1
Q
what does the Peripheral nervous system consist of
A
sensory neurones - carrying sensory info from receptors to the CNS
motor neurones - carrying motor commands from CNS to its effectors
2
Q
what is the somatic nervous system
A
voluntary
stimulates the skeletal muscles
3
Q
is the autonomic nervous system voluntary
A
no it is involuntary and stimulates, smooth muscles, cardiac muscle and glands
4
Q
what does the sympathetic nervous system do
A
preps the body for fight or flight
5
Q
what does the parasympathetic nervous system do
A
prepares the body for ‘rest and digest’
6
Q
what’s a neurone
A
a singular nerve cell
7
Q
what does a nerve contain
A
contains a bundle of axons of neurones surrounded by a protective cover
8
Q
what does a neurone contain
A
has a cell body and nucleus with basic organelles within a cytoplasm
9
Q
what are the 2 types of thin extensions of neurones
A
dendrites
axons
10
Q
what do dendrites do
A
conduct impulses towards the cell body
11
Q
what is the role of the axon
A
transmits impulses away from the cell body
12
Q
where is the cell body in a motor neurones
A
cell body situated within the CNS and the axon extends out ad conducts impulses from the CNS to the effectors
can have extremely long axons
also known as effector neurones
13
Q
where is the cell body in sensory neurones
A
cell body is situated along the axon
has dendrites at each end to connect with other nerve cells
also known as connector neurones and interneurones
14
Q
what is the myelin sheath
A
fatty insulating layer around the axon
15
Q
what is the myelin sheath made up of
A
schwann cells
16
Q
what does the myelin sheath do
A
affects how acting nerve impulses pass along the axons
axons with a myelin sheath are called “myelinated”
17
Q
what are reflexes
A
rapid involuntary responses to stimuli
18
Q
Describe the reflex arc
A
- receptors detect a stimulus and generate a nerve impulse
- sensory neurones conducts a nerve impulse to the CNS along sensory pathway
- sensory neurones enter spinal cord
- sensory forms a synapse with a relay neurone
- relay neurone forms a synapse w a motor neurone that leaves spinal cord through a ventral route
- motor neurone carries impulse to an effector whihc produces a response
19
Q
what controls the size of the pupil
A
iris
20
Q
what muscles does the iris contain
A
pair of antagonistic muscles - the radial and circular
21
Q
what are the radial muscles controlled by
A
sympathetic reflex
causes the pupils to dilate
22
Q
what are the circular muscles controlled by
A
the parasympathetic reflex
23
Q
what does light strike in the eye
A
photoreceptors located in the retina
24
Q
what happens once light strikes the photoreceptors in the retina
A
causes nerve impulses to pass along the optic nerve to sites within the CNS
the impulses from cells sent along the parasympathetic motor neurones to the circular muscles of the iris which contract
25
what happens when the radial muscles relax
reduces the amount of light entering the eyes
26
what has a potential difference inside a resting axon
all cells have a pd across surface membrane
27
what is the resting potential of a neurone
-70 mv
28
what is the axon called when the inside is ore negative than the outside
its polarised
29
why is there a potential difference in the cells of a resting axon
there is an uneven distribution of ions across the cell surface membrane because of the sodium/potassium pumps which carry sodium ions out of cell and potassium into cell
30
how many sodium ions are moved out of the axon and how many potassium ions into axon
3 sodium for every 2 potassium
31
how do sodium ions move out of the axons/ potassium ions move into axons
via active transport against the concentration gradient
32
one concentration gradients are established in a neurone by the sodium/potassium pumps, what happens to the potassium ions
they diffuse out of the neurone down the potassium concentration gradient ad pass through the potassium channels which make the outside of the cell surface membrane more positive and the inside more negative
33
at resting potential, what is the neurone membrane impermeable to
sodium ions
34
in simple terms, what is the difference in charge across the neurone membrane caused by at resting potential
diffusion of potassium ions
35
what is the concentration gradient in a neurone generated by
the sodium/potassium pump
36
the more potassium that diffuses out of the neurone cell, the ? the pd across the membrane
the larger
37
what does the potential difference in a neurone do to the potassium ions
pulls them back into the cell
38
what does the electrical gradient do to the chemical gradient in nerve cell at -70 mv
exactly balances it and there is no net movement of potassium ions
39
what happens to a nerve membrane when an electrical current is applied
the potential difference across the membrane is reversed - inside of axon is more positive than the outside
- depolarisatio
40
what is depolarisation of a nerve cell
when the inside is more positive than the outside
41
what happens during depolarisation of a nerve cell
change in pd changes shape of the sodium channels allowing them to open
sodium ions diffuse in and depolarisation increase, triggering more sodium gates to open further down the axon "all or nothing"
the higher the conc of sodium ions outside the axon, the more sodium ions flow towards the open voltage channels which builds up +ve charge inside and reverses the polarity of the membrane
42
what does the change in pd during depolarisation of a nerve cell do to the sodium channels
changes its shape which opens them
43
what is the potential difference of a depolarised nerve cell
+40mv
44
what causes a reverse in polarity of a nerve cell membrane during depolarisation
build up of positive charge inside the axon caused by the opening of the sodium ion voltage-gated channels
45
what occurs during repolarisation
sodium ion voltage gated channels spontaneously close and sodium permeability of the membrane returns to normal level
voltage dependent potassium ion channels open in response o depolarisation and the potassium ions move out of the axon down conc grad - attracted by -ve charge outside of axon csm
as potassium ions move out, the cell membrane becomes more -ve than the outside
46
how can you identify repolarisation of an axon on an oscilloscope trace
it is the falling phase
47
how is the resting potential eventually restored after an action potential
axon csm is highly permeable to potassium ions therefore more ions move out than occurs during usual resting pd therefore pd is currently more -ve than usual resting potential therefore hyperpolarisation of the membrane occurs and the voltage-gated potassium channels are closed and potassium ions diffuse back into the axon
48
what happens during hyperpolarisation of an axon
voltage-gated potassium ion channels close and potassium ions diffuse back into axon
49
how does an action potential travel along axon
triggers a sequence of action potentials along length of axon
50
when part of the axon membrane becomes depolarised, what occurs
local electrical current is created as charged sodium ions flow between depolarised parts of the membrane and the adjacent resting region where nearby sodium gates will respond by opening therefore triggering an action potential which is repeated along membrane which results in a wave of depolarisation passing along membrane
