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SNAB edexcel A-level biology > Grey matter > Flashcards

Grey matter Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

describe the function of a motor neuron

A
  • transmitting electrical signals from CNS to effectors - glands and muscles.
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2
Q

Describe the structure and function of a sensory neuron

A

Cell body in the middle of the cell
transmits impulses from receptors to CNS

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3
Q

describe the structure and function of a relay neuron.

A
  • located within the CNS, and transmit electrical impulses from sensory to motor neurons.
  • lots of short dendrites and a long axon, with the cell body at the end of the neuron.
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4
Q

Describe the function of myelin sheath

A
  • increases the speed of impulses by acting as an electrical insulator, allowing travel by saltatory conduction.
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5
Q

What factors affect transmission of an impulse?

A
  • thickness of the neuron.
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6
Q

Describe the process in an axon that allows nerve impulses to be detected.

A
  • potential difference across the axon changes from -70 to +40mV.
  • voltage gated sodium channels open.
  • causing sodium ions to move into axon.
  • this causes potassium channels to open
  • this causes repolarisation as potassium ions move out of the axon.
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7
Q

Describe the role of dendrites in a neuron.

A
  • forms connection with other neurons
  • receives impulses from other neurons
  • initiate an action potential to the cell body/axon.
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8
Q

Describe the process of synaptic transmission

A
  • on the arriving of action potential, the presynaptic neuron depolarises, and causes Ca2+ channels to open, and allow flow of Ca2+ ions into the neuron.
  • This causes the fusion of synaptic vesicles filled with a certain neurotransmitter to the presynaptic neuron membrane into the synaptic cleft (the gap between)
  • the neurotransmitter binds to receptors on the postsynaptic membrane, which stimulates Na+ ions to move in, causing another action potential (due to depolarisation)
  • following the breakdown of the neurotransmitter, its taken up by the pre synaptic membrane and reused - this (presence of receptors on only one side) and the refractory period allows for travel in only one direction.
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9
Q

Name 3 processes Schwann cells are involved in.

A
  • Phagocytosis
  • electrical insulation
  • nerve regeneration
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10
Q

Describe the role of the dendrites in a neurone.

A
  • connect neurons to each other
  • allow for receiving impulses from other neurons
  • involved in summation
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11
Q

Describe the sequence of events that leads to the formation of an image.

A
  • Light (stimulus) is received by the photoreceptor cells in the retina
  • this causes impulses to travel up the CNS via the optic nerve
  • info is passed on to the brain via a relay neuron
  • info is processed
  • Impulses sent down relay neuron to motor neuron
  • Motor neuron impulses received by effector which carries out response (radial muscles and circular muscles)
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12
Q

Describe what happens to the radial and circular muscles when there is very little light

A
  • pupil dialates
  • because circular muscles relax
  • radial muscles contract
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13
Q

Describe what happens to the radial and circular muscles when there is a lot of light

A
  • pupil contracts
  • circular muscles contract
  • radial muscles relax.
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14
Q

describe saltatory conduction

A
  • the idea of impulses ‘jumping’ from one node of Ranvier to another- which reduces the potential difference of the next node, causing the impulse to jump - initiating another action potential.
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15
Q

Excitatory neurons

A
  • neurons that make the membrane more permeable to Na+ ions
  • making it more likely that the threshold potential will be reached
  • and more likely that the neuron will depolarise.
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16
Q

Inhibitory neurons

A
  • make membrane more permeable to Cl- ions
  • so less likely that the threshold potential will be reached
  • so less likely the neuron will depolarise
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17
Q

Spatial summation

A
  • when simultaneous impulses from multiple different neurons come along a pre-synaptic neuron to a post synaptic neuron
  • number of these impulses coming determines response.
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18
Q

Temporal summation

A
  • multiple impulses coming one after another in a short amount of time on one pre-synaptic neuron
  • the time interval has to be short - only then can they summate and initiate an action potential.
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19
Q

what causes plant cells to elongate?

A
  • auxins
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20
Q

Where are auxins released

A
  • the darkest part of the shoot
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21
Q

what is a tropism

A
  • growth in response to a stimulus
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22
Q

What are shoots in a seed showing?

A
  • negatively gravitropic
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23
Q

Describe the role of photoreceptors
- name 2 types of photoreceptors in the eye.

A
  • to detect light
  • rods and cone
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24
Q

What do the rods and cones synapse with?

A
  • bipolar neurons
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25
Q

What do bipolar neurons synapse with?

A
  • ganglion neurons
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26
Q

Describe light reception in rod cells in the dark in terms of synaptic transmission

A
  • Na+ ions diffuse into the rod cell, moving down the conc gradient in the cell, and is then actively pumped out. This creates a state of constant depolarisation.
  • This results in synaptic vesicles of the rod cell constantly fusing with the synaptic membrane of the rod cell, releasing glutamate into the synaptic cleft.
  • Glutamate binds to bipolar cell, stopping it from depolarising.
  • this prevents an action potential from occurring in the Ganglion neuron, which prevents impulse reach optic neuron - no image is seen.
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27
Q

Describe light reception in rod cells in terms of synaptic transmission and action potential when its light.

