Chapter One The Human Body- An Orientation
Anatomy- study of the structure of body parts and their relationship to
one another
Physiology- study of the function of body parts; how they work to carry
out life-sustaining activities
Anatomy and physiology are inseparable
 Function always reflects structure
 What a structure can do depends on its specific form
 Known as the principle of complementarity of structure and
function
o Ex- Bones can support and protect body organs because
they contain hard minerals
Human body is very organized, from the smallest chemical level to
whole organism level:
 Chemical level: atoms, molecules, and organelles (basic
components of microscopic cells)
 Cellular level: single cell
o Smallest unit of living things
o Cells have some common function but vary widely in size
and shape
 Tissue level: groups of similar cells with common function
 Organ level: contains two or more types of tissues
o Extreme functions possible at this level
o Example – stomach
 Lining is epithelium (provides digestive juices)
 Bulk of the wall is muscle (churns and mixes contents)
 Connective tissue (reinforces the muscular wall)
 Nerve fibers (increase digestive activity by stimulating
muscle and gland)
 Organ system level: organs that work closely together
 Organismal level: all organ systems combined to make the whole
organism
Requirements for life
Maintenance of life involves
 Maintaining boundaries
 Movement
 Responsiveness
 Digestion
 Metabolism
 Excretion
 Reproduction
 Growth
BodyPlanes
Directional Terms
Anatomical Terminology
Cavities and Serous Membranes
1. Maintaining boundaries
 Separation between internal and external environments must
exist
o Plasma membranes separate cells
o Skin separates organism from environment
2. Movement
 Muscular system allows movement
o Of body parts via skeletal muscles
o Of substances via cardiac muscle (blood/circulatory
system) and smooth muscle (digestion, urination)
o Contractility- refers to movement at the cellular level
 Intracellular transport (movement within the cell)
3. Responsiveness (excitability)
 Ability to sense and respond to stimuli
4.
5.
6.
7.
o Withdrawal reflex prevents injury
 What happens when you cut your hand on glass?
You move your hand away from what is causing the
pain.
o Control of breathing rate, which must change in response
to difference activities
o Cell respond to neurotransmitters and hormones
o Organisms respond to changes internally; hunger, thirst,
cold, etc
Digestion
 Breakdown of ingested foodstuffs, followed by absorption of
simple molecules into blood
 Amino acids for protein; glucose for ATP
o Organism turns food into building blocks for the cell
Metabolism
 All chemical reactions that occur in body cells
o Sum of all catabolism (breakdown of molecules) and
anabolism (synthesis of molecules)
Excretion
 Removal of wastes from metabolism and digestion
o Cellular- through secretion and exocytosis
o Organ Systems
 Urinary- Urea (from breakdown of proteins)
 Respiration- carbon dioxide (from metabolism)
 Digestion- feces (unabsorbed foods)
Reproduction
 At the cellular level, reproduction involves division of cells
for growth or repair (mitosis)
 At the organismal level, reproduction is the production of
offspring (Meiosis)
8. Growth
 Increase in size of a body part or of organism
o Organism
 Height and weight
o Cell
 Skeletal muscle hypertrophies with exercise
Humans are multicellular, so to function, individual cells must be kept
alive
 Organ systems are designed to service the cells
 All cells depend on organ systems to meet their survival
needs
There are 11 organ systems that work together to maintain life
 Integumentary
 Skeletal
 Muscular
 Nervous
 Endocrine
 Cardiovascular
 Lymphatic
 Respiratory
 Digestive
 Urinary
 Male & Female Reproductive
Survival Needs
Humans need several factors for survival that must be in the
appropriate amounts; too much or too little can be harmful:
 Nutrients
 Oxygen
 Water
 Normal body temperature
 Appropriate atmospheric pressure
1. Nutrients
o Chemicals for energy and cell building; participate in
many reactions as coenzymes
o Carbohydrates: major source of energy
o Proteins: needed for cell building and cell
chemistry
o Fats: long-term energy storage
o Minerals and vitamins: involved in chemical
reactions as well as for structural purposes
2. Oxygen
o Essential for release of energy from foods
o The body can survive only a few minutes without
oxygen
3. Water
o Most abundant chemical in the body; it is 60-80% of
the cell volume, 50% of blood
o Provides the watery environment needed for
chemical reactions such as hydrolysis and
dehydration synthesis reactions
o Also is fluid base for secretions and excretions
4. Normal body temperature
o Stays a baseline for normal enzyme function
o If body temp falls below or goes abow 98.6, rates of
chemical reactions are affected
5. Appropriate atmospheric pressure
o Is the force that air exerts on the surface of the body
o Breathing and gas exchange in lungs depend on
appropriate atmospheric pressure
Homeostasis is the maintenance of relatively stable internal conditions
despite continuous changes in environment
 A dynamic state of equilibrium, always readjusting as needed
 Processes are designed to bring systems back to baseline
 Maintained by contributions of all organ systems
Homeostatic Controls
 Body must constantly be monitored and regulated to maintain
homeostasis
o Nervous and endocrine systems, as well as other systems,
play a major role in maintaining homeostasis
o Variables are factors that can change (blood sugar, body
temperature, blood volume, tec)
 Homeostatic control of variables involves three components:
receptor, control center, and effector
o Receptor (sensor)
 Monitors environment
 Responds to stimuli (things that cause changes in
controlled variables)
o Control center
 Processes the information
 Determines set point at which variable is
maintained
 Receives input from receptor
 Determines appropriate response
o Effector
 Receives output from control center
 Provides the means to respond
 Response either reduces stimulus (negative feedback)
or enhances stimulus (positive feedback)
o Negative Feedback
 Most used feedback mechanism in the body
 Brings the system back to base line
 Response reduces or shuts off original stimulus
 Variable changes in opposite direction of initial
change
 Examples
o Regulation of body temperature (a nervous
system mechanism)
o Regulation of blood glucose by insulin (an
endocrine system mechanism)
o Regulation of thyroid hormone levels
o Receptors sense increased blood glucose
(blood sugar)
o Pancreas (control center) secretes insulin
into the blood
o Insulin causes blood cells (effectors) to
absorb more glucose, which decreases
blood glucose levels
Negative Feedback
Positive Feedback
 Response enhances or exaggerates the original stimulus
 May exhibit a cascade or amplifying effect as feedback causes
variable to continue in same direction as initial change
 Usually controls infrequent events that do not require continuous
adjustment for example:
o Enhancement of labor contractions by oxytocin
o Platelet plug formation and blood clotting
Hormonal induction of Labor
Disturbance of homeostasis
 Increases risk of disease
 Contributes to changes associated with aging
o Control systems become less efficient
o Examples
 Diabetes mellitus- blood glucose is not brought back to
baseline
 Hypertension- blood pressure is not back to baseline