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A Level Biology (Salters-Nuttfield SNAB) > Topic 8: Grey Matter > Flashcards

Topic 8: Grey Matter Flashcards

1
Q

What is a nerve?

A

A bundle of neurones surrounded by a protective covering

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2
Q

What is a neurone?

A

A specialised cell of the nervous system which carry’s electrical impulses around the body.

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3
Q

What is the the three types of neurone?

A
  • sensory
  • relay
  • motor
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4
Q

What is the main structure of a neurone?

A

Axon > a long fibre that conduct impulses away form the cell body
Cell body > contains the nucleus and other organelles of the cell
Dendrites > extension that are involved in summation, form synaptic connections with other neurones
Dendron > nerve fibres that conduct impulse towards the cell body

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5
Q

What is a myelin sheath?

A

Some neurones are myelinated. This is a glyolipid layer wrapped around the axon. The myelin sheath is made up of specialised cells called Schwann cells.

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6
Q

What is the role of the myelin sheath?

A

Between the the Schwann cells are uninsulated gaps called nodes of Ranvier. In myelinated cells electrical impulses jump from one node to the next, speeding up the impulse transmission.

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7
Q

How does electrical impulses travel down non-myelinated neurones?

A

The impulse travels more slowly as it has to move through he entire length of the axon.

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8
Q

What is the structure and role of a sensory neurone?

A

It consists of a long myelinated dendron, with a cell body located in the middle of the neurone branching of in both directions. It also has a short myelinated axon.
role is to transmit a nerve impulse from receptors to relay neurones in the CNS

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9
Q

What is the structure and role of a relay neurone?

A

Consists of one long dendron, highly branched dendrites and an axon.
Located in the CNS and transmit impulses between sensory and motor neurones

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10
Q

What is the structure ad role of a motor neurone?

A

It consists of a large cell body at one end that lies within the spinal cord or brain. Consists of many short dendrites and a long myelinated axon.
Transmits impulses from the CNS to effector muscles or glands.

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10
Q

How does the nerve system cause effector to reposted to a stimulus?

A
  1. Receptor cells detect a change in the environment e.g. hot flame and generates an impulse
  2. Nerve impulses travel down the receptor cell along sensory neurones to the CNS
  3. CNS act as coordination centre, and relay neurones transmits the impulse to motor neurones
  4. Motor neurone send impulses to the effectors (muscle and glands) to bring about a responses (bicep contract away from flame)
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10
Q

How do your eyes change in bright light?

A
  1. Photoreceptors in the retina detect the bright light and generate an impulse
  2. Sensory neurones transmit impulse to relay neurones in the CNS
  3. CNS processes information and coordinates a response
  4. Relay neurones in CNS transmit impulse between sensory and motor
  5. Motor neurone transmit impulse to the eye muscles
  6. Circular muscles contract and radial muscles relax, constricting the pupil decreases the quantity of light that can enter the eye.
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10
Q

How do your eye change in dimmed light?

A
  1. Photoreceptors in the retina detect the dim light and generate an impulse
  2. Sensory neurones transmit impulse to relay neurones in the CNS
  3. CNS processes information and coordinates a response
  4. Relay neurones in CNS transmit impulse between sensory and motor
  5. Motor neurone transmit impulse to the eye muscles
  6. Circular muscles relax and radial muscles contract, dilating the pupil increasing the quantity of light that can enter the eye.
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11
Q

What is an electrical impulse?

A

A momentary reversal in the electrical potential difference across the neurone cell surface membrane.

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12
Q

Why is a neurones cell membrane polarised at rest potential?

A

The inside of the neurones in negatively charged and the outside of the membrane is positively charged. This is achieved due to the different number of ions on each side of the neurone cell surface membrane, creating a potential difference of -70 mV. Active transport moves three Na+ out of the neurone for every two K+ over into the neurone.

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13
Q

What is resting potential?

A

It is the state of a resting axon, one that is not transmitting impulses (inside has a negative charge)

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14
Q

How are sodium and potassium ion moved in and out of the neurone?

A
  • Carrier proteins called sodium,-potassium pumps are present in cell surface membrane
  • They use ATP to actively transport Na+ (can’t move back) out of the axon and K+ in (3;2)
  • creating a electrochemical and concentration gradient
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15
Q

Why is there a difference in membrane permeability between Na+ and K+ ions?

