Biology - 9201 OxfordAQA

Temperature Control

Muhtasari

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.

Malengo

  1. 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.
  2. Temperature receptors in the skin send impulses to the thermoregulatory centre, giving information about skin temperature.
  3. 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.
  4. 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.

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Maelezo ya Somo

A marathon runner finishing in hot weather may have lost three litres of water and still have a core temperature within a degree of the one she started with. That is the achievement. Her muscles have been pouring out energy for hours, the sun has been adding more, and yet the temperature of the blood reaching her brain has barely shifted. Nothing about that is passive. It is the output of a control system that has been measuring, deciding and correcting the whole way round the course.

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Tathmini ya Somo

Hongera kwa kukamilisha somo la Temperature Control. Sasa kwa kuwa umechunguza dhana na mawazo muhimu, ni wakati wa kuweka ujuzi wako kwa mtihani. Sehemu hii inatoa mazoezi mbalimbali maswali yaliyoundwa ili kuimarisha uelewaji wako na kukusaidia kupima ufahamu wako wa nyenzo.

Utakutana na mchanganyiko wa aina mbalimbali za maswali, ikiwemo maswali ya kuchagua jibu sahihi, maswali ya majibu mafupi, na maswali ya insha. Kila swali limebuniwa kwa umakini ili kupima vipengele tofauti vya maarifa yako na ujuzi wa kufikiri kwa makini.

Tumia sehemu hii ya tathmini kama fursa ya kuimarisha uelewa wako wa mada na kubaini maeneo yoyote ambapo unaweza kuhitaji kusoma zaidi. Usikatishwe tamaa na changamoto zozote utakazokutana nazo; badala yake, zitazame kama fursa za kukua na kuboresha.

  1. 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
  2. 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
  3. 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
  4. 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
  5. 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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