1) To function efficiently, many aspects of the human body’s must be maintained within tolerable limits.
2) Physiological is the name given to this maintenance of the internal environment despite changes in the .
3) Homeostasis operates on the principle of negative . By this means, a change in the internal environment is detected by which send messages to . These trigger responses, which negate the deviation from the norm and return the internal environment to its .
4) Although the initiates each hear-beat, the rate at which the heart beats is controlled by the action of the nervous system and the hormone adrenaline.
5) Rate and of breathing increase during exercise. The main stimulus for these changes is an increase in concentration of blood. This is detected by which send messages via the medulla to the muscular effectors.
6) During strenuous exercise, the cardiac increases significantly. In addition blood is diverted to and cardiac muscles and away from the digestive organs. Local distribution of blood is effected by some arterioles undergoing and others becoming vaso-constricted.
7) Receptor cells in the pancreas detect a rise in blood sugar level and produce . This hormone activates an enzyme in the liver which promotes the conversion of to glycogen.
8) Other receptor cells in the detect a drop in blood sugar level and produce . This hormone activates an enzyme in the liver, which promotes the conversion of glycogen to glucose.
9) In an emergency, inhibits the secretion of insulin and promotes the breakdown of glycogen to glucose.
10) is the condition suffered by people whose insulin secreting cells are partly or completely non-functional. Diabetic people fail to make a normal response to the glucose test.
11) The is the body’s temperature-monitoring centre. It possesses and communicates with effectors by sending out nerve impulses.
12) The skin acts as an effector in the control of body by bringing about several responses which exert negative feedback.
13) responses are also important in the regulation of body temperature.
14) Infants are less efficient at controlling body temperature because their involuntary response mechanism is not fully and they cannot employ voluntary means to warm up or cool down.
15) The elderly are often less efficient at controlling body temperature because their involuntary mechanisms are . If body temperature drops to a subnormal level, the person suffers .