51
what is the refractory period
when a new action potential cannot be generated in the same section of membrane for about 5 milliseconds
52
how long does the refractory period last and why
5 ms
lasts until all voltage-dependent sodium ion and potassium ion channels have returned to normal resting state and resting potential is restored
53
what is the function of the refractory period
ensures that impulses only travel in one direction
54
what does the all or nothing effect have on size of action potential
means that the size of stimulus has no effect on the size of impulse
55
what does the size of stimulus have an effect on
frequency of impulses
number of neurones in a nerve that are conducting impulses
56
what is an indication that there is a strong stimulus
high frequency of firing + firing of many neurones
57
what is the effect of diameter of axon on the speed of conduction
the wider the axon diameter, the faster the impulse travels
58
what is the function of a myelin sheath
acts as an electrical insulator along most of the axon and prevents any flow of ions across the membrane
59
what are the nodes of Ranvier
gaps in the myelin sheath at regular intervals and are the only places where depolarisation occurs
60
what is the effect of the myelin sheath on action potentials
ensure a faster impulse velocity
61
what is saltatory conduction
the process by which action potentials jump from one node of Ranvier to another along myelinated axons
62
what are the cells on the sides of axons
Schwann cells
63
what is a synapse
where 2 neurones meet but don't actually touch
64
what is the synaptic cleft and what does is separate
the gap between 2 neurones
separates presynaptic membrane of stimulating neurone from the postsynaptic membrane
65
what does the presynaptic neurone contain
synaptic vesicles which contain neurotransmitters
66
how do neurotransmitters travel across the synaptic cleft
diffuse across gap
67
what is the effect of neurotransmitters on the postsynaptic membrane
depolarises it and there is a propagation of impulse along the next cell
68
what does the presynaptic cell do to produce neurotransmitters and package them
expends energy
69
what is the role of calcium ions in neurotransmitter release
when the membrane depolarises, calcium ion channels open and enter the neurone
the ions cause synaptic vesicles containing neurotransmitter to fuse with the presynaptic membrane
70
what is on the postsynaptic membrane that allows for neurotransmitters to be used
receptors complementary in shape to neurotransmitter
71
what happens once neurotransmitters are released from the presynaptic membrane
they bind to the receptors on the postsynaptic membrane which change shape, this causes the cation channels to open and the membrane becomes permeable to sodium ions and depolarisation sequence occurs
72
what does the extent of depolarisation on the postsynaptic membrane depend on
frequency of impulses and the number of non-function receptors in the postsynaptic membrane
73
how can neurotransmitters be inactivated
some are actively taken up by presynaptic membrane and molecules are reused
others diffuse away from synaptic cleft are are taken up by other cells in the CNS
74
how is acetylcholine
broken down by acetylcholinase and can no longer bind to receptors
75
what can occur to the breakdown products of neurotransmitters
some are reabsorbed by presynaptic membrane is reused
76
what are the 2 roles of the synapses and what do they allow for
control of nerve pathways - allows for flexibility of response
integration of information from different neurones - allows for a coordinated response
77
what 2 factors determine whether a postsynaptic action potential is produced as these postsynaptic cells are likely receiving input from many synapses at the same time
type of synapse
no impulse received
78
what are inhibitory synapses
make it less likely for a postsynaptic membrane to depolarise
79
what does postsynaptic cell producing an action potential depend on
the balance of excitory and inhibitory synapses acting at any given time
80
what does an excitory synapse do
makes postsynaptic membranes more permeable to sodium ions
81
what is summation
when each impulses adds to the effect of others
82
what is spatial summation
impulses are from different synapses and likely from different neurones
83
what is temporal summation
several impulses arrive at a synapse having travelled along a single neurone which, combined, generates an action potential
84
how does an inhibitory synapse work
neurotransmitters open the chloride ion and potassium ion channels in the postsynaptic membrane which move down the conc grad
chloride ions move into cell carrying a -ve charge and potassium ions out of cell carrying +ve charge
causes a greater pd across the membrane making depolarisation less likely
85
how is nervous control transmitted vs hormonal
nervous: electrical transmission by nerve impulses and chemical transmission at synapses
hormonal: chemical transmission via the blood
86
compare the CNS to Hormonal coordination
CNS: electrical transmission by nerve impulses and chemical at synapses, is fast acting, associated with short-term change, action potential carried by neurones w connection to specific cells, response is local
Hormonal: chemical transmission via blood, slow acting, associated w long-term change
87
what do plants use as they lack a nervous system
use plant growth substances to coordinate growth, development and responses to environment
88
where is auxin made
in the tip of the shoot
89
how was the production site of auxin proven
removing the tip and placing it on top of an agar block and placing agar block on top of shoot - shoot began to grow again as auxin diffused through agar mutts
90
what is the effect of shade on one side of a tip on auxin production
the amount of auxin produced on both sides was total same but more auxin was passed down the shaded side, therefore increasing the concof auxin on the shaded side causing increased cell elongation (and decreased auxin conc on the illuminated side) causing the shoot to grow towards the light
91
what is the effect of auxin on plant cells
causes cell elongation
92
in what form are auxins synthesised
inactive
93
how are auxins transported around the plant
transported from site of synthesis to sites of action via phloem and specific carrier proteins
94
how does auxin have an effect
they bind to protein receptors in target cells
95
what does auxin activate in target cells once they bind to receptors
intracellular secondary messenger signal molecules which activate transcription factors
96
what is the effect of transcription factors on auxin production
controls the transcription of auxin related genes and proteins produced bring about metabolic changes that result in a range of responses via cell expansion, differentiation and division
97
what does cell expansion entail
requires "loosening" of the cell walls via the acidification of cell walls using auxin - lowers pH
98
what is the potential effect that auxin has on cell walls of plant cells
causes acidification if cell wall via stimulating the activity of proton pumps - pump hydrogen ions out of the cytoplasm and into the cell walls which lowers the pH and activates expansion
99
what effect does acidification of cell wall have on potential difference
increases PD and enhances uptake of ions into cell
