Stylostic pressure is the maximum pressure the heart produces
Diastolic pressure is the blood pressure between heartbeats
Can be increased by:
stress, high alcohol
intake, smoking and
being overweight
Can be decreased by:
regular exercise and
eating a balanced diet
High blood pressure can
cause blood vessels to burst.
It can cause damage to the
brain (stroke) and to the
kidneys
Low blood pressure can cause dizziness, fainting (because the blood
supply to the brain is reduced) and poor circulation to other areas such
as the fingers and toes.
Fitness and Health
Fitness is the ability to do
physical activity
Health is being free from
diseases such as those caused
by bacteria and viruses.
General level of fitness can be measured by your cardiovascular efficiency
Fitness can be measured for different activities
Strength - by the amount of weights lifted
Flexibility - by the amount of joint movement
Stamina - by the time of sustained exercise
Agility - by changing direction many times
Speed - by a sprint race
Therefore, you can
be very fit for a sprint
race but not perform
well in a marathon
(stamina)
Ways of measuring fitness should be evaluated to
check effectiveness in particular situations
Smoking
Smoking can increase blood
pressure in a number of ways
Carbon monoxide in smoke causes blood to carry less oxygen.
This means the heart rate increases so that the tissues receive
enough oxygen
Carbon monoxide decreases the oxygen-carrying capacity of blood
It combines with haemoglobin, preventing it from
combining with oxygen, so less oxygen is carried
Nicotine in cigarette smoke directly increases heart rate
Diet and Heart Disease
Heart disease is caused by a restricted
blood flow to the heart muscle
The risk is increased by having a high level of saturated fat in the diet,
which leads up to a build-up of cholesterol (a plaque) in arteries
Also increased by having high
levels of salt, which can
increase blood pressure
It is essential to be able to interpret data showing links between the
amount of saturated fat eaten ,the build-up of cholesterol and the
incidence of heart disease
The narrowing of the arteries (caused by plaques in the coronary arteries)
can reduce blood flow to the heart
The plaques also make blood clots or thrombosis more
likely to happen, which will also block the artery
Remember: It is the blood vessel into the heart muscle that is blocked,
not the blood flowing into the heart!
Human Health and Diet
A Balanced Diet
It is important for good
health to eat a balanced
diet
A balanced diet contains the correct
amounts of chemicals found in food
Three of these are:
carbohydrates (made of
simple sugars such as
glucose), proteins
(made up of amino
acids), fats (made up of
fatty acids and glycerol
A balanced diet varies according to factors including age,
gender, level of activity, religion, being vegetarian or vegan,
or because of medical issues such as food allergies
If you eat too much fat or carbohydrates they are stored in the body
Carbohydrates are stored in the liver as glycogen or converted into fats
Fats are stored under the skin and around the organs as adipose tissue
Although proteins are essential for growth and repair, they cannot be stored in the body
Although proteins cannot be stored in the body,
some amino acids can be converted by the body
into other amino acids
Protein Intake
Proteins are needed for growth and so it
is important to eat the correct amount
This is called the estimated average daily requirement (EAR)
It can be calculated using this formula:
EAR in g = 0.6 x body mass in kg
Example: Sue has a mass of 72.5kg.
Her EAR is 0.6 x 72.5 = 43.5 g/day
The EAR is only an estimated figure based on an average person
It may be affected by factors such as body mass, age, pregnancy or breast-feeding
Too little protein in the diet causes kwashiorkor.
This is more common in developing countries due
to overpopulation and lack of money to improve
agriculture
Proteins from meat and fish are called first-class proteins
They contain all the essential
amino acids that cannot be made
by the human body
Plant proteins are called second-class proteins as they do not contain all the essential amino acids
Overweight or Underweight?
To work out if a person is overweight or underweight you calculate their body mass index (BMI)
BMI = mass in kg / (height in m)2
Example: Tom is 170cm tall and has a mass of 80kg.
170cm = 1.7 m. BMI = 80 / 1.7 squared = 27.7
A BMI of more than 30 means the person is obese,
25-30 is overweight, 20-25 is normal, less than 20 is
underweight
Some people may become ill as they choose to eat less than they need.
