ALL my Biology Notes
Find your GCSE
science course for more help links to revision notes
Use your
mobile phone or ipad etc. in 'landscape' mode
This is a BIG
website, you need to take time to explore it [Website Search
Box]
email doc
brown
(a)
Introduction to the nervous system
The nervous system and hormones enable us to respond to external changes
- external stimuli.
The nervous system and hormones also help us to control
conditions inside our bodies.
Nerve cells (neurones)
are those that communicate with each other in complex systems that
include information messaging to all the structures of the body like
organs, glands ad muscles etc.
Infancy and childhood are critical
periods when most of these vital nerve cell connections are made and
they are crucial to our physical and mental development and general
wellbeing.
A 'simple' single celled organism can
only respond to its immediate environment, but the cells of
multicellular organisms must be able to communicate with each other
before responding to any internal or external changes.
Therefore complex multicellular
systems have evolved nervous and hormonal 'messaging' systems.
The nervous system enables humans to
detect changes in their situation, react to
their surroundings and coordinate their behaviour responses - which may be
deliberate from the conscious mind or autonomic, meaning an automatic
response of the nervous system like the reflex arc (described in detail
later).
Organisms need to be able to
respond to stimuli from changes in their environment, primarily to
survive!
Any change in your surroundings
eg temperature, visual, sound etc. is potentially a detectable stimulus to
one of you sensory organs eg skin, eyes, ears etc. The stimulus might be
chemical, light, pain, position, pressure, sound, temperature, touch etc.
You have five different sense
organs ears, eyes, nose, skin and tongue which contain receptors (groups of
cells) that are sensitive to particular stimuli.
In the receptor cells the
stimulus input is converted into an electrical nerve signal - an electrical
impulse which is sent to the central nervous system (CNS)
Although complex, the nervous
system has two main groups of nerve cell connections:
(i) The
central nervous system
(CNS) for vertebrates
(animals with backbones) consists of the
brain and spinal cord.
The CNS is effectively the
control centre.
(ii) The
peripheral nervous system
consists of all the rest of the nerve cells (neurones) that connect to
all the rest of the parts of the body.
All of these peripheral nerve
connections lead to and from the brain and spinal cord, so all
the messaging from anywhere in the body must occur by way of the
CNS.
The reflex actions that can
happen by virtue of our central nervous system help prevent injury from
various sources in potentially dangerous situations - details later.
With our varied receptor cells,
we as humans can react to our surroundings and coordinate our
behaviour to our best advantage - throughout millions of years all
animals exhibit survival adaptations.
TOP OF PAGE
and sub-index
(b)
Reminder - comparing two control systems
(hormones and nerve cells)
The nervous system and endocrine hormone
system are two quite different mechanisms of control in the body,
BUT, in principle they function in similar ways AND interact with each other
too.
The endocrine system uses chemical
molecule messengers (hormones) to communicate information.
See
Homeostasis - introduction to how it functions (negative
feedback systems explained)
and
Hormone system - Introduction to the endocrine
system - role of thyroxine
gcse biology
The nervous system uses electrical
impulse messages to communicate information
(This page).
Endocrine hormone system |
Receptor detects changes in the environment |
Chemical messenger - hormone molecule
signal
Slower, but acts for much longer - carried in
blood to all organs, but only affects target organ |
Coordination centre A gland
e.g. pancreas
Receives signal and processes information |
Chemical messenger - hormone molecule
signal
Slower, but acts for much longer - carried in
blood to all organs, but only affects target organ |
Effector
A gland that secretes a hormone to restore an
optimum level or trigger some other chemical response |
Nervous system |
Receptor detects changes in the environment |
Electrical signal - nerve impulse
Rapid and short duration - carried in nerve
fibres to specific locations like muscles |
Coordination centre Brain or
spinal cord
Receives signal and processes information |
Electrical signal - nerve impulse
Rapid and short duration - carried in nerve
fibres to specific locations like muscles |
Effector
Muscles that respond to the signal |
Comparing nerve
and hormone functions
Hormones effectively act as
'chemical messages' to trigger particular biochemical reactions and their
effects are ..
more general around the body, but
tend to affect particular cells in particular organs,
and relatively long-lasting compared to eg the
fast but short-term nervous impulses and responses of a reflex arc.
