APassage FiveIfwe had to rely on only five senses for survival, we would be in very sad shape indeed.Wewouldn′t know up from down. We wouldn′t know when to eat or drink. We wouldn′tknow what our muscles were doing or what position our limbs were in. Wewouldn′t know when our body was dam-aged because we wouldn′t feel pain. Wemight freeze to death without even a shiver, or overheat with-out a drop ofsweat. The five senses--touch,taste, smell, hearing and sight--respond only tostimulation from the outside world,but the inside world of our bodies must alsoreceive and respond to important messages. Our internal senseskeep us alive and enable us to use our external senses. In effect, the internalsenses tell our brains how to run our bodies. Hunger or thirst registers in apart of the brain called the hypothalamus(丘脑下部),when a lack of food chemicals are detected in the blood. Another internal sense that controls our balance is maintained by threefluid-filled loops in the inner ear. Changes in position and gravity affect themotion of this liquid and cause changes in the brain. A sense called kinesthesia(肌肉运动知觉)lets us know the relative positions ofparts of our bodies. Even our breathing is caused by a sense that identifies anoverabundance of carbon dioxide and a lack of oxygen in the blood. No one has been able to count the number of internal senses. Thepresence of delicate internal senses shows just how marvelously complex wehuman beings are.[单选题] This passage deal mostly withthe __ 查看材料 A.internal senses