the presence of ions causes the uptake of water via osmosis - cell swells
100
what occurs during cell expansion
low pH in cell wall disrupts bonds holding cellulose microfibrils and hemicelluloses together. during this, there is slippage of polysaccharides relative to each other and bonds reform in a new location
101
what is stimuli detected by
receptor cells
102
what is the function of sense organs
help protect receptor cells and improve efficiency
structures within sense organs ensure that receptor cells are able to receive appropriate stimulus
103
what do each detect
chemoreceptors
mechanoreceptors
photoreceptors
photoreceptors
thermoreceptors
chemicals
forces that stretch, compress, move
light
heat/cold
104
what is the function of the: conjuctiva, cornea, lens and iris
protects cornea
bends light
focuses light on retina
controls amount of light entering eye
105
what is the sclera
protective outer layer of the eye
106
what is the function of the ciliary muscles
alters the thickness of lens for focusing
107
what is the function of: the choroid and the retina
black layer that prevents internal reflection of light
contains light-sensitive cells
108
what is the blind spot or the yellow spot (fovea)
place where there are no light-sensitive cells as that is where the optic nerve leaves the eye
most sensitive part of the retina located within the macula - central area of the retina
109
what are the 2 types of photoreceptors
cones and rods
110
what are the functions of cones and rods
cones allow for colour vision in bright light
rods only give black and white vision but in both dim and bright light
111
what allows us to accurately pinpoint the source and detail of what is being observed
the centre of the retina which contains only cone cells
112
there is an arrangement of 3 layers of cells that make up the retina, in what order are they synapsed
the rods and cones synapse with bipolar neurone cells which synapse with ganglion neurones whose axons together make up the optic nerve
113
what makes up the optic nerve
axons of the ganglion cells
114
what absorbs light in the cones and rods and what does it result in
the photochemical pigment and it results on a chemical change
115
what protein do rod cells contain
rhodopsin p is a purplish pigment
116
what is the structure of a rod cell
has an inner segment and an outersegment
117
where is rhodopsin located in a rod cell
in vesicles in the outer membrane
118
what occurs in the outer and inner segments of rod cells in the dark
sodium ions flow into the outer segment through non-specific channels and move down the conc grad into the inner segment where pumps continuously transport them back out of the cell
influx of sodium ions cause slight depolarisation which triggers a release of neurotransmitter from rod cells which binds to bipolar cell and stops it depolarising
119
how frequently are neurotransmitters released in rod cells in the dark
continuously
120
what occurs in the rod cells in the light
rhodopsin absorbs light and breaks down into retinal and opsin (non-protein and protein) components
opsin activates a cascade of reaction that results in closing of non-specific cation channels (no sodium ions can get in)
influx of sodium ions into rod decreases while inner segment still pumps sodium ions - ceases neurotransmitter release and depolarisation of bipolar cell and optic nerve neurones
121
how are the non-specific cation channels closed in rod cells
hydrolysis of cyclic nucleotide attached to cation membrane in outer segment
breakdown of molecule which closes the cation channels
122
what is the role of opsin in rod cells
activates a series of membrane bound reactions ending in closing of cation channels
123
what do phytochromes consist of
protein component bonded to a non-protein light-absorbing pigment molecule
124
what do the non-proteins exist as
2 isomers
Pr - phytochrome red
Pfr - phytochrome far red
which are photoreversible
125
what does Pr and Pfr absorb
Pr - red light
Pfr - absorbs far red light
126
what does of absorption of red light convert and what does it convert to
converts Pr to Pfr
127
what does of absorption of far red light convert and what does it convert to
converts Pfr to Pr
128
in sunlight, what happens to Pfr and Pr
Pr → Pfr - dominates as more red light is absorbed than far red light
Pfr → Pr
129
which, out of Pfr and Pr, accumulates in the light
Pfr
130
which, out of Pfr and Pr, accumulates in the dark
all the Pfr is converted to Pr
131
in lettuce, what can trigger germination and what inhibits it
a flash of red light triggers it
if that flash of red light is quickly followed by a flash of far red light, then germination is inhibited
132
what is a photoperiod
relative length of day and night
133
what is a photoperiod to plants and what does it determine
environmental cue that determines time of flowering
134
what enables plant to determine length of day and night
ratio of Pr to Pfr
135
when do long-day plants flower
when day length exceeds critical value
- aka during a period of uninterrupted darkness is less than 12 hours long
136
what do long-day plant require to stimulate flowering
Pfr
137
when do short day plants flower
during a period of uninterrupted darkness that is more than 12 hours longs
138
what inhibits flowering in short day plants
Pfr
138
what do short day plants need to do in order to flower
convert all Pfr → Pr
139
what negates the effect of dark period in short-day plants
flash of red light
140
what is greening
changes a plant undergoes ince its its shoot has broken through soil into sunlight
141
what do phytochromes do in light
promotes the development of primary leaves, leaf unrolling and the production of pigment
142
what does exposure to light to do phytochromes
makes the change shape from one form to another
143
what do activated phytochromes do
bind to proteins/ disrupt the binding of a protein complex
144
the proteins that activated phytochromes are signal proteins but what else can they act as or do
act as transcription factors or may activate transcription factors that bind to DNA to allow transcription of activated genes
145
what do other receptors in plants do
3 pigments - used to detect blue light - include phototropins that determine phototropic response
146
what is the stimulus for a plant shoot to grow upwards and what does the response do
gravity
response ensures that developing shoots reach light while roots grow in the soil
147
what can result in shorter stems
rubbing of stems
thought that mechanical stimulus activates signal molecules whose end result is activation of genes that control growjt
148
why might some leaves fold very quickly and collapse when touched
specialised cells lose potassium ions and water follows via osmosis and the cells become flaccid and no longer support leaf
- thought to be an adaptation to protect against herbivores
149
what is the outer layer of the brain called
grey matter
150
describe the cortex and what is contains
grey and highly folded and composed mainly of nerve cell bodies, synapses and dendrites
151
what are the 4 lobes that the brain is divided into
frontal, parietal, occipital and temporal
152
what is below the grey matter
the white matter which is composed of nerve axons that connect neurones to parts of the body
153
why is the white matter white
colour of the myeline sheath
154
what are the 2 cerebral hemispheres connected by and what does it allow