Compared to the hormone
system of response and control in the body, nerve signals are
electrical (not chemical), the nerves act very fast - a short burst of a
nervous impulse for a short time, acting from one precise area to
another in the body.
TOP OF PAGE
and sub-index
(c) Function and
types of receptor cells
Cells called receptors
can detect stimuli (changes in
the environment outside the organism).
Receptor cells and the stimuli they detect include:
Light receptor cells in the
eyes that are sensitive to light,
the light energy creates electrical signals that are sent to the brain for
'processing'.
Light receptor cells, like
most animal cells, have a nucleus, cytoplasm and cell membrane.
Sound receptors in the ears that are sensitive to sound
vibrations in the air
There are also balance receptors in the ears that are sensitive to changes
in position and enable us to keep our balance.
The receptors on the tongue are
sensitive to chemicals and enable us to taste, and therefore detect, a wide
variety of different foods (bitter, salty, sour, sweet chemical stimuli etc.) or anything
else in contact with the tongue - good or bad!
The receptors in the nose are
also sensitive to chemicals and enable us to smell all sorts of different
things which may be a pleasant or unpleasant experience.
The receptors in the
skin that are sensitive to touch, pressure, pain and to
temperature changes.
Receptors are sometimes grouped
and function as one unit i.e. a sense organ.
TOP OF PAGE
and sub-index
(d) The structure
and function of the central nervous system (CNS)
All vertebrates, those animals
with backbones, have a CNS consisting of the brain and spinal cord.
Information
in the form of an electrical signal, from receptors, passes along cells in nerves
(neurones) to the brain through the central nervous system (spinal
cord ==> brain) and ...
... the brain then coordinates the response,
... reflex actions are
automatic and rapid,
... and often involve sensory,
relay and motor neurones.
The 'components' of the nervous
system
As mentioned already, the CNS
of vertebrates consists of the brain and spinal cord only.
The CNS is then connected to the
body by sensory neurones and motor neurones.
Brain reminder!
The
spinal
cord is a long column of neurones (nerve cells)
that runs from the base of the brain down through the spine -
physically protected by the bones of the vertebral column.
It is the spinal cord that
relays information between the brain and the rest of the body.
The electrical nerve impulses
('information') are relayed via sensory neurones, relay neurones and
motor neurones AND pretty fast too in a fraction of a second!
The structure and function of
different parts of the nervous system are described below.
Nerve cells, also called neurons/neurones, are,
elongated cells that carry electrical signals or impulses all
around the body.
The diagram on the right
shows the basic structure of a nerve cell or neurone.
Neurones can be very long!
The cell body, containing the nucleus, is about 0.1 mm across,
but the axon can be a meter long (1000 mm) - this single long
nerve cell acts faster in relaying electrical signals than a
series of individual smaller cells connected together.
The axon, which carries the
electrical signal, is covered in a
protective electrically insulating myelin sheath (not shown
here, but
see other cell diagrams below).
The cell body connects to
lots of other neurones.
Some general
points about nerve cell (neurone) structure:
(i) All
neurones,
like most other cells, have a cell body containing the nucleus in a
membrane surrounded cytoplasm and other subcellular
structures.
The cell body of all
neurones is found in the central nervous system (CNS)
The cell body has
fine tip extensions called
dendrites/dendrons that connect to other neurones and carry
the electrical impulses of the nerve signals.
As well as the
dendrites for nerve cell communication, neurones have an
extended shape so they can carry electrical nerve
impulses from one part of the body to another.
