Cholesterol is a substance which is suspected of causing problems in
the heart and circulatory system. What sort of substance is it (chemically)?
>fat (lipid)
Some people (but not all) are at risk because their bodies build up
cholesterol as a result of foods they eat. This may be one cause of
hardening of the arteries. What categories of food provide the most risk?
>animal fat/ dairy produce
If all the arteries in the body become narrower, the resistance to flow
increases. What effect do you think this increased resistance will have on the
heart?
> strain - more effort
required to pump How do you think a doctor will be able to measure this?
> measure blood pressure -
using sphygmomanometer
Similarly, some people (but not all) are at risk of developing high
blood pressure because of the effect of salt in foods that they eat.
This is especially true for prepared foods. What category of nutritional information on food packaging will
provide information about this risk?
> sodium content (/100g)
A thrombosis is a blockage in a blood vessel, usually an artery. Why are arteries more likely to get blocked than other blood vessels?
> narrower internal diameter -
and getting narrower as they branch into arterioles, etc. What in general is likely to happen as a result of stopping the
blood flow to a particular organ? (several stages)
> less oxygen, less glucose/
reduced activity / death
What is the name for a condition due to a blockage in a blood vessel
in part of the brain, and what symptoms does it cause?
> stroke > lack of some function,
e.g. paralysis, sensory input, processing e.g.speech What may result due to a blockage in a blood vessel supplying the
retina, in the back of the eye?
> death of (part of) retina,
blindness
The coronary arteries are
fairly small blood vessels on the outside of the heart, receiving
oxygenated blood directly from the aorta (main artery).
What (symptoms, name) may be felt as a result of a partially blocked
coronary artery? > chest pains, angina What (event) may happen as a result of a deterioration in the
situation?
> heart attack, death of part
of heart muscle (myocardial infarction), strain on heart, death of
individual
Heart surgery
If surgery is possible, the chest may be opened and a section of
another blood vessel may be inserted to replace the damaged and blocked
section of the coronary blood vessel - this is called a coronary
by-pass. There are several branches of these blood vessels, so
different sections may need to be replaced.
Another technique involves the insertion of a special flexible probe
(from the groin!) into the blood vessel, which is then expanded to
stretch the blood vessel slightly, or the insertion of a tube to keep
the blood vessels from constricting. This "keyhole surgery" has
several advantages, involving less trauma to the patient, and
after-care is also much cheaper.
The main artery (aorta), being nearest to the heart, may become
stretched due to the blood pressure, resulting in an aortic aneurism.
Reinforcement of damaged blood vessels with synthetic material may be
possible.
Lifestyle effects
With increased age, blood pressure may rise. This may be the
cause of a variety of other ill effects on the body. There are various
types of drugs available which may be used to reduce the strain on the
system - by reducing the effects of the nervous stimulation on the
heart, or by reducing the body's fluid content, or by generally opening
up blood vessels (vasodilation).
As well as having a number of bad effects on the lungs, smoking
has several effects on the heart and blood. How much greater is the risk of heart disease to a smoker?
> 3 times
Tobacco smoke contains small quantities of carbon monoxide, which
combines irreversibly with haemoglobin in the red blood cells.
Normally haemoglobin carries out this function:
oxygen + haemoglobin
oxy-haemoglobin
However when carbon monoxide is inhaled, the following occurs:
carbon monoxide + haemoglobin
carboxy-haemoglobin
What effect will this have on the functioning of the blood system?
> reduces oxygen carrying
capacity
On average, our heart beats (pulse rate) 72 times per minute. How many times is this per day?
> 103,680 Assuming this rate is constant, how many times does the heart beat
in a lifetime of, say, 70 years?
> 2.65 x 109
Why is this rate not constant over the years?
> faster when young, slower
when old> depends on activity
If we are fit, our heart beats faster when we exercise ourselves. In what other way can our heart also increase the flow of blood?
> pump greater volume per beat
(increased "stroke volume")
List 4 functions performed by our blood under these conditions
(exertion).