corpus callosum
allows communication between them
155
what is below the white matter
the thalamus, hypothalamus and hippocampus
156
what is the function of the frontal lobe
concerned with decisions, reasoning, planning and consciousness of emotion as well as making association and w ideas
157
what does the frontal cortex include
primary motor cortex
158
what doe the motor cortex contain
has neurones that directly connect to spinal cord and brain stem - to the muslces
sends info to the body via motor neurones to carry out movements and also stores information about how to carry different neurones
159
what is the parietal lobe concerned with
orientation, movement, sensation, calculation, some types od recognition and memory
160
what is the occipital lobe concerned with
concerned w processing info from the eyes, including vision, colour, shape recognition and perspective
161
what is the temporal lobe concerned with
processing auditory info such as hearing, sound recognition and speech, involved w memory
162
what is the thalamus responsible for
for routing all incoming sensory info to the correct parts of brain via axon of white matter
163
what is the hippocampus do
involved in laying down long term memory
164
what does the hypothalamus do and what does it contain
monitors core body temp and kin temp and initiates corrective action to restore the body to core body temp
also contains centres that control sleep, thirst and hunger
165
what can the hypothalamus act as
an endocrine gland as it connects directly to the pituitary gland which, in turn, secretes hormones
166
what is the base ganglia
collection of neurones that lie deep within each hemisphere and are responsible for selecting and initiating stored programmes for each movement
167
where is the cerebellum
lies at the top of spinal column
168
where is:
a. the frontal lobe
b. the parietal lobe
c. the occipital lobe
d. the temporal lobe
a. front of brain
b. mid top of brain
c. back of brain
d. underneath the frontal and parietal lobe
169
what is the cerebellum responsible for
balance
coordinates movement as its being carried, receiving info from the motor cortex
constantly checks whether the motor programme being used is the right one
170
how does the cerebellum constantly check if the motor programme being used is right
refers to incoming info about posture and external circumstances
171
what is the name of the structure that the brain stem extends from
medulla oblongata
172
what does the midbrain do
relays the info to cerebral hemispheres including auditory info to the temporal lobe and visual info to occipital lobe
173
what does the medulla oblongata do
regulates those body processes that we do not consistently control - breathing, heart rate and blood pressure
174
what does CAT stand for
computerised axial tomography
175
how do CAT scans work
narrow beam xrays are rotated around patients to pass through tissue from different angles - each narrow beam is reduced in strength according to density tissue in its path
176
what does attenuated mean
reduced in strength
177
what are the limitations of cat scans
only give a frozen moment picture
looks at structure rather than function
limited resolution
Uses ionizing radiation
178
what is a pro and con of using CAT scans
doesn't rely on harmful x-rays and can therefore be used more frequently
does sue ionising raditation
179
what does MRI stand for
magnetic resonance imaging
180
what do MRIs do
uses a magnetic field and radio waves to detect soft tissue
181
how does an MRI work
uses a magnetic field and radio waves
when placed in magnetic field, nuclei of atoms line up w the direction of magnetic field while another magnetic field is superimposed
the combined fields cause the direction and frequency of the nuclei to change - uses energy from radio waves to do so
when radio waves are turned off, the nuclei return to alignment and release energy when absorbed - energy is detected and sent to a computer
182
what is detected by computers in MRI scans
energy released by nuclei of protons when they return to their original alignment
183
how can u identify tissues using an MRI
different tissues respond differently to the magnetic field so produce contrasting signals and distinct regions in the image
184
what is fMRI
functional magnetic resonance imaging
185
what is the use of fMRI
used to look at functions of the different areas of the brain by following the uptake of oxygen in active brain areas
186
how is use of fMRI possible
bc deoxyhaemoglobin absorbs radio waves whereas oxyhaemoglobin doesn't
187
what is the effect of increased neural activity in the brain on oxygen demand
increases demand for oxygen in brain therefore increase in blood flow
188
what does an increase in oxyhaemoglobin levels in blood do to radio wave signal
less signal is absorbed
189
the less radio signal absorbed by a tissue, the ? of activity in a particular area
higher
190
what is a PET scan
positron emission tomography
191
what do PET scans do
produces detailed images and allow structure and functioning of tissues and organs to be evaluated
192
what can PET scans be used for
to help diagnose cancers, heart disease, brain disorders, to plan heart surgery, monitor cancer spread and observe the effect of treatment
193
what do PET scans use in order to function
isotopes with short 1/2 lives incorporated into compounds/ molecules that bind to receptors which are labelled - radiotracers
194
how do PET scans produce images
patients are injected with the radiotracers, as they decay, they emit positrons
when the tissue is active, there is increased demand for oxygen and glucose increases blood flow which chows up on imaging as more radiotracers are present
195
what occurs when a positron collides with an electron in a PET scan
2 gamma rays are emitted which can be picked up by detectors
196
what are the bright spots on a PET scan
areas of high levels of neurone activity
197
how is the plaque that causes alzheimers formed
when neurones die, pieces of beta amyloid protein that are found in the myelin sheath clump together to form clusters of plaque which blocks signalling of synapses
198
what does the plaque that causes Alzheimers activate
activates immune cells that triggers an inflammatory response
199
what kind of cells make up the optic nerve
ganglion cells
200
describe the visual pathway
impulses are sent along the axons of ganglion cells - which extend to areas of the brain - and then impulses are sent along further enurones to primary visual cortex
201
where do some neurones in each optic nerve branch off before reaching the thalamus
branch off the the midbrain where they connect to motor neurones involved in controlling the pupil reflex and movement of eye
202
where do axons from the retina grow to
the thalamus - forms synapses with neurones in the thalamus
203
where do axons from thalamus neurones grow towards
visual occipital lobe
204
what allows us to see in 3D
columns of cells that receive stimuli alternate from receiving stimuli from the left eye and from the right eye
- information from the same area of the retina in the left eye and the right synapse next to each other therefore allowing us to see in 3 dimensions - Neurons receive signals from matching areas of the left and right retinas. Because these signals arrive together, the brain can compare them and work out depth — giving us 3D vision.
