8

Question 1

nervous system

Answer 1

CNS (brain + spinal cord)peripheral NS (sensory nerves, motor nerves)autonomic NS (involuntary + stimulates smooth muscle, cardiac muscle and glands)Sympathertic NS ( preps body 4 fight or flight response)Parasympathetic ( preps body for rest and digest)somatic (voluntary+stimulates skeletal muscle)

Question 2

motor, sensory and relay

Answer 2

motor-cell body situated within the CNS and axons extends out, conducting impulses from CNS to effectorssensory neurons- carry impulses from sensory cells to CNSrelay- these are found within the CNS- large no. of connections with other nerve cells

Question 3

myelin sheath

Answer 3

fatty insulating layer around the axon- made up of Schwann cells wrapped around the axon

Question 4

how resting potential of -70mV maintained

Answer 4

3 Na+ pumped out of the axon and 2K+ pumped into the axon against conc gradient using energy provided by hydrolysis of ATPonce conc gradient established by sodium potassium pump, K+ move out of the axon down the conc gradient, cell membrane more preamble to K+ then Na+- move through open channelsinside axon negative and outside axon positive creating a potential difference- polarized

Question 5

what causes action potential

Answer 5

waves of depolarisation of the neurone- to pass electrical impulse down neurone once threshold stimulation occur action potential is caused by the change in permeability of axon membrane to Na+ and K+at resting potential voltage dependent gated channels are blocked by gates preventing the flow of ions through the,change in voltage across the membrane causes these gates to openwhen an impulse above the threshold is applied the PD across he membrane is locally reversed- depolarization- PD=+40 mV for brief instant- returns to -70 mV in repolarization

Question 6

depolarisation

Answer 6

occurs when impulse stimulates neuronein receptor cells sodium voltage gated channels are opened by energy changes in environment, Na+ diffusionChange in PD across the membrane causes change in shape of Na+ gate, opening some of the voltage dependent sodium ion channels. small depolarisation has no effect on voltage gated channels, however, if depolarisation is large enough to reach threshold potential, it triggers the opening of more gates increasing depolarisation further causing a large influx of Na+thus a depolarisation of +40 mV is reachedpositive feedback loop- rapid opening of all Na+ gates- no way of controlling the degree of of depolarisationaction potentials are either there or they are not- all-or-nothing

Question 7

hyperpolarization and repolarization

Answer 7

after about 0.5ms volatge gated Na+ channels spontaneously close and the permeability of the membrane to Na+ return to normal levelsdue to depolarisation of the membrane K+ voltage gated channels open and K+ ions flow out down eletrochemical and concentraton gradientinside axon becomes -ve again in comparison to outsidemembrane is now highly permeable to K+ and more ions move out than occurs at resting potential making PD more neg- hyper- resting potential re-established by closing the volatge dependent K+ channels and K+ diffusion into the axonif lots of action potentials occur in the neurone the Na+ conc inside cells rises significantly- sodium potassium pump starts to function restoring the og ion conc across the cell membrane - not used frequently if cell not transmitting many action potentialsrefractory period- immobilsies all ions channels- no further depolarisation

Question 8

how an impulse is passed along an axon

Answer 8

stimualted neurone triggers a sequence of AP at resting potential there is a postive charge on the outside of the mebrane and a negative charge on the isnide, with high Na+ conc outside and high K+ conc inside when stimulated votlage dependent nA+ channels open, and soidum ions flow into the axon depolarisng the membrane - localsied electric currents are generated in the membrane- sodium ions move to the adjacent polarised resting region causing a change is PD at this part of the membrane the chnage in pd in the membrane adjacent to the first action potential initiates a second action potential- at the site of the first action potential the voltage dependent sodium ion channels close and voltage dependent potassium ion channels open- K+ leave the axon repolarisng the membrane - membrane becomes hyperpolarised a third action potential is initiated by the second - in this way local electric currents cuase nerve impulses to move along the axon- at site of 1st action potential potassium ions diffuse back into the axon resotring the resting potentiala new action potential cannot be generated in the same section of the membrane for a bout 5 miliseconds- refractory period- lasts until all the voltage dependent sodium and potassium channels have returned to their normal resting stage and the resting potential is restored- ensures impulse only travels in one direction

Question 9

control of speed of impulse

Answer 9

diameter of axon- wider the dimaeter the faster the impulse
myelnation- myleniated neurones conduct impulses faster, mylein shiefs act as electrical inulators preventing the flow of ions, so depolarisation only occurs at the node sof tavier- salatory conduction

Question 10

saltatory conduction

Answer 10

the insulatin mylein seath prevents curents from passing through the memebrane, except in gaps between Schwann cells- nodes of ranvier- areas of membrane hat become dpeolarised- this forces the current to travel down the axon to the next gap- AP jump from one gao to thenext

Question 11

synapse structure

Answer 11

a

Question 12

how synase trnasmits impulses

Answer 12

arrival of AP at the presynaptic membrane causes the release of neurotransmitter into the synaptic cleft- the neurotransmitter diffuses across the gap, reslting in events that cause the depolarisation of the postsynaptic membrane and hence the propagation of the impulse along the next cell the presynaptic cell expends a considerable amont of enrgy to produce the neurotransmitter and packag it inot a vesicles reay for transport out of the cell