(ii)
Dendrites
(dendrons) are branched protoplasmic extensions of a
nerve cell that propagate the electrochemical stimulation
received from other neural cells to the cell body, or soma,
of the neuron from which the dendrites project.
(iii) An
axon
(nerve fibre), is a long, slender projection of a nerve cell
(neuron), in vertebrates, that typically conducts electrical
impulses known as action potentials away from the nerve cell
body.
(iv)
Neurones are
relatively long cells which helps the fast electrical
impulse transfer between one neurone and another - one long
nerve cell transfer is faster than through lots of
smaller-shorter cells.
(v) The
myelin sheath
is a fatty electrically insulating tissue layer around the
axon connections between neurones. The myelin sheath also
helps speed up the electrical impulse transfer and the axon in the neurone cells
carries the electrical signal - if there was no myelin insulation, the signal will be lost.
Axon endings (axon
terminals) are button-like endings of axons through which axons make
synaptic contacts with other nerve cells or with effector cells.
Receptors - groups of
cells that respond to a particular stimulus - e.g. they detects stimuli such
as heat, light, pain, sound, taste, smell, pressure (see previous
section for more details).
Receptors often form part of
a larger complex organs e.g. the taste buds on your tongue or
the retina cells of the eye which respond to light.
Receptors start what is known
as the 'reflex arc' described in the next section.
Sensory neurones - the
nerve cells that transmit the electrical impulse signal from the receptors in
the sense organs to the spinal cord and brain of the central nervous system.
Sensory neurone structure
A long dendron carries nerve
signals from receptor cells to the cell body which is at the
centre of the neurone.
A shorter axon then transfers the
electrical impulse from the cell body to the axon terminals that
connect to the CNS.
The CNS processes the
information and coordinates how the body should respond to the
information received from nerve impulses.
Relay neurones - the
nerve cells that transmit the electrical signals through the CNS (brain +
spinal cord) from sensory neurones to the
motor neurones.
Relay neurones have lots of dendrites
spreading out that carry
the nerve signals from the sensory neurones to the cell body and an
axon carries the nerve impulses to the motor neurones.
A
synapse
(diagram below) is a connection
between two neurones eg the thin gap of the junction between a sensory neurone and a relay
neurone, it enables the electrical impulse signals from receptors to reach the spinal cord
and brain (i.e. the central nervous system) and on to the effectors.
Between the end of one neurone,
and the start of another, chemicals are released in the gap that rapidly
diffuse across the gap in the synapse, triggering the transfer
the electrical signal.
You can think of the released
chemical as 'messenger molecule', and technically it is called a
neurotransmitter because it triggers the electrical
signal from one nerve cell (neurone) to another.
The transfer of the nerve
impulses is quite fast, but the diffusion of the
neurotransmitter molecules across the synapse gap does take a
short time, so things are slowed down a bit.
Synapse
structure
Neurotransmitter -
chemicals produced that transmit the electrical signal across a synapse gap
between one neurone cell and another (see text and diagram under synapse).
Motor neurones - the
nerve cells that transmit the electrical signals from the central nervous
system of the brain and spinal cord from one neurone to another to the
effector cells of the muscles or glands (see diagram above).
The signals trigger the
appropriate response by the muscles (e.g. contract) or gland
(e.g. hormone secretion)
Motor neurone structure
A motor neurone has many short dendrites
that carry
nerve impulses from the CNS to the cell body, then one long axon
carries the signal from the cell body to the effector cells.
The branches (dendrites)
connect with other nerve cells.
Receptor cells
have already been discussed.
Effector cells
in the muscles
or glands that respond in a variety of ways to the electrical signal from
the brain or spinal cord (CNS) - the cells respond to the nervous impulses
and cause things to happen.
Nervous impulses cause
muscles to respond and contract e.g. from receptors
detecting heat or pain.
Nerve impulses cause
glands to secrete hormones - chemical messengers to effect a
response.