205
what are critical periods/ windows
when the nervous system must obtain specific experiences to develop properly
206
how do cataract provide evidence for critical periods
cataracts = clouding of retina
if not removed before 10 years old, can result in permanent impairment of shape and for perception and difficulty in facial recognition where as elderly people with cataracts removed later in life don't report any differences to vision
207
what is monocular deprivation
deprivation of any light stimulus in one eye
208
what happens to the columns of cell in the visual cortex when the left eye is deprived of light
the columns with axons from the left eye are much narrower than those for the right eye receiving stimulus
209
how/ why can synapses be cut back
every time a neurone fires onto a target cell, synapses of another neurone sharing the target cell are weakened and release less neurotransmitter - if this occurs repeatedly, the synapses not firing eill be cut back
210
how can we perceive close objects - less than 30m away
presence of cells in the visual cortex that obtain info from both eyes simultaneously
visual field is seen from 2 different angles and cells in visual cortex and can compare the view from one eye with that from the other
211
what is stereoscopic vision
the ability to perceive the world in 3D
212
how can we perceive close objects - more than 30m away
the images on our 2 retinas are very similar so use visual cues and past experiences are used to interpret them
213
what does innate mean
inborn
214
does the visual cliff support the idea that depth perception is learned or innate - using animals that can walk as soon as they're born
innate as they have had too little time to learn the behaviour
215
what are the 2 different types of memory
short term and long term memory
216
how can memories be created
by altering pattern of connections or altering the strength of synapses
217
what is habituation and what does it give organisms the ability to do
is a type of learning
gives the ability to ignore unimportant repetitive stimuli so that limited sensory, attention and memory resources can be concentrated on more threatening or rewarding stimuli
218
what does long-term memory storage involve
increase in the number of synaptic connections and repeated use of a synapse leads to creation of additional synapses between neurones
219
how is habituation achieved
with repeated stimulation, calcium ion channels become less responsive so less calcium ions cross the presynaptic membrane therefore less neurotransmitter is released
therefore, there is less depolarisation of the postsynaptic membrane so no action potential is triggered in the motor neurone
220
what is utilitarianism
the belief that the right course of action is the one that maximises the amount of overall happiness or pleasure in the world
221
what is dopamine
a neurotransmitter secreted by neurones, including many located in part of the midbrain
222
where do the neurones that secrete dopamine extend to
extends through the frontal cortex, brains stem and spinal cord
223
what is the root cause of Parkinson's
the dopamine-secreting neurones in the base ganglia die therefore the motor cortexes receive very little dopamine and there is loss of control of muscular movement
224
what are the symptoms of Parkinson's disease
stiffness of muscles
tremors
slowness of movement
poor balance
walking problems
225
How does the MAO inhibitor help treat dopamine
slows the loss of dopamine from the brain
it inhibits monoamine oxidase (enzyme that breaks down dopamine) therefo increasing availability of dopamine
226
how can you treat the symptoms of Parkinsons
using drugs
a precursor to the manufacture of dopamine can be given where, in the brain, it can br converted to dopamine and control the symptoms of the disease
227
what are dopamine agonists
drugs that activate the dopamine receptor directly and often more than one is given
drugs mimic role of dopamine in brain - binds to dopamine receptors at synapses and triggering action potentials
they avoid higher than normal levels of dopamine in the brain
228
what is DBS
deep brain stimulation - is a type of surgery used to treat symptoms of disease and could help person reduce medication and reduce any side effects
229
What is believed to be the cause of schizophrenia
excess dopamine in the brain
230
how can schizophrenia be treated
drugs that block the binding of dopamine to its postsynaptic receptor site
drugs are similar in structure but unable to stimulate receptors
231
what is serotonin and what does it do
a neurotransmitter that plays a part in determining a person's mood
232
where are the neurones that secrete serotonin situated and where do their axons extend into
brain stem
extend into the cortex, cerebellum and the spinal cord
233
what is a multifactorial condition
a condition in which several genes may be involved with environmental factors contribute
234
what does ecstasy do
affects thinking, mood and memory
235
what is the effect of MDMA on synapses
increases the concentration of serotonin in the synaptic cleft by binding to molecules in the presynaptic membrane that are responsible for transporting the serotonin back into cytoplasm therefore preventing its removal from the presynaptic cleft
could also make the transport molecules work in reverse, further increasing the mount of serotonin outside of the cell
236
what are the short term side effects of using MDMA
clouded thinking, agitation, disturbed behaviour, sweating, dry mouth, increased heart rate, fatigue, muscle spasms and hyperthermia
237
how does MDMA cause hyperthermia
disrupts ability of the brain to regulate body temperature
238
what can repeated doses/ singular high dose of ecstasy do
hyperthermia, high blood pressure, irregular heartbeat, muscle breakdown and kidney failure
can be fatal
239
how can ecstasy cause depression
drug stimulates sm serotonin release that the cells cannot synthesise enough to meet demand once its gone
240
what does the HGP do
deciphering the base sequence in the human genome
241
how can the HGP help in diagnosing disease susceptibility
sequence the genome of people with the gene for susceptibility and sequence the genome of others without the gene
compare the base sequences to identify mutations found only i individuals with the condition
242
why might individuals have different responses to different medications
slight variations in each individual's genome
243
how is a GMO produced
artificial introduction of genetic material from another organism through genetic modification
transgenic/ genetically modified organism
244
what part of a bacterial cell can be used for genetic modification
plasmids
245
describe the process of using a bacterial plasmid for genetic modification to produce a protein
plasmid extracted from bacterial cell and human gene isolated (modified if needed)
plasmid cut with restriction enzyme and human gene spliced into plasmid
modified plasmid put back into bacterial cells, cell multiply in fermenter and produces protein
protein is extracted and purified and bacterial cells are destroyed
246
what is pharming
drug production
247
what is artificial selection
farmers picking out their best crops to save seeds from for next sowing
248
what are the potentials for genetically modified crops
mass produce medicines and other chemicals efficiently and cheaply
249
how can plants be genetically modified using bacteria
using a bacterium that infects many species - when bacteria invade plant cells, genes from plasmids are incorporated into chromosomes of plant cells
scientists insert the desired genes into a plasmid which then carries these genes into the plant DNA
250
how can pellets be used to genetically modify plants
minute pellets are covered with DNA carrying the desired genes are shot into plant cells using a particle gun
251
how are viruses used to genetically modify plants
viruses infect cells by inserting their DNA or RNA
they can be used to transfer the new genes into the cell
252
as gene insertion is not 100% successful, how can scientists screen to find out which cells actually contain the new gene
new gene is incorporated with gene for antibiotic resistance - the marker gene
the antibiotic is toxic to plant cells at high enough dose so plant cells are incubated and those cells that haven't taken up new genes are kileld
cells survive have successfully incorporated the new genes and are resistant
253
what is micropropagation
GM plants cells can be cultured in agar with nutrients and plant growth substances to produce new plants
254
how can genetic modification occur in animals
injecting DNA directly into nucleus of fertilised egg which is implanted into a surrogate female
retroviruses also used to introduce new genes into fertilised eggs
255
what are some concerns about genetic modifications in health
transfer of antibiotic-resistant genes to microbes
formation of harmful products by new genes
transfer of viruses from animals to humans
256
how could antibiotic-resistant genes be transferred to microbes
when plants are eaten, the gene could potentially be transferred to pathogenic microbes in the gut
257
what are the concerns with using viruses in genetic modificatin
they could infect animals and could be transferred to humans in products from GM animals
258
what are the environmental issues associated with GM crops
transfer of genes to non-target species
possible breeding of superweeds
could lead to increased use of chemicals in agriculture
259
how can genes from GM crops be transferred to other species
cross pollination
as some GM plants are related to non-target species, they can breed with them and cross, meaning that genes from GM crops inevitably spread to other plants
260
how can we prevent the production of superweeds
ensure that outcrosses between GM plants and other plants of a different variety are not fertile and cannot proliferate
261
wha are some economic issues associated with GM crops
developing countries may be unableto afford to pay for the licenses to use tech to produce gm crops
unlikely to be able to afford seeds for new plants
when they come to sell the crops, they have to compete with cheaper, higher quality products and will likely fall further into debt or be forced to sell off their land to survive
262
Describe how dopamine acts as a neurotransmitter.