Question 13

synaptic transmssison

Answer 13

an action potential reaches terminal end of pre-synaptic neuronthe membrane depolarises causing voltage gated calcium channeles to open Ca2+ rush inca cuase synaptic vesicles conatining neurotransmitter to fuse with the presynaptic membraneneurotransmitter s released into the synatic cleft- exocytosis- trvale down conc gradientneurotransmitter binds with receptors on the pstsynaptic membrane- cation channels open- sodium ionsflow through the channelsthe membrane depolarises and initiates an APwhen released from the receptor the neurotrnasmitter will be taken up acoss the presynaptic membrane or it can diffuse aay and be brokendownenzyes in the synaptic gap then breakdown the NT- products taken up by presynaptic neuron by AT

Question 14

stimulaton if the postsynaptic membrane

Answer 14

0.5 ms to diffuse across synaptic cleft and reach postsynaptic membrane
in postsynaptic memrane are specific receptor proteins that have binding sites with a complemntary shape to part of the acetylcholne molecules0 AM binds to receptor, chaninging the shape of theprotein, opening cation cannels and making the membrane permeale to sodium ions- flow of sodium ions across psotsy membrane causes depoarisation and if tehre is sufficent depolarisation an AP will be roduced and propgated along the postsynaptic neurone
the extent of the depolarisation will depedend on the amout of acetylcholine rraching the postsynaptic memane- depend on the frequency of impulses reaching the pre synaptc membrane- several required to generate enough neurotrsmitter to depolarise the ost synap membrne - no. of functioing receptros in post will alsoe influence degree of depolar

Question 15

inactivaton of neurotransmitter

Answer 15

some neurotrnsmitter are actively taken up byre syanptic membrane and the molecules are used again- with others the neurotrnamitter rapidly diffuses away from the synaptic cleft or is taken up by other cells of the nervous system- in case of acetylcholine a specific enzyme at the psotsynaptic membrane, acetylcholinesterase, breaks down the acetylcholine so that it can no longer bind to receptors- some of the breakdownproducrs are then reabsorbedby the presynatic membrane and reused

Question 16

role of synapses

Answer 16

control nerve pathways allowing flexibility of response
integration of info from diff neurones, allowing a coordinated response

Question 17

factors thata ffect likelood of postsynaptic cell to depolarise

Answer 17

type of synapse
the no. o impulses reived
postsynatic cell likely to be recievig input from many synapses at the same time- the overall effect of thses synapses will determine whether or not the post synaptic cell generates an action potential

Question 18

inhibitory and excitatory

Answer 18

make less likely for postsy membrane to depolarise and stimulate AP- post synaptic cll have manyof both so whether an AP result depends upon balnce of the two
Inhibitory: net decrease of neurotransmitters produced in post synaptic neurones
-Associated with parasympathetic nervous system, eg acetylcholine
Excitatory: net increase in NTs produced in post synaptic neurones
-Associated with sympathetic nervous system, eg adrenalin

Question 19

excitatory synapses

Answer 19

make postsy mem more permable to NA- single synapse does not typically depolarise mem to produce AP but several arriving in a short period of time produces sufficent depolar via the relase of neurotransmitter to produce an AP in pstsy cell- each impulse adding to effect known as summationspatial summation- impulses from diff synapses usually from diff neurones - no. of diff sensory cells stimulated can be reflected in the control of the responsetemporal ummation- several impulses arive at synapse having travelled along a single neurone- combined release of neurotransmitter generates an AP n post sy membrane

Question 20

inhibitory synapses

Answer 20

make it less likely for AP to result in post sy cell - neurotransmitters from these synapsesopen chanels for cl- and K+ in post sy membrane and these ions will move through the chanels down their diffusion gradient - cl_ will move into the cell carrying a negative charge an k+ move out cell caryying a pos charge - gretaer PD across membrane as inside becomes more neg than usual -90mV: hyperpolarisaton- makes subsquent depolarisation less leikely- more excitatory synapses required for depoalr

Question 21

nervous v hormonal coordination

Answer 21

nervouselectrical transmission by nerve impulses and chem trans at synapsefats actinshort term changes- muscle cotractionAP carried by neurones with conections to specific cells local espnsehormonalchem trnasmission through the bloodslower actinca control long term chnagesblood carries hormone to all cells but only traget cells are able to repsond reponse may be widespread such as in growth and devlopment

Question 22

cooridnation in plants

Answer 22

lack nervous system so must use chems to coordiante growth, development and repsosne to the environment

Question 23

auxins

Answer 23

chems made in the tip of a plany passed down the coleptile- deonstarted by removin the tip, placing it on a small block of agar jelly ad putting the agar on top of the cut end- coleptile started to grow again showing auxin has diffused down through the agar jelly
auxons stimuale growt resulting in cell elongation
measurment of he amount of chems produced on the shaded and unshaded side of shoot found that total mount produced did not chnage compared wth a shoot illuminated from all sides- instead auxins had passed dwon the shaded side - increased conc on shaded side increased cell elongation, reduced inhibited cell elongation- shoot grew towards light
auxins such as IAA ae synthesied in actively growing roots and shoots tips and in developing seeds, leaves and fruits. They are transported from these sites to sites of action
transpoted long distances in phloem and short distances between cells via carrier proteins in the cell membrane- auxins bind to protein receptors in target cells- activates intracellular second messanger signal molecules which activate tracription fcators - control transciption of auxin reguated genes and the protein prduced bring about metabolic chnages that reuslt in a range of resposne through changes in cell expansion, division and differentiation
auxins cause acidifcation f cell wall by stimualting the activvityof proton pumos that move H+ out of the cytoplasm and into the cell wall here the low ph activates proteins called expansis- disrupt the bonds that old cellulose microfibrils and hemicellulose together- loseining of cell wall ; slippage o polysacchardes relaive to each other, bonds form in new locations allowing expansion of the cell
acidification of cll wall increases the PD across the membrane: enhances uptake of ions io cell- in turn the presence of these ions causes water uptake by osmosis causing cell to swell- elongation
plant growth involves cell division and elargemnt in the eristem cells are actively dividing , most of these cells enlarge, forming a region of elongation adjacent to the meristem- cells go on to mature and differentiate

