4
Q
Photosensitive pigment in plants
A
Phytochrome
5
Q
Plant growth valid experiement
A
Standardise: water, mineral ion concentrations, light intensity, wavelength of light, CO2 conc., temp, pH, soil type
6
Q
Study could be changed to produce a more accurate conclusion
A
Using shorter time intervals e.g. 1 hour intervals, only known between 12-15h, repeat with 12, 13 hours
7
Q
Suggest one environmental cue other than day length stimulate flower production
A
Temperature Water availability the wavelength/quality of light Intensity of light edaphic factor
8
Q
State the location of rhodopsin within a rod cell
A
Outer segment (internal membranes, inner membranes, vesicles)
9
Q
Rhodposin responding to light
A
Opsin binds to the rod cell mebrane
Rhdoipsin bleaches
(ATP IS NOT USED)
10
Q
Rhodopsin being reset
A
ATP used
(Opsin DOES NOT bind to the rod cell mebrane)
(Rhdoipsin DOES NOT bleach)
11
Q
Medulla oblongata functions
A
Controls breathing/ heart rate
Involuntary muscles: swallowing, vomiting, sneezing
12
Q
Cerebral hemisphere/ cerebrum frontal cortex function
A
Feel emotions
13
Q
*GMO restriction enzymes - only one used
A
Cuts at a specific sequence of base (DNA sequence)
Generates sticky ends
so easier to join together
14
Q
*Chemical which causes a gene to be ‘switched on’
A
The chemaical could be a transcription factor/ horone
Interations at bacterial cell surqfce memebrane
Transcription factor being activated e.g. transciprtion initiation complex formed, binds to trasctoption factor, or counters inhibitor
Binds to promoter region
Transcription occurs eg.g RNA polymerase binds, mRNA is produced
15
Q
*Protein synthesis organelle structure
A
Ribosome has larger and smaller subunit: ribosomal protein and rNA.
16
Q
*GMO injecting into vein rather than artery
A
Larger lumen so easier to put into blood
Less muscle/thinner wall so wasier to penetrate
Bloodpressure is less so less damage to vein - less blood loss
Vein is easier to find: nearer skin surface
17
Q
Mitosis
A
PMAT - prophase, metaphase, anaphase, telophase
NOT cytokinesis or interphase
Produces two nuclei
Genetically identical to the orginal
18
Q
Motor neurone infection by virus can stop nerve impulse transmission and lead to muscle paralysis
A
Motor neurone (its cell body, nucleus) is destroyed
Depolarisation does not occur in neurone, insuffiecient so no action potential set up in the neurone
Depolarisation/action potential does not occur in the neurone: Na+ does not diffuse into neurone
Neutotansmitter not released ar junction with muscle (at motor newurone preseynaptic emebrane/ motor end plate)
Lack of neurotransmitter release: vesicales contain NT do not move or fuse with presymaptic memebrane
Ca++ not released into muscle cytoplasm
Ca++ not released from sarcoplasmic reticulum/sactoplasm
no Ca++ to activate troponin
Muscle does not contract
19
Q
*Provirus genetic structure and HeLa genetic structure similarities
A
Both contain bases Contain phosphate groups Have a pentose sugar Have phosphodiester bonds Discrete stands
20
Q
*Human genome map
A
all the DNA found in a huamn/ the huamn species (all bases, introns, and exons)
Genes on different chromosomes/ different loci on same chromosome)
21
Q
*Tumor suppressor gene
Could stop a potential tumour forming
A
Product stops/ regulates progression of cell cycle towards mitosis - keeps it in interphaae
Act as an inhibitor of transcription protien synthesis
DNA repair
Leads to apoptosis (shortens telomeres)
22
Q
Specific DNA sequence from a blood cell codes for what that allows it to be susceptible to HIV?
A
proteiun/glycoprtein, this being CD4, found on cell surface membrane, that acts as a recpetor for HIV
23
Q
What is the rod cell pigment, , made of?
A
opsin and retinal
24
Q
Light stimulates a rod cell and what pigment changes?
A
rhodopsin
25
Once the pigment has changed, the concentration of sodium ions inside the rod cell ...?
Once the pigment has changed, the concentration of sodium ions inside the rod cell DECREASES
26
After changing, the pigment takes time to become functional again. Why?
Because it has to bleach.
