Physiology
M.Ilker Gelisen MD
Agenda
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What is physiology?
•From cell to human (levels of organization)
•A review of the organ systems
•Introduction of the concept of homeostasis
•Themes in Physiology
Physiology
– Study of the normal functioning of a living
organism and its component parts
• Physiology is the study of the normal function
of cell, tissue, organs, systems and
organisms
The Specialties of Physiology
• Physiology can be divided into the following
specialties:
– Cell physiology – study of cell
– Special physiology - study of specific organ
– Systemic physiology – study of system
– Pathological physiology (Pathophysiology)
– study of the effect of disease on cell, tissue, organ
and system.
Levels of Organization
PHYSIOLOGY
CHEMISTRY
Atoms
MOLECULAR
BIOLOGY
Molecules
Cells
ECOLOGY
CELL
BIOLOGY
Tissues
Organs
Organ
systems
Organisms
Populations of
one species
Ecosystem of
different species
Biosphere
Levels of Organization
Levels of Organization - Human
Organ Systems in Review
Organ System
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Integumentary
Musculoskeletal
Respiratory
Digestive
Urinary
Reproductive
Circulatory / Cardiovascular
Nervous
Endocrine
Lymphatic / Immune
Major Functions
Integumentary
system
Protection from environmental
hazards; temperature control
Skeletal
system
Support, protection of soft
tissues; mineral storage;
blood formation
Muscular
system
Locomotion, support, heat
production
Nervous
system
Directing immediate responses
to stimuli, usually by coordinating
the activities of other organ
systems
Endocrine
system
Directing long-term changes
in the activities of other organ
systems
Cardiovascular
system
Internal transport of cells and
dissolved materials, including
nutrients, wastes, and gases
Lymphatic
system
Defense against infection and
disease
Respiratory
system
Delivery of air to sites where gas
exchange can occur between
the air and circulating blood
Digestive
system
Processing of food and absorption
of organic nutrients, minerals,
vitamins, and water
Urinary
system
Elimination of excess water,
salts, and waste products;
control of pH
Reproductive
system
Production of sex cells and
hormones
Human Body
Interrelationships Among Body
Systems
Necessary Life Functions
• Maintain boundaries
• Movement
– Locomotion
– Movement of substances
• Responsiveness
– Ability to sense changes and react
• Digestion
– Break-down and absorption of nutrients
Necessary Life Functions
• Metabolism—chemical reactions within the
body
– Produces energy
– Makes body structures
• Excretion
– Eliminates waste from metabolic reactions
Necessary Life Functions
• Reproduction
– Produces future generation
• Growth
– Increases cell size and number of cells
Survival Needs
• Water
– 60 of body weight
– Provides for metabolic reaction
• Stable body temperature
• Atmospheric pressure
– Must be appropriate
Survival Needs
• Nutrients
– Chemicals for energy and cell building
– Includes carbohydrates, proteins, lipids, vitamins,
and minerals
• Oxygen
– Required for chemical reactions
Homeostasis X
• Homeostasis—maintenance of a stable
internal environment
– A dynamic state of equilibrium
• Homeostasis is necessary for normal body
functioning and to sustain life
• Homeostatic imbalance
– A disturbance in homeostasis resulting in disease
Key Themes in Physiology:
1. Homeostasis (Body systems work together
(Integration of function) Internal vs. external
failure of homeostasis
2.Communication and movement across cell
membranes
Vital to integration & homeostasis
Cells communicate with other cells, tissues &
organs
Homeostatic regulation
• A homeostatic regulatory mechanism consist of :
– A receptor – senses an environmental change or
stimuli.
– A control center –processes information supplied by
receptor and generates a response (command)
– An effector – an organ or cell that responds to the
command of control center.
• A variation outside the desired range triggers an
automatic response to correct the situation
– Negative feedback
Maintaining Homeostasis
• The body communicates through neural and
hormonal control systems
– Receptor
• Responds to changes in the environment (stimuli)
• Sends information to control center
Maintaining Homeostasis
– Control center
• Determines set point
• Analyzes information
• Determines appropriate response
– Effector
• Provides a means for response to the stimulus
Feedback Mechanisms
• Negative feedback
– Includes most homeostatic control mechanisms
– Shuts off the original stimulus, or reduces its
intensity
– Works like a household thermostat
•In positive feedback an initial stimulus produces a response that enhances the change
in the original condition. For instance:
• Damage to blood vessel wall will cause release of chemicals.
