Summary Body Temperature Study Unit 1

FLG 332 Copyright Micaela de Jager




Unit 1 – Body Temperature


LECTURE 1 – THERMOREGULATION

BODY TEMP
 Significance of thermoregulation
Why do we need to regulate internal body temperature?

− Homeostatic mechanisms that keep body temperature within acceptable limits
o Regardless of environmental conditions

− NB = enzymes operate over a relatively narrow temperature range



Factors influencing the body temp:

1. Age
• infants vary according to environment
• In children ↑(0.5°C) than adult
• Old age ↓the body temperature

2. Sex/Gender
• Females ↓than males

3. Diurnal variation
• min values in am
• max values pm

4. Meals
• ↑after meals

5. Exercise
• heat production from skeletal muscles can ↑

6. Menstrual cycle
• ↑during ovulation

7. Sleep
• ↓by 0.5°C

8. Emotions
• body temp↑




MICAELA DE JAGER 1

,FLG 332 Copyright Micaela de Jager


Body temperature range is narrow, within 1 degree
 36.°C –37.5 °C


Temp influences metabolic processes:

 ↑temp : destroys protein Corrected by homeostasis
 ↓temp : inhibits enzymatic reactions = prevent biochemical process



Body is divided into a warm internal core and a cooler outer shell:


Core T Shell T

 temp of deeper tissues  temp of skin
o relatively constant o fluctuates substantially
- 36.5 °C–37.5 °C - 20 °C–40 °C
o metabolism works optimum o depends on surroundings
o shell insulates heat within the core



• Various parts of the body are at different T
• The extremities are generally cooler than the rest of the body
• T of scrotum is carefully regulated at 32°C
• Rectal T is representative of temp at core of the body and varies least with changes in environmental T


• Oral T < rectal T (normally 0.5°C ↓)
Affected by: ingestion of hot/cold fluids
gum chewing
smoking
mouth breathing




THERMOREGULATION
Skin plays major role

 Maintenance of a constant body T



Balance between heat gain and heat loss in body:

More heat gain than loss = T↑
Less heat gain than loss = T↓




MICAELA DE JAGER 2

,FLG 332 Copyright Micaela de Jager



Temp regulation

Heat gain Heat loss
Gained by: Lost by:

- Radiation and conduction - Radiation, conduction and convection
- Muscular exercise - Vaporization of water in the respiratory
- Assimilation of food passages and on the skin (sweat)
- Thermogenic effect of hormone - Evaporative cooling
- All vital processes that contribute to BMR - Small # are removed in urine and faeces




Heat exchange with environment

4 Processes/Mechanisms:

• Radiation
• Convection
• Evaporation
• Conduction




MICAELA DE JAGER 3

, FLG 332 Copyright Micaela de Jager



HEAT GAIN MECHANISMS
 Biochemical reactions contribute to body heat production
 Ingestion of food ↑heat production – sympathetic discharge ↓during fasting and is ↑by feeding

 Skeletal muscle contraction e.g. during exercise


 Heat production can be varied by endocrine mechanisms in the absence of food intake or muscular exertion:
a) Epinephrine and NE - produce rapid but short-lived ↑in heat production
b) Thyroid hormones - produce slowly developing but prolonged ↑

 Brown fat (infants) – highly metabolic and has a thermogenic function

 Metabolism: Major source of internal heat generation
7% increase in metabolic rate ⇒ 0.55°C ↑in body temp

1. Shivering thermogenesis ⇒ Skeletal muscle metabolism
2. Non-shivering thermogenesis ⇒ Brown fat metabolism




1. Shivering thermogenesis

 metabolic heat production by muscle contractions

↓body temp ⇒ somatic motor neurons

skeletal muscle contractions (agonist and antagonist muscles)
metabolism in muscles
heat production (↑body T )
degree of stimulation varies with demand
if heat-gain center is extremely active, you begin to shiver
shivering ↑rate of heat generation up to 400%




2. Non-shivering thermogenesis

 metabolic heat production by fat

↓body temp ⇒ sympathetic neurons & hormones

metabolism in brown fat
heat production (↑body T )




MICAELA DE JAGER 4