ws-gr12-msrevision igcse

8/12/2019 ws-gr12-msrevision igcse

http://slidepdf.com/reader/full/ws-gr12-msrevision-igcse 1/3

1. (a) 1. nature of abnormality e.g. bleeding, ref. to density;

2. {location / eq} of abnormality;

3. {extent / sie/ eq} of abnormality;

!. li"ely #roblems e.g. accessibility for surgery; 2 max

(b) 1. (found in) different {regions / eq} of brain / eq;

2. t$e rig$t $and brain $as {more / t%o/ eq} abnormalities;

3. different areas of brain $a&e different functions / eq;

!. {sym#toms / eq} de#end on region of brain affected / eq;

'. idea of different ty#es of abnormality can cause different sym#toms; 2 max

(c) 1. detects le&el of oxygenation of t$e blood /measures c$anges in blood flo%

%it$in brain / eq;

2. {increased flo% / more oxygen / eq} suggests increased acti&ity / eq;

3. study brain acti&ity related to {stimuli / tas"s / eq}; 2 max

(d) W X Y Z

![10]

2. (a) 1. de#olarisation of adacent {membrane / eq} / eq;

2. c$anges * across membrane / eq;

3. o#ens sodium {gates / eq};

!. sodium ions mo&e into (t$e neurone); 2 max

(b)

Position on Permeable to Permeable

diagram sodium ions to potassium

ions

+ ;

* ; 2

Al-NAjah Private School 1



(c) 1. correct {reference to / descri#tion of} diffusion gradient (of #otassium

ions);

2. correct {reference to / descri#tion of} electroc$emical gradient;

3. increased #ermeability (of membrane) to #otassium ions / eq;

!. reference to #otassium {gates / eq} o#en / eq;

'. reference to sodium {gates / eq} closed / eq; 3 max

(d) 1. * less negati&e / eq

2. idea t$at t$e membrane remains #ermeable to #otassium ions;

3. #otassium ions {mo&e because of c$arge difference / eq};

!. into {ner&e cell / neurone / axon / eq};

'. idea t$at #otassium ion is remo&ing a #ositi&e c$arge (from t$e outside);

. idea t$at equilibrium is establis$ed e.g. diffusion gradient

balanced by #otential difference; 3 max[10]

3. (a) -erebral $emis#$eres;

+cce#t cerebrum

eect $emis#$ere, cerebellum

y#ot$alamus;

0edulla oblongata

+cce#t medulla 3

(b) +%ard one mar" for eac$ of t$e follo%ing #oints in

context to a maximum of two mar"s.

1. ocality

2. ie

3. $at brain functions mig$t be affected 2[5]

4. (a) (i) ← 1




(ii)

Relay

neur

one

Motor

neu

ron

e

Sensory

neu

ron

e

-ell

-ell !

1 mar" for eac$ ro%. *o not a%ard t$e mar" if t$ere is more

t$an one cross in t$e ro%. 2

(b) (i) etinal

+cce#t transretinal, retinine

eect cis retinal, retinol 1

(ii) +%ard one mar" for eac$ of t$e follo%ing #oints in context to a

maximum of t"ree mar"s.

1. o#sin binding to membrane/eq

2. cation c$annels closed

3. sodium ions cannot enter cell by diffusion

!. acti&e #um#ing

'. of sodium ions is unaffected

. net loss of sodium ions 3

(iii) $y#er#olarised

+cce#t $y#er#olarisation

eect bleac$ed, de#olarised 1[8]


ws-gr12-msrevision igcse

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