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 Interstitial fluid: internal fluid

environment of vertebrates; exchanges nutrients and wastes

Homeostasis: “steady state” or internal balance

Negative feedback: change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation; i.e., body temperature

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

Catabolic processes of cellular respiration

Calorie; kilocalorie/C Endotherms: bodies warmed by

metabolic heat Ectotherms: bodies warmed by

environment Basal Metabolic Rate (BMR):

minimal rate powering basic functions of life (endotherms)

Standard Metabolic Rate (SMR): minimal rate powering basic functions of life (ectotherms)

Figure 41.13 The Mouse-to-Elephant Curve (Part 1)

Figure 41.13 The Mouse-to-Elephant Curve (Part 2)

Physiological Regulation and Homeostasis

Cells, tissues, and organs are effectors that respond to commands from regulatory systems. Effectors are controlled systems.

Regulatory systems obtain, process, and integrate information, then issue commands to controlled systems, which effect change.

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.

Feedforward information signals the system to change the setpoint.

Figure 41.4 Control, Regulation, and Feedback

Temperature and Life

Living cells tolerate only a narrow range of temperature. Most cell function is limited to the range between 0°C and 45°C.

Even within this range, temperature change may create problems for animals.

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

Most physiological processes are temperature-sensitive, going faster at higher temperatures.

The sensitivity of a physiological process to temperature can be described as a quotient, Q10.

Q10 is defined as the rate of a reaction at a particular temperature (RT) divided by the rate of that reaction at a temperature 10°C lower (RT-10).

Q10 = RT / RT-10

Temperature and Life

Most biological Q10 values are between 2 and 3, meaning that reaction rates double or triple as temperature increases by 10°C.

Since not all of the component reactions in an animal have the same Q10, temperature change can disrupt physiological functioning, throwing off the balance and integration that cell processes require.

To maintain homeostasis, organisms must either compensate for or prevent temperature change.

Figure 41.5 Q10 and Reaction Rate

Figure 41.12 “Cold” and “Hot” Fish

Figure 41.15 Brown Fat

Figure 41.17 The Hypothalamus Regulates Body Temperature

The Vertebrate Thermostat

Animals can save energy by turning down the thermostat to below normal (hypothermia).

Many animals use regulated hypothermia as a means of surviving periods of cold and food scarcity.

An adaptive hypothermia called daily torpor can drop body temperature 10–20°C and save considerable metabolic energy.

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.

A special kind of hypothermia in hot, arid environment is estivation.