(a) The spinal cord and the main
parts of the brain and their function
The brain and spinal cord are all part of the central nervous system.
The brain is extraordinarily complex, consisting of billions of
Using these interconnected neurones pathways the brain is responsible for
the control and coordination of all our complex behaviour -
everything that happens to us, either consciously, unconsciously. Its
Research over many years has shown that different parts of the brain
perform different functions.
VERY simplified diagram of the brain!
The brain can be considered to
have three main regions
The cerebral cortex
The cerebral cortex of the brain (part of the cerebrum - cerebral
The highly folded cerebral cortex is found in the upper
outer regions of the brain
and it dominates the mammalian brain both physically and
The cerebrum is largest part of the brain, rather wrinkly in nature and
split into two halves
called cerebral hemispheres.
The right hemisphere controls muscles on the left side of your
body and the left hemisphere controls the muscles on the right side
of your body.
The cerebral cortex is associated with all the higher functions
of the brain - in a very real way, it makes you who you are as an
The cerebral cortex is responsible for the coordination of many
things including consciousness, intelligence, language, memory,
movement and vision.
The cerebellum of the brain
The cerebellum is in the lower part of the brain near where it
connects with the spinal cord.
The cerebellum is responsible for conscious movement - muscle
coordination and posture-balance.
The medulla oblongata, part of the brain stem
The medulla oblongata is at the base of the brain where the brain connects
with the spinal cord.
The medulla oblongata is the lower part of the brain stem.
The medulla oblongata controls unconscious activities like
These are bodily functions you wouldn't normally think about -
they just happen thanks to the medulla.
The hypothalamus of the brain
The hypothalamus, in the centre of the brain, is involved with
keeping body temperature constant - so involved with aspects of homeostasis.
The hypothalamus produces hormones that control the functioning
of the pituitary gland.
The pituitary gland in the brain - adjacent to the
The pituitary is a gland that produces many important hormones
e.g. those involved in the menstrual cycle. It communicates with the
hypothalamus (see above).
The spinal cord
The spinal cord connects the brain to the rest of the central
The brain stem links the cerebellum to the top of the spinal
The spinal cord is built of a long column of nerve cells
(neurones) that run from the base of the brain down through the
spine of your body.
The spinal cord consists of tracts of ascending sensory
nerve fibres and descending effector nerve fibres. These of
course work together in negative feedback systems and reflex arcs -
so any damage to the spinal cord has serious consequences.
At various points down the spine, neurones branch off and connect
with all the rest of the parts of the body.
The spinal cord relays all the nerve pulses of information
between the brain and the rest of the body.
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(b) How do we study the brain? How can this help in
and the development of diagnostic techniques to help treat patients with
We understand quite a lot of how the brain works, but there is
awful lot we don't know about brain functions.
Because of its complexity and delicate nature,
investigation brain function is tricky and difficult to do without great
caution (its like a thick jelly).
To investigate brain function we need to 'get inside' the brain and
observe in some direct, but safe way, and preferably not by surgical
methods - cutting the skull open to examine brain tissue carries a high
risk of permanent brain damage!
with brain injuries
Much has been learned historically from people who have
suffered in some small way with brain damage - in other words damage
to one small part of the brain.
The effect of this brain damage on the patient can tell a
clinician what the function of the damaged part of the brain was
e.g. if an area at the back of the brain was damaged by a stroke
and the patient went blind, you would know that part of the brain
was involved with vision.
A stroke in the brain stem or cerebellum of a patient can affect
breathing and heartbeat. It can also cause speech impairment,
hearing and cause vertigo (difficulty in balancing).
People who have suffered massive brain injury, but survive, would
give us some insight, but, would it be ethical to study someone who
might not be in a position to grant (informal consent) the brain
You can study the brains of people who have died - in your will
or donor card system, you can leave parts or all of your body for
(ii) Connecting electrodes to
You can push tiny electrodes into brain tissue and give it
a tiny electrical stimulus.
You can then observe what happens on
stimulating various parts of the brain.
You can then relate that part of
the brain with what happens.
e.g. If you stimulate the part of he brain called the motor area,
it causes muscle contraction and movement.
An electroencephalogram (EEG) is
a test that detects electrical activity in your brain using small,
metal discs (electrodes) attached to your scalp - the electrodes
pick up patterns of electrical activity in the brain.
