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Chapter 1
Homeostasis: The Foundation of Physiology
Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning
Outline
• Physiology
• Levels of organization
• Basic Cell function
• Tissues/ organs/systems
Outline
• Homeostasis
–
–
–
–
Fluid compartments
Variables controlled
Contributions of systems
Control systems
• Intrinsic/extrinsic
• Feedfoward/feedback
• Positive/negative
• Disruptions of homeostasis
Physiology
• Study of body functions
• Two processes explain body functions
– Teleological
• Explanations are in terms of meeting a bodily need
– Mechanistic
• Explanations are in terms of cause and effect
sequences
– Body is viewed as a machine
Anatomy
• Study of the structure of the body
Physiological mechanisms are possible
through structural design
Structure-Function relationships of the body
Examples:
• Heart receiving and pumping blood
• Teeth tearing and grinding food
5
4
3
1 Chemical level
2
2 Cellular level
3 Tissue level
4 Organ level
5 Body system level
1
6 Organism level
6
Basic Cell Functions
• Obtain nutrients and oxygen from surrounding
environment
• Perform chemical reactions that provide energy for the
cell
• Eliminate carbon dioxide and other wastes to
surrounding environment
• Synthesize needed cellular components
• Control exchange of materials between cell and its
surrounding environment
• Sensing and responding to changes in surrounding
environment
• Reproduction
– Exception
• Nerve cells and muscle cells lose their ability to
reproduce during their early development
Tissues
• Groups of cells with similar structure and
specialized function
• Four primary types of tissues
–
–
–
–
Muscle tissue
Nervous tissue
Epithelial tissue
Connective tissue
Tissues
• Muscle tissue
– Specialized for contracting and generating force
– Three types of muscle tissue
• Skeletal muscle
– Moves the skeleton
• Cardiac muscle
– Pumps blood out of the heart
• Smooth muscle
– Encloses and controls movement of contents through
hollow tubes and organs
• Connective tissue
– Cells dispersed in a matrix
– Connects, supports, anchors tissue
Tissues
• Nervous tissue
– Consists of cells specialized for initiating and
transmitting electrical impulses
– Found in brain, spinal cord, and nerves
• Epithelial tissue
– Consists of cells specialized for exchanging
materials between the cell and its environment
– Organized into two general types of structures
• Epithelial sheets
• Secretory glands
Surface epithelium
Pocket epithelium
cells
Surface epithelium
Duct cells
Secretory exocrine
gland cell
Surface epitheliu
Connecting cells
lost
Secretory exocrin
gland cell
Blood vessels
Fig. 1.2a, p. 5
Credit: © Carolina Biological/Visuals Unlimited
Sweat gland duct in the skin. LM X5.
318237
Credit: © Dr. Wolf Fahrenbach/Visuals Unlimited
Surface of a human fingertip with sweat droplets. SEM X120.
196178
310887
Credit: © Carolina Biological/Visuals Unlimited
Simple Squamous Epithelium. LM X75.
Credit: © David Phillips/Visuals Unlimited
Microscopic technique series - Cheek cells. Nomarski view. LM X75.
308775
Credit: © David Phillips/Visuals Unlimited
Microscopic technique series - Cheek cells. Phase view. LM X75.
308777
301193
Credit: © G.W. Willis, MD/Visuals Unlimited
Stratified squamous epithelium from mouth mucosa. H&E stain. LM X100.
310845
Credit: © Carolina Biological/Visuals Unlimited
Simple columnar epithelium. LM X140.
164740
Credit: © G.W. Willis, MD/Visuals Unlimited
Human pseudostratified columnar epithelium lining the bronchus of the lung. H&E stain.
X180.
317178
Credit: © Carolina Biological/Visuals Unlimited
Areolar (loose) connective tissue. LM X60.
98769
Credit: © Dr. Fred Hossler/Visuals Unlimited
Hyaline cartilage. X64.
98964
Credit: © Dr. David Phillips/Visuals Unlimited
Collagen or dense connective tissue. X155.
98990
Credit: © Dr. Richard Kessel/Visuals Unlimited
Reticular fibers, silver preparation. X100.
164732
Credit: © G.W. Willis, MD/Visuals Unlimited
Human unilocular (white) fat and adipose (adult fat). H&E stain. LM X100.
319245
Credit: © Carolina Biological/Visuals Unlimited
Bone section showing osteocytes in lacunae arranged in concentric circles surrounding
Haversian canals. LM X75.
228388
Credit: © Dr. Richard Kessel & Dr. Randy Kardon/Tissues & Organs/
Visuals Unlimited
A long bone showing the compact bone (yellow) surrounding the spongy or cancellous bone
(orange). Compact bone consist of a dense matrix resembling a solid mass. The spongy
region consists of a network of bony spicules called trabeculae. SEM X40.
Organs
• Consist of two or more types of primary
tissues that function together to perform a
particular function or functions
• Example
– Stomach
• Inside of stomach lined with epithelial tissue
• Wall of stomach contains smooth muscle
• Nervous tissue in stomach controls muscle contraction
and gland secretion
• Connective tissue binds all the above tissues together
Body Systems
• Groups of organs that perform related
functions and interact to accomplish a
common activity essential to survival of the
whole body
• Do not act in isolation from one another
• Human body has 11 systems
Body Systems
•
•
•
•
•
•
Circulatory System
Digestive System
Respiratory System
Urinary System
Skeletal System
Muscular System
• Integumentary
System
• Immune System
• Nervous System
• Endocrine System
• Reproductive System
Body Systems
Know each system, organs within that system, function of each organ for lab exam 1
Body Systems
Know each system, organs within that system, function of each organ for lab exam 1
Homeostasis vs. Allostasis
• Homeostasis =
– ideal set point through local regulatory mechanism
– ex. Kidneys figure this out and decrease fluid output
• Allostasis:
– The brain coordinating body-wide changes often including
changes in behavior.