released from presynaptic membrane into the synaptic cleft and binds to the receptors on the post-synaptic membrane
alters permeability of the post-synaptic membrane and opens the sodium ion channels initiating depolarisation
263
Describe how the use of MDMA could affect the transmission of impulses in the brain.
MDMA stimulates release of serotonin and blocks the [re-synaptic receptors
nerve pathways using serotonin are more likely to be stimulated
264
Individuals who use MDMA may develop the symptoms of depression. Explain how the use of MDMA could result in the development of these symptoms.
MDMA use results in the depletion of serotonin
post synaptic membrane becomes less responsive to serotonin and serotonin levels affect mood
265
Describe how low serotonin levels in an individual can affect the transmission of impulses in their brain.
serotonin is a neurotransmitter which results in fewer depolarisations of post synaptic membranes therefore threshold is not achieved
266
'Most drugs cannot easily penetrate the brain' (paragraph 3).
Explain how the treatment of Parkinson's disease overcomes the difficulty of drugs passing from the blood into the brain.
L-dopa used which can cross the blood into the brain and is converted into dopamine in the brain
267
Explain how nicotine causes an action potential in the post-synaptic neurone that
releases noradrenaline.
nicotine similar in shape to acetylcholine
increases permeability of membrane to sodium ions
nicotine causes the depolarisation of the post-synaptic membrane and depolarisation reaches threshold level
268
State how an increase in calcium ion uptake by the neurone leads to the release of
noradrenaline.
calcium ions cause vesicles containing noradrenaline to fuse with the cell surface membrane
269
The transmission of an impulse between a neurone in the optic nerve and a cell in the
brain involves ions and neurotransmitter molecules. Describe how these ions and neurotransmitter molecules are involved in the transmission of an impulse.
calcium ions enter presynaptic neurone so vesicles with neurotransmitter can move towards the presynaptic membrane
neurotransmitter molecules diffuse across the synapse
neurotransmitter to bind with receptors on postsynaptic membrane
sodium ions diffuse into post-synaptic cell leading to an action potential
270
Acetylcholinesterase is an enzyme involved in regulating the transmission of nerve impulses across some synapses.
Alzheimer's disease is associated with the loss of neurones that produce acetylcholine.
It has been suggested that inhibitors of acetylcholinesterase may be useful in the treatment of Alzheimer's disease.
Explain why inhibitors of acetylcholinesterase could be useful in the treatment of Alzheimer's disease.
acetylcholinesterase breaks down acetylcholine and inhibitor prevents breakdown of acetylcholine so more acetylcholine is available to bind to the post-synaptic membrane therefore compensating for the reduced production of acetylcholine.
271
Describe the process that occurs at a synapse that leads to habituation.
repeated stimulus decreases permeability of pre-synaptic membrane so fewer calcium ions move into pre-synaptic neurone so fewer vesicles move towards pre-synaptic membrane so less neurotransmitter released
action potential less likely to occur in post-synaptic neurone
272
Deduce how adrenaline can cause a change in heart rate.
adrenaline is carried in the blood and acts on the sinoatrial node therefore increasing the frequency of impulses produced on the SAN node, increasing the rate at which the heart contracts
273
Describe the role of sodium ions in the functioning of a mammalian rod cell.
sodium ions are pumped out of the inner segment
in the light, sodium ions do not move back into the rod cell whereas in the dark sodium ions can move back into the rod cell
in the light, the rod cell is hyperpolarised whereas in the dark, the rod cell is depolarised
274
Stage 1: enzyme is used to join each copied gene for spider silk to a copied antibiotic resistance marker gene to form pairs of joined genes
Explain how an enzyme is involved in joining the two different genes together in stage 1.
DNA ligase joins the 2 genes by forming phosphodiester bonds by condensation reactions in the active site
275
the plasmids are placed in bacterial cells which are then exposed to antibiotic A
why is an antibiotic used
so that only bacteria with the antibiotic resistance gene survives therefore these bacteria will also have the gene for spider silk
276
Give reasons why the infected alfalfa plant cells are grown on agar containing IAA in
stage 5
IAA caused cell elongation
IAA alters the pH of the cell wall to allow for elongation
to grow plants that produce spider silk
277
The effect of gravity on the growth of lettuce plants with either upright or weary phenotype was investigated.
Explain why the plants were placed in a box in complete darkness.
plants respond to light therefore light must be excluded in order to study the effects of gravity therefore prevents light from having an effect
278
Explain why the stems of weary lettuce do not respond to gravity.
only have alleles that confer a lack of response to gravity so do not produce auxin therefore lack of stimulation of cell elongation on side of stem facing downwards
279
Explain how the IAA affects the growth of the coleoptile. (the early shoot)
IAA diffuses from the tip of the coleoptile therefore can be taken up by cells in zone of elongation which causes cells to elongate which leads to lowering of pH in cellulose of cell wall therefore causes the coleoptile to grow towards the light
280
Give one example of a growth response of a plant that is affected by phytochrome.
flowering
281
Explain the effect of increasing light intensity on the current produced by a rod cell.
increasing light intensity decreases the current bc rhodopsin is broken down into retinal and opsin
therefore more opsin binds to the channel proteins in the outer segment and sodium voltage-gated channels close therefore reducing influx of sodium ions
282
Describe the role of IAA (auxin) in the phototropic response of plants.
