chapter 40 physiology, homeostasis, and temperature regulation

Chapter 40: Physiology, Homeostasis, and Temperature Regulation

CHAPTER 40Physiology, Homeostasis,

and Temperature Regulation


Chapter 40: Physiology, Homeostasis, and Temperature RegulationHomeostasis: Maintaining the Internal EnHomeostasis: Maintaining the Internal Environmentvironment

Tissues, Organs, and Organ SystemsTissues, Organs, and Organ Systems

Physiological Regulation and Physiological Regulation and HomeostasisHomeostasis


Chapter 40: Physiology, Homeostasis, and Temperature RegulationTemperature and LifeTemperature and Life

Maintaining Optimal Body TemperatureMaintaining Optimal Body Temperature

Thermoregulation in EndothermsThermoregulation in Endotherms

The Vertebrate ThermostatThe Vertebrate Thermostat


Homeostasis: Maintaining the Internal Environment• Single-celled organisms and some Single-celled organisms and some

small, simple multicellular animals small, simple multicellular animals meet their needs by direct exchange meet their needs by direct exchange between their cells and an aqueous between their cells and an aqueous environment.environment.

• Larger, more complex animals must Larger, more complex animals must do so by maintaining a constant do so by maintaining a constant internal environment.internal environment.

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Homeostasis: Maintaining the Internal Environment • The internal environment consists of The internal environment consists of

the extracellular fluids. the extracellular fluids.

• Organs and organ systems have Organs and organ systems have specialized functions to keep certain specialized functions to keep certain aspects of the internal environment in aspects of the internal environment in a constant state. Review Figure 40.1a constant state. Review Figure 40.1

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Figure 40.1

Figure 40.1Figure 40.1

figure 40-01.jpg


Homeostasis: Maintaining the Internal Environment • Homeostasis is the maintenance of Homeostasis is the maintenance of

constancy in the internal environmentconstancy in the internal environment

• It depends on the ability to control and It depends on the ability to control and regulate organ and organ system regulate organ and organ system function.function.

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Tissues, Organs and Organ Systems• Cells with a similar structure and Cells with a similar structure and

function make up a tissue. function make up a tissue.

• There are four general types: There are four general types: EpithelialEpithelial ConnectiveConnective MuscleMuscle Nervous. Nervous.

Review Figure 40.2Review Figure 40.288


Figure 40.2


figure 40-02.jpg


Tissues, Organs, and Organ Systems • Epithelial tissues are sheets of tightly Epithelial tissues are sheets of tightly

connected cells that cover body connected cells that cover body surfaces and line hollow organs.surfaces and line hollow organs.

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Tissues, Organs, and Organ Systems • Connective tissues support and Connective tissues support and

reinforce other tissues. reinforce other tissues.

• They generally consist of dispersed They generally consist of dispersed cells in an extracellular matrix.cells in an extracellular matrix.

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Tissues, Organs, and Organ Systems • Muscle tissues contract. Muscle tissues contract.

• There are three types:There are three types: SkeletalSkeletal CardiacCardiac Smooth.Smooth.

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Tissues, Organs, and Organ Systems • There are two types of nerve cells:There are two types of nerve cells:

• Neurons generate and transmit Neurons generate and transmit electrochemical signalselectrochemical signals

• Glial cells provide supporting functions Glial cells provide supporting functions for neurons.for neurons.

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Tissues, Organs, and Organ Systems • Organs consist of multiple tissue Organs consist of multiple tissue

types, and organs make up organ types, and organs make up organ systems. Review Table 40.1systems. Review Table 40.1

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Table 40.1 – Part 1

Table 40.1 – Part 1Table 40.1 – Part 1

table 40-01a.jpg


Table 40.1 – Part 2

Table 40.1 – Part 2Table 40.1 – Part 2

table 40-01b.jpg


Physiological Regulation and Homeostasis• Regulatory systems have set points Regulatory systems have set points

and respond to feedback information. and respond to feedback information.

• Negative feedback corrects deviations Negative feedback corrects deviations from the set pointfrom the set point

• Positive feedback amplifies responsesPositive feedback amplifies responses• Feedforward information changes the Feedforward information changes the

set point. Review Figure 40.5set point. Review Figure 40.5

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Figure 40.5


figure 40-05.jpg


Temperature and Life

• Living systems require a range of Living systems require a range of temperatures between the freezing temperatures between the freezing point of water and the temperatures point of water and the temperatures that denature proteins.that denature proteins.

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• Most biological processes and Most biological processes and reactions are temperature-sensitive. reactions are temperature-sensitive.

• QQ10 10 is a measure of temperature is a measure of temperature sensitivity. Review Figure 40.6sensitivity. Review Figure 40.6

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Figure 40.6


figure 40-06.jpg



• Animals that cannot avoid seasonal Animals that cannot avoid seasonal changes in body temperature have changes in body temperature have biochemical adaptations to biochemical adaptations to compensate. compensate.

• These enable animals to acclimatize to These enable animals to acclimatize to seasonal changes. seasonal changes. Review Figure 40.7Review Figure 40.7

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Figure 40.7


figure 40-07.jpg


Maintaining Optimal Body Temperature • Homeotherms maintain a fairly Homeotherms maintain a fairly

constant body temperature most of constant body temperature most of the time; poikilotherms do not. the time; poikilotherms do not.