Question 24

cholodny-went model

Answer 24

circised due to small smaple size and diffuclty of measung small conc

Question 25

eye

Answer 25

functions

Question 26

receptors

Answer 26

stimuli detected by receptor cells that send electrical impulses to CNS

Question 27

photoreceptors

Answer 27

rods and cones cones allow colour vision in bright light rods only give black and white vision but work in dim light as well as bright light- allow us to percive light and dark every cone cell connected to 1 bipolar neurone 3 rod cells connected to one bipolar neurone

Question 28

retina

Answer 28

thin layer of thissue that lines inner part of the eye responsible for capturing the light rays that enter the eye light impulses then sent to the brain for processing via the optic nerve

Question 29

optic nerve

Answer 29

transmuts electrical impulses from the retina to the brain connects the back of the eye neurone the marcula when optic nerve meets the retina there is no light ensitve cells- blind spot macula- located roughly to teh centre of the retins- temporal to the optic nervesmall and highly ensitve part of the retina responsible for central visionallows apprectation of detailhighest conc of cones but low conc of rodes

Question 30

rods

Answer 30

allow us to perieve light and dark very sensitive and involved in vision at low intensities function dependes on the light stimulus being detcted by a photopigment called rhodopsin

Question 31

how light stimulates photoreceptor cells

Answer 31

photochem pigment absorbs the light resulting in a chem change in rods rhodopsin

Question 32

rods structure outer segment

Answer 32

contains pigment rhodospin in flatterned membrane vesicles called lamellae 1000 of thses lamellae outer region is connected to inner region by a narrow region containing cytoplasm and a pair of cillia

Question 33

rods structure inner segment

Answer 33

contains a large no. of mitochondria which provide ATP to synthesise rhodopsin contains polysomes which is where the production of rhodopsin occurs at the base of the inner membrane is a synapse connected to a bipolar neurone

Question 34

in light rhodopsin

Answer 34

contains protein opsin with rutinal, a deribative of vitimin a retinal can exist in either cis or trans isomers light causes the retinal to convert from cis to trans which can no longer bond to opsin and the retinal detaches opsin activates a series of membrane bound reactions ending in hydrolysis of a cyclic nucleotide molecule attached to the cation channel in the outer segment this breakdown results in the closing of cation channels influx of NA+ into rod cells decreases while inner segment continues to pump Na+ out makes inside of the cell more negative - becomes hyperpolarised and the release of the glutamate neurotransmitter stops (inhibitory synapse) results in the depolarisation of the bipolar cell with which the rod synapses the neurones that make up the optic nerve also depolarise and respond by making an AP

Question 35

in dark

Answer 35

in the dark sodium ions flow into the outer segment through non specific cation channel the sodium ions move down the conc gradient into the inner segment where pumps continuously transport them back out of the cell the influx of sodium ions produces a slight depolarisation of the cell- pd across the membrane is about -40mV compared to the resting -70 the slight depolarisation triggers the release of neurotransmitter from the rod cells- in dark released continuously- binds to bipolar cell stopping depolarisation- inhibitory synapse

Question 36

effector mechanisms

Answer 36

Stimulus > receptors > sensory neurones > CNS control centres > relay neurones > motor neurones > effectors eg glands/muscles system allows rapid response to environment for survival, electrical impulses are the quickest form of communication Example: dilation and constriction of iris muscles in response to light Dilation: dim light > photoreceptors > CNS and relay neurones > motor neurone > radial muscle contraction Constriction: bright light > photoreceptors > CNS and relay neurones > motor neurone > circular muscle contraction

Question 37

plants and environmental cues

Answer 37

plansts detecr quantty, direction and wavelength of light using phtoreceptors- most particullarly phytochromes

Question 38

phytochromes

Answer 38

consists ofa protein compound bound to a non-protein compound light absorin pigment molecule nn protein component exists in isomersPr- phtocrome red; absorbs redightPfr- phytochrome far red; absorbs far red light photoreversible- plants synthesise phtochomes in the pr form; absorbtion of red light converts Pr into Pfr absorbtion of far red light converts Pfr back into Pr in sunlight pr is converetd pfr and pfr is converted into pr- former reaction dominaes in sunliht bc more red than far red is absorbed so Pfr accumulates in light. In dark any pfr present is slowly converted into Pr

Question 39

phyochromes triggering germination

Answer 39

flash of red light triggers germination whilst far red ligt inhibits- if goes red far red then red- trigered- suggests reversible reactiom- final flash determine appearnce of Pfr triggers germination