IAA produced in the tip of the shoot and accumulates on the dark side of the shoot
it stimulates cell elongation, causing the shoot to grow towards the light source
283
Describe how the concentration of calcium ions around the myofibrils is controlled.
calcium ions released from sarcoplasmic reticulum in response to action potential
calcium channels open to allow calcium ion to cross the membrane
calcium ions taken back up into the sarcoplasmic reticulum by active transport
284
Describe the effect on saliva production shown by these results.
being show a cheeseburger increases saliva production
repeated occasions result in less saliva production
after six + occasions, there is less saliva produced than before being show a cheeseburger
285
People with Guillain-Barré syndrome (GBS) suffer from a rapid onset of muscle weakness. It is thought that GBS is caused by damage to the peripheral nervous system. In individuals with GBS, the immune system attacks and destroys the myelin sheath surrounding some neurones. Neurone conduction was studied in an individual with GBS and in an individual without GBS.
The results are shown in the table.
Explain why GBS caused muscle weakness in this individual.
no difference in action potential between individual with and individual without GBS
motor neurone conduction speed it reduced due to loss of myelin of the motor neurones and therefore loss of saltatory conduction
286
Analyse the data from these two studies to evaluate the most likely cause of the loss of
the withdrawal response
table: stimulated at one point and response is lost after repeated stimulation, if stimulation altered between two points then no habituation response
different nerves are stimulated by V and W
diagrams: response at X every time neurone is stimulated, repeated stimulation leads to no impulse being recorded at Y, electrode X is close to where stimulus applued and detects an impulse each time, Y is further from where stimulus is applied, there is a synapse between stimulus and neurone at Y
after repeated stimulation, the impulse cannot cross synapse due to lack of neurotransmitter, calcium ion channels not opening when impulse arrives at synapse and threshold not reached on the post-synaptic neurone and no action potential produced
287
Determine the effect of these TAU proteins on the maximum frequency at which nerve
impulses can be conducted along the axon of the neurone.
frequency is similar for all flies at 10 days
at 45 days old, flies with 0N4R, the error bars overlap with control therefore has little effect on the frequency of impulses
at 45 days old, flies with 0N3R, the error bars do not overlap with control therefore it decreases the frequency of impulses
288
Explain the electrical changes in an axon that allow these nerve impulses to be detected.
potential difference across axon changing due to increased permeability to sodium ions
sodium ions move into axon and cause depolarisation followed by an increased permeability to potassium ions
potassium ions move out of axons and cause repolarisation of the membrane
289
The axons of some neurones are surrounded by a myelin sheath. The main component of myelin is a glycolipid. Glycolipids are formed from lipids attached to a chain of
sugar molecules joined by glycosidic links
290
Describe the role of the dendrites in a neurone.
form synapses with other neurones
receive impulses from other neurones and is involved in summation
propagate a signal and initiates an action potential
291
Studies were carried out to investigate the withdrawal response in earthworms.
Devise an experiment to show that the frequency of the stimulation used in the first study should be 20 stimuli per minute.
use a range of frequencies above and below 20 per minute
touch with a cotton bud in the same place each time and leave 2 minutes between each
check for habituation by observing no response to touch
repeats with other earthworms of the same species
292
Compare and contrast the structure of a sensory neurone and a motor neurone
both have a cell body containing a nucleus, an axon and have dendrites at one end of the neurone and terminal branches at the other end
motor neurone cell body is at one end of axon whereas sensory neurone the cell body is located along the axon
293
Describe how positron emission tomography (PET) scans can be used to investigate brain
structure.
PET makes use of radioactive tracers/markers
PET scans detects emission of positrons and provides a 3D image
294
Describe the role of visual stimulation on the development of the visual cortex during the
critical period.
ocular dominance columns (columns of target cells) develop in visual cortex
neurones form synapses with these cells
stimuli along neurones required to strengthen connections with cells to ocular dominance columns
stimulation during the critical period is needed to form effective connections in the visual cortex
295
Functional MRI (fMRI) measures brain activity by detecting changes in
blood flow
296
Which of the following types of scanner uses X-rays?
A CT
B fMRI
C MRI
D PET
A
297
Which of the following terms describes a change in response as a result of repeated
stimulation?
A co-ordination
B habituation
C inhibition
D reduction
B
298
It is safer to use MRI than computed tomography (CT) because
CT uses X-rays that can cause mutations in the DNA of muscle fibres
299
Describe the functions of the enzymes used to genetically modify bacteria
restriction endonuclease/ restriction enzyme used to cut plasmid/ isolate gene
forming sticky ends
ligase enzymes used to add isolated gene to plasmid
ligase forms phosphodiester bonds between nucleotides
recombinant DNA produced
300
Evaluate the risks and benefits of producing varieties of plants using these methods.
Benefits: crops have increased yield due to pest control, reduced need to use pesticides, crops can be grown in wider range of conditions
hybridisation could allow crop plants to have genes for tolerance to harsh conditions from genome D, crops have higher nutrient content, or produce a greater range of chemicals, genetic modification can be beneficial if crops are herbicide resistant - can be sprayed w herbicide without being harmed
Risks:
Hybrid: can lead to pest species than can grow in wide range of conditions, could allow genes from genome D to enter pest species
GM: result in genes entering pest species - control is difficult, can introduce antibiotic resistance into other species
SB: reduced genetic diversity leading to loss of useful alleles and reducing ability of crops to adapt to environmental change
301
Explain how a single base mutation can lead to an altered primary structure of enzyme G.
changing base results in change in the triplet code and this changes the codons in the mRNA, resulting in a different amino acid sequence in the primary structure
302
Explain how human genome sequencing can be used to identify the mutations
associated with MPS I.
sequence of the genome of people with MPS1, sequence the genome of a number of people without the condition
compare base sequences to identify mutations found only in individuals with the condition
303
Explain why genetically modified bacteria delivering drugs 'to the exact tissue in the body where they're needed and nowhere else' would decrease side effects
drugs not delivered to healthy tissues and overall dosage needed is less
304
Genome sequencing and genetic modification (GM) can be used to develop proteins as
personalised medicines.
(i) Which of the following correctly describes the genome of an adult male?
A all of his alleles plus all of his genes
B all of his exons minus all of his introns
C all of his introns minus all of his exons
D all of his introns plus all of his exons
D
305
Describe how Drosophila flies could be genetically modified to produce one form of the human TAU protein
extract mRNA for one form of the protein
copy mRNA into DNA
use restriction enzymes to create sticky ends
insert the TAU DNA into the vector
introduce vector into fertilised egg
305
Describe how bacteria can be genetically modified to produce a cytokine for the
treatment of neurological and mental disorders
isolate gene for the cytokine, use a bacterial plasmid, cut the human DNA and the plasmid using the same restriction enzyme, splice the gene and plasmid together using DNA ligase, put the modified plasmids into bacterial cells
306
Give two reasons why some people may be concerned about the use of genetically modified alfalfa as a source of spider silk.
transfer of antibiotic resistance gene to other microorganisms
could lead to extended periods of infection tht could potentially be fatal
307
Describe how scientists could produce this short sequence of RNA needed to treat
someone with MPS I.
transcription of DNA containing the mutation using RNA polymerase
308
biotechnology company is developing a method of repairing the mutations in the gene for enzyme G.
