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Chapter 13 - The Nervous System -
Sensitiv Sensitivity ity -> -> abilit ability y to resp respond ond to to stimul stimulus us by moving moving in a way way that that
-
benefts itsel Nerv Nervou ous s syst system em -> cont contrrols ols body body’s ’s activ activit itie ies s + how how it react reacts s to surrounding Parts: brain nerves spinal cord sense organs Sense organs -> help to ad!ust rapidly to changes in envi + • •
•
enable parts o body to coordinate with one another "nvoluntary vs voluntary action "nvoluntary -> automatic a nd not controlled
consciously #oluntary -> controlled consciously $uma $uman n ner nervo vous us syst system em -> %NS %NS + PNS PNS %entral nervous system -> brain + spinal cord Peripheral nervous system -> cranial nerves spinal nerves
-
• •
-
•
sense organs Sense organs -> receive stimuli &receptors' inorm %NS by
•
sending nerve impulses transmitted through nerves (uscles -> e)ectors -> responds to the stimuli detected by
the sense organs Nervous tissue * types o neurones Sensor Sensoryr yrecep eceptor tor -> transm transmit it impuls impulses es rom rom sense sense •
•
•
organs to %NS ,elayintermediate -> transmit impulses rom sensory
neurons to motor neurons in %NS (oto (otor re) e)ec ecto torr -> tran transm smit it impu impuls lses es rom rom %NS %NS to
e)ectormuscles Neuro Neurones nes -> hv cell cell body body &nucle &nucleus us + cytopl cytoplasm asm'' + nerve nerve fbres &etension o cytoplasm rom cell body' (otor neurone structure %ell body Nucleu eus s cyto cytopl plas asm m cell cell su sur rac ace e memb membran rane e Nucl
other organelles "rregular
shape .endron Nerve
fbres
that transmit impulses to cell body end branches -> dendrites receive nerve impulses rom other neurones
/on
nerve fbres -> transmit impulses away rom cell
body long in motor neurone (yelin sheath layer o atty substance that insulates the aon Node o ,anvier regions with no myelin sheath nerve impulses -> cant be transmitted through myelin sheath -> hv to 0!ump’ rom one node to
•
the net -> aster transmission /on terminals motor neurone -> transmit nerve impulses to e)ector (otor end plate !unction between aon terminal and muscle fbre nerve impulses transmitted by chemicals ->
stimulate muscles Sensory neurone structure circular cell body one long
•
dendron short aon Synapse -> !unction between two
neuronesneurone
e)ector &muscles glands' nerve impulses
through •
and transmitted
!unctions
by
chemicals
called
neurotransmitters Nerves -> bundle o nerve fbres in a sheath o connective tissue
emerge rom brain &cranial nerves' or spinal cord &spinal nerves' contents: sensory nerve fbres only &rom sense organs' motor nerve fbres only &to e)ectors' mied fbres &both sensory and motor nerves' eg1 spinal nerves
neurones sensory neurones transmit impulses to spinal cord
•
rom receptor ganglion -> small swelling -> contains cell body o
sensory neurone #entral root &spinal cord' -> contains nerve fbres o motor neurones motor neurones transmit impulses rom the spinal cord
•
to e)ector Sensation -> eg1 when touching a piece o ice you eel the coldness impulses transmitted to brain receptor -> sensory neurones -> transmitted across a
synapse to relay neurones o spinal cord &grey matter' -> transmitted up the white matter o spinal cord -> •
orebrain #oluntary action -> eg1 deciding to raise hand to answer 6uestion in class impulses transmitted rom brain orebrain -> transmitted across a synapse to relay
neurones o spinal cord -> down the white matter o spinal
cord
->
grey
matter
o
spinal
cord
->
transmitted across a synapse to motor neurone -> -
e)ector ,e4einvoluntary action immediate response to specifc stimulus without conscious •
•
control re4e centres -> brain and spinal cord cranial re4ees -> controlled by brain occur in head
region e1 pupil re4e blin7ing salivation spinal re4ees -> controlled by spinal cord eg1 7nee !er7 re4e sudden withdrawal o hand when touching
•
hot ob!ect Nerve impulses pathway receptors &stimulate
produced'
->
sensory
nerve
endings
neurone
->
impulses
spinal
cord
&transmitted across a synapse to relay neurone then across another synapse to motor neurone' -> motor
neurone -> e)ectors &eg1 muscles contracts or relaes •
