FIS2603 – PHYSIOLOGICAL DEFENSE MECHANISM
QUESTION 1
1.1 Briefly discuss the mechanisms of heat loss. (4)
There are 4 Mechanism of heat gain and heat loss-
Radiation
• Radiation is the gain or loss of heat in the form of infrared rays between human body and elements around it
with a different temperature.
• By RADIATION body heats itself by absorbing rays of sunshine.
• And it is also RADIATION that it loses heat by radiating it out in turn in cold conditions.
• RADIATION accounts for majority of heat exchange carried out by the human body. Infact, radiation
constitutes the main source of heat loss for human beings (between 40 and 60%).
Convection
• Convection is defined as the exchange of heat between body and ambient air or water in which it moves.
• Isothermic point is temperature below which human body, in that particular environment, body tends to loses
heat.
• Isothermic point of air is 77°F > when the ambient air temperature is below 77°F, human body tends to loses
heat.
• Isothermic point of water is 98°C > when ambient water temperature is below 98°C, human body tends to loses
heat.
Conduction
• CONDUCTION is defined as the exchange of heat between two bodies in contact, without one moving away
from the other.
• Example of this in action when a seat stays warm after you have sat on it for a while.
Evaporation
• Evaporation is loss of heat linked to secretion of water by the body through body surface.
• EVAPORATION can be:
Passive, via RESPIRATION - air we breath out is laden with moisture.
• Active, via PERSPIRATION - body creates a layer of water on the skin in order to cool down.
• Evaporation represents around 25% of heat loss at rest but can reach up to 80% during exertion, mainly through
sweating, in the context of physical activity.
BY these methods heat is either gained or loss.
1.2 Erythropoietin is the hormone responsible to produce red blood cells. Draw a flow diagram to explain the
production of red blood cells when tissue oxygenation decreases. (8)
,1.3 Briefly describe each type of tissue/organ transplant. (4)
A transplant from one part of your body to another part is called an autograft and the process is called auto
transplantation. Some examples of autografts include:
• skin graft – uses healthy skin to help heal a wound or burn on another part of the body
• blood vessel graft – provides an alternative route for blood flow to bypass a blocked artery, for example, in
heart bypass surgery
A transplant between two people who are not genetically identical is called an allotransplant and the process is called
allotransplantation.
A transplant between identical twins is called an isograft. The recipient will almost never reject an isograft and so
immunosuppressants are not needed.
A transplant between species is called a xenotransplant and the process is called xenotransplantation. Heart valves from
cows and pigs have been used for many years to replace faulty heart valves in people.
Multi-organ transplants, while less common than single-organ transplants, occur each year. Common multi-organ
transplants include heart and lungs or pancreas and kidney.
QUESTION 2
Discuss the treatment condition of Acquired Immune Deficiency Syndrome (AIDS) in full. Include routes of
transmission, virus replication, development of AIDS and all treatment options. [14]
Acquired immune deficiency syndrome (AIDS) is caused by the human immunodeficiency virus (HIV), which incapacitates
the immune system. HIV belongs to the retrovirus family, whose nucleic acid core is RNA rather than DNA. Retroviruses
possess an enzyme called reverse transcriptase, which, once the virus is inside a host cell, transcribes the virus’s RNA
, into DNA, which is then integrated into the host cell’s chromosomes. Replication of the virus inside the cell causes the
death of the cell.
HIV causes the death of many uninfected helper T cells by apoptosis. Without adequate numbers of helper T cells,
neither B cells nor cytotoxic T cells can function normally. As a result, the AIDS patient dies from infections and cancers
that the immune system would ordinarily readily handle.
The path from HIV infection to AIDS commonly takes about 10 years in untreated persons. Typically, during the first
5 years, the rapidly replicating viruses continually kill large numbers of helper T cells in lymphoid tissues, but these are
replaced by new cells. Therefore, the number of helper T cells stays relatively normal (about 1000 cells/mm3 of blood)
and the person is asymptomatic. During the next 5 years, this balance is lost; the number of helper T cells, as measured
in blood, decreases to about half the normal level but many people remain asymptomatic. As the helper T-cell count
continues to decrease, however, the symptoms of AIDS begin—infections with bacteria, viruses, fungi, and parasites.
These are accompanied by systemic symptoms of weight loss, lethargy, and fever—all caused by high concentrations of
the cytokines that induce the acute phase response.
Certain unusual cancers (such as Kaposi’s sarcoma) also occur with relatively high frequency. In untreated persons,
death usually ensues within 2 years after the onset of AIDS symptoms. The major routes of transmission of HIV are
through (1) transfer of contaminated blood or blood products from one per son to another, (2) unprotected sexual
intercourse with an infected partner, (3) transmission from an infected mother to her fetus across the placenta during
pregnancy and delivery, or (4) transfer via breast milk during nursing
The present recommended treatment for HIV infection itself is a simultaneous battery of at least four drugs. Two of
these inhibit the action of the HIV enzyme (reverse transcriptase) that converts the viral RNA into the host cell’s DNA; a
third drug inhibits the HIV enzyme (a-protease) that cleaves a large protein into smaller units required for the assembly
of new HIV; and a fourth drug blocks fusion of the virus with the T cell.
QUESTION 3
During a hot summer day, you have begun sweating to promote heat loss from the skin surface. Discuss the
mechanism involved in this process in full. [10]
