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Summary FLG 332 Summaries

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Course
FLG 332

Institution
University Of Pretoria (UP)

An in depth summary of all the concepts and content that will equip you for a distinction in FLG 332. These summaries include lecture notes and extra information from lectures. Studying solely off these notes will be enough for the exam and tests. These notes are all you need!

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Uploaded on January 16, 2023
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FLG 332
STUDY UNIT 1
BODY TEMPERATURE
‐ Average body temperature is 37oC
‐ Body temperature range is 36oC-37.5oC
• Subject to considerable variation
• Varies from person to person
• Varies with metabolic activity & environmental circumstances even in one
individual
• Many factors influence body temperature
‐ Temperature determines the movement of molecules
‐ Heat energy allows chemical reactions
‐ Temperature influences metabolic processes → speeds up or slows down
‐ High temperature destroys proteins
‐ Low temperature inhibits enzymatic reactions & prevents biochemical processes
‐ Low or high temperature is corrected by homeostasis
‐ Skin plays large role in thermoregulation
‐ Body can be divided into 2 temperature regions:
• Warm internal core
• Cooler outer shell
‐ Core temperature:
• Temperature of the deeper tissues
• Relatively constant (36.5oC-37.5oC)
• Metabolism works optimum
‐ Shell temperature:
• Temperature of skin
• Fluctuates substantially (20oC-40oC)
• Depends on the surrounding
• Shell insulates heat within the core
‐ Core temperature is higher than shell temperature
TEMPERATURE

‐ Measure with thermometer
‐ 3 main scales: Celsius, Kelvin, & Fahrenheit
‐ Different areas to measure temperature – under armpit, in mouth, ear and rectum
‐ Rectal temperature is 0.5oC higher than oral temperature
• Rectal temperature considered most accurate
‐ Temperature generated in the core and then transferred to shell
‐ Blood serves as the major agent of heat transfer
‐ An increase in temperature more than 7oC is fatal, why?
‐ Body can survive decrease in core temperature up to 14oC

A Theron

, ‐ Low or high temperature is corrected by homeostasis
‐ Skin plays major role in thermoregulation
FACTORS INFLUENCING THE BODY TEMPERATURE
1. Age – temperature varies in infants & children; old age decreases temperature
2. Sex – females less than males due to women having lower metabolic rate
3. Diurnal variation – min. values in morning; max. values in evening
4. Meals – temperature increases after meals
5. Exercise – temperature increases due to heat production in skeletal muscles
6. Menstrual cycle – temperature increases during ovulation
7. Sleep – temperature decreases by 0.5oC
8. Emotions – body temperature increases
THERMOREGULATION

‐ Maintenance of a constant body temperature
‐ Balance between heat gain & heat loss in the body
‐ More heat gain than loss → temperature increases
‐ More heat loss than gain → temperature decreases
‐ Temperature regulating centre → hypothalamus
• Hypothalamus checks current temperature & compares it with normal body
temperature, according to that it will adjust whether body must produce more or
less heat

A Theron

,HEAT EXCHANGE

‐ Body uses 4 mechanisms of heat exchange
1. Radiation – transfer of heat from an object to its environment in the form of
infrared rays and vice versa
2. Conduction – exchange of heat between objects of different temperatures that
are in direct contact with one another
3. Convection – transfer of heat through circulation of air currents
4. Evaporation – transfer of heat due to the evaporation of water. Body heat is lost
through conversion of water on the skin into vapour

THERMOREGULATION

‐ Heat loss:
• Radiation
• Conduction
• Convection
• Evaporation → major heat loss
‐ Non-hypothalamic mechanisms:
• Exhalation
• Urination
• Defaecation
‐ Heat gain:
• Radiation
• Conduction
• Metabolism → heat production
 Shivering thermogenesis
 Non-shivering thermogenesis

A Theron

, HEAT LOSS

‐ Radiation: if the environmental temperature is lower than body temperature, body heat
is lost through radiation
‐ Conduction: blood conduct heat from core areas to the skin where heat conducts into the
skin
‐ Convection: heat is lost through the circulation of convective air currents along the skin
surface & hot air rises and is replaced by cooler air
‐ Evaporation: water is lost through sweat glands and heat is used to evaporate water
‐ Body heat is lost through conversion of water on the skin into vapour
‐ Under the control of sympathetic nervous system (acetylcholine as the
neurotransmitter)
‐ Only way by which the body loses heat is if the environmental temperature is higher
than the body temperature
HEAT GAIN

‐ Metabolism:
• Major source of internal heat generation
• Every 7% increase in metabolic rate → 0.55oC increase in body temperature
• Non-shivering thermogenesis → brown fat metabolism
• Shivering thermogenesis → skeletal muscle metabolism
• Constant exposure to cold leads to:
 Increase in sympathetic nervous system activity
 Increase in thyroxine in the long term
 Rise in metabolic rate by 30% in cold weather
 Causes more hunger to fuel the body metabolism
HEAT PRODUCTION

‐ Shivering thermogenesis:
• Metabolic heat production by shivering
• Rhythmic tremors caused by skeletal muscle contractions
• Muscle metabolism
• Generate heat
• Initiated by hypothalamus → due to activation of somatic motor neurons
• Controlled at spinal level
• Can increase heat production 3 to 5-fold

A Theron

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