Thermoregulation Across Systems - Anatomy and Physiology
- How does countercurrent heat exchange in the limbs conserve heat?
- Warm arterial blood transfers heat to cool venous blood returning in adjacent deep veins, so less heat reaches the skin.
- Which inputs tell the hypothalamus about body temperature?
- Peripheral thermoreceptors in the skin and central thermoreceptors in the hypothalamus, spinal cord and abdominal organs.
- Which core body temperature defines hypothermia?
- A core temperature below 35 °C.
- Which brain region serves as the body's main thermoregulatory center?
- The hypothalamus, especially the preoptic area, which compares body temperature with its set point.
- What are the main physiological responses to cold exposure?
- Skin vasoconstriction, shivering, and increased metabolic heat production (nonshivering thermogenesis).
- During prolonged exercise in the heat, why does stroke volume tend to fall?
- Skin vasodilation pools blood in the periphery and sweat loss reduces plasma volume, lowering venous return.
- How does thyroid hormone contribute to adaptation to prolonged cold?
- It raises basal metabolic rate, increasing heat production over days to weeks.
- What distinguishes heat stroke from heat exhaustion?
- Heat stroke involves a core temperature above about 40 °C with central nervous system dysfunction, such as confusion or seizures.
- How does brown adipose tissue produce heat?
- Uncoupling protein 1 (thermogenin) lets protons leak across the mitochondrial membrane, releasing energy as heat instead of making ATP.
- How does shivering raise body temperature?
- Involuntary, rhythmic skeletal muscle contractions convert ATP energy into heat without useful movement.
- Why does core temperature rise faster during exercise in hot, humid air than in hot, dry air?
- High humidity slows sweat evaporation, the main way the body loses heat during exercise in the heat.