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a level biology > Topic 8: Grey Matter > Flashcards

Topic 8: Grey Matter Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

which neuron is this and label it

A

one long dendron carries impulses from receptors, one short axon carries impulses from cell body to the CNS

cell body is in middle! that’s his fun fact

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2
Q

which neuron is this and label it

A

many short dendrites carry impulses form CNS to cell body
one long axon carries impulses from cell body to effector cells

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3
Q

which neuron is this and label it

A

many short dendrites carry impulses from sensory neurons to cell body
an axon carries impulses from cell body to motor neurones

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4
Q

outline myelination

A

the myelin sheath is an electrical insulator, made up of a Schwann cell (lipoprotein)
there are small patches of bare membrane between the Schwann cells, the nodes of Ranvier here sodium ion channels are concentrated

pg. 181 revision guide

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5
Q

how do we respond to a stimuli

A

stimulus —> receptor —> sensory neurone —> CNS —> effector —> response

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6
Q

how does the eye respond to stimuli

A

the muscles are in the iris and the radial and circular act as antagonistic muscle pairs

when excited, fight or flight etc.
sympathetic: radial muscles contract and circular muscles relax
parasympathetic: circular muscles contract and radial muscle relax

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7
Q

outline and explain resting potential

A

membrane = polarised
inside the neuron is more negative than the outside; with a -70mV potential difference

this still has to be maintained, by:
1. active transport of Na+ and K+
- sodium potassium pump (SPP) binds Na+ and 1ATP (ATP –> ADP + Pi)
or every 3Na+ out, 2K+ go in leaving a concentration gradient across the membrane
2. difference in membrane permeability;
more permeable to K+, so K can diffuse back out faster than Na can go in, making inside more negative

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8
Q

outline the formation of an action potential

A

depolarisation:
1. a stimulus (chemical/mechanical etc) opens some voltage dependent channels, so Na+ eNter, down the conc. gradient, making the p.d. slightly less -ve
2. if the stimulus is strong enough, the p.d. will reach the threshold level where all the Na voltage dependent channels open so lots of Na+ flood into the neurone
3. p.d. then increases to +40mV and causes action potential transmittance; its depolarised when the charge across the nerve cell is reversed completely and the inside is charged positively

Repolarisation:
4. all Na+ channels spontaneously close and the voltage dependent K channels open
5. K+ diffuse out of nerve cells and down conc gradient, causing the p.d. to increase back towards negative resting potential

hyperpolarisation:
6. K channels close slow and so excess K+ leaves and resting potential is lower than -70mV; aka refractory period, the membrane is unresponsive and so a new action can’t be generated

this means impulses can only travel one way because one direction would be too negative, making it harder to reach the threshold
the potassium channels then close and resting potential is reached again

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9
Q

what is the impact of neurons being myelinated

A

the myelin sheath doesn’t allow depolarisation because ions can’t diffuse in/out
action potential can occur only at the nodes of Ranvier
sodium ions diffuse along the axon within the schwann cells

pic

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10
Q

outline the transmission of nerve impulses between neurones

A
  1. action potential arrives at synaptic knob of pre synaptic neurone
  2. voltage gated Ca2+ channels in presynaptic neurone open and Ca2+ diffuse into synaptic knob
  3. influx causes synaptic vesicles to move to pre synaptic membrane and fuse, then releasing neurotransmitter into the synaptic cleft via exocytosis
  4. neurotransmitter diffuses across synaptic cleft and binds to specific post synaptic membrane receptors
  5. Na+ channels in post synaptic neurone open and influx of Na+ causes depolarisation
  6. if threshold is reached, an action potential is generated on the post synaptic membrane
  7. neurotransmitter is removed from the synaptic cleft to stop the response from continuing
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11
Q

what is synaptic divergence and synaptic convergence

A

synaptic divergence: one neurone connects to many neurones to disperse info around the body

synaptic convergence: many neurones connect to one neurone, amplifying info

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12
Q

what is summation

A

summation is where the effect of neurotransmitter released from many neurones (or one stimulated a lot in a short time frame) is added together

needed because sometimes a stimulus is weak and only a small amount of neurotransmitter will be released into cleft, which wouldn’t be enough to excite post synaptic membrane to the threshold and stimulate an action potential

