㊣㊣10marks㊣㊣ What is metabolic rate?

(i)When the temperature decrease, what changes for a people 's metabolic rate?
Ans:
When temperature decreases, a person's metabolic rate will increase. This is because we are endotherm(內溫動物). The colder the temperature, the more heat will be lost to surrounding due to radation and convection. Due to this reason, it is necessary for our body to produce more energy to compensate the loss so as to prevent the occurrence of hypothermia(低溫症).
(ii)how will metabolic rate be change?
Ans:
When themperature descreases, the thermoreceptors located on the skin will detects this temperature decreases. Besides the blood flowing through the thermo-regulatory centre located on the hypothalamus will also detect this changes. As a result, brings the following physiological changes:
(i)increases the secretion of both hormones, thyroxine(T4) and adrenaline. T4 increases the body's metabolic rate whiles adrenaline increases the heart beats so that more O2 will be delivered to the cell for oxidation of food substrates to occur. (i.e. oxidative phosphorylation). In aBoth increases our metabolic rate.
Additional information on how heat energy will be produced besides increasing the person's metabolic rate.
The reason for the increase in metabolic rate is to give us more heat so that our body temperature will also be kept at approximately 37度. There are several ways for our body to do so. (a)increase the muscle tones so as to produce more heat energy.即是令肌肉不停地震動.這種震動是不作任何功的(don't do anyｗork due to the contraction of both flexor and extensor) (b)sweating rate decrease so that less heat energy will be lost due to the evaporation of sweating. (c)erector pili muscle contraction so that hair stand at end. This makes ue to trap more heat energy.(這段指出除了increase body's metabolic rate外,身體還有其他的生理反應的)
希望你明白

2007-03-23 15:29:11 補充：
endotherm means we produce heat energy for our body. Hence we are warm-blooded animals. Comparing ectotherm which can't produce heat energy by themselves. They are cold-looded animals such as reptiles(i.e. lizard).

2007-03-23 15:29:22 補充：
They absorb heat energy from the surroundings such as lying on the ground to absorb heat energy from the sun.

metabolic rate=catabolic rate+ anabolic rate

when temperature decrease...
our body have to produce more heat to compensate the heat loss in order to maintain constant body temperature....
so that the metabolic rate increase,more energy is used and more heat is produced.

There is a close relationship between the metabolic rate and our nervous system.When we are under harsh condition,sympathetic nevours sysyem will be dominate....metabolic rate will be increase for energy releasing under nervous control.

hope that the above information can help you^^

新陈代谢率
You expend energy no matter what you're doing, even when sleeping. Thus your Basal Metabolic Rate is the number of calories you'd burn if you stayed in bed all day - a tempting idea for some. If you've noticed that every year, it becomes harder to eat whatever you want and stay slim, you've also learned that your Basal Metabolic Rate decreases as you age. Likewise, depriving yourself of food in hopes of losing weight also decreases your BMR, a foil to your intentions. However, a regular routine of cardiovascular exercise can increase your BMR, improving your health and fitness when your body's ability to burn energy gradually slows down.