gland secretes or stop secreting substances' ,e4e arc shortest pathway which nerve impulses travel rom
receptor to e)ector in re4e action consists o: receptor &sense organ' sensory neurone %NS motor neurone e)ector &musclegland'
Chapter 14 - The Human Eye -
Structure o eye 8ront part o eye Pupil -> hole in centre o iris1 allow light to enter eye •
damaging the retina &s6uinting' spread tears over the cornea and con!unctiva to wipe dust particles o) the
cornea &blin7ing' Sclerasclerotic coat -> tough white covering o the eyeball continuous with cornea protects eyeball rom
mechanical damage %on!unctiva -> thin transparent membrane covering the sclera mucous membrane secretes mucus to 7eep the ront o the eyeball moist continuous with s7in o
eyelid "ris -> circular sheet o muscle contains pigment or eye colour control the amount o light entering the eye
•
&by < sets o involuntary muscles = circular and radial' "nternal structure o the eye
%iliary body ; thic7ened ;
region
the ront end o choroid contains ciliary muscles ->
control
curvaturethic7ness
at
lens %horoid ; middle
layer
the o
o
;
eyeball &between sclera and retina' pigmented blac7 -> prevent internal
;
re4ection contains blood vessel -> bring < and nutrients
light
to eyeball remove metabolic waste products #itreous chamber ; space behind lens flled with vitreous humour -> transparent !elly li7e substance 7eeps eyeball
frm helps reract light to retina 8oveayellow spot ; small yellow depression in retina directly behind ;
; ; ptic ;
lens where image are normally ocused enabled a person to hv detailed colour vision in bright light has greatest concentration o cones has no rods nerve nerve -> transmit nerve impulses to brain when
photoreceptors in retina are stimulated 2lind spot ; region where optic nerve leaves eye ; no cones and rods -> not sensitive to light ,etina ; innermost layer o eyeball light-sensitive layer ;
where images are ormed contains light-sensitive cells &photoreceptors' = rods and cones -> connected to nerve endings rom optive nerve cones -> see colours in bright light o rods -> see blac7 and white in dim light o
?ens ; ;
transparent circular biconve elastic thic7nessshape changes to reract light
to retina /6ueous chamber ; space between lens and cornea
;
flled with a6ueous humour -> transparent watery 4uid 7eeps the ront part o the eyeball
frm helps reract light into pupil %ornea ; dome-shaped transparent layer continuous with ;
•
sclera reracts light rays into eye -> causes most o the
reraction o light in the eye Suspensory ligament ; connective tissue -> attaches edge o lens to ciliary body %iliary body ; thic7ened region ront end o choroid ; ciliary muscles -> control curvaturethic7ness o
lens 8unctions o photoreceptors in retina &rods and cones' %ones ; enable us to see colours in bright light ; * types: red blue green -> hv di)erent
pigments that
absorbs light
wave
o
di)1
wavelengths do not wor7 well in dim light
; ,ods ; more sensitive to light than cones ; enable us to see in blac7 and white in dim light ; sensitive to light with low intensity -> hv pigment called visual purple -> bleached when eposed to bright light ta7es a while to be reormed in order to see in the dar7 -> re6uired
•
vitamin / -> defcit -> night blindness $ow does iris control amt o light entering the eye@ siAe o pupil determines the amt o light entering the
eye -> amt must be right or a person to be able to see
clearly siAe o pupil -> controlled by < sets o involuntary and antagonistic muscles = circular and radial muscles o
the iris ; circular -> arranged in a circle around the pupil ; radial -> arranged radially circular muscle contract radial muscle dilate -> pupil becomes smallerconstricts -> reduce amt o light entering the eye
interprets -> see the ob!ect upright the same siAe and •
ront to bac7 8ocusingaccomodation -> ad!ustment o the eye lens so that clear images o ob!ects at di) distances are ormed on the retina
necessary -> can see ob!ect at di) distances clearly ocusing -> ad!usting the thic7nesscurvature o lens -> allow light rays to be ocused on retina ocusing on distant ob!ectB ; light rays almost parallel to each other -> no ;
need much reraction -> thinner lens process: ciliary muscles rela -> suspensory ligament become taut pull on the edge o lens -> lens become