– Ex brain figures this out , kidney changes, removal of
water from skin , mouth, nose, make you thirsty
Homeostasis
• Defined as maintenance of a relatively
stable internal environment
– Does not mean that composition, temperature,
and other characteristics are absolutely
unchanging
• Homeostasis is essential for survival and
function of all cells
• Each cell contributes to maintenance of a
relatively stable internal environment
Homeostasis
Homeostasis
• Body cells are in contained in watery
internal environment through which lifesustaining exchanges are made
• Extracellular fluid (ECF)
– Fluid environment in which the cells live (fluid
outside the cells)
– Two components
• Plasma, interstitial fluid
• Intracellular fluid (ICF)
– Fluid contained within all body cells (cytoplasm)
Homeostasis
Homeostasis
Factors homeostatically regulated include
• Concentration of nutrient molecules
• Concentration of O2 and CO2
• Concentration of waste products
• pH
• Concentration of water, salt, and other
electrolytes
• Volume and pressure
• Temperature
BODY SYSTEMS
Information from
the external
environment relayed
through the
nervous system
O2
CO2
Urine containing
wastes and
excess water and
electrolytes
NERVOUS
SYSTEM
Regulate
RESPIRATORY
SYSTEM
ENDOCRINE
SYSTEM
INTEGUMENTARY
SYSTEM
Sperm leave male
Sperm enter
female
EXTERNAL
ENVIRONMENT
Keeps internal
fluids in
HOMEOSTASIS
Keeps foreign
materials out
URINARY
SYSTEM
IMMUNE SYSTEM
Nutrients, water,
electrolytes
Feces containing
undigested food
residue
Body systems
maintain
homeostasis
DIGESTIVE
SYSTEM
REPRODUCTIVE
SYSTEM
MUSCULAR AND
SKELETAL
SYSTEM
Exchanges with
all other systems
Exchanges with
all other systems
Protects
against
foreign
invaders
Enables the
body to
interact
with the
external
environment
Homeostasis
essential for
cell survival
CELLS
CIRCULATORY SYSTEM
Cells make
up body
system
Fig. 1.6, p. 12
Homeostatic Control Systems
• In order to maintain homeostasis, control
system must be able to
– Detect deviations from normal in the internal
environment that need to be held within narrow
limits
– Integrate this information with other relevant
information
– Make appropriate adjustments in order to restore
factor to its desired value
Homeostatic Control Systems
• Control systems are grouped into two
classes
– Intrinsic controls
• Local controls that are inherent in an organ
– Extrinsic controls
• Regulatory mechanisms initiated outside an organ
• Accomplished by nervous and endocrine systems
Homeostatic Control Systems
• Feedforward
– Term used for responses made in anticipation of
a change
• Feedback
– Refers to responses made after change has been
detected
– Types of feedback systems
• Negative
• Positive
Homeostatic Control Systems
• Negative feedback system
– Primary type of homeostatic control
– Opposes initial change
– Components
• Sensor
– Monitors magnitude of a controlled variable
• Control center
– Compares sensor’s input with a set point
• Effector
– Makes a response to produce a desired effect
Homeostatic Control Systems
• Positive feedback system
– Amplifies an initial change
– Do not occur as often as negative feedback
system
– Example
• Uterine contractions become increasingly stronger until
the birth of the baby
Contributions of Body Systems to Homeostasis
• Circulatory system
– Carries materials from one part of the body to
another
• Digestive system
– Breaks down dietary food into smaller molecules
that can be distributed to body cells
– Transfers water and electrolytes from external
environment to internal environment
– Eliminates undigested food residues to external
environment in the feces
Contributions of Body Systems to Homeostasis
• Respiratory system
– Gets O2 from and eliminates CO2 to the external
environment
– Important in maintenance of proper pH of internal
environment
• Urinary system
– Removes excess water, salt, acid, and other
electrolytes from plasma and eliminates them in
urine
Contributions of Body Systems to Homeostasis
• Skeletal system
– Provides support and protection for soft tissues
and organs
– Serves as storage reservoir for calcium
– Along with muscular system enables movement
of body and its parts
– Bone marrow is ultimate source of all blood cells
• Muscular system
– Moves the bones
Contributions of Body Systems to Homeostasis
• Integumentary system
– Serves as outer protective barrier
– Important in regulating body temperature
• Immune system
– Defends against foreign invaders and against
body cells that have become cancerous
– Paves way for repairing or replacing injured or
worn-out cells
Contributions of Body Systems to Homeostasis
• Nervous system
– Controls and coordinates bodily activities that
require rapid responses
– Detects and initiates reactions to changes in
external environment
• Endocrine system
– Secreting glands of endocrine regulate activities
that require duration rather than speed
– Controls concentration of nutrients and, by
adjusting kidney function, controls internal
environment’s volume and electrolyte
composition
Contributions of Body Systems to Homeostasis
• Reproductive system
– Not essential for homeostasis (not essential for
survival of individual)
– Is essential for perpetuating the species