Question 40

photoperiods

Answer 40

relative light of day and night- environmental cue that determines time of flowering- ratio of Pr t Pfr in plan enables it to determine the length of day and night long winter nights gives ample time for Pfr to be converted into Pr- so by sunrse all Pr summer nights may not be long eough

Question 41

long day and short day plants

Answer 41

L- only flower when day exceeds critical value- flower when period of uninterrupted darkness is less than 12 hors- need Pfr S- flower when period uniterrupted darkness is greater than 12 hours- need long hpurs of darkness to convert all Pfr present at sundown to Pr- Pfr inhiit flowering in short day plants

Question 42

phytochrome and greening

Answer 42

once the light, phyochromes promote the devlopment of primary leaves, leaf unrolling and the production of pigments

Question 43

how phytochromes switch process on or off

Answer 43

exposure to light causes phytochrome molecules to change from one to anotherbrining about a change in shape- each activated phytochrome interacts with other proteins- bind to them to disprupt the binding of a protein complex- signal proteins may act as transcripton factors or activate other transcription fcators that bind to DNA to allow transcription of light-regulated genes- trans and transl of proteins result in plant's response to light

Question 44

why certain plants may not respond to gravity or other stimulus

Answer 44

do not have allele conferring ability to respond to gravity so do not produce auxins and therefore lack of stimulation of elongation of side facing down

Question 45

how auxins work (mark scehem)

Answer 45

IAA diffuse from tip taken up by cells in zone of elongation lowers pH of cellulose in cell walls- auxins cause acidifcation of cell wall by stimualting the activityo f proton pumps that move H+ out of the cytoplasm and into the cell wall here the low ph activates proteins called expansis- disrupt the bonds that old cellulose microfibrils and hemicellulose together- loseining of cell wall ; slippage of polysacchardes relaive to each other, bonds form in new locations allowing expansion of the cell leads to elongation causes to grow towards light- positive phototropism

Question 46

why change in PD in rod cell may not stimulate optic nerve

Answer 46

not enough rhodopsin converted into opsin change in voltage not sufficent neurotransmitters still released depolarization in bipolar neurons insufficient bipolar neurons already depolarized

Question 47

describe the roles of the circular and radial muscles in pupil dilation

Answer 47

work antagonistically- circular muscles relax radial muscles contract

Question 48

why impulses are faster on myleinated neurones

Answer 48

schwamm cells cover axon in myleinated neurones providing insulation action potemntial only occurs at nodes of ranvier whilst unmyelinated has a local current that occurs over a long distance - salatory conduction as impulse jumps from node to node

Question 49

role of dendrites

Answer 49

form synapses with other neurones recieve impulses from other neurones initiate AP to axon involved in summation

Question 50

depolarisation v Hyperpolarization

Answer 50

hyp is when the membrane potential becomes more negative at a particular spot on the neuron's membrane, while depolarization is when the membrane potential becomes less negative (more positive)

Answer 51

me if not lock in

Question 52

brain structure

Answer 52

left and rifgt cerebral hemispheres each coposed of 4 regions- frontal, parietal, occipital, temporal outer layer- grey matter- nerve bodies, synapses and dendrites white matter-below grey- nerve axons that connect neurones to diff parts of the brain 2 cerebral hemispheres held together by borad band of white matter-corpus callosum- allows communication between hemispheres- thalamus resposnible for toiting all the incoming sensory info to correct parts of brain

Question 53

brain structure pt2

Answer 53

hypothalamus- thermoregulatory centre- mointors core body temp and skin temp and initiates corrective action to restore body to optimum temp hipocampus- laying down long term memory basal ganglia area a collection of neurones that lie deep within each hemisphere and are responible for slecting and initiating movement

Question 54

cerebellum and brain setm

Answer 54

cerebellum- balance, coordinates movement as it is being carried out, recieving info from primary motor cortex + muscles + joints, constantly checks whether the motor programme being used is the correct one, midbrain-relays info to the cerebral hemispheres, including auditory info to the temporal lobe and visual info to the oppcipital lobe medulla oblongata- regulates body processes that we do not control consciously like heart rate, breathing and BP

Question 55

MRI

Answer 55

Magnetic resonance imaging: use of radio and magnetic waves to show body structures and tissues when placed in a magnetic field nuclei of atoms lineup with the direction of the magnetic fieldhydrogen atoms in water are monitored in MRI bc there is usch a high water content in tissues under investigation and hydrogen has a strong tendency to lineup with mag field \mag filed runs down the centre of the tube in which the paitent lies- another mag filed superimposed on this-comes from the high frequency radio wavescombined fields cause the direction and frequency of spin of the hydrogen nuclei to changetaking energy from radio waves to do so- when radio waves turned off hydorgen nuclei return to their OG alignment and released the nergy they absorbed - dtected and signal sent to computer Able to see and identify abnormal tissues eg tumours Safer than CT and PET scans (no X-rays or radioactive trackers)Expensive and is not suitable for all patients eg those with pacemakers Shows structure but not function

Question 56

fMRI

Answer 56

Functional MRI: detects changes in oxyhaemoglobin difference and indirectly shows brain activity - looks at function of diff areas of the brain by follwoing o2 uptake in active brain areas deoxyhaemoglobin absorbs radio wave signals Active areas in brain require more oxygen and show an increase in oxyhaemoglobinOxyhaemoglobin reflects radio/magnetic waves more and so appears differently in scans less radiowaves absorbed the areas of brain actvity Produces high resolution imagesIndirect measure of activity - multiple stimuli activate multiple parts of the brain at once, difficult to isolate