Reflex arc
Effectors complete what is
known as the 'reflex arc' described in the next section
which fully describes the sequence:
stimulus ===>
receptor ===> CNS coordinator ===>
effector ==> response
TOP OF PAGE
and sub-index
(e) The central nervous system (CNS) and
reflex actions - the reflex arc
You should know and understand the role of receptors,
sensory neurones, motor neurones, relay neurones,
synapses and effectors in simple reflex actions.
The
CNS coordinates the response
when it receives information from the receptors and causes the effectors
to respond to the stimulus detected e.g.
(i) suppose you start to cross
the road, but your eye detects a car coming along - the visual
stimulus.
(ii) Your receptor cells
(retina of eye) send nerve impulses to the brain which builds up an
image of the environment - including the approaching car.
(ii) The sensory neurones
convey the information from the receptor cells of the eye to the
CNS.
(iv) The CNS then decides what
to do e.g. how you will your brain respond to the
stimulus detected.
(v) The CNS then sends impulses
via the motor neurones which transmit the 'instructions' from
your brain, through the spinal cord, to your muscles.
(vi) Your effectors, that
is your muscles, contract and you step back from being hit by the
car, job done!
In this example both your brain
and spinal cord of your CNS are involved, and you have made a
conscious decision to avoid being hit by the car.
BUT, sometimes your body reacts
without any apparent conscious thought, but the CNS is still
involved either through the spinal cord or an unconscious part of
the brain (see next section on the reflex arc).
Reflex actions are
automatic responses to stimuli detected by the receptors in the organs of
the body.
Reflex actions are rapid automatic
responses to particular stimuli, that do NOT involve the conscious
part of the brain - they are an important defence
mechanism of our body to prevent injury eg
You don't have to think about
reflex actions, given a stimulus, they just happen!
Reflex action occur in simpler
organisms than humans and in evolutionary terms, they can be
considered an aid to survival,
e.g. if in danger, especially if you
get a shock - experience a traumatic situation, your body
automatically releases
the hormone adrenaline to heighten your mental and physical response
to the new situation.
If the intensity of light
impacting on your eye is too great, your pupil automatically gets smaller to
allow less light. In a dimly lit room, the opposite response occurs and your
pupil widens to let more light in.
If something hot touches your
skin, on feeling pain you immediately try to recoil from the heat source eg
on burning your hand, the muscles rapidly contract to take your hand away.
A baby grips a finger placed near
its hand - a grasping reflex.
In these reflex action situations, not
involving the conscious brain functions, the transfer of
information from the receptor to the effector is called a reflex
arc.
Know and understand that in a simple reflex
arc action
from a receptor to an effector - by way the spinal cord or an unconscious
part of the brain):
A stimulus detected by
receptors (receptor cells) causes impulses from a receptor to pass along a
sensory
neurone (nerve cell) to the central nervous system.
At a nerve junction (synapse) between a
sensory
neurone and a relay neurone in the central
nervous system, a chemical is released that
causes an impulse to be transmitted by a relay
neurone,
A chemical is then released at the
synapse
between a relay neurone and motor neurone in
the central nervous system, causing impulses to
be sent along by a motor neurone to the organ
(the effector) that brings about the response (of the effector cells).
The effector is either a muscle or a gland, a muscle
responds by contracting or a gland responds
by releasing (secreting) chemical substances called hormones.
The central nervous systems
decides what is to be done depending on what stimulus is received
Examples of reflex arc
responses:
Muscles in your arm may
contract to withdraw your hand from a heat source, sharp point
or wasp/bee sting!
Glands may secrete a
particular hormone in response to a particular stimulus eg adrenalin
in a 'flight response' from a dangerous situation.
The pupils in your
eyes respond by decreasing/increasing in size if the light level is
too high/low.