27
The cell that links a rod cell to a sensory neurone is a ... neurone,
The cell that links a rod cell to a sensory neurone is a bipolar neurone,
28
Decrease in light leads to pupil dilation
Muscles work antagonistically
Circular muscle relaxes
Radial muscle contracts
29
CT vs/ mRI for studying brain structures
CT can only identify larger structures, MRI can identify smaller structures
Both identify soft tissue: MRI is better for soft tissue, CT for bones/tissues of different density, both for tumours
MRI uses radio waves/magnetic field, CT uses X-rays
Both give 2d/3d images - easier to get 3D from MRI
MRI IS NOISY, NEED TO KEEP STILL, NOT SO GOOD FOR PEOPLE WITH METAL IMPLANTS, PACEMAKERS
CT USES X-RAYS SO THERE ARE SAFETY ISSUES
Both images are only at one point in time]
MRI is more expensive than CT.
30
fMRI better than CT for studying brain function
View brain directly
Seeing brain activity over a period of time
Safer as does not used X-rays
No need to use special dyes.
31
Tumour appeared white in the MRI scans
Tumour tissue differs from brain tissue
Effect on scan : energy source - magnetic field/ radio waves - absorbed
Difference in blood supply -oxygen presence
32
Using info. diagrams - effect on the treatment on the tumour: a large circle, becoming a smaller cirlce
Treatment has been partially sucessful
Tumour reduced
In contact with less brain tissue, affecting less brain tissue, halved in size
33
(fMRI)
Functional magnetic resonance imaging or functional MRI
34
Two brain functions that would improve after treating a tumour at the front of the brain.
Two appropriate functions given, e.g. think, learn, show emotions, memory, personality, reasoning
Because tumour is situated in the frontal lobe/ cerebrum
35
Functions of enzymes in a metabolic process
Enzyme 1 converts subrate p to product q
This product becomes the substrate of the next step
Specificity
Controls the conversion
Speeds up the conversion
By reducing activation energy
Whole process can be controlled by end product inhibition
36
Suggest one NT that might bind to receptors on cell surface membrane in cardiac muscle cell in SAN
Acetylcholine or noradrelaine
37
Eye-like feature protruding from axon in sensory neurone.
Cell body
38
The simplest line in neurones that runs through the myelin sheaths
Axon
39
Describe the relationship
| Between concentration of eugenic and % inhibition Na+ movement
Increasing Eugenol concentration increases percentage inhibition
Positive correlation
Non-linear correlation
40
Eugenol affects Ca2+ movement and reduces pain
Reduced Ca2+ enters presynaptic membrane into sensory neurone
Due to Ca2+ channel not opening - decreased sensitivity to Ca2+
Fewer vesicles move towards and fuse with presynaptic membrane.
Less neurotransmitter released into/less diffuses across synaptic gap.
Less neurotransmitter binds to receptors on post-synaptic membrane/adjacent neurone
Reduced depolarisation/ less Na+ or cation channels open
Threshold intensity/action potential, less likely to occur
Pain not being sensed as impulse stopped before entering CNS /leaving the sensory neurone.
41
IAA experiment control?
Cut shoot without IAA present/without agar blocks
42
How did Auxin affect growth of shoot?
Both sides of shoot taller
Than control
Both IAAs diffuse down, out of agar, to zone of elongation
Cell elongation occurs
Shoot beds to the right - bends away from side with (artificial) IAA
Due to more growth on left side of shoot/side with artificial IAA
43
*IAA is known to bind to transcription factors. How can IAA stimulate cells to synthesise protein?
IAA enters the cell.
Movement within cell/IAA in cytoplasm to nucleus
Effect when binds to transcription factor e.g. forms a transcription initiation complex or countering an inhibitor, joins to promotor region, activates transition factor
Switching on gene
Activity at promoter region, RNA polymerase activity
Allows formation of mRNA
Translation produces protein
44
Cellulose vs. Starch
Alpha glucose in starch and beta glucose in cellulose
Only starch/amylopectin can be branched, while cellulose is only a linear molecule
Starch contains two types of molecules, cellulose only one
Alternate monomers rotated through 180' in cellulose only.