Explain why the use of CRISPR-Cas9 technology can be described as personalised
medicine.
individuals have different mutations
the RNA molecules used will be specific to each individual
309
Describe why a region of the brain might appear lighter in an image obtained
by a functional magnetic resonance image (fMRI) scan.
due to more activity, an increase in oxygenated blood and fMRI signals are reflected/ not absorbed by oxygenated blood
310
Describe why a combined PET and CT scan may be better for diagnosing cancer than a PET or CT scan on its own.
using both provides information on function and structure
PET scans show areas that are more metabolically active, CT scan gives location, each scan uses a different technique - CT uses X-rays and PET uses radioactively labelled tracers
311
Describe the interaction of the muscles in the eye that led to this dilation of
the pupils.
antagonistic interaction of the muscles in the iris
radial muscles contract and the circular muscles relax
312
Explain the changes in the sodium and potassium ion concentrations in the
cytoplasm of the neurone from point W to point X on the graph. (the point before and after depolarisation)
voltage gated sodium ion channels open and sodium ions move in from outside the cell therefore causing an increase in sodium ion concentration
voltage gated potassium ion channels open and potassium ions diffuse out from the inside therefore causing a decrease in potassium ion conc at +40mv
313
Explain why the neurone becomes hyperpolarised after point X on the graph (after depolarisation decreases too much)
potassium ons continue leaving the axon therefore preventing another depolarisation occurring, allowing time for the neurone to reset so that nerve impulses travek in one direction only
314
Describe how the neurotransmitter crosses this synapse.
vesicles fuse with presynaptic membrane releasing acetylcholine
acetylcholine crosses the synapse by diffusion
315
Which one of the following allows the development of personalised medicines?
A differences in the genome between people
B medicines having the same effects on people
C similarities in the genome between people
D the genome does not affect the activity of medicines
A
316
Explain the role of ATP in the transmission of impulses along neurones.
ATP is required for sodium potassium pumps to move ions against conc grad to maintain potential difference across the axon membrane
317
Motor neurones = 50% lipid & 40% protein
Schwann cell = 70% lipid & 30% protein
Discuss the relative importance of lipids and proteins in the cell surface
membranes of motor neurones and Schwann cells.
more lipid than protein in each - Schwann cells are more lipids than motor neurone, many of the lipids and proteins eill have the same roles in both cell types
Lipids: (both) phospholipids as a bilayer, barrier to polar and non-polar substances so most movement must be through channel/ carrier proteins allowing regulated movement against conc grad
(schwann) part of myelin sheath, stops ions moving across neurone membrane so no depolarisation where #schwann cell is present and allows saltatory conduction
Proteins: channel/carrier proteins - sodium/potassium voltage-dependent gates and allows action potential to occur and stop
318
Rod cells form synapses with bipolar neurones. Describe how movement of sodium ions in a rod cell affects depolarisation in a bipolar neurone.
in dark, sodium ions moving in through sodium ion channels, sodium ins removed at inner segment so rod cell depolarises causing the neurotransmitter to be released, inhibits depolarisation in adjacent bipolar neurone
319
Describe the role of the photosensitive pigment phytochrome in the flowering
of long-day plants.
increased red light due to a long day, phytochrome red converted to phytochrome far-red in the day, accumulation of phytochrome far red stimulates flowering
320
Devise an investigation to find out if a species of plant is a long-day plant or a
short-day plant.
grow in conditions with different periods of time in light per day, control temperature + light intensity, record whether the plant flowers or not
321
Describe the advantages of using PET and fMRI rather than MRI scans to investigate a possible tumour in the brain
both can assess brain activity and images are formed in real time
322
State how image 1 can be identified as being produced by CT and image 2 by MRI.
CT is less detailed and MRI is more detailed
323
Brain tumours can change brain function.
Describe the possible effects of brain tumours in parts P and Q.
(P at back of brain and Q is beneath P)
P - inability to see
Q - change in ability to balance
324
State why the retina can be described as a tissue
retina is made of a group of specialised cells working together for a specific function
325
Describe the process of rhodopsin formation in rod cells after exposure to bright light
rhodopsin reformation occurs in the dark, retinal joins to opsin, trans retinal is converted to cis retinal in the dark
326
What happens to phytochrome in the dark
slowly converted to red phytochrome
327
Explain how the response of phytochrome to a light stimulus can cause an
increase in plant growth
phytochrome far red is formed in light which is the active form therefore stimulates cell division
phytochrome far red is a transcription factor
328
Describe why mice were used to determine the level of toxicity
they are mammals therefore will react in a similar way, no risk to humans and can control variables
329
The neurotoxins conotoxin and TTX work in different ways:
* Conotoxin inhibits calcium ion movement across the cell surface membrane
* TTX inhibits sodium ion movement across the cell surface membranes
Discuss how the investigations support the potential use of neurotoxins as
painkillers and treatments for uncontrolled muscle movement in humans
Conotoxin: reduced exocytosis of neurotransmitter into synapse so less stimulus of post-synaptic membrane so could be used to reduce uncontrolled muscle movement
TTX: less likely for neurones to depolarise as sodium ions do not move in during depolarisation so fewer nerve impulses reach synapse - painkiller
Concerns: study forpufferfish only done on one species and 5 individuals of species, mice studies only done to ascertain toxicity levels not therapeutic, mice may not be a good human model for neurotoxins and only 2 neurotoxins considered
330
explain how fMRI can be used to identify the part of the brain involved in interpreting information from the visual cortex
fMRI detects blood flow/ oxygen use in the brain
increased brain activity results increased blood flow in the area of activity
oxyhaemoglobin absorbs fewer radio waves/ fMRI detects areas where less signal absorbed
331
what is a dendron
conducts electrical impulses along its length but leads to the cell body
identical otherwise to axon
332
Why can’t you generate an action potential during the refractory period
because membrane potential is too negative therefore threshold for depolarisation cannot be reached
SNAB Biology Edexcel
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