A
  • rhodopsin broken down into opsin and retinal
  • the presence of opsin closes the ion channel, resulting in no Na+ ions diffusing into the rod cell, but still being actively pumped out.
  • thus, this causes no action potential in the rod cell, meaning no glutamate can be diffused across the synaptic cleft to the bipolar neuron.
  • this allows the bipolar neuron to depolarise, allowing the flow of Na+ ions into the bipolar neuron
  • Thus, an action potential can be initiated in the optic nerve, allowing for the formation of the image.
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28
Q

Define dark adaptation

A

the reforming of rhodopsin after its breakdown from exposure to light.

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29
Q

What is a phytochrome

A

consists of a protein component bonded to a non protein component, and acts as photoreceptors in plants

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30
Q

What will happen if Pr is exposed to red light

A

it will be converted to Pfr

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31
Q

What will happen if Pfr is exposed to far-red light

A
  • it will be converted to Pr
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32
Q

What happens to Pfr in the dark

A

Its converted (reverted) back to Pr

33
Q

What triggers and inhibits germination?

A

red light: triggers
far red light: inhibits

34
Q

Define what is meant by a photoperiod

A

The relative length of day and light that determines time of flowering - allows for determining the ratio of Pr: Pfr

35
Q

Give 3 characteristics of long day plants

A
  • flower when day length exceeds a critical value
  • flower when period of uninterrupted darkness is less than 12 hours
  • need Pfr to stimulate flowering \
36
Q

Give 3 characteristics if short day plants

A
  • tend to flower when periods of uninterrupted darkness exceeds 12 hours
  • need long hrs of darkness to convert all their Pfr to Pr for flowering
  • a flash of red light in the middle of the dark period may negate the effect of the dark period.
37
Q

Describe what is meant by greening

A
  • when a shoot has broken through soil into sunlight and goes through profound changes in both its form and biochemistry.
38
Q

How do phytochromes switch processes on or off?

A
  • exposure to light means that they may change shape
  • the phytochrome may also bind to other proteins and act as transcription factors, or activate transcription factors
  • these transcription factors can bind to DNA that allows transcription that result in the plants response to light
  • thus translation can take place, allowing for the amino acid chain to be formed, and thus the protein.
39
Q

Name the 4 lobes of the brain

A
  • frontal
  • temporal
  • parietal
  • occipital
40
Q

Function of the frontal lobe

A
  • higher brain functions- eg decision making, reasoning, planning, consciousness of emotion, associations
41
Q

Function of parietal lobe

A
  • orientation
  • movement
  • sensation
  • calculation
  • recognition + memory
42
Q

Function of temporal lobe

A
  • auditory information, hearing sound
  • speech recognition
  • memory
43
Q

Function of thalamus

A
  • responsible for routing sensory information to the correct part of the brain via axons of the white matter
44
Q

function + location of the hypothalamus

A
  • underneath the thalamus
  • contains thermoregulatory centres, to maintain body temp.
  • sleep, thirst and hunger control centres.
  • acts as an endocrine gland, eg releasing ADH
45
Q

Function of hippocampus

A
  • involved in laying down long term memory
46
Q

Function of midbrain

A
  • relays info to the cerebral hemispheres, including auditory info to the temporal lobe, and visual info to the occipital lobe.
47
Q

Explain how PET scans work.

A
  • use radioactive markers
  • detect position of gamma rays
  • provides 3d image.
48
Q

Explain how fMRI can be used to identify the part of the brain involved in interpreting
information from the visual cortex.

A
  • detects oxygen in the brain.
  • increased activity results in more blood flowing to that area, carrying oxygen
  • oxyhaemoglobin absorbs fewer radio waves, and fMRI detects this signal which helps produce an image with an area of the brain ‘highlighted’
49
Q

Describe CT scans

A
  • narrow beamed X-ryas fired
  • each narrow beam is reduced in strength on its path depending on the density of the tissue it passes through
  • this is detected and an image is produced.
50
Q

Describe how MRI works

A
  • magnetic field created
  • radio waves fired which generates an image
51
Q

Name 4 uses of genetic modification

A
  • produce medicines which are scarce
  • remove impact of diseases
  • improve characteristics of an organism
  • speed up production of foods.
52
Q

Describe the process of genetic modification in microorganisms such as bacteria.

