THE HUMAN BODY: AN ORIENTATION Chapter 1. © 2013 Pearson Education, Inc. OVERVIEW OF ANATOMY AND...

The Human Body:An Orientation

Chapter 1

© 2013 Pearson Education, © 2013 Pearson Education, Inc.Inc.

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)


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


Principle of Complementarity

Anatomy and physiology are inseparable Function always reflects structure What a structure can do depends on its specific form


Figure 1.2 Examples of interrelationships among body organ systems.

Digestive system Takes in nutrients, breaks them down, and eliminates unabsorbed matter (feces)

Food O2 CO2

Respiratory systemTakes in oxygen and eliminates carbon dioxide

Cardiovascular systemVia the blood, distributes oxygen and nutrients to all body cells and delivers wastes and carbon dioxide to disposal organs

BloodCO2

O2

Heart

Nutrients

Interstitial fluid

Integumentary system Protects the body as a whole from the external environment

Nutrients and wastes pass between blood and cells via the interstitial fluid

Feces Urine

Urinary system Eliminates nitrogenouswastes andexcess ions

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 maintainstable internal conditions.

Slide 1

Output: Information sentalong efferent pathway toeffector.

Input: Informationsent along afferentpathway to controlcenter.

3

Receptordetectschange.

2

Stimulus produceschange invariable.

1

4

Responseof effectorfeeds back toreduce theeffect ofstimulus andreturnsvariableto homeostatic level.

5

ControlCenter

Afferentpathway

Efferentpathway

Receptor Effector

BALANCE

IMBALANCE

IMBALANCE



Slide 2


1

BALANCE

IMBALANCE

IMBALANCE



Slide 3


1


2

BALANCE

IMBALANCE

IMBALANCE

Receptor



Slide 4

Afferentpathway


1


2


3

BALANCE

IMBALANCE

IMBALANCE

Receptor

ControlCenter



Slide 5

Afferentpathway

Efferentpathway


1


2


3

BALANCE

IMBALANCE

IMBALANCE

Receptor

ControlCenter

Effector


4



Slide 6

Afferentpathway

Efferentpathway


1


2


3

BALANCE

IMBALANCE

IMBALANCE

Receptor

ControlCenter

Effector


4

Responseof effectorfeeds back toreduce theeffect ofstimulus andreturnsvariableto homeostatic level.

5


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)


Figure 1.5 Body temperature is regulated by a negative feedback mechanism.

Control Center(thermoregulatory

center in brain)

Afferentpathway

Efferentpathway

ReceptorsTemperature-sensitivecells in skin and brain)

EffectorsSweet glands

Sweat glands activated

ResponseEvaporation of sweatBody temperature falls;stimulus ends

Body temperaturerises

Stimulus: Heat

ResponseBody temperature rises;stimulus ends

EffectorsSkeletal muscles

EfferentpathwayShivering begins

BALANCE

IMBALANCE

IMBALANCE

Afferentpathway

Control Center(thermoregulatory

center in brain)

ReceptorsTemperature-sensitivecells in skin and brain

Stimulus: Cold

Body temperaturefalls


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


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

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


Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug. Slide 1

Releasedchemicalsattract moreplatelets.

Positivefeedbackloop

Plateletsadhere to site andrelease chemicals.

Feedback cycle endswhen plug is formed.

Platelet plugis fully formed.

Break or tearoccurs in bloodvessel wall.

Positive feedback cycle is initiated.

1

23

4





1





1


2






1


2 Releasedchemicalsattract moreplatelets.

3




Feedback cycle endswhen plug is formed.



1


2

Platelet plugis fully formed.

4

Releasedchemicalsattract moreplatelets.

3


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)

Homeostatic Imbalances

Most diseases cause homeostatic imbalances (chills, fevers, elevated white blood counts etc.)

Aging reduces our ability to maintain homeostasis

Heat stress

THE HUMAN BODY: AN ORIENTATION Chapter 1. © 2013 Pearson Education, Inc. OVERVIEW OF ANATOMY AND...

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