OCR GCSE Biology, B4 (Homeostasis)

Chapter B4 of GCSE Biology, Exam Board OCR

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B4 Homeostasis
Homeost
asi
s
is
keepi
ng
a steady state
insi
de
the
body
Thi
s i
nvol
ves:
Keeping
a const
ant
b ody
tempe r
ature
Keeping
the
corr
e ct
l
evels
of
w at
er and
salt
Contr
oll
ing
the
amo unt
of
n ut
ri
ents
su ch
as
g l
ucose
Breat
hing
in
enoug h
oxygen for
r
e spi
rat
ion
Remo vi
ng wast
e products
fr
om t
he body
Cont
rol
Syst
ems
Thi
si
sd
oneb
y
control systems.A
l
l
cont
rol
syst
ems,
bot
ha
r
ti
fi
ci
al
andi
nt
heb
ody,
have:
A
recept
or,
which
detects the stimuli
(ch ange)
A
processi
ng
ce nt
re,
w hi
ch
receives the information
An
eff
ector
,
w hi
ch produces an automatic response
Ani
ncubator
isa
na rt
if
ic
ial
cont
rol
sy
stem.
It
hasa
thermostat,
whi
chd
et
ect
st
he
t
emp er
ature(
recept
or)
. Wh ent
he
t
emp er
aturef
al
lst
ol
ow,
theh
eater
i
s t
urned
off
(
e f
fect
or)
.
Negative feedback i
s a cont
rol
syst
em w h er
e a n y c hange is
r
everse d.
For
examp let
her
mo stat
s
workb
yn
e gati
vef
eedback
i
fthe
t
emp eratured
r opst
ool ow
itt
u r
ns
t
heh
e atero
n ,
i
f i
t get
st
ooh
o t
it
t
urns t
h e
h eater
off
.
Antagonistic effectors have
opposite effects, f
or e xampl
e
accel
e ratora
n db
r eakso
nac
a r.
Thi
s ma kes t
he response more
sensitive.

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Enzymes
Enzymesa
rec
a t
alyst
s
they
speed up chemical reactions.T
h eya
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ep
rotei
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arge
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ec ul
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o mee n zymesb
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ot
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Temper
atur
e
Y our
bo dyg
a i
n sa
n dl
o oses
heat
toth ee
n v i
ronmen t
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owh ot
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War
ming
up
Shiver
ingw
a r
msu pt
heb
odyb
yma
kingmu
sclec
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contract quickly,
t
husr
espi
ri
n g
fast
era
n d pr
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h i
ch keeps us warm. I ti
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Hai
rss
tandu
po
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Heat
st
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H e at strokeo
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or
exa mp l
ei
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es. C oreb
o dyt
emp e ratur
eso
f abov e 42 degrees Celsius af
fec tst
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atur
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apidl
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Di
ff
usi
on
D i
ffu si
oni st
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v erall
mo v
e me nt
o f
pa rti
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rom high concentration
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h i
so cc urs
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ecu l
es in gase s an d
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a ndomly,a
n d
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D i
ffusi
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Wat
er
Ani
ma l
st ha tl
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he sea do not
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yh
a veap
r oblem w i
thw a terb
a lance ,
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Ki
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Ki
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