A
  • Due to the concentration gradient both sodium and potassium ions can diffuse back across the membrane by facilitated dissuasion.
  • However the surface membrane is less permeable to sodium ion so potassium ion diffuse in and out at a faster rate
  • resulting in the positive charge inside the cell and negative on the outside (-70 mV)
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16
Q

How is action potential generated?

A
  1. Stimulus arrives at neurones cell membrane, this causes the membranes to depolarise. This causes the Na+ channels to open causing an influx of Na+ into the neurone (due to electrochemical and concentration gradient)
  2. If a threshold potential of -55mV is reached more sodium channels will open and Na+ will continue to influx
  3. Once +30 mV is reached sodium channels will close, and the K+ channels open (making membrane more permeable for K+) causing an flux of K+ moving out of the neurone (conc gradient).
  4. This causes the neurone to depolarise (inside negative an outside positive) and an action potential generated.
  5. the delayed closure of the K+ ion channels creating a slight hyper polarisation (-90 mV)
  6. The channels are reset and resting potential recovered. (repolarisation)
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17
Q

What is depolarisation?

A

the reversal of electrical potential difference across a membrane.

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18
Q

What is the refractory period?

A

This is the delay (hyperpolarisation) between action potentials as the ions channels are recovering and cannot be opened.

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19
Q

How is the action potential transmitted between neighbouring neurones?

A

In unmyelinated neurones, the first action potential causes Na+ ions to diffuse sideways through a neurone, causing the Na+ channels in the adjacent neurone to open alloying Na+ ions to diffuse into the neurone generating another action potential. (Wave of depolarisation)

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20
Q

What is saltatory conduction?

A

This occurs in myelinated neurones where gaps between Schwann cells (nodes of Ranvier) contained a concentrated amount of Na+. This means depolarisation can only occur at these nodes meaning action potentials are generated here and the impulse will jump form node to node.

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21
Q

What is the all of nothing principle?

A

This is the idea that an action potential are either generated or not generated. If the threshold potential of -55 mV is reached can action potential will be gernerated and the voltage will remain constant. The magnitude of a stimulus is conveyed vie the frequency of impulses and the number neurones conducted impulses.

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22
Q

How do you prevent a neurone transmission?

A

drugs that bind to sodium ion channels preventing them from opening, preventing influx of Na+ preventing depolarisation and meaning an action potential cannot be generated.

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23
Q

What is a synapse?

A

The gap between adjacent neurones that allow an impulse to be transmitted between neurones.

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24
Q

What is the structure of a synapse?

A
  • synaptic cleft (the gap between adjacent neurones)
  • presynaptic neurone (the neurone before the synapse, it has a rounded end called the synaptic knob)
  • post synaptic neurone (neurone after synapse)
  • vesicles (contain neurotransmitters)
  • receptor proteins (found of the postsynaptic membrane, which are complementary to a specific neurotransmitters)
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25
Q

What is the process of synaptic transmission?

A
  1. An action potential arrives at the presynaptic neurone, causing it to depolarise. This depolarisation causes the voltage gated calcium ion channels to open.
  2. The calcium ions diffuse into the synaptic knob via calcium ion channels (down concentration gradient).
  3. The influx of calcium ion cause the vesicles in the synaptic knob to fuse with the presynaptic membrane and release their neurotransmitters (acetylcholine) through exocytosis.
  4. the neurotransmitters diffuse across the synaptic cleft and bind with the complementary receptors molecules on postsynaptic membrane.
  5. This causes the associated sodium ion channels to open and sodium ion diffuse into the postsynaptic cell.
  6. As a result the postsynaptic neurone will depolarise and an action potential will be generated.
  7. the neurotransmitters will then disuse back into presynaptic neurone or will be broken down by enzymes.
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26
Q

What are the additional role of synapse?

A
  • unidirectionality (ensure the one way transmission of impulses)
  • divergence (one neurone can connect to several other neurones at a synapses allowing never signals to be sent in several directions)
  • amplification (an impulse does not always cause an impulse to be generated to then next a weak impulse with releases less neurotransmitters meaning less binding onto receptor proteins meaning less voltage as less sodium ions diffusing and less depolarisation meaning an action potential threshold may not be reached)
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27
Q

What is the structure and function of the eye?

