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Chapter 1 Characteristics and Maintenance of Life
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Chapter 1
Characteristics and Maintenance of Life
Characteristics of Life
1. Ability to respond and adapt to the environment.
Characteristics of Life
2. Growth– Increase in mass.
Characteristics of Life
3. Growth and Development– Growth is increase in size.– Development is the formation of new structures.
Characteristics of Life
4. Reproduction– Ability to produce new organisms.
Characteristics of Life
5. Metabolism– Physical and chemical changes that occur through
the digestion of a food source that allows an organism to obtain, release, and utilize energy.
Table 01.03
Maintenance of Life
• Except for the reproductive system, and body structures and functions work in ways that maintain life.
Maintenance of Life
• Environmental factors needed for life:1. Water• Transports substances• Important for regulating body temperature• Required for many metabolic processes• Most abundant substance in the body
Maintenance of Life
• Environmental factors needed for life:2. Food• Provides energy and raw materials for building new
living matter.
Maintenance of Life
• Environmental factors needed for life:3. Oxygen• Used in the process of releasing energy from food.
Maintenance of Life
• Environmental factors needed for life:4. Heat• Partly controls the rate at which metabolic reactions
take place.• Heat is a form of energy. Temperature is a
measurement of the amount of heat present.
Maintenance of Life
• Environmental factors needed for life:5. Pressure• Application of force on an object or substance.• Examples:
– Atmospheric pressure » Caused by air particles
– Hydrostatic pressure» Caused by particles of a liquid such as water» Blood pressure is a type of hydrostatic pressure
Table 01.04
Maintenance of Life
• Homeostasis– The maintenance of a stable internal
environment.– Requires most of a human’s metabolic energy.– Homeostasis is maintained through self-regulating
control systems called homeostatic mechanisms.
Maintenance of Life
• Homeostatic Mechanisms– Have 3 components:• Receptors
– Provide info about specific conditions (stimuli) in the internal environment.
• Control Center– Tells what a particular value should be (set point).
• Effectors– Elicit responses that alter conditions in the internal
environment.
Maintenance of Life
• Homeostatic Mechanisms– Have 3 components:• Receptors
– Provide info about specific conditions (stimuli) in the internal environment.
• Control Center– Tells what a particular value should be (set point).
• Effectors– Elicit responses that alter conditions in the internal
environment.
Maintenance of Life
• Homeostatic Mechanisms
Maintenance of Life
• Homeostatic Mechanisms– Work through negative feedback.• If a change from the set point is detected by the
receptors, the effectors are triggered to bring the conditions back (negative) to the set point.• As conditions get closer to the set point, the receptors
begin to shut down so that conditions do not move past the set point.
Maintenance of Life
• Homeostatic Mechanisms– Although homeostasis is usually maintained
through negative feedback, there are some positive feedback systems (which move conditions away from the normal) such as blood clotting that also contribute to homeostasis.
Homeostatic mechanism regulates body temperature
Slide number: 2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
StimulusBody temperature rises above normal.
too high
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ReceptorsThermoreceptors sendsignals to the control center.
StimulusBody temperature rises above normal.
too high
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control centerThe brain detects thedeviation from the setpoint and signals effectororgans.
ReceptorsThermoreceptors sendsignals to the control center.
StimulusBody temperature rises above normal.
too high
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 5
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control centerThe brain detects thedeviation from the setpoint and signals effectororgans.
ReceptorsThermoreceptors sendsignals to the control center.
EffectorsSkin blood vessels dilateand sweat glands secrete.
StimulusBody temperature rises above normal.
too high
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
StimulusBody temperature rises above normal.
too high
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ReceptorsThermoreceptors sendsignals to the control center.
StimulusBody temperature rises above normal.
too high
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control centerThe brain detects thedeviation from the setpoint and signals effectororgans.
ReceptorsThermoreceptors sendsignals to the control center.
StimulusBody temperature rises above normal.
too high
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 5
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control centerThe brain detects thedeviation from the setpoint and signals effectororgans.
ReceptorsThermoreceptors sendsignals to the control center.
EffectorsSkin blood vessels dilateand sweat glands secrete.
StimulusBody temperature rises above normal.
too high
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 6
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control centerThe brain detects thedeviation from the setpoint and signals effectororgans.
ReceptorsThermoreceptors sendsignals to the control center.
EffectorsSkin blood vessels dilateand sweat glands secrete.
StimulusBody temperature rises above normal.
ResponseBody heat is lost to surroundings,temperature drops toward normal.
too high
Normal bodyTemperature37oC (98.6oF)
too low
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 7
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
StimulusBody temperature drops below normal.
ReceptorsThermoreceptors sendsignals to the control center.
too low
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 8
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
StimulusBody temperature drops below normal.
ReceptorsThermoreceptors sendsignals to the control center.
too low
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 9
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
StimulusBody temperature drops below normal.
Control centerThe brain detects thedeviation from the set pointand signals effector organs.
ReceptorsThermoreceptors sendsignals to the control center.
too low
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
StimulusBody temperature drops below normal.
Control centerThe brain detects thedeviation from the set pointand signals effector organs. If body temperature
continues to drop, controlcenter signals muscles tocontract involuntarily.
EffectorsSkin blood vessels constrict andsweat glands remain inactive.
ReceptorsThermoreceptors sendsignals to the control center.
too low
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 11
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
StimulusBody temperature drops below normal.
EffectorsMuscle activitygenerates body heat.
Control centerThe brain detects thedeviation from the set pointand signals effector organs. If body temperature
continues to drop, controlcenter signals muscles tocontract involuntarily.
EffectorsSkin blood vessels constrict andsweat glands remain inactive.
ReceptorsThermoreceptors sendsignals to the control center.
too low
Normal bodyTemperature37oC (98.6oF)
Homeostatic mechanism regulates body temperature
Slide number: 12
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
StimulusBody temperature drops below normal.
ResponseBody heat is conserved,temperature rises toward normal.
EffectorsMuscle activitygenerates body heat.
Control centerThe brain detects thedeviation from the set pointand signals effector organs. If body temperature
continues to drop, controlcenter signals muscles tocontract involuntarily.