Summary of the reflex arc
sequence via the central nervous system:
stimulus ===>
receptor ===> coordinator ===> effector
==> response
and in a little more detail ...
stimulus ==> receptor cells
==> sensory neurone ==> synapse ==> relay neurone and
synapse in CNS (spinal cord or unconscious brain) ==> motor neurones ==> effector
cells/organ => response
Note the three neurones in
the reflex arc do NOT link physically, there is a gap, the
synapse, between each pair enabling lots of neurones to be
connected together.
The reflex arc action is
automatic and fast, no thinking involved - doesn't involve the conscious brain, just a rapid automatic response on the
part of your body!
Another good example is when facing
and experience a threat situation! When an insect bites your hand, the
reflex arc goes into action and your body muscles (e.g. in your arm) rapidly
withdraw your hand from the threat - descriptive details to go with the
diagram above, are set out below. CNS = central nervous system.
(i)
Stimulus
A stimulus is detected by
receptor cells.
The pain receptor cells
in your skin are
stimulated by the insect bite!
Its the same 'painful'
sequence as if your hand touches a hot surface.
(ii)
Sensory neurones
The receptor cell response
triggers a response by sensory neurones.
The stimulated receptor cells
cause the sensory neurones to send
electrical nerve signals to the relay neurones in the CNS -
impulse transmission to the spinal cord.
(iii)
Nerve impulse transmission by relay neurones and synapses
When the nerve impulses reach a
synapse (gap) between a sensory neurone and a relay neurone in the CNS
(or between a relay neurone and a motor neurone), they
trigger the release of a chemical (neurotransmitter
molecules) causing the
impulse to be sent across the gap (diagram below).
In other words, when the
electrical impulse reaches the end of the 1st neurone, it
triggers the release of chemical transmitter molecules into
the gap and they diffuse across the gap and bind to receptor
sites on the next neurone.
This triggers the 2nd
neurone to re-transmit the nerve impulse signal.
So, the synapses allow
the relay
neurones in the spinal cord to transmit the nerve impulse
from the sensory neurones to the motor neurones.
Although neurones
themselves transmit the impulses quickly because of their
electrical charge nature, synapses do slow down the
transmission of impulses because the diffusion of the
neurotransmitter molecules takes a little time.
However, the overall
process is fast, the average time for 'reflex arc' reaction
to take place is 0.25 seconds, 0.17 s for audio stimulus and
0.15 s for a touch stimulus.
(iv)
Motor neurones - pain experienced -
decision automatically made!
The motor neurons convey the
response signal to the effector cells
In this case the biceps muscle cells of
your arm, but it could be to a gland to secrete hormones.
The spinal cord of the CNS processes the nerve
signals and starts the response 'procedure'.
When the impulses reach a
synapse between a relay neuron in the CNS and a motor neurone they trigger
the release of a chemical (neurotransmitter) causing the impulse
to be sent along motor neurones.
Note that other neurones in
the spinal cord via synapses also send a nerve impulse
message to your brain after your hand withdraws - which is
when you actually experience the pain of a bite or hot surface,
but everything is so fast that your hand effectively withdraws
at the same time as you feel the pain.
(v)
Effector response
The motor neurone signals
triggers the response of effector cells.
On receiving the nerve signal
from the motor neurones, the effector cells act i.e. your
muscles contract to produce the automatic response - the rapid
recoil of your arm and hand from the vicinity of the insect or
hot surface.
If you experience danger,
the body's adrenal gland responds by secreting the hormone
adrenaline - makes you more alert and increases metabolic
rate, particularly in the muscles.
and this is how a reflex
arc works and its faster than normal conscious decision making
processes BECAUSE you don't have to think about it !!!!
(procrastination is
NOT part of a reflex arc action!)
|
For a detailed description of the
eye's iris reflex action see
The eye -
structure, function,
reflex action, vision defects and
correction
TOP OF PAGE
and sub-index
(f) Simple physical response tests
- how fast is your reaction time!
