BIOL 221 Study Guide - Final Guide: Thermogenesis, Basal Rate, Skeletal Muscle
11 Feb 2020
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Document Summary
Heat is produced by cellular metabolism due to basal activity in the internal organs (e. g. , brain, heart, kidneys). Inactive skeletal muscle accounts for 20-30% of this basal rate. Heat is produced because the reactions that produce atp capture less than half of the energy available in glucose; the rest is released as heat. Thyroxine and epinephrine increase metabolic rates in cells, especially skeletal muscle, thus generating more heat. Increased activity in skeletal muscle increases heat production regardless of whether that increase is due to a simple increase in metabolic rate or whether it is to movements such as shivering. Shivering occurs when antagonistic muscle groups alternate contractions. Fast-acting mechanisms that keep the body warm either reduce heat loss or increase heat production. Vasoconstriction of cutaneous blood vessels is one mechanism to decrease heat loss. Unfortunately, prolonged exposure to cold can reduce blood flow enough that frostbite results.
