Temperature Regulation
Dr Dileep Verma
Associate Professor
Deptt of Physiology
KGMU
Lecture-1 :Topics

Core and Shell body temp.

Heat Balance

Factors promoting a) Heat gain
b) Heat loss

Temp. regulatory mechanisms
Learning Objectives

Normal Body Temperature

Ways of measuring Body Temp

List the mechanisms of heat
production & heat loss

Regulation of Body Temp.
Body Temperature






Normal Body Temperature (NBT) –
98.60F(370C)
Range of NBT ----- (970F to 990F)
Rectal Temp ----- (0.50F to 10F) above
the Oral
Rectal Temp reflects the internal body
Temp (Core Body Temp)
Core Body Temp remain almost constant
Skin Temp (Shell Temp)-----Variable
Temperature Homeostasis
Keep the body temp within a very narrow
range
 Range of NBT
(970F to 990F)


Temperatures above this:
denature enzymes and block metabolic
pathways

Temperatures below this:
slow down metabolism and affect the brain.
Heat Balance
Heat balance maintains the body temp
 Balance between heat production & heat
loss (Heat Balance)
 Heat Balance

 Heat production= Heat loss
Heat production is called thermogenesis
 Heat loss is called as thermolysis

Heat Production (Thermogenesis)
BMR
Specific Dynamic Action of food
Activity of skeletal muscle
Shivering
Exercise
 Chemical Thermogenesis
Epinephrine &Norepinephrine
Thyroxine
 Brown FatSource of considerable heat production
Abundant in infants



Heat Loss (Thermolysis)
Radiation
 Conduction
 Convection
 Evaporation
 Perspiration
 Respiration
 Loss through urine & feces

Role of Skin
Heat Exchange in the Skin
Vasoconstriction and
Vasodilatation
Thermoregulation
Temperature is regulated by nervous feedback
mechanisms
 Thermoregulatory center located in the
Hypothalamus
 Thermoregulatory regulatory responses
include

Autonomic
Somatic
Endocrine
Behavioural changes
Feedback system
1) Receptor
◦ Sensor that responds to changes (stimuli)
 2) Control Center
◦ Sets range of values
◦ Evaluates input and
◦ Sends output
 3) Effector◦ Receives output from control centre
◦ Produces a response

Body Temperature Control System

Hypothalamus
◦ Acts as a thermostat
◦ Receives nerve impulses
from cutaneous
thermoreceptors
◦ Thermoreceptors
Cold
&Heat

Hypothalamus- also has
thermoreceptors called
central thermoreceptors

These detect changes in
blood temperature
Thermoregulatory regulatory responses

Activated by Exposure to Cold
1.
Shivering
Increase voluntary activity
Increase TSH secretion
Increase Catecholamines
Vasoconstriction
Horripilation
Curling up
2.
3.
4.
5.
6.
7.
Thermoregulatory regulatory responses

Activated by Exposure to Heat
1.
Vasodilatation
Sweating
Increase in Respiration
Anorexia
Apathy
Decrease TSH secretion
2.
3.
4.
5.
6.
Thermoregulatory regulatory responses
Exposure to Cold
Exposure to Heat
Shivering
Increase voluntary activity
Increase TSH secretion
Increase Catecholamines
Vasoconstriction
Horripilation
Curling up
Vasodilatation
Sweating
Increase in Respiration
Anorexia
Apathy
Decrease TSH secretion
1-A major source of heat
production in infants is
A.
B.
C.
D.
Increased muscular activity
Brown fat
Increased sympathetic activity
Specific dynamic action of food
2-At normal room temperature
most body heat loss is byA. Convention
B. Conduction
C. Radiation
D. Sweating
3-Constituents of secreted sweat are similar to
plasma except for
A.
B.
C.
D.
Proteins
Chloride
Bicarbonate
Potassium
4-The only available mechanism of heat transfer
when the environmental temperature is greater than
the body temperature is
A.
B.
C.
D.
Radiation
Conduction
Convection
Evaporation
5-Cause of thermogenesis in the body
is
A.
B.
C.
D.
Skeletal muscle relaxation
Assimilation of food
Decreased cardiac metabolism
Hypothyroidism
6-A major factor resulting in increase in
body temperature during exercise is-
A. Heat dissipating mechanisms
inefficient
B. Enormous thermogenesis
C. Vasoconstriction on non-working
muscles
D. Resetting of thermostat
7-Site which reflects the true
value of core temperature
A. Oesophagus and rectum
B. Tympanic membrane
C. Vagina
D. All of the above
8-BMR is dependent on
A.
B.
C.
D.
Body weight
Surface area
Amount of lean body mass
Height
9-One feels hotter on a humid day
because-
A. Rate of sweating increases
B. Surrounding temperature is more
C. Heat loss by the body via process of
radiation decreases
D. Rate of evaporation of water from
body decreases
10-A major factor resulting in increase
in body temperature during exercise is-
A. Heat dissipating mechanisms
inefficient
B. Enormous thermogenesis
C. Vasoconstriction on non-working
muscles
D. Resetting of thermostat
Temperature Regulation
Dr Dileep Verma
Associate Professor
Deptt of Physiology
KGMU
Lecture-2 :Topics
Life in Hot environment
-Effect of acute heat
 Thermoregulatory responses
 Heat syndrome
-Heat cramps
-Heat exhaustion
-Heat stroke