Only amylopectin/starch can have 1-6 glycosidic bonds, while cellulose has 1,4 glycosidic bonds only
45
Rank air tunnels of naked mole rats adapted
| It would leave us gasping for air
This air has higher CO2 content
CO2 level in blood increases/pH of blood falls
Change detected by chemoreceptors in carotid body/artery/aortic body/aorta/medulla
Sends more impulses along neurones
To intercostal muscles/diaphragm
Causing an increased ventilation rate, rate of breathing, depth of breathing
46
Non-motile sperm structure
Irregularity of flagellum
| Irregularity associated with mid region - mitochondria non-functional, less effective, not enough mitochondria
47
Importance of dispersion of colonies
```
Reduces inbreeding depression
Increases outbreeding
Leading to increase in genetic diversity
Colony size regulation
Increase in fecundity/fertility
Increased chance of survival
```
48
The maximum change in pd across the membrane of this neurone during depolarisation
100mv
-70 to +30
49
Stage when the concentration of positive ions is greatest inside the axon
At +30, peak of graph, Na+ diffuse in, voltage-gated Na+ open
50
Stage when hyper polarisation first occurs
Curve goes down to -80
| K+ leaves
51
Stage showing resting potential
First stage, before peak, at -70mv
52
After NT (ACh) release
NT diffuses across gap and binds to receptors on post-synaptic membrane
Gated channels open.
Na+ travels through post-synaptic membrane.
This causes a depolarisation
If sufficient present, an action potential is set up in post synoptic membrane/adjacent cell
Temporal or spatial summation occurs
This allows coordination one way flow of information,
It allows integration in post-synaptic cell.
NT is broken down by enzyme.
So that you do not get prolonged action potential in post synaptic membrane and to make receptors available again.
The fate of the products of NT break down: reabsorbed through presynaptic membrane.
53
```
The hydrogen (H) from the Krebs cycle enters the electron transport chain and oxidative phosphorylation occurs.
Explain oxidative phosphorylation.
```
Electrons are passed along the electron transport chain.
Energy is lost.
And used to add a phosphate to ADP to make ATP.
ATPase catalyses this.
Chemiosmosis occurs
Oxygen is the final acceptor.
54
Phytochromes are photoreceptors found in many plants.
Phytochrome can be converted back to inactive form, other than by exposing it to far red light.
Pfr (active) to Pr (in active)
Pfr (active) to Pr (inactive)
Leave it in the dark
Pr (inactive) to Pfr (active)
Leave it in the sunlight
55
Woodlands Stem Length Advantage
Taller faster growing seedling receiving more light to maximise photsynthesis and allows more phytochrome to be made
56
Significance
Less red light increases mean stem length.
The significant difference in mean stem length is not due to chance.
The mean length for repeat was close to the original, suggesting it is likely to be reliable.
57
Changes in the heart to bring about increases cardiac output
```
Heart rate increases
Stroke volume increases
SAN activity increases
AVN time delay decreases
More blood returns to the heart and causes the heart muscle to stretch,
Ventricles contract with greater force.
```
58
Resting breathing rate
6 breaths over 30s
| Therefore 12breathsmin-1
59
Resting tidal volume
Height of waves - 0.5dm-3
60
Spirometer after exercise
More peaks in the same time
Distance between peaks would decrease
Distance from peak to trough would increase
61
Control variables
| Spirometers for Trumpeters vs. Violinists
```
How often they play
Age
Body size/BMI
Gender
Fitness level
Health status
Lifestyle, e.g. Smoker or swimmer
```
62
Cerebellum
Maintain balance
Coordination of movement
Muscle control
63
Medulla oblongata
Regulation of breathing
| Regulation of heart beat
64
Thermoregulation during exercise by blood vessels
More blood flows near skin surface due to vasodilation - dilation of arterioles
Vasoconstriction of shunt vessels
More blood to capillaries
More heat lost via radiation
65
Cruciate ligament
Two ligaments in a cross shape in the knee
| Connective tissue that connects vine to bone in the knee (behind knee cap) (two cross-shaped ligaments)
66
Keyhole surgery benefits
```
Smaller incision decreases:
infection chance
recovery time
Likelihood of osteoarthritis/knee joint replacement later
Blood loss
Pain
Costs as fewer staff needed
Scar tissue
```
Use of local anaesthetic means less associated risk.
67
*GMO
1-Gene for protein removed from animal cell. Inserted into plasmid.
