Chapter 40 - Mastering Biology

Integrator. (An integrator sends instructions to an effector based on sensory information.)

Which component of a homeostatic system compares sensory information to a target value? Effector. Integrator. Set point. Sensor

Thermoregulation is the maintenance of the body's temperature within a tolerable range. All animals regulate their body temperatures to a certain extent, but some animals maintain a more constant temperature than others. The maintenance of body temperature is critical for physiological and biochemical processes, many of which rely on enzymatic activity.

describe thermoregulation**

Shivering (Shivering generates metabolic heat and warms the body.)

Which of the following actions acts to warm a homeothermic body? Dilating blood vessels. Shivering. Panting. Sweating.

Allows the internal environment to alter its conditions to match those of the external environment. (The epithelium allows the internal environment to remain constant even if the external environment changes.)

Which of the following actions is not a function of the epithelium? Allows the internal environment to alter its conditions to match those of the external environment. Creates an internal environment that is different from the external environment. Regulates the excretion of waste. Controls the exchange of nutrients between the internal and external environments.

a. vasodilation b. body temperature decreases c. homeostasis d. body temperature increases e. vasoconstriction f. negative (Thermoregulation relies on negative feedback. Negative feedback works to return a system to homeostasis by reducing a stimulus, such as a change in temperature. By contrast, positive feedback systems amplify or speed up a response. In thermoregulation in mammals, the stimulus is either a decreased body temperature or an elevated body temperature. If the temperature is too low, one response is vasoconstriction in the skin and extremities, resulting in lower blood flow and less heat lost to the environment through the skin. When body temperature increases to normal, homeostasis is regained. If the temperature is elevated, one of the body's responses is vasodilation in the skin and extremities. This response increases the amount of heat lost to the environment, and body temperature decreases. In mammals, the "thermostat," or temperature control system, is located in the hypothalamus. When cells in the hypothalamus detect a body temperature below the normal range, the hypothalamus will inhibit heat loss mechanisms and activate mechanisms such as shivering and vasoconstriction. When the cells detect a body temperature above the normal range, the thermostat activates heat loss mechanisms such as vasodilation, sweating, and panting.)

Part A - Identifying parts of a feedback systemPart complete Thermoregulation in the body is accomplished by several feedback systems. The feedback system shown here uses vasoconstriction and vasodilation in the skin and extremities to regulate body temperature. Drag the labels to their appropriate locations on the diagram of the feedback system below. Labels can be used once, more than once, or not at all.

In a sea turtle's flippers, heat is transferred from (1) to (3). In a dolphin, blood cools as it flows from the aorta to the testes. At a dolphin's testes, heat is transferred from (1) to (2). (Many marine animals, including sea turtles and dolphins, have adaptations that allow them to regulate heat gain and loss. In cooler water, the countercurrent heat exchanger in the sea turtle's flippers transfers heat from arteries to veins, resulting in heat retention in the body and cooler temperatures in the flippers. In addition to countercurrent heat exchangers in its flippers, a male dolphin's testes have a countercurrent heat exchanger to help keep them cool. The testes are surrounded by abdominal muscle that warms with activity, such as vigorous swimming. Because high temperatures can damage sperm, a countercurrent heat exchanger transfers heat from the arteries near the testes to veins carrying cooler blood from the tail. In this way, the testes are kept cool enough to protect the sperm from damage, and heat is retained in the body core.)

Part B - Overview of countercurrent heat exchangersPart complete The images below show two countercurrent heat exchangers in marine animals: in the flipper of a sea turtle (left) and in the abdomen of a dolphin (right). Which three of the following statements are consistent with the images?

•homeothermic endotherm: walrus, eagle, coyote •homeothermic ectotherm: arctic shrimp •poikilothermic ectotherm: salamander, freshwater catfish, butterfly [[Animals can be described according to whether they generate their own body heat (endothermic) or gain most of their body heat from external sources (ectothermic). They can also be described according to whether they maintain a relatively constant body temperature (homeothermic) or allow their body temperature to fluctuate with the environment (poikilothermic). The diagram below illustrates that animals are not strictly endotherms, ectotherms, homeotherms, or poikilotherms but rather that there is a continuum. Although birds and mammals are generally homeothermic endotherms (upper right in the graph), there is no fixed relationship between the source of body heat and the stability of body temperature. For example, the arctic shrimp is an ectotherm; yet it is also a homeotherm due to the fact that its environment's temperature is relatively stable.]]

Part C - Identifying modes of thermoregulationPart complete Animals can be classified according to their mode of thermoregulation. Sort the animals below, indicating their likely thermoregulatory strategy. Note that poikilotherms are sometimes referred to as heterotherms. Drag each animal [arctic shrimp, butterfly, eagle, salamander, walrus, freshwater catfish, coyote] to the appropriate bin [homeothermic endotherm, homeothermic ectotherm, poikilothermic ectotherm].

True (Enzyme activity depends on conditions within a cell, such as temperature and pH, which must be kept within a certain narrow range.)

True or false? Organisms must maintain homeostasis because optimal enzyme activity is achieved within a very narrow range of conditions. True False

Sensor (A sensor perceives changes in some parameter of the environment.)

Which component of a homeostatic system perceives changes in some parameter of the environment? Effector. Sensor. Integrator. Set point.

After a meal, blood sugar levels in the body rise; insulin is secreted to lower blood sugar levels. (The actions of insulin reverse the internal conditions of high blood sugar levels in the body.)

Which of the following statements describes a negative feedback response? After a meal, blood sugar levels in the body rise; insulin is secreted to lower blood sugar levels. A person who loses 3 pounds continues to diet to lose an additional 10 pounds. The arrival of platelets at a wound site stimulates the recruitment of more platelets to form a clot. The onset of contractions during childbirth stimulates the release of a hormone that stimulates further contractions.

Regulatory homeostasis. (Regulatory homeostasis involves adjusting the internal conditions of an organism to stay within a narrow range without regard to the external conditions.)

Which term describes a steady state in which the internal conditions of an organism are kept within a narrow range without regard to the external conditions? Conformational homeostasis. Thermoregulation. Regulatory homeostasis. Negative feedback.