BODY TEMPERATURE HEAT BALANCE Mechanisms of heat gain Mechanisms of heat loss VARIATIONS OF BODY TEMPERATURE REGULATION OF BODY TEMPERATURE Thermoreceptors Hypothalamus: the thermostat Thermoregulatory effector mechanisms ABNORMALITIES OF BODY TEMPERATURE

1. Body Temperature &
Regulation
Pandian M
Dept of Physiology
DYPMCKOP

2. At the end of the session, the students must be able to
1. Explain correctly concept of set point for body
temperature in human body
2. Describe correctly role of thermoreceptors in
temperature regulation
3. Describe correctly role of hypothalamus in
temperature regulation
PY 11.1 Describe and discuss mechanism of
temperature regulation

3. Objectives
• BODY TEMPERATURE
• HEAT BALANCE
• Mechanisms of heat gain
• Mechanisms of heat loss
• VARIATIONS OF BODY TEMPERATURE
• REGULATION OF BODY TEMPERATURE
• Thermoreceptors
• Hypothalamus: the thermostat
• Thermoregulatory effector mechanisms
• ABNORMALITIES OF BODY TEMPERATURE

4. INTRODUCTION
• Living organisms are classified into two groups,
• Depending upon the maintenance (regulation) of body
temperature:
1. Homeothermic animals
2. Poikilothermic animals.

5. HOMEOTHERMIC ANIMALS
• This type of animals body temperature is maintained at a
constant level,
• They are also called warm blooded animals.
• E.g - Birds and mammals

6. POIKILOTHERMIC ANIMALS
• This animals body temperature is not constant.
• It varies according to the environmental temperature.
• These animals are also called coldblooded animals.
• E.g. All animals except birds and mammals

7. Body Core Temperature and Skin
Temperature
a. Deep tissues temperature
remains very constant (within a
0.6 ̊C)
b. Skin temperature rises and falls
with the temperature
of the surroundings
c. Range of core temperatures is 36-
37.5 ̊C and 97-99.5 ̊F

8. BODY TEMPERATURE
• Body temperature can be measured by placing the clinical
thermometer in different parts of the body such as:
1. Mouth (oral temperature)
2. Axilla (axillary temperature)
3. Rectum (rectal temperature)
4. Over the skin (surface temperature).

9. NORMAL BODY TEMPERATURE
• when measured by placing the clinical thermometer in
the mouth (oral temperature).
• It varies between 35.8°C and 37.3°C (96.4°F and
99.1°F).

10. TEMPERATURE AT DIFFERENT PARTS
OF THE BODY
•Axillary temperature is 0.3°C to 0.6°C, lower
than the oral temperature.
•The rectal temperature is 0.3°C to 0.6°C,
higher
•The superficial temperature (skin or surface
temperature) varies between 29.5°C and 33.9°C,
than oral temperature.

12. VARIATIONS OF BODY TEMPERATURE
Physiological Variations
1. Age
2. Sex
3. Diurnal variation
4. After meals
5. Exercise
6. Sleep
7. Emotion
8. Menstrual cycle

13. Pathological Variations
•hyperthermia or fever & hypothermia

14. HEAT GAIN OR HEAT PRODUCTION
IN THE BODY
1. Metabolic Activities
2. Muscular Activity
3. Role of Hormones
• Thyroxine and adrenaline increase the heat production by accelerating the
metabolic activities.
4. Radiation of Heat from the Environment
5. Shivering
6. Brown Fat Tissue
its one of the two types of adipose tissues, the other being white
adipose tissue. It produces enormous body heat, particularly in infants.

15. HEAT LOSS FROM THE BODY
•Conduction
•Radiation
•Convection
•Evaporation – Insensible Perspiration
•Panting

16. Basic Physics of How Heat is Lost from the Skin Surface

17. Body Temperature is Controlled by Balancing Heat
Production and Heat Loss
• Heat Loss- determined by two factors
(1) how rapidly it can be conducted to the skin, and
(2) how rapidly it can be transferred from the skin to the
surroundings.
• Blood flow to the skin from the body core provides heat
transfer

18. Cont…..
Heat conduction in the skin is controlled
by the sympathetic nervous system; controlled
by vasoconstriction

19. Sweating and Its Regulation by the ANS
a. Stimulation of the anterior hypothalamic-preoptic area
causes sweating
b. Mechanism-sweat gland is a tubular structure consisting
of (1) deep subdermal coiled portion - secretes the
sweat,
(2) duct portion that passes outward through the
epidermis

20. Sweating and Its Regulation by the ANS
Sweat gland innervated
by an Ach secreting
sympathetic nerve

21. c. Acclimatization to heat:
•Exposed to heat for several hours everyday will
develop ↑se tolerance to heat & humid conditions in
1-3 wks.
•Two fold increase in the maximum rate of sweating.
•Increase plasma volume, decrease loss of salt in the
sweat & urine almost to none.
•Last two effects are because of increased aldosterone
Secretion.

22. Thermoregulation
• It is a process by which the body temperature of
an organism is regulated for the effective
functioning of the body.
•Body temperature is controlled by balancing heat
production against heat loss.