2-modified plasmid incorporated into bacterium which is then introduced into a plant.
3- Genetically modified plant grows and produces protein
Restriction enzymes/endonuclease is used to cut gene out of animal DNA
Amplification in PCR used DNA polymerase a
Enzymes are used to open plasmid
Same endonuclease to produce sticky ends at base sequence
H bonds are formed between bases at sticky ends using ligament to join gene to plasmid
Phosphodiester bonds are formed in the sugar phosphate backbones.
68
*Modified plasmid structure
Circle of DNA
| Containing bacterial genes and protein/animal gene and a marker gene
69
*Plant used in GM rather than bacteria in final stage
Easier to a manage growth, e.g.do not need sterile conditions
It is safer than bacteria
More protein can be made
Bacteria may not have correct amino acid to make protein
It could produce edible drugs
Plants have introns/bacteria do not so gene does not need modifying
It is cheaper
70
*GMO risks
Gene transfer to other species
Consequences:resistance to pesticides/antibiotics, super weeds
Possible harmful effects from genes .e.g. Biochemical changes to substances that could act as allergens, long-term effects of consuming
Benefit focused on developed countries: less developed at disadvantage: cannot afford licences
Risk related to use of viral vectors
Effect on organic farmers
71
Coordination of movement is controlled by
Cerebellum ( at the bottom back)
72
During exercise, chemoreceptors in the carotid artery detect a decrease in pH due to increased carbon dioxide.
A nerve impulse is sent to...
Medulla oblongata
73
At the start of depolarisation, the ions that move into the axon causing the action potential
Sodium
74
When an impulse arrives at a synapse, the ions that enter the pre-synaptic membrane are
Calcium
75
Acetylcholine is a chemical which acts as
A neurotransmitter
76
The drug MD!A (ecstasy) changes behaviour
by increasing the concentration of serotonin in the brain synapses.
77
Human Genome
All the DNA/ genes of a human species
78
Human genome use ethics
Discrimination - insurers might have access to a person's DNA
Who decides whether a person's DNA
Who decides whether a person is tested?
Need for confidentiality
Expensive medical treatments might help be restricted
79
Suggest how to work on the Human Genome Project helped in the development of a drug for melanoma
Identifies allele related to melanoma e.g mutant allele
Drug targets this allele
Mutant allele can no longer express itself
Drug preventing translation
Such a drug is more effective
80
*Suggest how drug causes melanoma to shrink in only a few months
```
Drug affects expression of the allele
Protein is not produced
Melanoma cells are killed
Melanoma cells do not divide
They are replaced with normal body cells
Through mitosis
Specific part of mitosis is affected: e.g no spindle fibres.
```
81
Phase III trial
```
Randomised trial
Large number of patients
Double blind
Use of placebo/ current treatment
Testing how effective the drug is on patients
```
82
*Why GMO yeast us inhuman DNA to produce collagen for synthetic corneas are not rejected
Yeast cells have human colleges gene
New collagen is recognised as self - eg has no non self antigens
Do not trigger immune response
83
Describe how the rats in control group would have been treated in food maze
Cage with no rewards
Same regime e.g. Starvation time, feeds time, time in cage.
84
Why were rats not fed
Motivation: to encourage them to look for food.
85
Effect of first food reward maze, not control
Exploration has been encouraged due to hidden food/enrichment
They are more intrepid e.g. They visit more of the maze
Better /more adept at looking for food /learnt to look for food.
86
The effect or food reward maze and their ability to find food
Increase in mean spine density
More synapses
More connection between neurones
Better learning capacity
87
Why does the pupil appear black
Pigment at the back of the eye absorbs light - no light is reflected out from the choroid
88
Radial and circular muscles
| Why are antagonistic muscles needed?
Circular muscles contract and radial muscles relax to constrict pupil.
Radial muscles contract and circular muscles relax to dilate pupil
Fine control of aperture (opening) to allow a pupil to be a different size, allowing changing to take into account varying light intensity
These muscles can only shorten
Antagonistic muscles have opposite effects
Contraction of one muscle set stretches the other
89
The pupil increases in diameter in dim light
| How do neurones allow this change to occur?
```
An impulse travels to a bipolar neurone
Then travels to a sensory neurone
Then travels to the optic nerve
Then to motor neurone
Which contracts the radial muscles
```
90
Pupil construction in bright light
Circular muscles contract and radial muscles relax to constrict pupil.