A
  • Isolate the gene of interest from organism
  • Use bacterial plasmid as a vector
  • cut the human DNA and plasmid using the same restriction enzyme
  • splice the gene together using ligase
  • put the modified plasmids into bacterial cells
  • allow bacterial cells to divide in a fermenter.
  • purify and extract protein of interest.
53
Q

Define micropropagation

A
  • propagation of plantlets through tissue culturing them, then planting them.
53
Q

What are the main arguments FOR GMOs? (3)

A
  • to make them more resistant to diseases
  • To produce enzymes/vaccines
  • To improve nutritional value of foods
54
Q

define innate

A
  • something that is natural and not learned
55
Q

describe the route of neurons in the brain to form an image.

A
  • optic nerve goes to the thalamus
  • neurons from the thalamus go to alternative columns of cells in the visual cortex in the.
56
Q

define depth perception

A

ability to determine dimensions, including size and how far a certain stimulus is.

57
Q

Define stereoscopic vision

A
  • the sense of depth derived by both eyes for images less than 30m
58
Q

Define the critical period

A
  • the period of time early in the life of animals in which exposure to visual stimuli is vital to ensure proper development of the visual cortex.
59
Q

Describe what happens to neurons of the visual cortex during visual development

A
  • synapses that do not receive visual stimuli during the critical period are destroyed.
  • the rest are retained and synapse with the visual columns in the visual cortex.
  • This is because neurons compete for space on the visual columns.
60
Q

Describe the procedure, findings and conclusions of Hubel and Wiesel’s experiments to study development of the visual cortex of young kittens

A
  • conducted on young kittens.
  • one eye was stitched shut, and kept like this for several months.
  • on unstitching the eye, they found that the eye was blind.
  • repeated the experiment with monkeys, and found the same results.
  • concluded that ocular dominance columns remain normal in both eyes if stimulated early in life.
61
Q

Arguments AGAINST GMOs? (3)

A
  • often patented and seeds expensive - disadvantage to farmers in developing countries
  • GM plants cross-pollinating other species, potentially creating superweeds that are resistant to herbicides.
  • long term impact of GMOs cannot be predicted.
62
Q

Arguments FOR the use of animal studies? (2)

A
  • unethical to carry out on humans, so animals still allow to test effects on a whole organism without risking human lives.
  • animals and humans are similar so we can apply results to humans.
63
Q

Arguments against the use of animal research?

A
  • unethical to cause pain or suffering to a living being
  • alternatives to using animals - cell cultures
  • animal studies not necessarily applicable to humans.
64
Q

Define habituation

A
  • repeated exposure to stimuli which causes the individual to ignore the stimuli.
65
Q

Why is habituation important?

A

-so that limited attention and memory resources can be concentrated on on more threatening or rewarding stimuli.

66
Q

Describe how habituation takes place.

A
  • fewer calcium ions move into the presynaptic neurone when its depolarised
  • leading to fewer neurotransmitter molecules are released.
67
Q

Describe the role of dopamine

A
  • neurotransmitter that makes you feel satisfied, motivated.
68
Q

Which neurons secrete dopamine into the motor cortex

A
  • neurons in the basal ganglia
69
Q

Describe 3 symptoms of low dopamine levels

A
  • poor balance
  • walking trouble
  • stiffness/tremors
70
Q

Describe the mechanism of Parkinson’s disease.

A
  • Parkinson’s disease causes low dopamine levels
  • thus, less dopamine available to bind with post-synaptic neuron
  • so fewer sodium channels open, firing less action potentials
71
Q

Describe the mechanism of L-Dopa in the treatment of Parkinson’s disease.

A
  • it is a precursor to dopamine(it gets converted to dopamine itself)
  • drug is converted to dopamine by dopa-carboxylase in the brain
  • thus more dopamine is available to bind to post-synaptic neuron, making it more likely for sodium channels to open and for an action potential to fire.
72
Q

Describe the mechanism of MDMA for the treatment of depression

A
  • It increases the level of serotonin in brain by inhibiting the reuptake of serotonin by presynaptic neurons as it blocks the reuptake proteins.
  • This means serotonin level remain high in synapse, which results in more action
    potential across synapses that control mood.
73
Q

Define the term genome

A

all the DNA, including inter-organelle DNA inside of an organism.

74
Q

Name 2 outcomes of the Human Genome project

A
  • can identify genes that relate to disease, or increase susceptibility to a disease.
  • personalised medicine, as genetic variation can determine how people respond to drugs.
75
Q

Outline 3 ethical issues for the outcomes of the Human Genome project.

A
  • higher research costs may mean that only wealthier people have access to personalised medicine.
  • insurance companies unfairly discriminating against people who may have a genetic vulnerability to a disease.
  • distress caused to the patient and their families knowing that the only available meds might not work.
76
Q

Explain how genome sequencing could be used to identify genes related to a certain disease.

A
  • sequence the genome of people without the disease.
  • sequence the genome of people with the disease.
  • compare the base sequences, and identify mutations only present in people with the condition.
77
Q
A

SNAB edexcel A-level biology (8 decks)

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