24. Regulation of Body
Temperature

25. Hypothalamus has two centers which
regulate the body temperature:
1. Heat loss center
2. Heat gain center.

26. Role of the Hypothalamus
- body temperature is regulated almost
entirely by nervous feedback mechanisms
-the regulating centers located in the
hypothalamus
Detection of Temperature by Receptors in
the Skin and Deep Body Tissues

27. Heat loss center/ Anti rise center
• Its situated in preoptic nucleus (PN) of anterior
hypothalamus.
• Neurons in PN are heat sensitive nerve cells so called -
thermoreceptors
Stimulation of preoptic nucleus
• Causes vasodilatation cutaneous and sweating.
• Removal or lesion of this nucleus increases the body
temperature.

28. Heat gain center/ Conservation area /Anti drop
center
•It is situated in posterior hypothalamic
nucleus.
•Stimulation of this nucleus causes
shivering.
•The removal or lesion of this nucleus
leads to fall in body temperature.

31. Summary

34. Applied

37. Hypothermia…

38. Definition
•Core body temperature less than 35oC
•Mild: 34-36oC
•Moderate: 30-34oC
•Severe: < 30oC

39. Causes…
Causes of Hypothermia
1. Exposure to cold temperatures
2. Immersion in cold water
3. Drug abuse
4. Hypothyroidism
5. Hypopituitarism
6. Lesion in hypothalamus

40. Signs and Symptoms
TABLE 110-2. Clinical Manifestations of Hypothermia
System Mild Hypothermia Moderate Hypothermia Severe Hypothermia
CNS Confusion, slurred speech,
impaired judgment,
amnesia
Lethargy, hallucinations, loss of
pupillary reflex, EEG
abnormalities
Loss of cerebrovascular
regulation, decline in
EEG activity, coma,
loss of ocular reflex
CVS Tachycardia, increased
cardiac output and
systemic vascular
resistance
Progressive bradycardia
(unresponsive to atropine),
decreased cardiac output and
BP, atrial and ventricular
arrhythmias, J (Osborn) wave
on ECG
Decline in BP and cardiac
output, ventricular
fibrillation (< 28°C)
and asystole (< 20°C)
Respiratory Tachypnea, bronchorrhea Hypoventilation (decreased rate
and tidal volume), decreased
oxygen consumption and
CO2 production, loss of
cough reflex
Pulmonary edema, apnea

41. Signs and Symptoms, cont’d
TABLE 110-2. Clinical Manifestations of Hypothermia, cont’d
System Mild Hypothermia Moderate hypothermia Severe Hypothermia
Renal Cold diuresis Cold diuresis Decreased renal perfusion
and GFR, oliguria
Hematologic Increased hematocrit and
decreased platelet, white
blood cell count,
coagulopathy, and DIC
GI Ileus, pancreatitis, gastric
stress ulcers, hepatic
dysfunction
Metabolic endocrine Increased metabolic rate,
hyperglycemia
Decreased metabolic rate, hyper-
or hypoglycemia
Musculoskeletal Increased shivering Decreased shivering (< 32°C,
90°F), muscle rigidity
Patient appears dead,
"pseudo-rigor mortis"

42. Rewarming Techniques
• Passive rewarming:
Removal from cold environment
Insulation, Warm blankets
Active external rewarming:
Warm water immersion
Heating blankets set at 40°C
Radiant heat
Active core rewarming at 40°C:
Inhalation rewarming
Heated IV fluids

43. Hyperthermia…

44. Benefits of fever:
Many organisms grow best within a
relatively narrow temperature range.
Increase in temperature inhibit
bacterial growth.
Antibody production is increased
when the body temperature is
increased.
Slows down growth of some tumors.

46. Signs and symptoms depend upon the
cause of fever:
• Headache
• Sweating
• Shivering
• Muscle pain
• Dehydration
• Loss of appetite
• General weakness.
TREATMENT
- Immediate removal
- Cold sponging
- Drugs:- paracetamol
(crocin) and others

47. Definition
•Core body temperature > 38oC
•Spectrum of heat-related illnesses
•Heat cramps
•Heat exhaustion
•Heat stroke

48. Causes of Hyperthermia…
• Heat stroke usually occurs when heavy physical work
is performed in hot and humid environment.
• In this condition normal response to increased
temperature (sweating) is impaired and core
temperature increases to the point of tissue damage.
• Convulsion, loss of consciousness and even death may
occur when body temperature exceeds 41°C.

49. Signs and Symptoms, cont’d
•Heat Stroke
•Mortality of 10-20% with current treatment
•Coma, seizures, confusion
•No sweating
•Temperature >41.1oC
•Classic triad: hyperpyrexia, CNS dysfunction,
anhidrosis
•Classic vs. Exertional

50. Treatment
• Cooling
• Remove to cool environment!

51. Reference
• Text book of Medical Physiology
• Guyton & Hall, Ganong
• Human Physiology
• Vander
• Text book of Medical Physiology
• Indukurana. A.K.Jain, Sembu
• Principles of Anatomy and Physiology
• Totora
• Hutchinson Clinical Methods
• Net source

52. THANK YOU . . .