Question 57

Positron Emission Tomography

Answer 57

allow structure and functioning of tissues and organs to be evaluated use isotopes with short half life such as carbon-11- incorparated into a glucose or water compound or molecules that bind to receptors radioactive tracer introduced to blood in advanc, decay releases positrons which can be measured- tissue active there will be increased energy used in that area- more o2+glucose required so increased blood flow- will show up on PET image as more radiotracer atoms presentwhen a positron collides with an electron two gamma rays emitted which are picked up by by detectros- bright areas indicate high kevels of neurone activity Eg radioactive labelled glucose will show on scan in more active areas of the brain as metabolism occurs Can detect structure and function simultaneously Ingestion of radioactive materials can cause damagedetect alzheimers- neuroen dies B-amyloid protein found in mylein sheath builds up which blocks signals at synapses

Question 58

CT scans

Answer 58

Computed tomography: X-rays are sent through the body to see tissues- thousands of narrow beam X rays rotated around the paitent to pass through the tissue at diff angles - each beam reduced in strength according to the density of the tissue in its path - used to produce and image of a thin slice of the brain Different tissues absorb the rays to different extent and show as different shades Dangerous due to dangers associated with X-rays ie DNA mutations Not suitable for all patients eg pregnant/children as radiation is higher than regular X-ray give structure not function as only a frozen moment

Question 59

development of the visual coretx

Answer 59

Visual cortex - region of cerebral cortex in occipital lobe in which visual information is processed- collums of visual cells make up the cortex axons from the retina grow to the thalamus where they form synapses with neurones in the thalamus - grow towards visual cortex is occipital lobe Only develops correctly with adequate neuronal stimulation in critical period from visual stimuliCritical period is time in which continual visual stimuli are necessary for the proper development and organisation of columns of ocular dominance occursInadequate stimulation leads to destruction of neurones and improper development of sightColumns organised for left and right - contralateral to eyeOrganised into columns of ocular dominance with cells which are responsive to visual input from eyesColumns of ocular dominance are strengthened and develop with visual stimulation

Question 60

4 marker process of dvelopment

Answer 60

Stimulation of eyes in critical period activates neurones in visual cortex to make connections Columns of ocular dominance develop Neurones form synapses with columns Light/ visular info strengthens connections

Question 61

Animal studies in the development of the visual cortex

Answer 61

Hubel & Wiesel conducted studies with monkey and cats to research the development of the visual cortex in mammalsStitched one eye of young kitten and left the other eye open, left for several monthsUnstitched eye and found the stitched eye was blind and the open eye developed properlyOcular dominance columns for open eye were strengthened more so to compensate for blindnessFewer synaptic connections were found to weak columns- after light depravation in one eye colums with axons are narrower- dendrites and synapses in light stimulated eye take up more territory in visual cortexwhen one eye is deprived of light the axons from that eye will not be stimulated- every time a neurone fires onto a target cell, the synapse of another neurone sharing it are weakened and release less NT- synapse cut backRepeated with adult cats and found no change in sight as columns of ocular dominance had already developedrepetition of study with monkeys found same results

Question 62

benefits of animal testing

Answer 62

Similar structure of monkeys/cats/mammals in general allows study without harm to humans Must be tested on living cells Medical testing on humans is unethical but is more acceptable in animals Animal studies only carried out when no alternatives are available

Question 63

weaknesses of animal studies

Answer 63

Alternative research options are available eg computer modelling/isolated tissue cell research Animals still have rights and do not deserve to be harmed Animals suffer regardless of sins of research and may need to be dead to gather tissue access/research at cellular level Anatomy is not identical and may not be entirely generalisable

Question 64

habituation

Answer 64

Process of learning to NOT respond to unimportant stimuli if they are repeated over time for survival - Saves energy so it can be used for maximum feeding effortRepeated stimulation decreased sensitivity of presynaptic neurone to specific stimulus- ca ion channels become less responsive Calcium ions at presynaptic knobs are not released andNT vesicles are not exocytosed and do not fuse with membraneNo release of NT through synapse and so action potentials at post synaptic membrane occur less frequently- less depolarisation so no ap triggered in motor neurone

Question 65

CORE PRAC 18

Answer 65

CORE PRACTICAL 18 - Investigating habituation to a stimulus Aim: investigate habituation to a stimulus in snails Independent variable: time taken fro eyestalks to re-emerge from the shell (s) Control variables: age and size of snail, point where bud touches, same cotton wool bud, surface on which snail is method:Place snail on clean and even surface and give it time to acclimate to new surrounds, until snail has fully emerged form shell Touch the snail between eye stalks with cotton bud and start the stopwatch Measure the length fo time taken for the eye stalks to fully re-emerge Repeat 15 times, timing how long eye stalks take to re-emerge (time should go down, negative correlation)Ethics: return snail to original environment, use only gentle touches, try to complete the study as quickly as possible, and avoid any increase in temperatures/dry environments for comfort of the snail

Question 66

Effect of drugs on synaptic transmission

Answer 66

Imbalance in neurotransmitters in the brain can result in various disorders eg Parkinson’s disease and depression

Question 67

Parkinson’s

Answer 67

brain disorder affecting coordination of movement Caused by the loss of dopamine-producing neurones Less dopamine released into synaptic cleft, so less sodium channels open on post synaptic membrane Less frequent impulses are sent to effectors and produce infrequent APs Results in shaking and loss of control