A

conjunctiva > thin membrane which cover and protects the front of the eye
Sclera > tough connective tissue layer surrounding, protection and maintenance of shape
cornea > thick transparent layer that focuses light rates onto the retina
iris > pigmented layer containing muscles which contract and dilate the public in order to control the amount go light that enters.
lens > stacks of transparent cells which foscu light of retina
Ciliary muscles > contract and relax to control the shape of the lens
vitreous humous > transparent fluid that maintain pressure and shape
retina > contains photoreceptors which absorb lights and generate an impulse through bipolar neurones and optic nerve
photoreceptors > contain vesicles containing a light sensitive pigment called rhodopsin which absorb light (cone and rod)
Fovea > part of the retina high concentration of cone cell receptors increasing resolution of vision
chord > black layer behind the retina which absorbs lights and prevent reflection
optic nerve

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28
Q

What are the two types of photoreceptor?

A

cone cell > in fovea responsible for coloured visions (3 types: blue, red and green)
rod cell > found in peripheral parts of the retina, responsible for monochromatic visions (black and white)

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29
Q

How is nerve impulses generated to from the eye in bright light?

A
  1. Photoreceptors generate action potentials when stimulated by bright enough lights
  2. this causes bleaching in which rhodopsin is broken down into opsin and retinal releasing energy.
  3. this causes the sodium channels to close and the membrane is no longer permeable to Na+ ions
  4. the rod cell will being to hyper-polarise and the release of an inhibitory neurotransmitters will be inhibited.
  5. The bipolar neurone can then depolarises and generate an action potential that travels to the brain via the optic nerve
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30
Q

How is nerve impulses generated to from the eye in bright light?

A
  1. Rhodopsin is reformed for opsin and rental with ATP
  2. Sodium ions diffuse back down he concentration gradient into the rod cells via sodium channels
  3. This causes the rod cell to depolarise
  4. triggers the realises of neurotransmitters which diffuse across a synapse to a bipolar neurone, this neurotransmitter inhibits the bipolar neurone being is can depolarise and generate an action potential
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31
Q

What are phytochrome and their role?

A

These are photoreceptors found in seeds, roots and leaves of plants. They consist of light absorbing pigments and are responsible for co-ordinating plant responses (seed germination and response to environmental cues)

32
Q

What are the two types of phytochrome and their conversions?

A

P(R) > The inactive form of phytochrome, it absorbs light from the red part of the spectrum
P(FR) > Active phytochrome it absorbs light from the far red part of the spectrum

  • When PR absorbs red lights is is converted into PFR (during the day)
  • When PFR absorbs far red light it is converted back into PR
  • In the absence of red light the PFR gradually converts back into PR (during the night)
33
Q

What is the process of phytochrome co-ordinating plant response?

A
  1. During the summer days are longer meaning phytochrome exposed to more red light and less far red light meaning PR –> PFR
  2. This build up of PFR cause the production of transcription factors which activator light-regulated genes
  3. these proteins will produce plant response (germination and plant flowering)
34
Q

What is tropism and main types?

A

The growth of a plant in response to a directional stimulus.
phototropism > growth of a plant in response to the direction of light, plant shoots grow in the direction of light whereas plant root grow away from the light.
Geotropism > growth of a plant in response to the direction of gravity. Plant shoot grow away from gravity and plant roots in direction of gravity

35
Q

What is idoleaceantic acid?

A

IAA is a type of auxin which brings about plant responses (e.g. phototropism) by altering the transcription of genes inside plant cells. It is transported from cells to cell through diffusion and active transport bringing about uneven plant growth.

36
Q

How does phototropism and geotropism occur in plant roots and shoots?

A
  1. The auxin IAA is produced in plant shoots and root tips
  2. directional light causes the redistribution of IAA, transporting it to the shaded/darker side of the plant.
  3. In the shoot the higher concentration of IAA on the darker site causes the cells to elongated and stimulate faster growth and the shoot bends towards the source of light
  4. In the roots the IAA is transported towards then lower side of the plant roots which inhibit cell elongation
  5. This means the lower side grows at a slower rate than the upper side of the roots causing the roots to bend downward
37
Q

How is co-ordination brought about through hormonal control?