91
Pupil dilation in dim light
Radial muscles contract and circular muscles relax to dilate pupil
92
Suggest how tripicamide makes it easier to examine the retina
Has an effect on the nervous system of the iris
Radial muscles contract
Prevention of pupil constriction - nor circular muscle contraction
Larger aperture/ pupil dilates
Letting more light in
So we can see more all retina
93
Retinal is the most common form a dietary vitamin A and retinal is part of the structure of rhodopsin. From the diagram, you can see retinal and retinal are very similar in structure.
Suggest how a deficiency of vitamin A would adversely affect a person's vision.
Retinal and retinol are very similar in structure.
Retinol is needed to make retinal.
Shortage of retinol in diet leads to less retinal in rods
This leads to reduced vision in low night/at night.
94
Photoreceptors Phytochromes
Cause cell depolarisation
Affected by all wavelength of light
Involved in plant growth and development
Affected by darkness
Cause cell depolarisation FALSE elongation
Affected by all wavelength of light FALSE red and far red
Involved in plant growth and development TRUE
Affected by darkness TRUE
95
Rod cells are found in what layer
Outer segment of rod cells
96
The neurones of the optic nerve begin in which layer
The neurones furthest away from the back of the eye
97
In this diagram of the retina, the light would pass through from
top (front of eye) to back of eye ( outer segments, choroids)
98
After critical window, surgeries may not work
Lack of visual stimulation limits
Brain development
Due to lack of connections within the visual cortex
Brain cannot interpret visual information correctly
The critical window has passes
Mice are different from humans
99
Suggest why this type of treatment embryonic-derived stem cells and animal tested treatment for blindness in humans could be regarded as controversial.
Embryo supplies cells
Some people have ethical objections to use of embryonic cells
Objections to the use of animals
Risk of stem cells becoming cancerous
100
Blindness treatment. Suggest why the stem cells will be injected into the cerebral hemisphere.
Cerebral hemisphere is the site of vision perception.
It is where the visual cortex is.
Stem Cells differentiate
This treatment will help to establish neurone connections.
Can not get stem cells to this location any other way than injection.
101
Eye shut after birth
| Why should environment be kept constant in this investigation
Reduce number of variables to keep all variables constant
| So that only the effect of the treatment is measured
102
Explain the validity of the statement that 'OCD is an inherited condition'
If a person has a close relative with this illness, the risk is only 100%. Therefore other factors must be involved as well. There will be environmental influences, e.g. Learnt behaviour
103
Face view of neuron
Axon in centre
Cytoplasm of Schwann cell
Myelin sheath is the collect layers ( caused by the Schwann cell wrapped around)
Nucleus of Schwann cell can be seen
104
Myelin sheath nerve impulse conduction
```
Electrical insulation
Depolarisation at nodes
Impulse jumps from node to node
Salta torn conduction
Faster conduction
```
105
Axon cell membrane for conduction
Phospholipid restricts ion movement
Protein spans the membrane
Sodium potassium pump moves ions
Protein gates/channels allow diffusion movement of ions
106
High auxin concentration on left
Shoot bends to right
107
Mechanisms for this bending
```
Phototropism
Light causes redistribution of auxin
High concentration away from light
Auxin diffuses down shoot
Stimulates cell elongation
Change in cell: fewer cross links in cellulose, cell wall more plastic, acidification, stimulation of enzyme production, vacuolation
Side away from light longer
```
108
Compare auxins vs. Endocrine system in animals
Both chemical
Both transported away from production site
Diffusion in plants, blood system in animals
Slower in plants, some animal hormones are faster
Some animal hormones have a shorter term effect.
Plant response involves growth/cell elongation only
Animal hormones do not just affect growth
109
Skin to Gill neurone pathway
Skin to Sensory neurone, relay neurone, to motor neurone to Gill.
110
Repeated stimulus leads to less Gill response
```
High frequency of impulses
Depletes NT
Ca2+ channels do not open, are less responsive at synaptic membrane.