Contd…
Life in cold environment
-effect of acute & long term
cold exposure on body
 Applied
-Hypothermia
-Harmful effects of extreme
cold

Learning Objectives

Effect of Hot & Cold environment on
the body.

Thermo-receptors

Regulation of Body Temperature
Life in Hot environment



Hot climates- These are two types
a) Hot-dry
b) Warm-humid
Hot-dry climateFound in deserts
Temp >500 C
Not humid
Warm-humid climate –
Found in tropical forest
Temp usually<350 C
Humidity >75%
Contd--- Effects
of acute heat -
Effects of acute exposure to heat
are divided intoa) Thermoregulatory responses
b) Other effects
Contd---
Thermoregulatory regulatory responses
Vasodilatation
Sweating
Increase in Respiration
Anorexia
Apathy
Decrease TSH
secretion
Contd---
Other effects of acute heat exposure onCellular metabolism
Rate of respiration
Work of breathing
Pulse rate
Dehydration
Urinary volume
Contd--- Heat
Syndromes- adverse reaction
to heat exposure
a) Heat Cramps
b) Heat Exhaustion
c) Heat Stoke
Life in cold environment
Effect of cold exposure on bodya) Acute cold exposure
b) Long term cold exposure
 Applied
-Hypothermia
-Harmful effects of extreme
cold

Contd---
Effect of acute cold exposure on body
Shivering
Increase voluntary
activity
Increase TSH secretion
Increase Catecholamines
Vasoconstriction
Horripilation
Curling up
Contd---
Effect of long term cold
exposure
Metabolic Responses
Insulative Responses
Hypothermic Responses
Contd--- Hypothermia –Body temp below
the normal lower limit (<970F)
 Thermoregulatory responses
Greatly impaired at (<940F)
Lost at body temp(<850F)
Contd---
Frostbite
Occurs at very low temp
Surface area freezes
Ice crystals formed

Common sites-
Lobes of the ears
Digits of hands
Digits of feet

Cold induced vasodilatation-
Final protection against frostbite
Summary of Effector Mechanisms
in Temperature Regulation
1- Thermal sweating differs from nonthermal sweating in that
A. Eccrine glands are responsible for it
B. Occurs due to activation of sympathetic
cholinergic nerves
C. Found mainly over palm, sole and axilla
D. All of the above
Core temperature of 260C leads to death
due to:
a)
b)
c)
d)
Brain damage
Respiratory insufficiency
Cardiac failure
All of the above
2- Which area of hypothalamus functions
as thermostat?
A.
B.
C.
D.
Preoptic
Paraventricular
Dorso medial
Lateral
3- Insensible water loss (perspiration) will be
absent if humidity is
A.
B.
C.
D.
50%
70%
90%
100%
4- Pyrogens raises body temperature by
A. Setting the thermostat to higher level
B. Releasing interleukins
C. Decreasing peripheral heat liberating
mechanism
D. Causing peripheral vasoconstriction
5- Heat loss process of the body not
directly under physiological control is
A.
B.
C.
D.
Radiation from body
Conduction and convection to surroundings
Vaporization of sweat
Warming of inspired air
6- Fever is usually caused by
A.
B.
C.
D.
Interleukin-1
Substance- p
Endorphins
Encephalin
7- During exposure to cold, body
temperature is raised by
A.
B.
C.
D.
Vasoconstriction in the skin
Horripilation
Thermogenesis
All of the above
8- Profound hypothermic signs include all
except
Show breathing
B. Bradycardia
C. Hypotension
D. Hyperactivity
A.
9- Aspirin decreases the body temperature
by
A.
B.
C.
D.
Inhibiting interleukin-1
Inhibiting pyrogens release
Killing fever producing organisms
Inhibiting prostaglandin synthesis
10- When the core temperature of the body falls
below the hypothalamic set-point temperature
A.
B.
C.
D.
The blood vssels of the skin constrict
Heat production increases within minutes
The basal metabolic rate increases
All of the above