A
  1. receptor cells on organs detect a stimulus (e.g. pancreas detects low blood glucose concentration)
  2. effector cells such as glands produce a hormone (glucagon)
  3. hormones transported in the blood to where they are needed
  4. hormones bring about a response (glucagon converts glycogen into glucose increase blood glucose concentration)
38
Q

How to nervous and hormonal controls differ?

A
  • electrical impulses vs chemical messengers
  • nervous control faster than hormonal as dependant on speed of blood stream
  • nervous is a short terms reposes and hormone in long term as broken down slower than neurotransmitters
  • localised response vs widespread response
39
Q

What is the structures of the brain?

A

Brain is part of the CNS made up of interconnecting neurone. It is made up of different regions that carry out different functions.
- cerebrum
- hypothalamus
- cerebellum
- medulla oblongata

40
Q

What is the structure and function of the cerebrum?

A

This is found in the forebrain and consists of two halves the cerebral hemispheres which control opposite sides of the body. It has a thin outer layer called the cerebral cortex (grey matter) which is highly folded increasing surface area for brain activity. It can then me further divided into frontal, periental, temporal and occipital lobes. It role includes
- visons
- hearing
- speech
- thinking
- memory

41
Q

What is the structure and function of the hypothalamus?

A

Found in the midbrain. It is responsible for thermoregulation (blood temp), control over sleep, hunger and thirst. It works my monitoring blood flow and releasing hormones itself or stimulate the pituitary gland to realises hormones.

42
Q

What is the structure and function on the cerebellum?

A

Found as the back of the hindbrain. Responsible for coordinating movement such as balance, coordination and posture.

43
Q

What is the structure and function of the medulla oblongata?

A

Responsible for maintaining basic physiological functions such as breathing and blood flow. (cardiac and respiratory centres)

44
Q

What is computerised tomography?

A

CT scans produce a cross-section images of the brain using X-ray radiation, denser structures show up brighter as they absorb more radiation. This shows the physical structures of the Brian and allows visitation of tissue damage.
+ allows neurologists to work out which regions not the brain are responsible for which functions
- x-rays pontentially carcinogenic

45
Q

What is Magnetic resonance imaging (MRI)?

A

Uses a combination of a magnetic fields and radio waves to generate static cross sectional images off the brain.
+ Identifys areas of abnormal or damaged tissues (e.g. tumours)
- don’t indicate brain activity (can’t determine the functions)
+ don’t carry health risks associated with x-rays
- expensive
- interfere with medical devices (pacemakers)

46
Q

What is functional magnetic resonance imaging (fMRI)?

A

Uses radio waves and magnetic fields to produce a dynamic cross-sectional images of the brain by showing the location of oxygenated blood in the brain, indicating which brain regions are active at one time (measures deoxygenated to oxygenated haemoglobin).
- expensive
+ not associated with x-rays

47
Q

What is positron emission tomography?

A

PET uses radioactive tracers which collect in areas where there is increased blood flow, metabolism or neurotransmitter activity. The tracer in introduced into the blood in advance, and the scanner then detects areas of high radioactivity and thus whether a region is activated to inactive.
+ indicate real time brain activity
- expensive
- potential to be carcinogenic

48
Q

What is the visual cortex and what happens to it during the critical period?

A

The visual cortex in the region in the cerebral cortex in which visual information is process.
After birth the neurones in the visual cortex of babies being to form synapses allowing vial information to be transferred through a processed by the visual cortex.
- for neurones to be organised correctly both eyes need to be visually stimulated as synapses the pass nerve impulse are strengthen and become permeant and neurones that don’t pass nerve impulses during critical period are losses and cannot be reformed.

49
Q

What is the critical period?

A

An important period in early development of the postnatal visual cortex.

50
Q

Why are animals used in medical research?

A

The human Brian is very difficult to study as is easily damaged during surgical examination, different region work together and so cannot be studied in isolation. Some animals have similar brain structure, so findings canoe applied to the human brain.

51
Q

How was brain development investigated by Hubel and Wiesel?

A
  1. they stitched one of a subjects (moneys and cats) eye closed soon after birth meaning as the animal grew it could only see out of one eye.
  2. When the eye was unstitched is was discovered that the eye that had been closed was blind and the ocular dominate columns in the open eye has expanded to take over the the other columns that weren’t being stimulated (switched dominance in neurones)
  3. The research was then repeated identically on adult mammals
  4. they found that once the eye was unstitched that vision fully recovered and no change took place in the distribution of the ocular dominance columns.
  • showed the importance of the critical period on development of vision
52
Q

What are the arguments of the use of animals in medical research?

