Fig. 2. (A) Biological basis of T_b control. a_m, metabolic proportionality factor; endoc. law, endocrine controllers law; shiv, shivering thermogenesis; non-shiv, non-shivering thermogenesis. These four blocks constitute the metabolic rate controller/process in our model (see B). Behav. law, posture controllers law; a_K, proportionality factor for non-evaporative heat transfer; a_EHL, proportionality factor for evaporative heat transfer; shape, body positioning; vasomotor: peripheral blood perfusion; S/P, sweating and panting. These six blocks constitute the thermal conductance controller/process in our model (see B). HP, heat production; HL, heat loss; T_C/S, core and skin temperatures. The thermal characteristics of the body correspond to the thermal inertia and `disturbances' to T_A in our model. Notice that our model does not take into account local loops and other central nervous system areas interfering in the control. (Scheme based on fig. 2 of Cooper, 2002). (B) Schematic representation of the T_b control system modelled in Eq. 1-3. See text for details. Compare this control system to the biological one presented in A.