Question 68

treatment parks

Answer 68

Patient can be given dopamine agonist to replace the function of dopamine and increase overall levelsInhibitors can stop the activity of enzymes which break down dopamine also increasing overall levelseg monoamine oxidase BGene and stem cell therapy can be used T an be used to add dopamine-producing genes and enzyme inhibiting genesaim to replace dopamine-producing neuronesAddition of dopamine precursor eg L-DopaDopamine cannot be internalised into the brain so a precursor has to be given which can then break down into dopamine- allows pass of blood brain barrierAid of dopadecarboxylase for breakdown- broken down in brainMore binding of dopamine = more APs = more Na+ channels open = more impulses reach brain = more control over movement

Question 69

depression

Answer 69

mental illness associated with low serotonin levels- multifactorial conditions- one gene 5-HTT, known to influence depression codes for a transport portein that xontrols serotonin reuptake into presynaptic neurones- shor versions likely to develop despressionserotnin a neurotransmitter - neornes that secrete it are situated in the brain stem-axons extend into the cortex, the cerebellum and the spinal cord, targetting a huge areas of the braindopamine and nonradrenaline can be involvedwhen someone is depressed fewer nerve impulses than norma; are transmitted around the brain, low levels of NT being produced. Pathways involving seratonin have a no. of abnormalities w ppl w depression- molevules needed for seratonin synthesis are often present in low conc, but seratonin binding sites are more numerous than normal possibly yo compensate for low level of molecule Treatment: patient is given selective serotonin reuptake inhibitors- prozacblocks reabsorption/reuptake of serotonin at presynaptic neuronesincreases binding of serotonin to post synaptic membrane and therefore APshow drug affects synaptoc transmission

Question 70

MDMA

Answer 70

illegal recreational drug which can effect multiple neurotransmitters but mostly serotonin increases seratonin in synaptic dleft- binding to molecules in presynaotic membrane that are responible for trnasporting seratonin back into cyto- may cause molecules to work in reverse- higher levels bring about mood changesinhibits reuptake of serotonin by binding to proteins enabling reuptake and blocking actionTriggers release of additional serotonin and dopamineRepeated ingestion can cause desensitisation of post synaptic neurone causing depressioneffects]euphoria well being and enhacned sensesclouded thinking, agitation and disturbed behaviourdisrupt ability of the brain to regulate body temp

Question 71

why repolaristion occurs

Answer 71

potassium ions leave the axons, through potassium votage gated channels.,preventing another depolaristion to occur in refractory period, allowing time for neurone to reset and RP to be reached again, ensures impulse only travels in one direction

Question 72

role of phospholipids and proteins in schamm cells and motor neurones

Answer 72

both role- lipids- provide a bilayer-sperates interior and exterior envirnments- barrier to polar and non polar moleculres, movement must occur through channel proteins-Allowing regulated movement / movement against the concentration gradient schamm cells role-lipids- Part of myelin sheath / electrical insulation • Stops {ions / Na+ / K+ } moving across (neurone) membrane • So no depolarisation where {Schwann cell / myelin} is present / depolarisation only occurs at nodes of Ranvier • Allows saltatory conduction / process described role of proteins in motor neurone- Channel / carrier proteins / gated channel proteins • Na+ / K+ voltage-dependent gates / Ca2+ channels / Na+ / K+ pump • Role in allowing action potentials / resting potential in the axon

Question 73

differences between myleinated sensory and motor neurones

Answer 73

senosry: dendorns longer + myelainted + axon longer, cell body in middle instead of end

Question 74

Personalised medicine

Answer 74

deciphering of the base sequence in the human genome as part of the HGP the human genome is thought to be 3200000000 bases in length- containing 20k to 25k genes avghuman gene is known to consist of 3k bases - coding DNA makes up lessthan 2% of the human genome- non coding regions are highly conserved - suggest a selective advantage in respecting of perserving certain useful biological traits and/or minimising othertraits scientists have identified 1.4mil locations where single nucleotide polymorphisms occur in humans- DNA sequence variation that occurs when a single nucleotide in the genome sequence is altered in at least 1% of the pop, with one base substuted for another- possession of certain SNPs could predispose ppl to diseases or influence their response to a drug drug targets- a specific molecule that a drug interacts with to bring about its effect. Genome sequencing allows for at-risk individuals to take preventative measures and change lifestyle accordingly - identifies disease genesPersonalised medicine (medicine targeted to specific individuals) allows effective treatmentIssues: research cost, possible refusal of meds by insurance if risk of med not working is high, psychological damage of knowledge

Question 75

GM microorganisms

Answer 75

Restriction enzymes remove gene coding for desired protein from genome PCR is used to amplify desired gene, leaves sticky ends DNA ligase binds sticky ends of gene to plasmid DNA (vectors) in microorganisms - plasmid alos cut using restriction Microorganisms is cultured to mass produce new protein - fermented

