Unit 6 - Organisms respond to changes in their internal and external environments
Summary
Summary The entire specification for AQA A-level biology topic 6 homeostasis
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Course
Unit 6 - Organisms respond to changes in their internal and external environments
Institution
AQA
I meticulously created these AQA A-level Biology notes during my studies, and they helped me achieve an A*. Organised according to the 8-unit specification, each unit has its own dedicated A4 page with all relevant information, making your study sessions streamlined and efficient. Within each unit,...
system .. inside =-
survivalof
environmental
by responding to .
S g ·
uses voltage
- due to polarisation theres a 1 in voltage across
changes
anmumbrane mot
- linked Nat
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: -
D a
externali n e a sy
· Channels
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-
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set point
internal factor
: levelled va l u e which a
conditions within
hey indecator
organisms that
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must be maintained
maintained at for heathly functioning + survival
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e
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·leternal
: homeostas a
-upon stimulation the ancon becomes
.
:
detectable changes in the environment ·
cenwal nevous
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Stimuli
identify
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·
receptor R. system Shimur > Nat channels to open
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atferentpathwaymessagewhichgeommruointegration+
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o re Nations ona a
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henesis : movements in random directions in respone to unfavourable conditions
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REPOLARISATION
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:
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response DESCRIBE EXPLAIN
nari
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um vanition
INVERTABRATES v
·
simple animals respond to stimul in the environment by tascist henesis
Imperature IN HIBATOR + EXCITORY
· t a i d animals to escape predators find food locate habitats
they are involuntary movements , ,
ascon wider = sistance +
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s
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Salvatory
TROPISMS + FLOWERING PLANTS conduction.
as
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B SYNAPSES
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:
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EXPERIMENTAL EVIDANGE FOR AUXINS +TROPISMS
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auxins from the blocks cause complimentary receptors 2
potential is created plate
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3 diffuse into the motor newone end
.
4 vesicles containing accrylcholine migrate + tuse
- acetylcholinesterase is
with the pre-synaptic membrane .
5 accrylcholine is released by exocytosis
.
6. accrylcholine diffuses across cyet and binds to
R ECEPTORS So A P can . repolarize
>
-
receptors on the Sarcolemma
Nat channels open on sarcolemma
.
. Nat
8 diffenses into muscle fibers : Sarcolemma
Stimuli
-
products of acetylcholine
specific stimulus-electrochemical energy used
detect and are
deppowithtransmitted down T-Lubes
receptors t convert
:
they ,
energy from in neurones ->
impuses is reabsorbed into pre S M . .
a .
outside receptor 10 .
Sarcoplasmic recrilium depolarises and releases
HOW DO RECEPTORS WORK ? cal+ into sarcoplasm
ECF
SYNAPSE FUNCTION Muscle contac ts
energy causes stimuli linked Nat channels to open and Nat more into receptors by
i
11 .
I . Stimulus .
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.
2
if stimulus energy isn't strong enough , enough Natchannels open to build a 2 temporal summation , weal stimuli doesn't release enough newowansmitters are pleased > depolarisation
spartial us -
generator potential that breaches threshold level of depolovisation
enough c a n be made by : Temporal = 1 newore stimulated repeated or spatial : several new ores combine
.
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3 excitory vs inhibition newotransmitters. exitory synapees
all or . ... more -
.
by facilitated diffusion (further depolarisation ( hyperpolarisation by
+
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.
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Nat Microscopic muscle structure
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time
receptor generator potentials
membrane has
resting potential NERVOUS COMMUNICATION
a
Sacomees
nation
PACINIAN CORPUSCLE -
concious
I
Slow or fast twitch muscles
pin ·
Stimula ·
slow:specanized for slow contractions
and are adapted to
long perioder
A in contaction of excercise as they don't fatigue
~
region
micic
sarcomere shorter
Features
-
unconcious :
Earned r.
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log
fast 12 Synapes + 1 neurotransmitter junc
ent
· tion SLIDING FILAMENT THEORY
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·
short-lived blood vessels + Lots of Mitochordia
Sig potential
Localized 1 when an action arrives at a NMJ
fast : adapted to release energy quickly
-
aplasmic r liumdelarisandrassat
a
·
into scrops
-
autonomic (no decisions made , protec + is s ? during intensive exercise. Thick
-
aids survival
4. me myosin binding sites on actin
this exposes myosin filaments , high conc. glycogen
potential transmitted and lots of
hydrolysed enzymes for
action S N to CNS
as neve impube along Pi to release energy that's used to anerobic
·
tip is by Alpase > ADP +
. .