A
  • animals physiologically very similar to humans resulting in numerous breakthroughs in drug and medical research
  • only carried out when there are no alternative method
  • regulated by regulatory bodies ensuring their proper care
  • cell cultures and computer models produce inaccurate results
53
Q

What are the arguments against the use of animals in medical research?

A
  • small differences in physiologically produces inaccurate results
  • causes pain and distress to theses animals (unethical)
  • there are other alternatives (cell cultures and computer models)
  • animals have a right to life and a right not to be experimented on
54
Q

What is habituation?

A

A change in the response to a stimulus as a result of repeated exposure over time. It is beneficial as reduces the waste of time, effort and biological resources with a responding to non0threatening and frequent stimulus.

55
Q

What is the process of habituation?

A
  1. repeated exposure to a stimulus over time reduces the number of calcium ion channels in the presynaptic neurones that open resulting in a smaller number of calcium ions influx in the synaptic knob
  2. smaller influx of calcium ions causes less vesicle to fuse with presynaptic membrane and release their contents via exocytosis (less neurotransmitters that bind to complementary protein receptors)
  3. resulting in a smaller influx of sodium ions into the postsynaptic membrane and less depolarisation
  4. this decreases the likelihood of an action potential being generated as threshold potential not reached
56
Q

What are neurotransmitters?

A

chemicals that transmit nerve impulses across synapses.

57
Q

What are neurotransmitters?

A

chemicals that transmit nerve impulses across synapses.

58
Q

What is and causes of Parkinson’s disease?

A

A brain disorder that affects the co-ordination of movement causes by the loss of neurones in some parts of the brain. The lost neurones would have produced the neurotransmitter dopamine (involved in muscle control)
- less dopamine released into synaptic cleft meaning less binding to protein receptor on postsynaptic membrane
- fewer action potentials generated creating symptoms such as tremors and slow movement

59
Q

What are the different types of drugs used to treat Parkinson’s?

A
  • dopamine agonist (same effects of dopamine by binding to dopamine receptors on postsynaptic neurones)
  • dopamine precursors (chemicals that can be converted into dopamine in the neurones)
  • enzyme inhibitors (inhibits that enzymes that would normally break down dopamine)
  • gene therapy (addition of genes to affected cells)
  • stem cell therapy (replace lost dopamine producing cells)
60
Q

What is and cause of depression?

A

A neurological disorder that occurs as a result go a serotonin neurotransmitters (controls mood) deficit in the brain.
- less serotonin released in to synaptic cleft, less binding less sodium ions less depolarisation and action potential not generated as threshold potential not reached
- reduce the nerve transmissions in parts of the brain that control mood

61
Q

What are the different types of drugs used to treat depression?

A

selective serotonin reuptake inhibitors (SSRIs) > antidepressants that prevent that uptake of serotonin at synapses increasing overall levels of serotonin in the brain
Tricyclic antidepressants (TCAs) > increase level of both serotonin and noradrenaline
MAOB inhibitors > inhibit enzymes that would usually break down the neurotransmitters

62
Q

What is L-dopa and how does it treat Parkinson’s disease?

A

L-dopa is a drug used to treat the symptoms of Parkinson’s disease
- L-dopa has a very similar structure to dopamine meaning L-dopa crosses the blood brain barrier and is converted into dopamine (catalyst by dopa-decarboxylase)
- increases the likelihood of depolarisation and threshold potential generating an action potential
- given patients more control over their movement

63
Q

What is personalised medicine?

A

The development of targeted drugs to treat a variety of human diseases in individual with different genotypes. The drug is test of synthetic tissues which is genetically identical to a patient.

64
Q

What genome sequences have been essential in the development of personalised medicine?

A
  • The human genome project > (involves the sequencing of the entire human genome), the information gathered is stored in a data base and genes that code for certain proteins found an analysed. By knowing the sequences and stature of proteins involved in a disease allow drug to target specific proteins.
  • genetic screening > allow individuals with a high chance of developing a disease to be know and can implement preventative measures and how they might responds to a specific treatment
65
Q

What the issue with personalised medicine?

