1. The Human Body: An Orientation
Chapter 1
You are about to begin the study of one of the most engaging subjects available; the study of your own body.
You will learn...
how your body works
techniques for evaluating and detecting disease
how to stay healthy
how to stretch
In this chapter you will learn the three essential concepts of the course address...
the complementarity of structure and function
hierarchy of structural organization
homeostasis
terminology of anatomy

2. Overview of Anatomy and Physiology
Study of structure
Subdivisions:
Gross or macroscopic (e.g., regional, systemic, and surface anatomy)
Microscopic (e.g., cytology and histology)
Developmental (e.g., embryology)
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3. Overview of Anatomy and Physiology
Study of the function of the body
Subdivisions based on organ systems (e.g., renal or cardiovascular physiology)
Often focuses on cellular and molecular level
Body's abilities depend on chemical reactions in individual cells
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4. Principle of Complementarity
Anatomy and physiology are inseparable
Function always reflects structure
What a structure can do depends on its specific form
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5. Figure 1.2 Examples of interrelationships among body organ systems.
Digestive system
Takes in nutrients, breaks them down, and eliminates unabsorbed matter (feces)
Respiratory system
Takes in oxygen and eliminates carbon dioxide
Food O2
CO2
Cardiovascular system
Via the blood, distributes oxygen and nutrients to all body cells and delivers wastes and carbon dioxide to disposal organs
Blood
CO2 O2
Heart
Urinary system Eliminates nitrogenous
wastes and
excess ions
Nutrients
Interstitial fluid
Nutrients and wastes pass between blood and cells via the interstitial fluid
Integumentary system Protects the body as a whole from the external environment
Feces
Urine
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6. Hierarchy of Structural Organization
Chemical
Cellular
Tissue
Organ
Organ System
Organism

7. Homeostasis
The ability of the body to maintain relatively stable internal conditions even though there is continuous change in the outside world
A state of dynamic equilibrium
The body functions within relatively narrow limits
All body systems contribute to its maintenance

8. Control Mechanisms
Regardless of the factor or event (variable) being regulated, all homeostatic control mechanisms have at least three interdependent components
Receptor (stimuli of change is detected)
Control center (determines response)
Effector (bodily response to the stimulus)

9. Control Mechanisms
Regulation of homeostasis is accomplished through the nervous and endocrine systems

10. 3 4 Control Center Receptor Effector 2 5 1 IMBALANCE BALANCE IMBALANCE
Figure 1.4 Interactions among the elements of a homeostatic control system maintain stable internal conditions.
Slide 1
Input: Information
sent along afferent
pathway to control
center. 3
Output: Information sent
along efferent pathway to
effector. 4
Control
Center
Afferent
pathway
Efferent
pathway
Receptor
Effector
Receptor
detects
change. 2
Response
of effector
feeds back to
reduce the
effect of
stimulus and
returns
variable
to homeostatic
level. 5
Stimulus
produces
change in
variable. 1
IMBALANCE
BALANCE
IMBALANCE
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11. IMBALANCE 1 BALANCE IMBALANCE
Figure 1.4 Interactions among the elements of a homeostatic control system maintain stable internal conditions.
Slide 2
IMBALANCE
Stimulus
produces
change in
variable. 1
BALANCE
IMBALANCE
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12. Receptor 2 IMBALANCE 1 BALANCE IMBALANCE
Figure 1.4 Interactions among the elements of a homeostatic control system maintain stable internal conditions.
Slide 3
Receptor
Receptor
detects
change. 2
IMBALANCE
Stimulus
produces
change in
variable. 1
BALANCE
IMBALANCE
© 2013 Pearson Education, Inc.

13. 3 Control Center Receptor 2 1 IMBALANCE BALANCE IMBALANCE
Figure 1.4 Interactions among the elements of a homeostatic control system maintain stable internal conditions.
Slide 4
Input: Information
sent along afferent
pathway to control
center. 3
Control
Center
Afferent
pathway
Receptor
Receptor
detects
change. 2 1
IMBALANCE
Stimulus
produces
change in
variable.
BALANCE
IMBALANCE
© 2013 Pearson Education, Inc.

14. 3 4 Control Center Receptor Effector 2 1 IMBALANCE BALANCE IMBALANCE
Figure 1.4 Interactions among the elements of a homeostatic control system maintain stable internal conditions.
Slide 5
Input: Information
sent along afferent
pathway to control
center. 3
Output: Information sent
along efferent pathway to
effector. 4
Control
Center
Afferent
pathway
Efferent
pathway
Receptor
Effector
Receptor
detects
change. 2 1
IMBALANCE
Stimulus
produces
change in
variable.
BALANCE
IMBALANCE
© 2013 Pearson Education, Inc.