Copied and re-edited from
Reaction times and vehicle stopping distances
gcse physics revision notes
Simple reaction
time experiments
Your reaction time to a situation may be typically 0.2 to
0.8 seconds when fully alert. However your reaction time can be affected by
tiredness, feeling unwell, drugs, alcohol, in other words anything that
affects the speed of your brain function.
You can conduct quite simple experiments to test your
reaction time to a particular situation. However, since the reaction time is
too short.
(i)
Computer screen reaction test - responding as quickly as possible to
something appearing on the screen.
In this situation, the computer
software generates something up on the screen and your click the mouse
or tap the keypad in response to the visual (or sound?) stimulus.
The computer automatically times
your response by monitoring your contact with the keyboard or by
clicking the mouse - its more accurate, especially as it can measure
reaction times in milliseconds.
Computer generated stimuli give more
accurate response reaction times than e.g. the dropped ruler experiment
described in section (b) which potentially involves human error -
computer experiments avoid the possibility of the person anticipating
when the event is to happen e.g. reading the body language of someone
dropping the ruler in experiment (b) described below.
I've quickly written an extremely
simple computer programme to test your response to a X appearing on
the screen.
Response time
test: It probably only works on Microsoft platforms, and
maybe not all of them?
Your anti-virus protection might
query it, because it is a .exe file, but its written with
compiled BBC BASIC and should not pose any threat. Unfortunately I
never learned to write in a multi-platform professional computer
programming language, but I'm not exactly short of website projects!


(ii)
Catching a falling object test
Fraught with human error, but a bit
of classroom fun!
You get someone to hold a ruler vertically, with
thumb and first finger, above someone else's hand, who is ready to catch
it with their thumb and first finger.
First image on the right. The
ruler should be held at the top of the scale and steady hands from
both people.
The catching person should have
the middle of their thumb and finger adjacent to zero on the cm
scale - squat down to make sure you are reading the scale
horizontally.
Then, without warning, the person holding the ruler,
lets go of it. The second person has to react as fast as possible and
catch the dropped ruler between their thumb and first finger.
Second image on the right.
The
longer the distance d, the slower your reaction time!
When caught, you then read how far
the ruler as fallen by taking the reading, to the nearest centimetre,
from where the middle of their thumb and finger are.
You repeat the experiment a number
of times to get an average, but its not a particularly accurate
experiment.
You need to have steady hands and not
let the ruler wobble about or fall at an angle other than vertical.
Controlling variables - fair test
criteria:
You should drop the ruler from
the same height each time the experiment is performed.
You
should also use the same ruler and the same hand to catch the ruler.
Use the same person/people
dropping the ruler and catching it though, obviously, you can compare
one person's results with another.
The slower your response time, the
further the ruler falls before being caught.
You might repeat the
experiment by having e.g.
having some background distractions - a group of people
talking nearby, or somebody trying to engage you in conversation or
music playing,
or taking a caffeinated drink
like coffee or cola to act as a stimulant. - a drug that speeds up
neural activity in the central nervous system.
Extension of experimental
results
You can pool class results and
produce a histogram of number of pupils versus equally spaced
reaction times.
You can do the same thing
with a computer screen test too.
You can investigate the effect of
stimulant like caffeine in coffee.
i.e. do the test 10 times,
have a rest, drink a cup of coffee and later repeat the test.
You should find that you a
bit faster, a smaller response time because caffeine is a
central nervous stimulant. It makes you more alert.
How to calculate the response
time from your results
There is a simple formula you can
use to calculate the actual reaction time (t in s) from the
distance the ruler falls (d in m), under the acceleration due
to gravity (a = 9.81 m/s2).
t = √(2d / a) =
√(2d / 9.81)
e.g. if the ruler falls 10 cm
(0.10 m), reaction time = √(2 x 0.1 / 9.81) = √ =
0.14 s
Where does the reaction time
formula come from?