Question 76

GM plants

Answer 76

for artificial selectionRestriction enzymes remove gene coding for desired protein from genome PCR is used to amplify desired gene, leaves sticky ends DNA ligase binds sticky ends of gene to plasmid DNA (vectors) in bacteriabacteria is introduced to plants and infects cells so gene is transferred to plant nucleus and grows into adult - when bacterium infect plant cells genes from plasmids incorporated into chromosome of plant celleach new cell will contain gene coding for desired proteinsprotein can be purified from plant tissues and eaten other way: minute pellets covered with DNA carrying desired genes are shot into plant cells using particle gun, viruses inserting DNA or RNA never 100% successful so scietists incorporate a gene for antibiotic resistance, called a marker gene, along wioth desired gene- antibiotic toxic to plant cells at a higher enough dose so the plant cells are incubated with the antibiotic which kills off any cells that have not taken up the new gene - those that survive are ones with antibiotic resitant gene GM cells can be cultured in agar with nutrients and plant growth subs to produce a new plant- micropropagation- multiply to form a callus- differentiates to form plantlets

Question 77

GM animals

Answer 77

Gene coding for desired protein is inserted into zygote nucleus zygote is implanted to adult animal and allowed to develop,all future cells will contain Copt of desired protein protein can be purified from the animal eg milk

Question 78

advanatges of gmos

Answer 78

Diseases can be treated with human-produced proteins and not animal, decreasing chance of rejection Vaccines in plant tissues do not need refrigeration and so are widely accessible Overall lower cost decreased use of pesticides decreases cost

Question 79

disadvs `GMOs

Answer 79

Moral objections to modifying animals for human benefit Production of superweeds which are resistant to antibiotics - transfer of gene to non target species- cross pollination Unknown long term effects Transference of genetic material- tranfer of viruses from aanimals to humans- transfer of antibiotic resistant genes to microbes,- GMS need desired gene and marker gene- when eaten can transferto pathogenic microorganisms in gut formaation of harmful products of new gene- Production of monocultures are bad for biodiversity

Question 80

Nature v nurture studies

Answer 80

Innate mechanisms controlling behaviour or learned mechanisms Newborn babies newborn babies have no influence from external environment and so brain development has not been affected only nature is influencing brain nurture is still important for some skills eg speaking Animal experimentsmanipulation of living environments and comparison of same animal species allows influence of nurture to be studied similarities will be from effects of genes Brain damage Change in characteristics after brain damage can allow study of development development of trait with associated area suggests influence of nurture - not innate no developemnt suggests nature Twin studiesComparing characteristics of monozygotic and dizygotic twins allows influence of genetics to be studies MZ twins grow up in ‘same’ environment Comparing MZ to DZ with different genes will show result of environment Cross-cultural studies large groups of children of similar ages from different cultures are compared similarities are due to nature, differences due to nurture

Question 81

how ligase joins genes

Answer 81

DNA ligase joins two genes by forming phosphodiester bonds in a condensation reaction

Question 82

firm (mark scheme)

Answer 82

detects blood flow/oxygen use in brain increased brain activity results in increased demand for oxyge/blood flow to active area Oxyhemoglobin reflect waves, area with where less signals are absorbed/ radio waves

Question 83

PET(mark scheme)

Answer 83

uses a radioactive tracer- PET scans detect emission of gamma rays/positrons- produces a 3D image-

Question 84

habituation mark scheme

Answer 84

reduced permeability to pre synaptic membrane to calcium ions so fewer vesicles with NT are stimulated to fuse with pre synaptic membrane therefore less NT bind with receptors on post synaptic membeerane meaning an action potential may not be produced

Question 85

visual stimulation mark scheme

Answer 85

coloumns of ocular dominance form in the visual cortex, these cells from synapses with neurones, these sysnapses/connections are strengthened by visual stimulation and action potentials along neurones during critical period, stimulation during critical period required to form effective connections to the visual cortex

Question 86

role of enzymes GM

Answer 86

restriction endonuclease used to cut plasmid and isolate gene forming sticky ends ligase enzyme used to add isolate gene to plasmid ligase gene forms phosphodiester bonds between nucleotides recombinant DNA/plasmid produced

Question 87

6 marker- GM, hybridisation and selective breeding

Answer 87

benefitsincreased yield due to pest resistance or drought resistance + diseasereduced need for pesticidesgrown in a wider range of conditionshigher nutrient content, producer a greater range of useful chefs can be sprayed with herbicidesriskshybridisation- can lead to pest species being able to grow in a wide range of conditions, allow genes to enter pests- natural selection- If a few pests have a mutation that makes them resistant to the toxin (e.g., Bt toxin), they survive and reproduce-Over generations, the resistant pests dominate the population.- , pests (especially microorganisms like bacteria or fungi) could acquire genes from the crop through horizontal gene transfergenes entering pest species-introduce antibiotic resistance in other species- If a GM crop cross-pollinates with a closely related wild plant (a weed species growing nearby), the herbicide resistance gene can be transferred.selective breeding causes genetic drift reducing genetic diversity - loss of useful alleles

Question 88

how mutations are single out using gene sequencing

Answer 88

sequence genome of those with condition, sequence a number of people without condition, compare bases sequences to identify mutation present in those with condition

Question 89

how GM in animals carried out (human gene)

Answer 89

extra mrNA for gene copy mRNA into DNA use restriction enzyme enzyme to create sticky ends on DNA and vector integrate DNA and vector inegrate vector into zygote

Question 90

Cerberum

Answer 90

Higher brain functions: Conscious thought Decision making Voluntary movement (motor cortex) Sensory perception (sensory cortex) Language, memory, emotions

Question 91

cerebellum

Answer 91

Coordination and balance Fine-tunes voluntary movements Maintains posture and balance Controls motor skills and coordination