Your brain cells communicate via
electrical impulses and are active all the time, even when
you're asleep. With electroencephalography you can monitor this
activity, which shows up as wavy lines on an EEG recording.
(iii) Modern technology
techniques external to the body
The advancement in new technology is helping academics research
the brain with plenty of spin-offs to help patients with brain
conditions. We can now examine the brain without intrusive surgery using
various 'high-tech' scanning machines.
A magnetic resonance imaging scanner (MRI machine) is
a complex and costly way of producing a very detailed picture of the
MRI uses strong magnetic fields and radio
waves to produce a highly detailed image of the nervous system
of the brain (and any other part of the body too).
You can monitor the brain's activity while a person is doing
particular things e.g. solving a problem, doing a skilled or
unskilled physical task or doing a memory test and while they
are enclosed in the MRI scanner.
An fMRI scanner (functioning magnetic resonance imaging) is a
more advanced MRI scanner which is able to detect increased
blood flow in the activated areas of the brain, an MRI scanner
MRI is a very safe non-invasive technique
that doesn't use ionising radiation, so safer than CF scanning
and PET scans (both briefly described next).
CT scanner uses X-rays to produce an image of the
main structures of the brain.
However, a CT scanner cannot show the functioning of the
imaged parts of the brain.
BUT, the CT scan can show a damaged or diseased part of the
brain which can be related to some loss of function by the
e.g. loss of mobility or loss of vision can be related to
damaged areas of the brain in the CT scanner image.
PET scanners are much more sophisticated and involve
the use of radioactive tracer
Positron emission tomography (PET) scans
are used in medicine to produce highly detailed
three-dimensional images of the inside of the human body.
images can clearly show the part of the body being investigated
e.g. brain function,
including any abnormal behaviour.
The patient is injected with a
radioisotope, whose emitted radiation is monitored by detection
screens. The radioisotope (radioactive tracer) atom is
incorporated in a molecule that moves around the body e.g. a
derivative of glucose. This molecule accumulates in more active
You can actually monitor the patient's brain activity
while they are in the PET scanner.
The PET scan can show which parts of the
brain are active and behaving normally or abnormally - unusual
reduced activity or not functioning at all.
PET scans are so detailed you can
investigate brain structure in real time and see how the
patient's brain is
functioning while they are in the PET scanner.
This means PET scans can be used to study
disorders that change the brain's activity like Alzheimer's
Here, certain parts of the brain become less active
e.g. the memory region, and
the PET scan can be compared with that of a normal brain.
For more details on pet scans see
Uses of radioactive isotopes
PET scans are often combined
with computerised tomography (CT) scans to produce even more
detailed 3D images, known as PET-CT scans.
PET scans may also
occasionally be combined with a magnetic resonance imaging (MRI)
scan, known as a PET-MRI scan.
Techniques are getting increasingly
sophisticated and costly, but all for the patient's benefit.
Transcranial magnetic stimulation (TMS) uses a
magnetic field to change brain activity in targeted areas of the
TMS uses magnetic fields to stimulate
selected nerve cell activity and has been used to treat
Footnotes on scanners: Despite the
wonderful technology, interpreting these scans for diagnostic
purposes is not always clear cut i.e. it can inform to help in a
prognosis and affect a treatment decision, but its not always that
One problem is that the brain function
observed in the scanner, might not be what you would
'theoretically' observe in real life outside the scanner. The
mere fact that you are lying down and enclosed inside the
scanner means you are not in an everyday state!
Another problem is that our knowledge is
still inadequate in knowing how treat certain brain conditions
and we cannot adequately access some areas of the brain - so
test results can be hard to fully interpret for the benefit of
For more see the
uses of radioactive
materials in medicine notes
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(c) What are the causes,
risks, consequences & treatment of brain damage?
As our knowledge of how the brain works increases, so it is possible to
devise appropriate treatments for different disorders of the brain.
The brain is so delicate and complex that there are many causes of
Sadly, its hard to repair damage to any part of
the central nervous system - anything faulty in spinal cord or brain.
Lots of things can go wrong with the central
nervous system e.g. physical injuries to the brain or spinal cord from
severe impacts in accidents, tumours from pathogen caused mutations,
diseases like Alzheimer's and Parkinson's disease.
All of these are difficult to treat, one reason
being the difficulty in repairing damage to the neurones in the CNS, the
neurones cannot repair themselves and we have not yet devised techniques
to repair damaged nerve tissue.
