Human Biology Summer Preparatory Work 2012 - pt1

1. *
HEALTH AND DISEASE

2. * What is health?
* ‘The state of complete physical, mental and
social well-being’
* What is disease?
* Disease is a disorder or malfunction of the mind
or body, which leads to a departure from good
health.
*

3. * Microorganisms-pathogens
* Bacteria, Viruses, Fungi, Protozoa
* Genetic causes
* Inherited
* Lifestyle
* Risk Factors
*

4. *
* Micro-organisms, or microbes for short, are very small living
creatures.
 Most of them cannot be seen without using a microscope.
Bacteria (orange) on the
tip of a pin.
Magnification x1600 when
the image is printed 10 cm
high.
The tip of the pin is
approximately 20 µm across
and the bacteria are around
5 µm long.

5. What is a pathogen?
* A pathogen is a micro-organism that has the potential to
cause disease.
What is an infection?
* An infection is the invasion and multiplication of pathogenic
microbes in an individual or population.
What is disease?
* Disease is when the infection causes damage to the
individual’s vital functions or systems.
*
An infection does not always result in disease
WHY?

6. *
Vertical – kissing
* Herpes simplex VIRUS causes cold sores.
* Initial infection occurs through direct skin contact when the
secretions from another person’s cold sore, containing the virus
particles, come into contact with cells of the skin around the
mouth.
A
couple
kissing. Cold sores
on lip and
mouth.

7. Vertical – sexual intercourse
* The bacterium Treponema pallidum
causes syphilis.
* The bacterium enters the body
through very tiny cuts on the skin or
mucous membranes when there is
contact with an infected person or
their bodily fluids.
*
Interlocking gender symbols
representing sexually transmitted
diseases.

8. Vertical – touching (faecal-oral route)
* Norwalk virus causes a type of gastroenteritis.
* Norwalk virus is found in the
faeces or vomit of infected people.
It is highly contagious.
* Infection occurs by having direct
contact with another person who is
infected and not maintaining good
*
hygiene e.g. washing hands.
Human hand contaminated
with colonies of bacteria
(blue/pink patches).

9. * Rubella virus causes German measles.
* When infection occurs during pregnancy
the virus crosses the placenta in the
blood leading to infection of the fetus.
Horizontal across the placenta or via breast milk
* The virus can affect all the
organs of the developing fetus.
* The risk to the baby is highest in the
first 3 months – up to 85% of babies are
affected if infected during this period.
* Eight week old foetus
attached to its placenta by
the umbilical cord.

10. *
Air/dust
* The bacterium Mycobacterium tuberculosis causes tuberculosis (TB).
* TB is spread from person to person through the air.
* When a person with active TB coughs or sneezes, droplets loaded with the
infectious organism are propelled into the air.
* The moisture evaporates from these particles to leave droplet nuclei that
can remain airborne for days and spread long distances.
* The Mycobacterium has a waxy coat, which protects it from drying out
allowing it to survive for many months in the air and dust.

11. * The parasitic protozoan called
Cryptosporidium parvum causes a gut
infection called cryptosporidiosis.
Via water
 C. parvum has a complex life
cycle, which it completes in one
host, in this case the human.
 The infective stage, the oocyst, (spore) is
excreted in the faeces of infected humans
or animals.
*
 It is spread by drinking contaminated
water.

12. Internal – biological
* Malaria is a vector-borne disease caused by a single celled
protozoan parasite called Plasmodium, which is transmitted by
mosquitoes.
* The primary vector for malaria is the mosquito Anopheles
gambiae.
* Only female mosquitoes transmit
malaria when they feed on the
human host’s blood.
A. gambiae feeding on
human blood.
*

13. Antibody
* An antibody is a protein that
is produced by lymphocytes
(type of white blood cell) in
response to the presence of a
specific antigen.
* Specific antibodies bind
to specific antigens
and cause their destruction.
Antibody
*

14. * You can become immune to a disease through vaccination.
Immunization programmes and the
development of new vaccines play
an important role in protecting
individuals against illness.
* Vaccination works by safely
exposing individuals to a specific
pathogenic microbe, artificially
increasing their immunity
to it. Vaccination
*

15. * Antibiotics are chemical compounds
produced by soil fungi and bacteria.
* They are used to treat bacterial infections.
* Alexander Fleming accidentally discovered
penicillin, the first antibiotic, in 1928.
* He isolated it from the mould Penicillium Antibiotic drugs (discs)
prevent the growth of
notatum and found it prevented the growth bacteria (white)
of bacteria. demonstrated by clear
zones around the discs.
* Penicillin was not available for commercial
use until Florey and Chain purified it in 1940.
*

16. Factors leading to microbes becoming resistant to antibiotics include:
* Pressure on doctors, by patients, to prescribe
antibiotics even when they are not needed.
* Patients being prescribed antibiotics
without the doctor knowing the cause
of the infection.
MRSA
* Use of antibiotics in animals for growth
promotion and prophylaxis, which allows
them to enter the human food chain.
*

17. * DNA present in cells codes for proteins
* Mutations in DNA results in production of faulty
proteins
* Examples of inherited diseases
* Cystic fibrosis
* Sickle cell anaemia
* Huntingtons chorea
*

18. * CHD and some cancers caused by lifestyle
* Risk factors include
* Smoking
* Obesity
* Diet high in cholesterol
* Lack of exercise
*

19. * Diabetes causes excess glucose to be found in
urine
* High blood pressure causes proteins to be
found in urine
* Examine the urine samples. Identify the
substances present, diagnose possible
disease, identify possible reasons for
substances being present and suggest advice
you would give to the patient.
*

20. * Examine the petri dishes provided containing a
smear taken from a patient
* Which antibiotic(s) would you recommend
prescribing to the patient and why?
*