Transcript 1_Introduction - Bloodhounds Incorporated

THE HUMAN BODY:
AN ORIENTATION
Chapter 1
OVERVIEW OF ANATOMY AND
PHYSIOLOGY
 Anatomy
 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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Inc.
OVERVIEW OF ANATOMY AND
PHYSIOLOGY
 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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Inc.
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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Inc.
FIGURE 1.2 EXAMPLES OF INTERRELATIONSHIPS AMONG BODY ORGAN SYSTEMS.
Digestive system
Respiratory system
Takes in nutrients, breaks them
down, and eliminates unabsorbed
matter (feces)
Takes in oxygen and
eliminates carbon dioxide
O2
Food
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
Nutrients
Interstitial fluid
Urinary system
Eliminates
nitrogenous
wastes and
excess ions
Nutrients and wastes pass
between blood and cells
via the interstitial fluid
Integumentary system
Feces
Protects the body as a whole
from the external environment
Urine
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Inc.
HIERARCHY OF STRUCTURAL
ORGANIZATION
 Chemical
 Cellular
 Tissue
 Organ
 Organ System
 Organism
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
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)
CONTROL MECHANISMS
Regulation of
homeostasis is
accomplished
through the
nervous and
endocrine systems
FIGURE 1.4 INTERACTIONS AMONG THE ELEMENTS OF A HOMEOSTATIC CONTROL SYSTEM MAINTAIN
STABLE INTERNAL CONDITIONS.
3 Input: Information
sent along afferent
pathway to control
center.
2 Receptor
Receptor
Control
Center
Afferent
pathway
Efferent
pathway
4 Output: Information sent
along efferent pathway to
effector.
Effector
5 Response
detects
change.
1 Stimulus
produces
change in
variable.
Slide 1
BALANCE
of effector
feeds back to
reduce the
effect of
stimulus and
returns
variable
to homeostatic
level.
© 2013 Pearson Education,
Inc.
FIGURE 1.4 INTERACTIONS AMONG THE ELEMENTS OF A HOMEOSTATIC CONTROL SYSTEM MAINTAIN
STABLE INTERNAL CONDITIONS.
Slide 2
1 Stimulus
produces
change in
variable.
BALANCE
© 2013 Pearson Education,
Inc.
FIGURE 1.4 INTERACTIONS AMONG THE ELEMENTS OF A HOMEOSTATIC CONTROL SYSTEM MAINTAIN
STABLE INTERNAL CONDITIONS.
2 Receptor
Slide 3
Receptor
detects
change.
1 Stimulus
produces
change in
variable.
BALANCE
© 2013 Pearson Education,
Inc.
FIGURE 1.4 INTERACTIONS AMONG THE ELEMENTS OF A HOMEOSTATIC CONTROL SYSTEM MAINTAIN
STABLE INTERNAL CONDITIONS.
3 Input: Information
sent along afferent
pathway to control
center.
2 Receptor
Receptor
Slide 4
Control
Center
Afferent
pathway
detects
change.
1 Stimulus
produces
change in
variable.
BALANCE
© 2013 Pearson Education,
Inc.
FIGURE 1.4 INTERACTIONS AMONG THE ELEMENTS OF A HOMEOSTATIC CONTROL SYSTEM MAINTAIN
STABLE INTERNAL CONDITIONS.
3 Input: Information
sent along afferent
pathway to control
center.
2 Receptor
Receptor
Control
Center
Afferent
pathway
Efferent
pathway
Slide 5
4 Output: Information sent
along efferent pathway to
effector.
Effector
detects
change.
1 Stimulus
produces
change in
variable.
BALANCE
© 2013 Pearson Education,
Inc.
FIGURE 1.4 INTERACTIONS AMONG THE ELEMENTS OF A HOMEOSTATIC CONTROL SYSTEM MAINTAIN
STABLE INTERNAL CONDITIONS.
3 Input: Information
sent along afferent
pathway to control
center.
2 Receptor
Receptor
Control
Center
Afferent
pathway
Efferent
pathway
4 Output: Information sent
along efferent pathway to
effector.
Effector
5 Response
detects
change.
1 Stimulus
produces
change in
variable.
Slide 6
BALANCE
of effector
feeds back to
reduce the
effect of
stimulus and
returns
variable
to homeostatic
level.
© 2013 Pearson Education,
Inc.
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)
© 2013 Pearson Education,
Inc.
FIGURE 1.5 BODY TEMPERATURE IS REGULATED BY A NEGATIVE FEEDBACK MECHANISM.
Control Center
(thermoregulatory
center in brain)
Afferent
pathway
Efferent
pathway
Receptors
Effectors
Temperature-sensitive
cells in skin and brain)
Sweet glands
Sweat glands activated
Response
Evaporation of sweat
Body temperature falls;
stimulus ends
Body temperature
rises
BALANCE
Stimulus: Heat
Stimulus: Cold
Response
Body temperature
falls
Body temperature rises;
stimulus ends
Receptors
Effectors
Temperature-sensitive
cells in skin and brain
Skeletal muscles
Shivering begins
Efferent
pathway
Afferent
pathway
Control Center
(thermoregulatory
center in brain)
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Inc.
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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Inc.
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.
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
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
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
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.
Slide 1
FIGURE 1.6 A POSITIVE FEEDBACK MECHANISM REGULATES FORMATION OF A PLATELET PLUG.
1 Break or tear
occurs in blood
vessel wall.
Positive feedback
cycle is initiated.
3 Released
chemicals
attract more
platelets.
Positive
feedback
loop
2 Platelets
adhere to site and
release chemicals.
Feedback cycle ends
when plug is formed.
4 Platelet plug
is fully formed.
© 2013 Pearson Education,
Inc.
Slide 2
FIGURE 1.6 A POSITIVE FEEDBACK MECHANISM REGULATES FORMATION OF A PLATELET PLUG.
1 Break or tear
occurs in blood
vessel wall.
Positive feedback
cycle is initiated.
© 2013 Pearson Education,
Inc.
Slide 3
FIGURE 1.6 A POSITIVE FEEDBACK MECHANISM REGULATES FORMATION OF A PLATELET PLUG.
1 Break or tear
occurs in blood
vessel wall.
Positive feedback
cycle is initiated.
2 Platelets
adhere to site and
release chemicals.
© 2013 Pearson Education,
Inc.
Slide 4
FIGURE 1.6 A POSITIVE FEEDBACK MECHANISM REGULATES FORMATION OF A PLATELET PLUG.
1 Break or tear
occurs in blood
vessel wall.
Positive feedback
cycle is initiated.
3 Released
chemicals
attract more
platelets.
Positive
feedback
loop
2 Platelets
adhere to site and
release chemicals.
© 2013 Pearson Education,
Inc.
Slide 5
FIGURE 1.6 A POSITIVE FEEDBACK MECHANISM REGULATES FORMATION OF A PLATELET PLUG.
1 Break or tear
occurs in blood
vessel wall.
Positive feedback
cycle is initiated.
3 Released
chemicals
attract more
platelets.
Positive
feedback
loop
2 Platelets
adhere to site and
release chemicals.
Feedback cycle ends
when plug is formed.
4 Platelet plug
is fully formed.
© 2013 Pearson Education,
Inc.
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)
© 2013 Pearson Education,
Inc.
HOMEOSTATIC IMBALANCES
 Most diseases cause homeostatic imbalances (chills, fevers,
elevated white blood counts etc.)
 Aging reduces our ability to maintain homeostasis
 Heat stress