Fever is a higher than normal body temperature that is part of the body's natural response to infection. The hypothalamus acts as the body's temperature regulator and raises the temperature set point in response to pyrogens like cytokines released during an immune response. This causes changes like reduced sweating and increased shivering that conserve heat and raise the temperature. A fever benefits the immune system by limiting bacterial/viral growth and activating immune cells. Common symptoms of a fever include fatigue, body aches, loss of appetite and headaches.

1. BY : RUN RATTANAK
Pharmacist student.
Assignment :
Fever

2. Contents
I. Fever and Temperature regulation
II. Cause of Fever
III. Hypothalamic Control of Temperature
IV. Mechanism of Fever
V. Role of Fever
VI. Systematic Changes
VII.Symptoms

3. Fever = Pyrexia = Febrile
- Pyrexia – Greek Pyr meaning Fire
- Febile – Latin Febris meaning Fever.
I. Fever and Temperature regulation.
 A fever is a higher than normal body temperature and one of the body’s natural
responses to infection.
 The body temperature refers to the temperature of viscera and tissue of the body.
 The normal body temperature varies from 36.2°C to 37.3°C. When your body's
temperature rises a few degrees above normal, it is a sign that your body is fighting
infection.
Fever
Temperature > 37°C

4.  All parts of the body do not have the same temperature.
 Temperature : Rectal > Oral > Axillary
 Temperature at the Rectal is generally 0.5°C higher than at the Oral.
 The internal temperature varies normally in response to activity, environmental
temperature, and fluctuation of circadian rhythm.
Site Normal ( °C ) Fever ( °C )
Axilla 36.4 >36.9
Oral 36.8 >37.3
Rectal 37.3 >37.7

5.  Temperature Regulation :
• Heat production
• Heat conservation
• And Heat loss.
 Temperature regulation is mediated hormonally by the hypothalamus.
 The internal temperature varies normally in response to activity, Environmental
temperature and daily fluctuation of Circadian rhythm.

6. II. Cause of Fever
 When infection occur, blood and lymphatic system produce WBCs which are what
fight off infection.
 As the WBCs increase into fight and attack the germs, this cause body to heat up.
 The WBCs that are produced to fight the germ, has affected the Hypothalamus in the
brain which is the body's heat regulating mechanism.
 When the body's fighting an injury or injection, the Hypothalamus sets the body
temperature at higher level.
 The body compensates for this by moving blood away from the skin so the amount of
heat lost through the skin in reduced.
 Therefore, the muscle might repeatedly contract to keep the body warm, which cause
shivering.

7. III. Hypothalamic Control of Temperature
Temperature regulation is mediated hormonally by the hypothalamus :
1- Peripheral themoreceptors ( in skin )
2- central thermoreceptors ( in hypothalamus , Spinal cord, Abdominal Organs).
Increased heat p production is initiated by a series of hormonal mechanisms involving the
hypothalamus and its connections with the Endocrine system.
TSH-RH (thyrotropin stimulating hormone-releasing hormone) stimulated the anterior
pituitary(TSH) to release thyroid gland , Thyroxine (T4).
- This hormone then acts on the Adrenal medulla release of Adrenaline or Epinephrine into
the bloodstream.

8. IV. Mechanism of Fever
Pyrogen : Any substance that cause Fever,
Pyrogen
Exogenous Endogenous

9.  Exogenous pyrogen : Such as bacteria or viruses are a host of exogenous substances
are capable of inducing Fever by stimulating endogenous pyrogens if introduced to the
body.
 Endogenous pyrogen : A variety of exogenous agents generate fever through their
capacity to stimulate the production of Endogenous pyrogen. and cause the increase in
the thermoregulatory set point in the hypothalamus.
• The endogenous pyrogen include Cytokine ( Produced and releases by phagocytes) :

10. Cytokine ( Produced and releases by phagocytes) :
- Interleukin-1 (IL-1): Produced by activated macrophages, and wide number of
cells in response to injury or inflammatory activation.
- Tumor necrosis factor ( TNF alpha): Produced by macrophages, lymphoid cells,
endothelial cells, etc.
- Interferon (IFN) : Produced by lymphocytes, NK cells, fibroblasts, etc.
- Interleukin 6 (IL-6) : produced by mononuclear cells fibroblast, endothelial
cells,etc.
• Endogenous pyrogen increase set point hypothalamic control of temperature

11. Endogenous pyrogen increase set point hypothalamic control of temperature
Exogenous pyrogen Endogenous pyrogen
Hypothalamus
Change in temperature
set pointFever
Mechanism of Fever

12. Hypothalamus response :
- Release of glucocorticoid ( stress response)
- Blood directed to deep dermal and vessels
- Increase heart rate and blood pressure
- Decreased sweat production
- Decrease in ADH , Which reduces body fluid volume.

13. V. Role of Fever
Fever plays an important role in body's defenses against infection
during fever:
- Increase immune function
- Activate T-cell production
- increase effectiveness of some IFN
- Limits the replication of some viruses/bacteria
- Increase phagocytosis

14. VI. Systematic Changes
- Nervous system
- Cardiovascular system
- Respiratory system
- Digestive system
- Immune system

15.  Nervous system :
- Headache
- Hallucination
- Twitch
 Digestive system
- Indigestion, anorexia
- Abdominal distension
- Constipation
 Cardiovascular system:
- Increase of heart rate
- Blood pressure change.
 Respiratory system:
- Increase of respiratory rate
- Hyperventilation.
• ( may cause acid – base imbalance )

16. VII. Symptoms
When somebody has a fever, signs and symptoms are linked to what is
known as sickness behavior, and may include:
- Increase temperature
- Chills
- Shivering
- Muscle aches
- Lack of energy
- Depression
- lethargic
- Headache
- Loss of appetite
- Dehydration…

17. • Basic principle for common fever :
- Care
- Suitable medication when necessary
• Need to be treated immediately when :
- Temperature > 39°C
- Heart disease patients
- Cachexia patients
- Pregnant women. THANK YOU

18. References :
• Book : Pathophysiology
• https://en.wikipedia.org/wiki/Fever
• https://www.slideshare.net/prabeshrajjk/04-fever
• https://www.slideshare.net/dramritdelhi/fever-44712323
• https://my.clevelandclinic.org/health/symptoms/10880-fever
• https://www.slideshare.net/GirishJain10/fever-76088303