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13
Q

how does light enter the eye

A
  • it enters through the pupil and the amount entering is controlled by the iris muscles
  • light rays are focused onto the retina by the lens
  • the retina contains photoreceptor cells which detect light, the fovea of the retina has lots of receptors
  • nerve impulses from the receptor cells are carried from retina to brain via optic nerve
    –> where the optic nerve leaves the brain is a blind spot where there are no photoreceptor cells and so is not sensitive to light
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14
Q

how do rod cells work in light

A
  1. light bleaches rhodopsin: rhodopsin –> retinal + opsin, causing Na+ channels to close so it can’t diffuse in but it’s being actively transported out
  2. Na+ build up outside of cell makes inside of membrane more negative and so, is hyperpolarised
  3. rod cell is hyperpolarised and stops releasing inhibitory neurotransmitter, so bipolar neurone is not inhibited and bipolar depolarises
  4. if pd change reaches threshold, an action potential is transmitted to brain via optic nerve
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15
Q

how do rod cells work in the dark

A

the rod cells are not stimulated by any light
1. Na+ is pumped out by active transport but it diffuses back in via open Na+ channels
2. the inside of cell is made only slightly negative vs outside, cell membrane is depolarised
3. inhibitory neurotransmitter release is triggered, they diffuse across the synapse and inhibit the bipolar neurone, stopping it from firing an action potential so no info reaches the brain

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16
Q

outline PET scans

A
  • detailed 3D images
  • radioactive tracer is injected (eg. radioactive glucose)
  • positron emission is detected

colourful

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17
Q

outline a CT scan

A
  • cross-section brain images
  • x-ray tube rotates around your body
  • shows physical brain structures
  • denser areas absorb more radiation and appear lighter

can be used for medical diagnosis which show up damaged/abnormal areas like where bleeding occurs in the brain after a stroek

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18
Q

how do MRI’s work

A
  • combo of strong magnetic fields and radio waves
  • shows soft tissues and blood vessels
  • can be used to identify and locate tumours
  • can get high contrast dye injection
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19
Q

what are fMRIs and how are they interpreted

A

the images are compared before and during doing an activity to see colour differences

when the brain area is more active more oxygen is needed so there’s more blood flow, less radio wave/fMRI signal gets absorbed and this leaves more colour on the image

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20
Q

outline the cerebrum

A

it carries out many activities and is involved with conscious activities such as:
vision, thinking, hearing, speech and memory

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21
Q

outline the development of the visual cortex

A

soon after birth, the neurones in the visual cortex of mammals begin to form connections aka synapses which allows the transfer and processing of visual information

hubel and weisel did studies with kittens and found that both eyes need to be visually stimulated during the critical period for visual cortex neurones to be correctly organised into alternating right and left ocular dominance columns

synapses passing in nerve impulses in this critical period are cemented into the visual cortex whilst those that don’t receive stimulation are lost and can’t be reformed

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22
Q

define habituation

A

a learned behaviour is which an organism no longer responds to a stimulus as it is unimportant

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23
Q

explain the process of habituation

A
  1. with repeated stimulation, the Ca2+ channels of the pre synaptic neurone become less responsive to voltage changes associated with action potentials
  2. fewer Ca2+ enter the pre synaptic neurone
  3. fewer vesicles fuse and less neurotransmitter released from pre synaptic neurone binds to post-synaptic membrane receptors
  4. fewer Na+ channels opened in the post synaptic neurone, so less depolarisation of the membrane
  5. action potential may not be generated in post synaptic membrane
  6. nerve impulse doesn’t reach effector organ and animal doesn’t respond to stimulus
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24
Q

why does habituation exist

A

animals shouldn’t waste energy responding to non-threatening stimuli
so once a stimulus repeats many times with no negative outcome, the animal learns not to respond

allows for maximum feeding effort

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25
Q

outline the hypothalamus

A

located just beneath the middle part of the brain
involved in thermoregulation and produces hormones controlling the pituitary gland which is just below

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26
Q

outline the medulla oblongata

A

found at the base of the brain/top of the spinal cord and automatically controls breathing and heat rate

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27
Q

outline the cerebellum

A

found underneath the cerebrum and has a folded cortex
important in movement coordination and balance

