u Chapter 40 ~ An Introduction to Animal Structure and Function

Figure 41.1 Maintaining Internal Stability while on the Go

Figure 41.2 Four Types of Tissue

Internal regulation u Interstitial fluid: internal fluid environment of vertebrates; exchanges nutrients and wastes u Homeostasis: “steady state” or internal balance u Negative feedback: change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation; i.e., body temperature u Positive feedback: physiological control mechanism in which a change in some variable triggers mechanisms that amplify the change; i.e., uterine contractions at childbirth

Metabolism: sum of all energy- requiring biochemical reactions u Catabolic processes of cellular respiration u Calorie; kilocalorie/C u Endotherms: bodies warmed by metabolic heat u Ectotherms: bodies warmed by environment u Basal Metabolic Rate (BMR): minimal rate powering basic functions of life (endotherms) u Standard Metabolic Rate (SMR): minimal rate powering basic functions of life (ectotherms)

Figure The Mouse-to-Elephant Curve (Part 1)

Figure The Mouse-to-Elephant Curve (Part 2)

Physiological Regulation and Homeostasis u Cells, tissues, and organs are effectors that respond to commands from regulatory systems. Effectors are controlled systems. u Regulatory systems obtain, process, and integrate information, then issue commands to controlled systems, which effect change. u Regulatory systems receive information as negative feedback, which causes effectors to reduce or reverse a process; or positive feedback which tells a regulatory system to amplify a response. u Feedforward information signals the system to change the setpoint.

Figure 41.4 Control, Regulation, and Feedback

Temperature and Life u Living cells tolerate only a narrow range of temperature. Most cell function is limited to the range between 0°C and 45°C. u Even within this range, temperature change may create problems for animals. u Heat always moves from a warmer to a cooler object, so any environmental temperature change will cause change in the temperature of an organism—unless the organism can regulate its temperature.

Temperature and Life u Most physiological processes are temperature-sensitive, going faster at higher temperatures. u The sensitivity of a physiological process to temperature can be described as a quotient, Q 10. u Q 10 is defined as the rate of a reaction at a particular temperature (R T ) divided by the rate of that reaction at a temperature 10°C lower (R T-10 ). Q 10 = R T / R T-10

Temperature and Life u Most biological Q 10 values are between 2 and 3, meaning that reaction rates double or triple as temperature increases by 10°C. u Since not all of the component reactions in an animal have the same Q 10, temperature change can disrupt physiological functioning, throwing off the balance and integration that cell processes require. u To maintain homeostasis, organisms must either compensate for or prevent temperature change.

Figure 41.5 Q 10 and Reaction Rate

Figure “Cold” and “Hot” Fish

Figure Brown Fat

Figure The Hypothalamus Regulates Body Temperature

The Vertebrate Thermostat u Animals can save energy by turning down the thermostat to below normal (hypothermia). u Many animals use regulated hypothermia as a means of surviving periods of cold and food scarcity. u An adaptive hypothermia called daily torpor can drop body temperature 10–20°C and save considerable metabolic energy. u Regulated hypothermia lasting days or weeks with drops to very low temperatures is called hibernation. The reduction in metabolic rate results in enormous energy savings. u A special kind of hypothermia in hot, arid environment is estivation.