Temperature Homeostasis & Diet Flashcards
HUMANS ARE HOMEOTHERMIC.
TRUE OR FALSE?
TRUE
Homeothermic= warm-blooded
WHY IS A WOMAN’S BASAL BODY TEMPERATURE HIGHER DURING THE SECOND HALF OF HER MENSTRUAL CYCLE?
Due to effects of progesterone
BODY TEMPERATURE BALANCE
- A dynamic equilibrium between heat input and output
- Heat input – internal production and external input
–internal: metabolism and muscle contraction
–external: from the environment via radiation or conduction
•Heat output - losses to the environment
–radiation, conduction, convection and evaporation
HEAT BALANCE IN THE BODY
BODY TEMPERATURE IS HOMEOSTATICALLY REGULATED
- Generally, body T > ambient (environmental) T
- Thermoneutral zone (TNZ): the range of ambient T over which the heat from basal metabolism is sufficient to maintain body core T (≈ 25-30 oC)
–above TNZ there is net bodily gain of heat
–below TNZ there is net bodily loss of heat
–in both cases homeostatic compensation is required
•A naked human can thermoregulate at ambient air T between 10-55 oC
–the main physiological thermoregulatory challenge is low T
ENVIRONMENTAL (AMBIENT) TEMPERATURE IS GENERALLY HIGHER THAN BODY TEMPERATURE.
TRUE OR FALSE?
False
Body temperature tends to be higher
WHAT IS THERMONEUTRAL ZONE (TNZ)?
The range of ambient T over which the heat from basal metabolism is sufficient to maintain body core T (≈ 25-30 oC)
WHERE IS THE THERMOREGULATORY CENTRE?
In the hypothalamus
THE THERMOREGULATORY CENTRE IS IN THE HYPOTHALAMUS
Integrates sensory input from thermoreceptors located in the core and periphery (skin).
–↑ blood T is detected in the anterior hypothalamus
–↓ blood T is detected in the posterior hypothalamus
- Input T is compared with the desired setpoint (37 oC)
- Appropriate regulatory response is output
–> 37 oC – sweating, cutaneous vasodilation
–< 37 oC – cutaneous vasoconstriction (and horripilation)
–< 37 oC – non-shivering thermogenesis (infants)
–< 37 oC – shivering
WHERE IS A DECREASE IN BLOOD TEMPERATURE DETECTED?
In the posterior hypothalamus
WHERE IS AN INCREASE IN BLOOD TEMPERATURE DETECTED?
In the anterior hypothalamus
THERMOREGULATORY REFLEXES 1
THERMOREGULATORY REFLEXES 2
THERMOREGULATORY RESPONSES: CUTANEOUS BLOOD FLOW VASOCONSTRICTION
THERMOREGULATORY RESPONSES: CUTANEOUS BLOOD FLOW VASODILATION
HOW MANY SWEAT GLANDS DO WE HAVE?
3-4 million
THERMOREGULATORY RESPONSES: SHIVERING
Voluntary (behavioural) & involuntary muscular thermogenesis
NON-SHIVERING THERMOGENESIS
Hormone-induced, uncoupling of mitochondrial oxidation from phosphorylation in brown adipose tissue.
Only of significance in infants
BODY TEMPERATURE RANGES
FEVER (PYREXIA), 38oC=
•Result of a chemical resetting (↑) of the thermal set point
–release of endogenous pyrogens (EPs) in response to infection
•EPs – cytokines released into the circulation include IL-1β, IL-6 and TNFα
–body triggers thermoregulatory responses
•↑ heat production and ↓ heat loss= core temperature rises
–body temperature stabilises at new (elevated) set point
Augmentation of the immune response (innate & adaptive)
•Body temperature remains elevated until fever ‘breaks’
WHAT IS ADEQUATE (HEALTHY) NUTRITION?
An integral part of daily life that contributes to the physiological, mental and social well-being of individuals.
A balanced diet that contains adequate amounts of nutrients in relation to bodily requirements.