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28
Q

what is Parkinson’s disease and why does it occur

A

its a brain disorder that affects movement coordination, caused by loss of neurones in the basal ganglia
symptoms: tremors, slow movement, speech changes and balance difficulties

the lost neurones would have produced dopamine, so there’s less dopamine formed

  • less dopamine released into synaptic cleft
  • less dopamine binds with receptors on postsynaptic membrane and fewer Na+ channels are opened so it isn’t depolarised
  • leads to fewer action potentials, so symptoms like tremors and slow movement
29
Q

outline how MDMA works

A

aka ecstasy
affects multiple neurotransmitters, but mostly serotonin
- it inhibits serotonin reuptake into presynaptic neurone by binding to serotonin reuptake proteins
- more depolarisation of post-synaptic which activates the limbic system and feelings of extreme euphoria

also triggers release of further serotonin from presynaptic neurones

30
Q

outline how L-dopa works

A

it treats Parkinson’s disease symptoms
the structure is very similar to dopamine

  • L-dopa is transported in the blood to the brain where its converted into dopamine, increasing dopamine levels in the brain
  • increased dopamine means more impulses are transmitted in brain areas controlling movement, giving sufferers better movement control
31
Q

what can happen when you stop taking MDMA

A

serotonin production is reduced, leaving people feeling more anxious, depressed and drowsy because there is a loss of post synaptic membrane receptors and a lack of serotonin is linked with depression

32
Q

how are genome sequencing projects being used

A

the human genome project took 13yrs and identified all the genes in the humane genome

  • the info obtained is stored in databases
  • genes and so, proteins that are involved in disease can be identified
  • new drugs can be created that target identified proteins
  • the project highlighted common genetic variations between people; it’s known that some of these can make drugs less effective so personalised medicines to people with these variations can be designed
  • treatment can be personalised by determining how well a pt will respond to each drug and prescribing the ones that will be most effective
33
Q

evaluate the use of genome sequencing

A

– creating drugs for specific genetic variations will increase drug company research costs; drugs will be more ££ and could form a two-tier health service

– people might be refused a drug because their genetic makeup suggests that it won’t be very effective, even if it’s the only available one

– info in someones genome could be used by employers and insurance to discriminate

– revealing that a drug might not work for a person could be psychologically damaging, especially if its their only hope

34
Q

what do you call a root growing towards gravity

A

positive geotropism

35
Q

what do you call a root growing away from light

A

negative phototropism

36
Q

what is IAA and how does it work like howwwww

A

a type of auxin produced in meristems/tips of roots and shoots and is transported to cells via diffusion and active transport

it brings about plant responses (like tropisms) by altering transcription of genes in plant cells

37
Q

how does IAA act in plant shoots

A

involved in phototropism
in shoots: IAA causes cell elongation
- IAA builds up on the shaded side of a shoot, causing it to grow bending towards the light

38
Q

how does IAA act in plant roots

A

involved in geotropism
in shoots: IAA inhibits cell elongation
- IAA builds up on the bottom of a (sideways) plant root, causing it grow bending down

39
Q

outline the formation of genetically modified microorganisms

A
  • restriction enzyme is used to isolate the wanted gene
  • this forms sticky ends
  • PCR is used to make more copies
  • ligase enzyme is used to add the isolated gene to the plasmid
  • ligase forms phosphodiester bonds between nucleotides and recombinant DNA is produced
40
Q

outline the formation of genetically modified plants

A
  • restriction enzymes remove the gene coding for a desired protein from an organisms genome
  • PCR is used to make more copies of the gene
  • the copes are inserted into plasmids (the vectors). this is catalysed by the ligase enzyme
  • this is then inserted into a bacteria cell which is used to infect the plant cell (the bacteria is the vector to infect the plant cells)
  • or, a ‘gene gun’ can be used where tiny pellets are coated with the desired DNA and fired into the plant cell
    gene is inserted into plant cell’s nucleus!
41
Q

outline how you can produce genetically modified animals

A
  • the gene coding for a desire protein is injected into a zygote’s nucleus
  • the nucleus is implanted into the uterus of a surrogate animal where it can develop
42
Q

evaluate using genetic engineering

A

+ crops can be modified to have higher yield and nutritional value, decreasing famine and malnutrition

+ vaccines can be made in GM plant tissues, no refrigeration needed makes them more accessible in rural areas