Post synaptic membrane not depolarised
Impulses do not reach Gill
```
111
Habituation benefits
Avoids wasted effort, time, resources
To non-threatening, unimportant, stimulus
Natural frequent stimuli, e.g. Wave action
112
pH and Ca2+ sensitivity
| % contraction
Lower pH, both sensitive to calcium ions
Effect on slow twitch is greater
Lower pH decreases contraction in both
Lower pH has no effect at high calcium ion concentration in both
113
Lower pH in living muscle
Anaerobic conditions, lack of oxygen, process that reduces pH
114
pH sensitivity in fast/slow twitch
Fast twitch anaerobic
Slow twitch aerobic
Fast twitch more likely to experience low pH
Low pH due to lactate
Fast twitch is less affected by change in pH
Can continue to respond to stimulus at lower pH
115
Troponin from slow twitch can replace troponin in fast twitch and then have the same sensitivity as slow twitch.
How does troponin account for Ca2+ and pH. Sensitivity?
```
Troponin binds calcium ions
Tropomyosin moved
Causing myosin binding sites exposed
On actin
Calcium binding site sensitive to pH
Troponin is different in each fibre
```
116
Phytochromes under crtical period
Not enough time in the dark
Pfr, active phytochrome, levels remain too high
Once Pfr below a certain level, flowering happens
Flowering stimulated by fall in Pfr
117
Benefits monitoring day length
```
Flowering, development, happens at right time
Therefore flowers when insects available
Leaf fall in Autumn
Same species flower at the same time
Seeds germinate at the right time
```
Day length changes to a set pattern, e.g always short days in winter, long days in summer
Comparison with other less regular stimuli, e.g temperature
118
Conclusions about leaf covering and Phytochromes
Leaf is a photo receptor
Phytochrome, Pfr, Pr, in leaves
Signal must be passed to growing points, site of flowering production, from leaves
119
L-Dopa treatment for Parkinson's
L-Dopa can reach the brain unlike dopamine treatment
Converted to dopamine in the brain
Increases dopamine levels in the brain
Parkinson's disease has low dopamine levels
Reduces symptoms of the disease
120
MDMA and serotonin levels
High levels of serotonin
At synapse
Inhibits reabsorption into neurone
May reverse pumps to release more serotonin
121
Animal trail
| Drug to reduce dopamine given to Marmoset ( small monkeys)
To mimic Parkinson's disease
| Parkinson's disease has low dopamine
122
Ethical issues of animal testing
Rationalist view - overall good should outweigh harm
Absolutist view - all use of animals uncapped able
As few animals as possible used in the trail
Welfare of animals should be important
123
PhaseI- animal trials
| After this?
Phase II
Test small sample for safety on healthy individuals
Phase III
Large sample of patients to test for effectiveness
Clinical trials on larger sample, 1000s
Double blind trials
Placebo
Representative sample e.g. Take into account sex, age
124
CT information about abnormalities
Nature of abnormality e.g bleeding, its density
Location of abnormality
Extent of abnormality
Likely problems e.g accessibility for surgery
125
Why different symptoms?
| One vs. Two abnormalities
Found in different regions of brain
The right hand brain has more abnormalities
Different areas of brain have different functions
Symptoms depend on region of brain affected
Different types of abnormality can cause different symptoms
126
How fMRI works
Detects level of oxygenation of the blood
Measures changes of blood flow within the brain
Increased flow, more oxygen, suggests increased activity
Study brain activity related to stimuli, tasks
127
Hypothalamus
Cerebellum
Medulla
Frontal Cortex
Hypothalamus (middle) - regulating core temp
Cerebellum (back, bottom) - climbing stairs
Medulla ( a above brain stem) - regulating CO2 in the blood
Frontal Cortex (top front) - choosing a gift
128
Events that begin depolarisation
Depolarisation of adj membrane
Changes potential difference across membrane
Opens sodium gates
Sodium ions move into the neurone
129
Permeable to sodium or potassium ions?
Before depolarisation
After depolarisation
Before depolarisation - sodium only
| After depolarisation - potassium only
130
Movement of ions just after the top of the peak
```
Diffusion gradient of post assign ions
Electrochemical gradient
Increased permeability of embrace to post assign ions
Post assign gates open
Sodium gates closed
```
131
Potential difference returned to resting level
PD is less negative
The membrane remains permeable to potassium ions.
Potassium ions move because of charge differences
Into nerve cell
Potassium ion is removing a positive charge from the outside
Equilibrium is established e.g. Diffusion gradient balance by potential difference