•Chemicals will trigger blood clotting
•Clotting process increases release of chemicals
•More chemicals means accelerated clotting
•Accelerated clotting means more chemicals
Homeostasis
Variable
(in homeostasis)
Stimulus:
Produces
change
in variable
Variable
(in homeostasis)
Receptor (sensor)
Change
detected
by receptor
Stimulus:
Produces
change
in variable
Variable
(in homeostasis)
Input:
Information
sent along
afferent
pathway to
Control
center
Receptor (sensor)
Change
detected
by receptor
Stimulus:
Produces
change
in variable
Variable
(in homeostasis)
Input:
Information
sent along
afferent
pathway to
Control
center
Effector
Receptor (sensor)
Change
detected
by receptor
Stimulus:
Produces
change
in variable
Output:
Information sent
along efferent
pathway to activate
Variable
(in homeostasis)
Input:
Information
sent along
afferent
pathway to
Control
center
Output:
Information sent
along efferent
pathway to activate
Effector
Receptor (sensor)
Change
detected
by receptor
Stimulus:
Produces
change
in variable
Variable
(in homeostasis)
Response of
effector feeds
back to
influence
magnitude of
stimulus and
returns variable
to homeostasis
Negative Feedback: The Control of Body
Temperature
Feedback Mechanisms
• Positive feedback
– Increases the original stimulus to push the
variable further
– In the body this only occurs in blood clotting and
during the birth of a baby
Function versus Process
• Function explains the “why”
– Teleological approach
• Process or mechanism describes the “how”
– Mechanistic approach
• Red blood cell example
– “Because cells need oxygen and red blood cells
bring it to them.”
– “Oxygen binds to hemoglobin molecules
contained in the red blood cells.”
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Homeostasis
Most cells contact extracellular fluid
Out out
Out
In
In in
External environment
of the body
Material enters
and leaves
the body
Material enters
and leaves
the body
Intracellular
fluid of
most cells
Extracellular fluid:
the internal environment
of the body
Homeostasis
• External
or
internal change
• Loss of
homeostasis
– Sensed by
organism
• Physiological
attempt to
correct
• Negative
feedback loop
and Controls
Homeostasis and Controls
• Successful
compensation
– Homeostasis
reestablished
• Failure to
compensate
– Illness
– Death
• Study of failure to
compensate is
pathophysiology
Homeostasis and Controls
Organism in
homeostasis
External
change
Internal
change
Internal change
results in
loss of homeostasis
Organism attempts
to compensate
Compensation fails
Illness or disease
Compensation succeeds
Wellness
Themes in Physiology
• Homeostasis
– Control systems
• Biological energy use
• Structure-function relationships
– Molecular interactions
– Mechanical properties of cells, tissues, and organs
• Communication
– Chemical and electrical signals
Themes in Physiology
• A simple control system
Input
signal
Controller
Output
signal
Concept Mapping
• Organizational tool for relationships and
processes
• Schematic diagram of structure and function
– Cells, tissues, and organs
• Flow charts
– Diagram processes in sequence
Concept Mapping: Types of Maps
Person working
outside on a hot,
dry day
Loses body water
by evaporation
Body fluids become
more concentrated
Internal receptors
sense change in
internal concentration
Thirst pathways
stimulated
Person seeks out
and drinks water
Water added
to body fluids
decreases their
concentration
(b) A process map, or flow chart
Process of maintaining stable internal
environment compatible for life
– Most organ systems contribute to homeostasis
– Exception: reproductive system
Homeostasis
– Primary mechanism for maintaining homeostasis
– External change  triggers change in regulated
variable in internal environment  triggers
reaction to oppose the change and return
regulated variable toward normal (set point)
Negative Feedback Control in
Homeostasis
– Set point = desired level of regulated variable
– Sensors detect level of regulated variable and provide input to
integrating center
– Integrating center compares set point to actual level of
regulated variable
– Error signal = difference between actual level and set point
– Integrating center sends output to effectors to return
regulated variable toward set point
Negative Feedback Mechanisms
Negative Feedback Control of Car
Speed
Negative Feedback Control of Body
Temperature
Negative Feedback Loop
Positive Feedback Loop
Positive feedback loops
cause a rapid change in a
variable.
– Homeothermic animals – regulate body
temperature within a narrow range
– Poikilothermic animals – do not regulate body
temperature
Thermoregulation
– Normal body temperature = set point
• Differs in animal species
• Humans: 37oC (98.6oF)
– Hypothermia = decrease in body temperature
– Hyperthermia = increase in body temperature
• above 41oC, dangerous
• above 43oC, deadly
Homeothermic Animals
Mechanisms of Heat Transfer Between
Body and External Environment
– Radiation - thermal energy as electromagnetic
waves
– Conduction - thermal energy through contact
– Evaporation - heat loss through evaporation of
water
• insensible water loss
• sweating
– Convection - heat transfer by movement of fluid or
air
– Thermoregulatory system maintains core
body temperature
– Detectors - thermoreceptors (central and
peripheral)
– Integrator - hypothalamus
– Effectors - sweat glands, blood vessels in
skin, skeletal muscles
Components of Thermoregulatory
System
Range of outside temperature where
alterations in blood flow alone regulates
body temperature
25-30oC
– Body temperature increase:
• blood flow to skin increases
– Body temperature decrease:
• blood flow to skin decreases
Thermoneutral Zone
Negative Feedback Control of Body
Temperature
Thermoregulation
– Fever accompanies infections
– White blood cells secrete pyrogens
– Body temperature set point increases
– Fever enhances immune response
Fever
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