– concerns about long-term human health impact of consuming GM things

– GM crops are often grown in large fields; forms monocultures that are bad for biodiversity

43
Q

how do plants detect light

A

by using phytochrome (a type of photoreceptor)
they can be red or far-red and absorb the respective wavelengths of light
Pr –> Pfr when exposed to red light
Pfr –> Pr when exposed to far red light
slow Pfr –> Pr when in darkness

44
Q

why are phytochromes important and how do they work

A

they can be red or far-red and absorb the respective wavelengths of light
Pr –> Pfr when exposed to red light
Pfr –> Pr when exposed to far red light
slow Pfr –> Pr when in darkness

daylight has more red > far-red light; so more Pr –> Pfr vs Pfr –> Pr
the amount of each phytochrome controls response to light by regulating gene transcription

45
Q

how can phytochromes be linked to flowering

A

in some plants, high Pfr levels cause flowering and when nights are short in summer, there’s not much time to convert Pfr back to Pr, so there’s Pfr build up and flowering genes are transcribed

46
Q

what are the different types of photoreceptors found in the retina

A

rod cells and cone cells

47
Q

what are rod cells

A

primarily located around the outer retina
detect info about light intensity
if only these are used, info will be black and white

48
Q

what are cone cells

A

mostly found grouped together in the fovea
sensitive to different wavelengths of visible light and detect colour
the number of different colour sensitive cone cells will determine the colours seen

49
Q

give arguments against animal research

A

there are alternatives like testing on human cells
many animals can experience pain and distress
animals can’t give consent and any think they should have the same rights to consent and welfare as humans do

50
Q

what are possible alternative Parkinson’s treatment options

A

gene therapy
stem cell therapy

51
Q

what is the function of ligase

A

it forms phosphodiester bonds between DNA fragments by condensation reactions

52
Q

what is personalised medicine

A

the development of targeted drugs to treat diseases in individuals with different genotypes

53
Q

label the different parts of the brain

A
54
Q

advantages of using MRIs

A

better resolution than CT so can see more detail

no x-rays used so less risk of mutation and can be used more often

55
Q

when is Pr converted to Pfr and when is Pfr converted to Pr

A

Pr—> Pfr occurs when exposed to red light/day light
Pfr —> Pr occurs in dark/low light and if exposed to far red light, this is slower

56
Q

which phytochrome is active vs inactive

A

active = Pfr
inactive = Pr

57
Q

what neurotransmitter affects parkinson’s disease

A

dopamine

58
Q

what neurotransmitter does MDMA mostly affect

A

serotonin

59
Q

that one neurotransmitter

A

acetylcholine

60
Q

what are some ethical views for and against the use of performance enhancing drugs by athletes

A

absolutist: never use them because of the damage to the body from side effects

rationalist: use is acceptable where there’s a justifiable outcome because it could help overcome inequalities in training

61
Q

label and outline the parts of the brain

A

blue: cerebrum, different parts are used in vision, learning, emotion thinking and movement ,has a thin outer layer called the cerebral cortex which is highly folded so it fits

green: hypothalamus, involved in thermoregulation and produces hormones to control the pituitary gland which is just below

purple: medulla oblongata, automatically controls breathing and heart rate

greenyblue: cerebellum, found under the cerebrum and also has a folded cortex, important for coordinating movement and balance

62
Q

what happens to ocular dominance columns if right eye is shut in critical period

A

more left ocular dominance column
synapses

63
Q

when is Na+ used in the pre synaptic neurone

A

only for rod cells!!

64
Q

give examples of plant growth factors

A

IAA
giberellins: stimulate flowering and seed germination
cytokinins: stimulate cell division and differentiation
ethene: fruit ripening and flowering

65
Q

how are ions involved in action potential

A

Na+ in and depolarise when they enter it increases CONC when they leave it decreases CONC

K+ enter to repolarise when they enter it increases CONC when they leave it decreases CONC

66
Q

what is positive geotropism

A

when a root grows toward gravity

67
Q

why don’t stems respond to gravity

A

don’t have cells that detect gravity, so no IAA i la produced and there’s a lack of stimulation of cell elongation on downward facing side of stem

68
Q

which brain scans show just structure vs both structure and function

A

CT and MRI show just structure vs PET and fMRI show function too

a level biology (13 decks)

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