15. 3 4 Control Center Receptor Effector 2 5 1 IMBALANCE BALANCE IMBALANCE
Figure 1.4 Interactions among the elements of a homeostatic control system maintain stable internal conditions.
Slide 6
Input: Information
sent along afferent
pathway to control
center. 3
Output: Information sent
along efferent pathway to
effector. 4
Control
Center
Afferent
pathway
Efferent
pathway
Receptor
Effector
Receptor
detects
change. 2
Response
of effector
feeds back to
reduce the
effect of
stimulus and
returns
variable
to homeostatic
level. 5 1
IMBALANCE
Stimulus
produces
change in
variable.
BALANCE
IMBALANCE
© 2013 Pearson Education, Inc.

16. Negative Feedback Most feedback mechanisms in body
Response reduces or shuts off original stimulus
Variable changes in opposite direction of initial change
Examples
Regulation of body temperature (a nervous system mechanism)
Regulation of blood volume by ADH (an endocrine system mechanism)
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17. Figure 1.5 Body temperature is regulated by a negative feedback mechanism.
Control Center
(thermoregulatory
center in brain)
Afferent
pathway
Efferent
pathway
Receptors
Temperature-sensitive
cells in skin and brain)
Effectors
Sweet glands
Sweat glands activated
Response
Evaporation of sweat
Body temperature falls;
stimulus ends
Body temperature
rises
IMBALANCE
Stimulus: Heat
BALANCE
Stimulus: Cold
Response
Body temperature rises;
stimulus ends
Body temperature
falls
IMBALANCE
Effectors
Skeletal muscles
Receptors
Temperature-sensitive
cells in skin and brain
Efferent
pathway
Afferent
pathway
Shivering begins
Control Center
(thermoregulatory
center in brain)
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18. Negative Feedback: Regulation of Blood Volume by ADH
Receptors sense decreased blood volume
Control center in hypothalamus stimulates pituitary gland to release antidiuretic hormone (ADH)
ADH causes kidneys (effectors) to return more water to the blood
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19. Positive Feedback Response enhances or exaggerates original stimulus
May exhibit a cascade or amplifying effect
Usually controls infrequent events that do not require continuous adjustment
Enhancement of labor contractions by oxytocin (chapter 28)
Platelet plug formation and blood clotting
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20. Control Mechanisms A chain of events . . .
Stimulus produces a change in a variable
Change is detected by a sensory receptor
Sensory input information is sent along an afferent pathway to control center
Control center determines the response
Output information sent along efferent pathway to activate response
Monitoring of feedback to determine if additional response is required

21. Negative Feedback Mechanisms
Most control mechanisms are negative feedback mechanisms
A negative feedback mechanism decreases the intensity of the stimulus or eliminates it
The negative feedback mechanism causes the system to change in the opposite direction from the stimulus
Example: home heating thermostat

22. Positive Feedback Mechanisms
A positive feedback mechanism enhances or exaggerates the original stimulus so that activity is accelerated
It is considered positive because it results in change occurring in the same direction as the original stimulus
Positive feedback mechanisms usually control infrequent events such as blood clotting or childbirth

23. Positive Feedback Response enhances or exaggerates original stimulus
May exhibit a cascade or amplifying effect
Usually controls infrequent events that do not require continuous adjustment
Enhancement of labor contractions by oxytocin (chapter 28)
Platelet plug formation and blood clotting
© 2013 Pearson Education, Inc.

24. Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug.
Slide 1
Break or tear
occurs in blood
vessel wall. 1
Positive feedback
cycle is initiated. 3
Released
chemicals
attract more
platelets.
Platelets
adhere to site and
release chemicals. 2
Positive
feedback
loop
Feedback cycle ends
when plug is formed.
Platelet plug
is fully formed. 4
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25. Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug.
Slide 2
Break or tear
occurs in blood
vessel wall. 1
Positive feedback
cycle is initiated.
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26. Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug.
Slide 3
Break or tear
occurs in blood
vessel wall. 1
Positive feedback
cycle is initiated.
Platelets
adhere to site and
release chemicals. 2
© 2013 Pearson Education, Inc.

27. Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug.
Slide 4
Break or tear
occurs in blood
vessel wall. 1
Positive feedback
cycle is initiated. 3
Released
chemicals
attract more
platelets.
Platelets
adhere to site and
release chemicals. 2
Positive
feedback
loop
© 2013 Pearson Education, Inc.

28. Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug.
Slide 5
Break or tear
occurs in blood
vessel wall. 1
Positive feedback
cycle is initiated. 3
Released
chemicals
attract more
platelets.
Platelets
adhere to site and
release chemicals. 2
Positive
feedback
loop
Feedback cycle ends
when plug is formed.
Platelet plug
is fully formed. 4
© 2013 Pearson Education, Inc.

29. Homeostatic Imbalance
Disturbance of homeostasis
Increases risk of disease
Contributes to changes associated with aging
Control systems less efficient
If negative feedback mechanisms overwhelmed
Destructive positive feedback mechanisms may take over (e.g., heart failure)
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30. Homeostatic Imbalances
Most diseases cause homeostatic imbalances (chills, fevers, elevated white blood counts etc.)
Aging reduces our ability to maintain homeostasis
Heat stress