• Endotherms produce metabolic heat; Endotherms produce metabolic heat; ectotherms depend mostly on ectotherms depend mostly on environmental sources of heat. environmental sources of heat. Review Figure 40.8Review Figure 40.8

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Figure 40.8


figure 40-08.jpg


Maintaining Optimal Body Temperature • Ectotherms and endotherms can Ectotherms and endotherms can

regulate body temperature through regulate body temperature through behavior. Review Figure 40.9behavior. Review Figure 40.9

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Figure 40.9


figure 40-09.jpg


Maintaining Optimal Body Temperature • Heat exchange between a body and Heat exchange between a body and

the environment is via:the environment is via: radiationradiation conductionconduction convectionconvection Evaporation Evaporation

Review Figure 40.11Review Figure 40.112828


Figure 40.11


figure 40-11.jpg


Maintaining Optimal Body Temperature • Ectotherms and endotherms can Ectotherms and endotherms can

control heat exchange with the control heat exchange with the environment by altering blood flow to environment by altering blood flow to the skin. Review Figure 40.12the skin. Review Figure 40.12

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Figure 40.12


figure 40-12.jpg


Maintaining Optimal Body Temperature • Some ectotherms can produce Some ectotherms can produce

metabolic heat to raise their body metabolic heat to raise their body temperatures. Review Figure 40.13temperatures. Review Figure 40.13

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Figure 40.13


figure 40-13.jpg


Maintaining Optimal Body Temperature • Some fish have circulatory systems Some fish have circulatory systems

that function as countercurrent heat that function as countercurrent heat exchangers to conserve heat produced exchangers to conserve heat produced by muscle metabolism. Review Figure by muscle metabolism. Review Figure 40.1440.14

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Figure 40.14 – Part 1

Figure 40.14 – Part 1Figure 40.14 – Part 1

figure 40-14a.jpg




figure 40-14b.jpg


Thermoregulation in Endotherms • Endotherms have high basal metabolic Endotherms have high basal metabolic

rates. rates.

• Over a range of environmental Over a range of environmental temperatures, the thermoneutral zone, temperatures, the thermoneutral zone, their resting metabolic rates remain at their resting metabolic rates remain at basal levels. basal levels. Review Figure 40.15 Review Figure 40.15

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Figure 40.15


figure 40-15.jpg


Thermoregulation in Endotherms • When environmental temperature falls When environmental temperature falls

below a lower critical temperature, below a lower critical temperature, endotherms maintain their body endotherms maintain their body temperatures through shivering and temperatures through shivering and nonshivering metabolic heat nonshivering metabolic heat production.production.

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Thermoregulation in Endotherms • When environmental temperature rises When environmental temperature rises

above an upper critical temperature, above an upper critical temperature, metabolic rate increases as a metabolic rate increases as a consequence of evaporative water consequence of evaporative water loss.loss.

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Thermoregulation in Endotherms

• Endotherms in cold climates have Endotherms in cold climates have adaptations that minimize heat loss: adaptations that minimize heat loss: a reduced surface area-to-a reduced surface area-to-

volume ratiovolume ratio increased insulation.increased insulation.

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Thermoregulation in Endotherms

• Endotherms may dissipate excess heat Endotherms may dissipate excess heat generated by exercise or the generated by exercise or the environment via evaporation. environment via evaporation.

• However, water loss can be dangerous However, water loss can be dangerous to endotherms in dry environments.to endotherms in dry environments.

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The Vertebrate Thermostat• The vertebrate thermostat is in the The vertebrate thermostat is in the

hypothalamus. hypothalamus.

• It has set points for activating It has set points for activating thermoregulatory responses. thermoregulatory responses.

• Hypothalamic temperature provides Hypothalamic temperature provides negative feedback information.negative feedback information.

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The Vertebrate Thermostat • Cooling the hypothalamus induces Cooling the hypothalamus induces

blood vessel constriction and blood vessel constriction and increased metabolic heat productionincreased metabolic heat production

• Heating it induces blood vessel dilation Heating it induces blood vessel dilation and active evaporative water loss. and active evaporative water loss.

• Thermoregulatory behaviors are Thermoregulatory behaviors are induced by changes in hypothalamic induced by changes in hypothalamic temperature. Review Figure 40.18temperature. Review Figure 40.18

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Figure 40.18


figure 40-18.jpg


The Vertebrate Thermostat • Changes in set point reflect the Changes in set point reflect the

integration of information that is integration of information that is relevant to the regulation of body relevant to the regulation of body temperature. Review Figure temperature. Review Figure 40.1940.19

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Figure 40.19


figure 40-19.jpg


The Vertebrate Thermostat • Fever, which results from a rise in set Fever, which results from a rise in set

point, helps the body fight infections.point, helps the body fight infections.

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The Vertebrate Thermostat • Adaptations in which set points are Adaptations in which set points are

reduced to conserve energy include reduced to conserve energy include daily torpor and hibernation. daily torpor and hibernation. Review Figure 40.20 Review Figure 40.20

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figure 40-20a.jpg


Figure 40.20 – Part 2Figure 40.20 – Part 2Figure 40.20 – Part 2

figure 40-20b.jpg

chapter 40 physiology, homeostasis, and temperature regulation

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