> provide more oxygen
>remove carbon dioxide
> provide more glucose/"food"
> remove heat carry adrenalin to muscles
etc Can you think of any reasons why it has long been thought that the
heart is central to a person's emotions, and character?
> speeds up when you get
excited
stops when you die!
in middle of chest?
The effects of exercise
People who are physically fit have a lower rate of heart beat
than those who are unfit, and although it also speeds up by less under
exertion, it also returns more quickly to normal.
Fit people also have a steadier heartbeat than unfit ones.
Use the information above to draw 2 lines, one for a fit and one for
an unfit person, to show how their heartbeat is likely to vary minute
by minute before, during and after a period of exertion:
Include a key:
fit person
unfit person
In what ways does exercise improve the body?
> strengthens heart muscle
> makes heart bigger!
> makes body muscles more
efficient
Exercise and oxygen debt
The function of the circulatory system is to provide oxygen for, and to
remove carbon dioxide resulting from, respiration inside cells of the
body, so the circulating blood contains a certain amount of oxygen, in
combination with haemoglobin inside the red cells.
Transfer of this oxygen to the tissues relies on diffusion via tissue
fluid, which may be too slow for some activities, such as
sprinting. If the (muscle) tissues use up oxygen faster than it can be
supplied by the blood, then they may respire anaerobically and
a condition known as oxygen debt is built up. The anaerobic
respiration is inefficient and results in the production of lactic
acid, which must then be transported (in the blood) to the liver for
reprocessing. The accumulation of this acid may be the cause of muscle
fatigue, and exercise may increase the efficiency of the body in
dealing with this.
It is fairly obvious that exertion causes increased breathing, for
example when running for a bus. Why do you continue to breathe deeply and be out of breath even
though the activity has ceased?
> oxygen debt must be "repaid"
- restoring blood to normal level of oxygenation
Our heart normally varies its output automatically according to our
body's requirements. However, it may stop beating, or its rhythm may
become erratic if it is damaged, for instance due to a heart attack.
The heart's natural beating may be restarted within a few seconds as a
result of cardiac massage, or external blows to the chest, or
strong electrical impulses (several hundred volts), perhaps in
combination with powerful stimulatory drugs.
Why are these drastic actions performed with such priority, but
abandoned so quickly if there is no immediate response?
> it is no use if the brain is
dead due to lack of oxygen
If the heart's own speed controlling centre ("pacemaker") is damaged,
an artificial electronic pacemaker device may be substituted, but this
is unlikely to be able to respond flexibly to increased demands by the
body when exercising, for example.
Transplants
Like other organs, a heart may be removed from the body of a person who
has recently died (the donor), and transplanted into somebody whose own
heart is failing (the recipient).
However, it is not a simple operation surgically, and there are a
number of problems, apart from expense, which is an important
consideration in the National Health Service today. It should be
realised that a heart transplant is not a large scale life saving
operation, as it relies on the death of one person for each operation,
and it may merely improve the quality of life for one other, rather
ill, person.
Why is it a simpler process to transplant a heart and lungs in
combination, than to transplant a heart alone?
In the case of people suffering from cystic fibrosis, the lungs
are sometimes damaged due to buildup of thick mucus secretions and a
heart+lung transplant may be a possible solution. Surprisingly, the
heart of such individuals are often extremely healthy, and may be
transplanted on to other individuals!
If the body's defence mechanisms recognise the transplanted organ as
"foreign", then it may undergo rejection. In order to counteract this,
immunosuppressive drugs may be used.
Tissue typing (like blood groups, but more complex) is carried out to
attempt to match up as closely as possible the donor and recipient, but
there are many different factors which may cause incompatibility.
What is meant by "the body's defence mechanisms"?
> white cells, etc.
Why are kidney transplants between members of the same family
often quite successful?
> shared genes mean less
tissue incompatibility
Why are kidney transplants between identical twins usually the
most successful?
The coronary arteries are
fairly small blood vessels on the outside of the heart, receiving
oxygenated blood directly from the aorta (main artery).
oxy-haemoglobin
carboxy-haemoglobin 
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