Temperature Control
Visão Geral
Walk out of an air-conditioned room into a hot street and almost nothing about you changes. Your skin flushes, you start to feel damp, and within a few minutes you are uncomfortable. What has not changed is the number that matters: the temperature deep inside your chest and skull, which your body defends near 37 °C whether the air outside is at 5 °C or 40 °C. Enzymes are the reason. Let the core drift a few degrees either way and the reactions that keep you alive slow down or stop entirely.
This lesson follows the control system that does the defending. You will find out where in the brain the decision is made, what two separate sets of receptors it listens to, and why the skin is the organ that carries out almost every instruction. You will learn what really widens when someone says a person's blood vessels have dilated, why a layer of sweat only cools you once it evaporates, and why a shivering muscle is warming you with a chemical reaction you already know by name.
Objetivos
- Body temperature is monitored and controlled by the thermoregulatory centre in the brain. The thermoregulatory centre has receptors sensitive to the temperature of the blood flowing through the brain. The name of the centre in the brain (hypothalamus) is not required.
- Temperature receptors in the skin send impulses to the thermoregulatory centre, giving information about skin temperature.
- If the core body temperature is too high: blood vessels supplying the skin capillaries dilate so that more blood flows through the capillaries and more energy is transferred from the skin to the environment; sweat glands release more sweat, which cools the body as sweat evaporates. Sweating helps to cool the body. More water is lost when it is hot, and more fluid has to be taken through drink or food to balance this loss.
- If the core body temperature is too low: blood vessels supplying the skin capillaries constrict to reduce the flow of blood through the capillaries; muscles may ‘shiver’ - their contraction needs respiration, which transfers some energy to warm the body.
Mapa mental
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Nota de Aula
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- What do the receptors inside the thermoregulatory centre respond to? A. The temperature of the air around the body B. The temperature of the blood flowing through the brain C. The temperature of the skin surface D. The concentration of glucose in the blood Answer: B
- The core body temperature rises above normal. Which response takes place? A. The blood vessels supplying the skin capillaries constrict B. The sweat glands stop releasing sweat C. The blood vessels supplying the skin capillaries dilate D. The skeletal muscles begin to shiver Answer: C
- Sweat cools the body when it A. is produced by the sweat glands B. runs off the surface of the skin C. evaporates from the surface of the skin D. is wiped away with a towel Answer: C
- How does shivering help to raise body temperature? A. Friction between the moving limbs produces heat B. Muscle contraction requires respiration, which transfers some energy that warms the body C. It increases the flow of blood through the skin capillaries D. It reduces the amount of sweat produced by the sweat glands Answer: B
- Which statement about the skin capillaries during vasodilation is correct? A. The capillaries widen so that more blood flows through them B. The capillaries move closer to the surface of the skin C. The vessels supplying the capillaries widen so that more blood flows through the capillaries D. The capillaries carry blood away from the surface of the skin Answer: C
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