A
  • increased research costs (drug companies will just increased price of drugs)
  • insurance companies and employers may use medical data unfairly to discriminate against individuals.
  • patient may refuse personalised medicine
66
Q

What is genetical modification?

A

a technique used to deliberately modify a specific characteristics of an organisms. This is done by removing a gene from one organisms and transferring it into another organism where the desired gene is then expressed.

67
Q

What’s the process of genetically modifying micro-organims to produce drugs?

A
  1. restriction enzymes used to remove the gene coding for a desired protein from an organisms genome
  2. many copies of the gene is made using PCR
  3. The copies are then inserted into small loops of DNA called plasmids transferring the copies into microorganisms
  4. the genetically modified micro-organisms are grown in larger fermenters enabling them to multiply
  5. protein then isolated and purified
    e.g. human insulin and human blood clotting factors
68
Q

How can plants be genetically modified to produce drugs?

A
  1. restriction enzymes used to remove the gene coding for a desired protein from an organisms genome
  2. many copies of the gene is made using PCR
  3. the gene is then inserted into a plasmid and transferred into a bacteria and the bacteria allowed to infect the cell
  4. the gene is transferred from the bacteria into the plant nucleus and the plant is stimulated to multiply and grow
  5. the protein can then be purified or eaten
    e.g. human insulin and cholera
69
Q

How can animals be genetically modified to produce drugs?

A
  1. a gene that code for a protein for the desired protein is injected into the nucleus of a zygote
  2. zygote implanted into uterus and develop to become an adult
  3. very cell know has the gene to produce this protein as it can be obtained (e.g. milking)
    e.g. human blood clotting proteins
70
Q

What are the benefits of GM?

A
  • Crops can be modified to produce a higher yield and increase nutrition values reduce famine and malnutrition
  • crops can be modified to be pest resistance
  • disease can be treated
  • vaccine can be produced in modified plants making them more accessible
  • low cost supply of come medication
71
Q

What are the negative of GM?

A
  • Concerns about the Lon term impacts of GM food on human health
  • poser may develop a resistance
  • transmission of genetic matters between organisms GM and non GM
  • Can be very expensive (drug companies)
72
Q

What is meant by the terms ‘nature vs nurture’?

A

Brain development is affect by both nature (genetic) and nature (environmental) conditions affecting the growth of the brain and the formation of connection between neurones. The argument is whether nature of nature has the greater influence over brain development (as they interact with each other)

73
Q

How is animal experiments used to text for ‘nature vs nurture’?

A

Scientist study the effects that different environments have on the brain development of individuals of the same species.
- the environment can be manipulated animals of the same species would have similar genes making it more likely that any difference are due to environmental factors.
- genetic modification can be used to switch off certain genes. by raising genetically altered organism with non gm modified impact of genetic factors can be studies

74
Q

How is twin study experiments used to text for ‘nature vs nurture’?

A

identical twins are genetically identical one raised in different environment, any difference in the brain would be due to nature and similarities nature.
- can be compered to non-identical twins

75
Q

How is cross-cultural studies used to text for ‘nature vs nurture’?

A

different cultures provide different environmental influences on the brain development of children.
- scientist can compare large grouped of children of similar ages from different cultural backgrounds
- any diference are more likely be down to nurture rather and nature

76
Q

How is newborn studies used to text for ‘nature vs nurture’?

A
  • environment outside the womb would not have impacted the brain development of a new born baby.
  • level of brain development most likely due to nature rather than nature
77
Q

How is brain damage used to test for ‘nature vs nurture’?

A
78
Q

How is newborn studies used to test for ‘nature vs nurture’?

A
  • environment outside the womb would not have impacted the brain development of a new born baby.
  • level of brain development most likely due to nature rather than nature
79
Q

How is newborn studies used to test for ‘nature vs nurture’?

A
  • environment outside the womb would not have impacted the brain development of a new born baby.
  • level of brain development most likely due to nature rather than nature
80
Q

How is brain damage studies used to test for ‘nature vs nurture’?

A
  • in adult brain damage cannot be easily repaired as brain fully developed, in children scientist can deduce the effect of damage on development
  • if characteristics (speech, movement) don’t develop more likely t be down to nature.

A Level Biology (Salters-Nuttfield SNAB) (8 decks)

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