This may be caused by low self-esteem, poor self-image or a desire for
what they think is perfection
Staying Healthy
Malaria
Malaria is caused by a protozoan called Plasmodium
which feeds on human red blood cells
Plasmodium is carried by mosquitoes, which are vectors
Vectors are not affected by the disease
It is transmitted to humans by mosquito bites
Plasmodium is a parasite and humans are its host.
A parasite is an organism that feeds on another
living organism, causing it harm
Knowledge of the mosquito's life cycle has helped stop the spread of malaria (by
draining stagnant water, putting oil on the water surface and spraying insecticide).
This knowledge has also helped to develop new treatments
Cancers
Change in lifestyle and diet can
reduce the risk of some cancers
Not smoking reduces the risk of lung cancer
Using sunscreen reduces the risk of skin cancer
Benign tumour cells such as warts divide slowly and are harmless
Cancers are malignant tumours:
the cells display uncontrolled
growth and may spread
Ways of interpreting data on cancer and
survival/mortality rates should be considered
The Fight Against Illness
Pathogens (disease causing organisms) produce the symptoms of an infectious disease
by damaging the body's cells or producing waste products called toxins
The body protects itself by producing antibodies
These lock onto antigens on the surface of pathogens such as a bacterium.
This kills the pathogen
White blood cells produce antibodies resulting in
active immunity. This can be a slow process but has a
long-lasting effect
Vaccinations using
antibodies from
another human or
animal result in
passive immunity,
which has a quick
but short-term
effect
Each pathogen has its own antigens so a
specific antibody is needed for each pathogen
The process of
immunisation is
also called
vaccination
It starts with
injecting a
harmless
pathogen carrying
antigens
The antigens trigger a response by white
blood cells, producing the correct antibodies
Memory cells (a type of T-lymphocyte cell) remain in the body,
providing long-lasting immunity to that disease
Immunisation carries a small risk to the
individual, but it avoids the potentially
lethal effect of the pathogen, as well as
decreasing the risk of spreading the
disease
Treatments and trials
Antibiotics (against bacteria and fungi) and
antiviral drug are specific in their action
Antibiotics destroy pathogens, antiviral
drugs slow down pathogen's development
New treatments are tested using animals, human
tissue and computer models before human trials.
Some people object to causing suffering in animals
in such tests
The Nervous System
How Do Eyes Work
Light rays are refracted (bent) by the cornea and lens
The retina contains light receptors. Some are sensitive to different colours
Binocular vision helps to judge distance by comparing the images from each eye;
the more different they are, the nearer the object
Accommodation is where the eye can focus light from
distant or near objects by altering the shape of the lens
The ciliary
muscles relax and
the suspensory
ligaments tighten
(so the lens has a
less rounded
shape) to focus
on distant objects
The ciliary muscles contract and the suspensory ligaments slacken
(so the lens regains a more rounded shape due to its elasticity) to
focus on near objects
Faults In Vision
Red-green colour blindness is
caused by a lack of specialised
cells in the retina
Long or short sight are caused by the eyeball or lens being the wrong shape
In long sight, the eyeball is too short or the lens is too thin,
so the image is focused behind the retina
In short sight, the eyeball is too long or the lens is too rounded so the lens refracts light too much,
so the image would be focused in front of the retina
Corneal surgery or a lens in glasses or contact lenses corrects long and short sight.
A convex lens is used to correct long sight, a concave lens to correct short sight
Nerve Cells
Nerve cells are called neurones.
Nerve impulses pass along the axon
What happens in a reflex action is shown by a reflex arc. The links in a reflex arc are:
stimulus-->receptor-->sensory neurone-->central nervous system-->motor
neurone-->effector-->response
The pathway for a spinal reflex is:
receptor-->sensory neurone-->relay
neurone-->motor neurone-->effector
Neurones are adapted by being long, having branched endings
(dendrites) to pick up impulses and having an insulator sheath
The gap between neurones is called a synapse.
The arrival of an impulse
triggers the release of a
transmitter substance, which
diffuses across the synapse.
The transmitter substance
binds with receptor
molecules in the membrane
of the next neurone causing
the impulse to continue