Thermoregulation lab

Flashcards for Thermoregulation Lecture Review

THERMOREGULATION

Ability to keep body temperature within the strict values, characteristic to the species.

Optimal Temperature

Range of environmental temperatures ideal for the processes of growth and development, characteristic for the species or population.

Core temperature (Tco)

Is in dynamic equilibrium as a result of balance between heat gain and heat loss.

Mean body temperature (Tbody)

Represents an average of skin and internal temperatures.

Thermoregulatory Center

Located in the hypothalamus, it integrates information related to thermoregulation.

Thermoreceptors

Mammalian warmth receptors are thought to be unmyelinated C-fibres, while those responding to cold have both C-fibers and thinly myelinated A delta fibers.

Warm receptors

Warming increases their action potential discharge rate, while cooling decreases it.

Cold receptors

Firing rate increases during cooling and decreases during warming.

Triumvirate of Thermoregulation

Thermoreceptors and thermodetectors, thermoregulation centre (analysis and integration of information), and effectors of thermoregulation.

Effectors of thermoregulation

Circulatory system, sweat glands, skeletal muscles, liver, adipose tissue (creation, saving or elimination of heat).

Hypothalamus

Acts as thermostat that makes thermoregulatory adjustments to deviations from temperature norm in the brain (37 ± 1 °C or 98.6 +1.8 °F).

Vascular adjustments in cold

Constrict peripheral blood vessels.

Muscular activity in cold

Exercise energy metabolism and shivering.

Hormonal output in cold

Epinephrine and norepinephrine increase basal heat production; prolonged cold - thyroxin.

Skin blood vessels dilate

Capillaries become flushed with warm blood; heat radiates from skin surface.

Increased body temperature

Activates heat-loss center in hypothalamus.

Decreased body temperature

Blood cooler than hypothalamic set point

Heat Loss by Radiation

Objects emit electromagnetic heat waves without molecular contact with objects.

Heat Loss by Conduction

Direct transfer of heat through a liquid, solid, or gas from one molecule to another.

Heat Loss by Convection

Effectiveness depends on how rapidly the air (or water) adjacent to the body is exchanged.

Heat Loss by Evaporation

Heat transferred as water is vaporized from respiratory passages and skin surfaces.

Heat Loss in High Humidity

Total sweat vaporized from skin depends on surface area exposed to environment, temperature and humidity of ambient air, and convective air currents about the body.

Heat Balance of the Organism (Ht)

Hm + Hc + Hr + He + Hs, where Hm=metabolic heat, Hc=conduction, Hr=radiation, He=convection and evaporation, Hs=stored heat.

Anastomoses in heat loss

Increased flow through blood vessels promotes skin heat loss.

Anastomoses in heat conservation

Contraction of precapillary arterioles and blood flow through arteriovenous anastomoses reduces heat loss.

Direct Calorimetry

Measurement of temperature changes in the isolated system. A calorimeter is a chamber surrounded by a water jacket and the heat expelled by an animal in the chamber increases the temperature of the water jacket.

Calorific Value

Amount of heat created during complete oxidation of unit of given substance.

Indirect Calorimetry

Technique used to estimate energy expenditure via a measure of oxygen consumption and carbon dioxide production.

Respiratory Quotient (RQ)

A ratio used in physiology and metabolism to determine which macronutrients (carbohydrates, fats, proteins) are being metabolized for energy.

Resting Metabolism - Man

No motion, horizontal position, no psychological stimulation, optimal ambient temperature, 12-14 h postprandium.

Resting Metabolism - Mouse

Basic motion, prior to morning meal, and optimal ambient temperature.

Energy balance - gains and loses

Digestible energy, reserves, stored energy, internal transformations, useful energy, mechanical energy, and heat.

Metabolic Rate

A function of body mass (M=70 W 0.75). Metabolic mass (W0.75) is mass of an animal to the exponent of % equalisation of differences in the mass to the surface area (allometry).

BROWN ADIPOSE TISSUE

Oxidation in mitochondria,generation of CAMP,lipolysis,FFA,abundant sympathetic innervation,abundance of mitochondria.