Question 92

Medulla Oblongata

Answer 92

Autonomic control Regulates heart rate Controls breathing rate Reflexes like coughing, sneezing, swallowing

Question 93

Hypothalamus

Answer 93

Hypothalamus Role: Homeostasis & hormonal control Functions: Monitors blood temperature, water balance, and glucose levels Links nervous system to endocrine system via pituitary gland

Question 94

Frontal Lobe

Answer 94

Frontal Lobe Functions: Decision making, problem-solving, planning Voluntary motor control (via motor cortex) Personality, emotions, speech production (Broca’s area)

Question 95

Parietal Lobe

Answer 95

Parietal Lobe Functions: Processes sensory info (touch, pressure, pain, temperature) Spatial awareness Integrates sensory input from various parts of the body

Question 96

Occipital Lobe

Answer 96

Occipital Lobe Functions: Processes visual information from the eyes

Question 97

Temporal Lobe

Answer 97

Temporal Lobe Functions: Processes sounds and language (Wernicke’s area) Memory formation Understanding speech

Question 98

mri v CT

Answer 98

produces a higher resolution image meaning more detail can be seen- MRI provides higher resolution because it gives more detailed contrast between soft tissues by detecting differences in water content, whereas CT scans have lower contrast for soft tissues and are less detailed overall.-MRI uses strong magnetic fields and radio waves to detect the behavior of hydrogen nuclei (protons) in water molecules — this gives very detailed information about soft tissues, especially the differences in water content between tissues. MRI can distinguish between very similar soft tissues, such as grey and white matter in the brain — something CT scans struggle with.no use of X-rays therefore less of a risk of mutations can be sued more often

Question 99

habituation benefits

Answer 99

prevents wasting energy (1) allows maximum feeding effort

Question 100

how SSRIs maintain a feeling of well being

Answer 100

SSRIs bind to {channel / reuptake} proteins (1) serotonin levels remain high in synapse (1) serotonin binds to receptor proteins in post-synaptic membrane (1) depolarisation of post-synaptic membrane (1) {action potentials / impulses / transmission} continues (

Question 101

respiratory centre following exercise

Answer 101

High CO2 in the blood stimulates the respiratory centre (1) Increase in lactate / fall in pH stimulates the respiratory centre (1) Reference to chemoreceptors in the medulla/carotid bodies/aortic bodies (1) More impulses sent to diaphragm and intercostal muscles (1) Resulting in an increase in the rate and depth of breathing (1) pH returns to normal as CO2 is removed and ventilation rate decreases

Question 102

how eyes realy info mation to the brain

Answer 102

light is decte by rod cells rod cell membrane becomes hyper polarised stops release of guatamine the inhibiotry neuro trnamitter- depolairsation of bipolar neurone impulse tranmitted along optic nere to the visula cortex

Question 103

what is the critical period

Answer 103

period of time during early development (1) when the nervous system must obtain specific experiences to develop properly (1) so that synapses are strengthened / unstimulated synapses are removed eye need to recieve visual sitmaltion to strengtehen the synapses betwen the coolumns of occular domiance in eyes and the visual cortex

Question 104

questions on human genome example

Answer 104

sequencing the {genome / genes / DNA} of people with (and without) ASD (1) identify (genes that have) {mutations / differences in sequence} (between ASD and non-ASD individuals)

Question 105

animal testing

Answer 105

Argument in favour a utilitarianism – the overall benefits of the experiments are greater than any harm done (1) welfare argument - animals can be used if they are treated well as far as possible (1) Argument against rights argument - all animals have rights (not just humans) (1) results may not be applicable to humans (1) consent argument - animals are unable to give consent (as is required for human trials) (1)

Question 106

parkinsons (mark scheme)

Answer 106

Parkinson’s symptoms arise due to low dopamine levels (1) • transmission of nerve impulses disrupted causing lack of control of {muscle movements / tremors} (1) • schizophrenia drugs lower {neurotransmitter / dopamine} levels (1) Plus two from: • therefore less dopamine in synaptic / knob secreted into cleft / diffuses across cleft (1) • therefore less dopamine available to bind to receptors (1) • therefore no/little change in membrane structure / permeability of post– synaptic cell (1) • therefore fewer sodium ions enter postsynaptic cell (1) • therefore less depolarisation of postsynaptic cell (1)

Question 107

ethical issues

Answer 107

undeveloped nervous system so don’t feel pain and there aren’t ethical issues (1) • unethical to use any living organism in an experimental procedure (1) • relativism would state that it is acceptable under certain circumstances to use invertebrates (i.e. if there is potential benefit to human health) (1) • absolutism promotes use of invertebrates under any circumstance or under no circumstance (1)

Question 108

what is the HGP

Answer 108

all the {DNA / genes / eq} of (the human species)

Question 109

ethical issues of HGP

Answer 109

1. idea of discrimination e.g. insurers might have access to a person’s DNA / 2. idea of who decides whether a person is tested / 3. idea of need for confidentiality / 4. expensive medical treatments might be restricted / eq ;

Question 110

how HGP helps develop specific medicine

Answer 110

1. idea that (Human Genome Project) identifies allele related to melanoma e.g. mutant allele, aberrant allele ; 2. idea that drug targets this allele ; 3. (mutant) allele can no longer express itself / eq 4. idea of drug preventing translation ; 5. idea that such a drug is more effective

Question 111

wha