Any operation to remove a brain tumour is
tricky, and it is difficult to avoid damage to surrounding areas of
otherwise healthy brain tissue.
Such damage can leave the patient with
problems with speech or vision.
In some cases, no treatment is impossible e.g.
it is not possible to remove tumours growing certain regions of the
Surgery on a patient with spinal cord damage
risks further damage to the spinal cord, which can cause permanent
paralysis - loss of movement capability because nerve signals from
the brain can't get through to the effector cells.
Neurones in the nerve systems cannot readily repair themselves and
medical science hasn't found a way yet to repair nerve tissue.
Cell differentiation is the process by which a less specialized
cell becomes a more specialized cell type. Once neurones have
differentiated they don't undergo mitosis - they can't divide to
replace lost neurones.
Medical research scientists are investigating the use of stem
cells to replace damaged tissues of cells in the nervous system -
the idea being to get stem cells to differentiate and change into
The use of stem cells raises ethical issues - the use of
embryonic stem cells offends many people because destroying an
embryo is destroying a potential life. Others would argue curing
somebody of a very disabling medical condition should override other
moral considerations - a tricky one! and lots more dilemmas to come
as medical science gets cleverer and cleverer!
Any treatment of a central nervous system disorder carries risks of
further permanent damage.
A stroke in the brain
may be caused by a blocked artery or the
leaking or bursting of a blood vessel causing brain damage. Some
people may experience only a temporary disruption of blood flow to the
brain. The former is much more serious and can lead to permanent brain
After a stroke, depending on which area of the brain is affected, you
can be left with paralysis down one side of your body - mobility
problems, speech, vision and memory impairment.
If treatment is initiated rapidly, its amazing how good patient
recovery can be.
Parkinson's disease is a progressive disease of the nervous system
characterised by involuntary shaking of the body - tremors, muscular
rigidity, and slow imprecise movement. It mainly affects middle-aged and
elderly people. It is caused by the brain becoming progressively damaged by
loss of nerve cells over a period of many years.
Although there's currently no cure for Parkinson's disease,
treatments are available to help reduce the main symptoms and maintain
quality of life for as long as possible.
supportive treatments – such as physiotherapy and
in some cases, brain surgery
electrical stimulation using tiny electrodes has been used to
reduce muscle tremors in nervous system disorders like
Serious head injuries
from a physical impact to the head in an accident can lead to brain damage.
Alzheimer's disease is a progressive degenerative condition of the
brain, which means the symptoms develop gradually over many years and
eventually become more severe.
It affects multiple brain functions e.g. memory problems, confusion,
disorientation and getting lost in familiar places, difficulty planning
or making decisions, problems with speech and language, problems moving
around or performing self-care tasks and personality changes. Its
basically the brain degenerating as you get older and difficult to
Spinal cord injuries in an accident can cause paralysis of the
Surgery for a spinal cord injury carries the risk of permanent and
greater injury e.g. paralysis.
Brain cancer tumours will cause disruption of brain function and
the surgery to remove them carries high risks of further brain damage.
Depending on the part of the brain affected where the tumour is
growing, some tumours can be treated with radiotherapy or chemotherapy,
other tumours can be removed surgically, but others cannot be dealt with
Since you cannot be always sure of completely
removing all of the cancerous tissue of a tumor, post-surgery treatment
may include radiation therapy or chemotherapy.
In removing a brain tumour you might, however inadvertently, damage
other areas of the brain adjacent to where the tumour was.
As with any invasive surgery, there is always a
risk of infection.
Whatever the treatment on offer, you have to make
a decision based on benefits (potentially increasing life span)
versus risk (brain damage and limited capability of life).
Medical scientists are always looking for safer
and more effective treatments e.g.
monoclonal antibodies and gene therapy might
used to treat brain cancer,
and stem cell culture techniques may help to
repair damaged nerve tissue.
Boxers are particularly susceptible to brain damage because of the
repeated bangs to the head. Over a period of time brain damage can
accumulate as nerve cells are destroyed.
The sheer complexity of the brain and its delicate nature means any
procedures like surgery that impact directly on the brain does increase the
risk of brain damage. With intrusive procedures the risk of brain damage is
always there and its effect on brain function e.g. inhibited limb movement,
speech problems etc.
BUT, it may be the case where you are balancing risk of brain damage
versus saving someone in a life threatening situation - difficult
to the nervous system including the reflex arc
gcse biology revision notes
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