Don't worry, you don't have to
know this for either your GCSE/IGCSE biology or physics exams!,
but here is the derivation for my own satisfaction and perhaps some
keen students too?
KEY: a = acceleration (= g =
9.8 m/s2), u = initial velocity (m/s), v =
final velocity (m/s), t = time (s), d = distance (m)
If a body is moving with an
initial velocity of u and accelerates in a uniform manner
(constant acceleration a),
the increase in velocity in a
time is given by: t = at.
Therefore the final velocity v
after time t is given by
(equation 1)
v = u + at
Now, if a body is moving with
uniform acceleration its average velocity is equal to half of
the sum of the initial velocity u and final velocity v.
average velocity = (u + v)
/ 2
but from equation (1),
v = u + at, and substituting in the above equation gives
(equation 2) average
velocity = (u + u + at) / 2 =
u + ½at
Now the distance d, moved
(displacement) = average velocity x time (remember v = ∆d
/ ∆t)
so, d = (u + ½at) x t
and, multiplying out gives
(3): d = ut + ½at2
now in the experiment, u =
0, so the equation simplifies to (4):
d = ½at2
this can now be rearranged to
give equation (5):
t = √(2d
/ a)
which is the equation you can
use to calculate your actual reaction time from how far the
ruler fell before you stopped it.
See also
The brain - what the different parts do and the dangers
if damaged gcse biology revision notes
TOP OF PAGE
and sub-index
Any practical work and
investigations you did should also be revised
(which should also
be revised, helps in understanding 'how science works' and context
examination questions):
reaction times – measuring
reaction times using metre rules, stop clocks or ICT,
using forehead thermometers
before and after exercise,
demonstrating the speed of
transmission along nerves by candidates standing in a semi-circle and
holding hands and squeezing with eyes closed,
designing an investigation to
measure the sensitivity of the skin,
demonstrating the knee jerk
reaction,
investigation to measure the
amount of sweat produced during exercise,
TOP OF PAGE
and sub-index
General HUMAN BIOLOGY revision notes
See also cell biology index above
Introduction to the organisation of cells =>
tissues => organs => organ systems (e.g. in humans)
Examples of surfaces for the exchange of substances in
animal organisms gcse biology revision notes
See also
Enzymes - section on digestion and synthesis gcse
biology revision notes
The human circulatory system - heart, lungs, blood,
blood vessels, causes/treatment of cardiovascular disease
Homeostasis - introduction to how it functions (negative
feedback systems explained) gcse
biology revision notes
Homeostasis - control of blood sugar level
- insulin and diabetes
gcse biology revision notes
Homeostasis - osmoregulation, ADH, water control, urea and ion
concentrations and kidney function, dialysis
Homeostasis - thermoregulation, control of temperature
gcse biology revision notes
The brain - what the different parts do and the dangers
if damaged gcse biology revision notes
An introduction
to the nervous system including the reflex arc
gcse biology revision notes
Hormone systems - Introduction to the endocrine
system - adrenaline & thyroxine hormones
gcse biology revision
Hormone systems - menstrual cycle, contraception,
fertility treatments
gcse biology revision notes
Respiration - aerobic and anaerobic in plants and animals. gcse
biology revision notes
Keeping healthy - communicable diseases -
pathogen infections gcse
biology revision notes
Keeping healthy - non-communicable diseases
- risk factors for e.g. cancers gcse
biology revision notes
Keeping healthy - diet and exercise
gcse biology revision notes
Keeping healthy - defence against
pathogens, infectious diseases, vaccination, drugs, monoclonal antibodies
See also
Culturing microorganisms like bacteria - testing
antibiotics/antiseptics gcse
biology revision
Food tests for reducing sugars, starch, proteins and
lipids gcse
biology revision notes
The eye - structure and function - correction of vision
defects gcse
biology revision notes
Optics - lens types (convex, concave, uses),
experiments, ray
diagrams, correction of eye defects (gcse physics)