Chapter 1
The Human Body:
An Orientation:
Part A
Overview of Anatomy and
Physiology
 Anatomy: The study of structure of the body
 Subdivisions:
 Gross or macroscopic (e.g., regional, surface,
and systemic anatomy)
 Microscopic (e.g., cytology and histology)
 Developmental (e.g., embryology)
Overview of Anatomy and
Physiology
Essential tools for the study of
anatomy:
Anatomical terminology
Observation
Palpation
Auscultation
Overview of Anatomy and
Physiology
Physiology: The study of function
of the body at many levels
Subdivisions are based on organ
systems (e.g., renal, digestive,
cardiovascular physiology)
Overview of Anatomy and
Physiology
 Essential tools for the study of
physiology:
Ability to focus at many levels (from
systemic to cellular and molecular)
Basic physical principles (e.g.,
electrical currents, pressure, and
movement)
Basic chemical principles
Principle of
Complementarity
Anatomy and physiology are
inseparable.
Function always reflects
structure
What a structure can do
depends on its specific form
Levels of Structural
Organization
 Chemical: atoms and molecules (Chapter 2)
 Cellular: cells and their organelles (Chapter 3)
 Tissue: groups of similar cells (Chapter 4)
 Organ: contains two or more types of tissues
 Organ system: organs that work closely
together
 Organismal: all organ systems
Atoms
Organelle
Smooth muscle cell
Molecule
1 Chemical level
Atoms combine to form molecules.
Cardiovascular
system
Heart
Blood
vessels
2 Cellular level
Cells are made up of
molecules.
Smooth muscle tissue
3 Tissue level
Tissues consist of similar
types of cells.
Blood vessel (organ)
Smooth muscle tissue
Connective tissue
Epithelial
tissue
4 Organ level
Organs are made up of different types
of tissues.
6 Organismal level
The human organism is made up
of many organ systems.
5 Organ system level
Organ systems consist of different
organs that work together closely.
Figure 1.1, step 6
Overview of Organ Systems
 Major organs and functions of
the 11 organ systems
 Digestive system
 Nervous system
 Respiratory system
 Cardiovascular system
 Lymphatic system
 Urinary system
 Muscular system
 Skeletal system
 Integumentary system
 Endocrine system
 Reproductive system
Organ Systems
Organ Systems
Interrelationships
All cells depend on organ systems
to meet their survival needs
Organ systems work cooperatively
to perform necessary life functions
Necessary Life Functions
1. Boundary: Maintaining boundaries
between internal and external
environments
 Plasma membranes
 Skin
2. Movement: (contractility)
 Of body parts (skeletal muscle)
 Of substances (cardiac and smooth
muscle)
Necessary Life Functions
3. Responsiveness: The ability to
sense and respond to stimuli
 Withdrawal reflex
 Control of breathing rate
4. Digestion:
 Breakdown of ingested foodstuffs
 Absorption of simple molecules into
blood
Necessary Life Functions
5. Metabolism: All chemical
reactions that occur in body cells
 Catabolism and anabolism
6. Excretion: The removal of
wastes from metabolism and
digestion
 Urea, carbon dioxide, feces
Necessary Life Functions
7. Reproduction:
 Cellular division for growth or
repair
 Production of offspring
8. Growth: Increase in size of a
body part or of organism
Survival Needs
1. Nutrients:
 Chemicals for energy and cell
building
 Carbohydrates, fats, proteins,
minerals, vitamins
2. Oxygen:
 Essential for energy release (ATP
production)
Survival Needs
3. Water:
 Most abundant chemical in the body
 Site of chemical reactions
4. Body temperature:
 Affects rate of chemical reactions
5. Atmospheric pressure:
 For adequate breathing and gas
exchange in the lungs
Homeostasis
 It is the maintenance of a relatively
stable internal environment despite
continuous changes both inside and
out
 A dynamic state of equilibrium
Homeostatic Control
Mechanisms
Involve continuous monitoring and
regulation of many factors
(variables)
Nervous and endocrine
systems accomplish the
communication via nerve impulses
and hormones
Components of a Control
Mechanism
1. Receptor (sensor)
 Monitors the environment
 Responds to stimuli (changes in
controlled variables)
2. Control center
 Determines the set point at which the
variable is maintained
 Receives input from receptor
 Determines appropriate response
Components of a Control
Mechanism
3. Effector
 Receives output from control
center
 Provides the means to respond
 Response acts to reduce or
enhance the stimulus (feedback)
3 Input: Information
sent along afferent
pathway to control
center.
2
Receptor
detects
change.
Receptor
4 Output:
Control
Center
Afferent
Efferent
pathway
pathway
1
Stimulus
produces
change in
variable.
BALANCE
Information sent along
efferent pathway to
effector.
Effector
5
Response
of effector
feeds back
to reduce
the effect of
stimulus
and returns
variable to
homeostatic
level.
Figure 1.4, step 5
Negative Feedback
 The response reduces or shuts off the
original stimulus
 Examples:
 Regulation of body temperature (a
nervous mechanism)
 Regulation of blood volume by ADH (an
endocrine mechanism)
Control Center
(thermoregulatory
center in brain)
Information sent
along the afferent
pathway to control
center
Afferent
pathway
Information sent
along the efferent
pathway to
effectors
Efferent
pathway
Receptors
Temperature-sensitive
cells in skin and brain
Effectors
Sweat glands
Sweat glands activated
Response
Evaporation of sweat
Body temperature falls;
stimulus ends
Stimulus
Body temperature
rises
BALANCE
Stimulus
Response
Body temperature rises;
stimulus ends
Body temperature falls
Receptors
Temperature-sensitive
cells in skin and brain
Effectors
Skeletal muscles
Shivering
begins
Efferent
pathway
Information sent
along the efferent
pathway to effectors
Afferent
pathway
Control Center
(thermoregulatory
center in brain)
Information sent
along the afferent
pathway to control
center
Figure 1.5
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 the kidneys (effectors) to
return more water to the blood
Positive Feedback
 The response enhances or exaggerates the
original stimulus
 Enhancement of labor contractions by
oxytocin (Chapter 28)
 Platelet plug formation and blood clotting
1 Break or tear
occurs in blood
vessel wall.
Positive feedback
cycle is initiated.
3 Released
chemicals
attract more
platelets.
2 Platelets
Positive
feedback
loop
adhere to site
and release
chemicals.
Feedback cycle ends
when plug is formed.
4 Platelet plug
forms.
Figure 1.6, step 4
Homeostatic Imbalance

Disturbance of homeostasis
 Increases risk of disease
 Contributes to changes associated
with aging
 May allow destructive positive
feedback mechanisms to take over
(e.g., heart failure)