.
5
-
RODS + CONES -recoch' myosin head-recovery stone respiration and store of phosphocrea
tin so ATP can regenerate
6 myosin head binds to actin filiment using Aip- cross bridge
-
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.
·
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pulling actin fillment oor a
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=>
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breaks
·
the remind at me back contains
of the
eye photoreceptors (rods/zones) detects light
of Cat and ATP in muscle contraction
t
how do photoreceptors work ? Roles
lightsensitive pigments : rods (Rhodopsin) and Comes (lodopsin) ca?
"
·
photoreceptors contain =
: Calt is released by sarcoplasmic recilium into sarcoplasm
when pigments absorb light, they undergo a chemical change called bleaching
pomyosintomoves
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on
·
during this reaction energy is released providing a stimule to increase the permeability acrin to
of photosystem membranes to Nat
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·
and to the brain
newone to optic neve
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i
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s arcoplasmic few
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Light
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apper an ce
diagram I synapses
diameter minne micher
distributed concentrated in the torea
distribution evenly
on the peripheral sparsely found
in peripheral
revina
on
pariso theren, is
sensitivitighvi e
, absent
partsofretina
om is mechanism that amplifies a change away
positive feedback = a
forea
insensitive
+ blind spot
to colour ensitive ourtype
a
HOMEOSTASIS ·
from me normal level ( not involved in homeostasis)
gives a rapid activation of a process (labow) + associated
in me CSM
or
colour I black and while w i l a breakdown of control systems .
Light
time of day used for dayvision involves maintain internal environment within restricted limits
used for night vision homeostasis = a physiological control systems mat
connectivity many rodsjoin to one each cone joins to one bo
a
↳ Vital for cells to l i s t -
> enough ATP avoid
to damage + enzymes remain at optimum conditions
neurone
Light sensitivity ② stimulus-change
sensitivity
Drama a
Low
high light sensitivity increase in BGC
Response to an
acuity low visual acuity high visual acuity
langer hands
↳
defeated by B cells in the pancreas islets of
· : less maina = Bceus secrete insulin
compliment, i s
high light intensities
light intensitis
low in
-
·
more control 3-
bloodguecoebybinding
insurances
to
pigment bleaches even i n
-
·
types of control 4 more guico se carriers placed into plasma CSM
dim
several rods
Light
with
only bright light T HE HIDNEYS funcion of me hidneys : excretion of area reversedina =temperatu
a 5 more guicose entus a l l by facilitated diffusion
synapse
·
avaenmm
on e cone
synapses osmoregulation - mis
one bipolar neurone so with one bipolar = pu , vol , pressure of blood
-
blood guelose
containse
ession ↳
many weak generator new one so
-
water potential
potentials combine to reach
generator J
potential must reach
is
striggean ai
rations pancrea
thresholdalon
a Response to a decrease in BGC
&
low
several rods
visual acuity
synapse with
Dipolar neurone
↳ deepanrasistlageman
-
see
highVisuaatten a receptors on liver cells
newnessobranas
bipa 4
·
to stimulate
activating enzymes
-
-glucose)
guconeogenes agycogen
rod light falls upon atty ↓ acids + amino acids + glycol
brain can tell whee
>
-
to glucose
indistinct images tell + distinct image
Light
1. ultrafiltration The role of adrenaline :
CONTROL OF RATE >
- myogenic a
conro ·
secreted
by adrenal glands when BGC ↓ below normal , stess + exece
pion
2 adrenaline
.
cycle
binds to its
complimentary receptors and activates
1 as the
left ventricle contracts ↑ hydrostatic pressure adenylyl cylase enzyme in liver cells
.waeandalso
2
plamcomponent
gomea b
3- activated adenyly cylase converts ATP into AMP and CAMP
aa
-Campasasodaymessengemaiacivares
n
protein
sends impuses and epimeli of ponocyte to form filtrate
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which spread a
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,
through me
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have + guylogen same
arria : sincatrial waves of depolarisation
stimulate contraction
rays
-
arrio verticula · diet t in
au values sugar-sucrose digested by
11 11
no
a TIDM T2DM rapid
5.
- enzyme us stach w i r 2
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problems in Diabetics production of glucose ingut . BJC
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= TYPE insulin
ensuring unidirectional
blood How = aorra Mitochondria
-
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&m
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ascending
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sympameric motor
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parasympathetic m o to r
①
has LionSJ/T longer the loop ofh eute binds to receptors and actives the
6 the enzyme
SA node receptors SA node receptors
pini
deeper into the meduled
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3.
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