Regulation of body temperature

Is it true to say that when the temperature raises above the body temperature, the blood vessel shrinks to reduce the heat gain by radiation/convention/conduction, and dilates when the surrounding temperature falls below? I am confused of the role of blood vessel in body regulation. Please relate your answers to CE. Biology

Update:

If so, then when the atmospheric temperature rises above body temperatures, the action,which is the dilation, is the feedback to regulate temperature? But as you said, the body absorb heat instead of losing heat, it is impossible that it is a feedback.

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  • 1 decade ago
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    No

    人體於氣溫熱的時候,血管舒張以助加快散熱,所以人在運動時會面紅。

    人體於氣溫冷的時候,血管收縮以減少熱力散失,天氣冷的時候會臉會白一點。

    兩者的界線在於個人覺得熱或冷,可能有人覺得30已經很熱,老人家可能覺得35度才算很熱,劇列運動的時候可能18度都面紅耳熱流汗。

    至於溫度高於37度,會否又反其道而行、血管收縮呢?答案是否定的,想想一個人正在享受桑拿浴、浸溫泉等,外溫高於體溫甚多,大家都只會面紅紅,不會變成面青青,就知道血管正在舒張,不能散熱之餘,實質在加速吸熱。

    2009-04-07 21:39:09 補充:

    低於體溫的negative feedback無問題,若高於體溫的話negative feedback的效果瓦解,但是否等同於『沒有feedback』呢?有點玩文字遊戲的感覺。

    或者咁講,身體體溫會陷入『positive feedback』之中,即環境愈熱,身體吸熱愈快,metabolic rate愈高,體溫進一步上升,若不及時離開過熱環境,將會熱死。

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