Introduction to Physiology
Dr. Ranjay Choudhary
College Of Applied Medical Sciences
Majmaah University
Thought for Every One
If you succeed in cheating someone,
Don't think that the person is a fool...
Just realize that the person
Trusted you much more than you deserved!
Don’t be over smart and think that some one may
be more smart than you as he has left the job many
years before which you are trying to learn now.
PHYSIOLOGY
What is Physiology?
Greek Origins: Physis: Nature; Logy: Study
Physiology is the study of biological function—of how
the body works,
•
•
•
•
From cell to tissue,
Tissue to organ,
Organ to system, and of
How the organism as a whole accomplishes particular tasks
essential for life.
Physiology and pathophysiology
• Physiology (physio = nature; logos = study): study of how
the body works to maintain life
• Study of the functions of cells, tissues, organs,
organ systems, and organisms
- cell  tissue  organ  organ system  organism
• Pathophysiology: how physiological processes are altered
in disease or injury
PHYSIOLOGY
THE SCIENCE OF PHYSIOLOGY BEGIN BEFORE
THE BIRTH OF CHRIST.
HOWEVER, THE FATHER OF
MODERN PHYSIOLOGY
IS THE FRENCH PHYSIOLOGIST
CLAUDE BERNARD (1813-1878).
Physiology
• Science of body functions
• Teleological vs Mechanistic views
– Teleological – the why, explains purpose of a
physiological process
– Mechanistic – the how, explained in terms of
cause and effect of physiological process
• Example: shivering
• Teleological - shivering elevates a low body
temperature
• Mechanistic - when body temperature drops below
normal, a reflex pathway causes involuntary oscillating
skeletal muscle contractions which produce heat
Body fluid in Human
Definition: Physiology (physo = nature; logos = study): study of
how the body works to maintain life
- cell  tissue  organ  organ system  organism
• Definition: human body contain many body fluid like blood,
urine, saliva, sputum, tears, semen, milk, or vaginal secretions
• The major component of the human body is water,
which is for 50 to 80% according to the age and
gender.
• Changes with age: :
• Changes with age: Newborns – 75-80% of body weight is water
• One year – 65 % of body weight is water
• Adult – males 60%, females 50%
Organismal Level
Atoms
Organelle
Molecule
Smooth muscle cell
2 Cellular level
Cells are made up
of molecules.
1 Chemical level
Atoms combine to
form molecules.
Smooth muscle tissue
Cardiovascular
system
Heart
Blood
vessels
Blood vessel
(organ)
3 Tissue level
Tissues consist of
similar types of cells
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.
Organism
Level
Organ System Level
Endocrine
Muscular
Nervous
Cardiovascular
Lymphoid
Respiratory
Digestive
Skeletal
Urinary
Integumentary
Reproductive
The heart
Organ
Level
Cardiac
muscle
tissue
Atoms in
combination
Tissue Level
Heart muscle cell
Complex protein
molecules
Protein filaments
Chemical or
Molecular Levels
Cellular Level
Levels of Structural
Organization
•
•
•
Chemical Level - atomic and molecular
level
Cellular level - smallest living unit of
the body
Tissue level
•
•
Group of cells and the materials
surrounding them that work together on
one task
4 basic tissue types: epithelium, muscle,
connective tissue, and nerve
Chemical and Molecular Level
Other Elements:
Hydrogen
62%
Oxygen
26%
Carbon
10%
Calcium
Phosphorus
Potassium
Sodium
Sulfur
Chlorine
Magnesium
Iron
Iodine
Trace elements
0.2%
0.2%
0.06%
0.06%
0.05%
0.04%
0.03%
0.0005%
0.0000003%
(see caption)
Water
67%
Proteins
20%
Lipids
10%
Carbohydrates 3%
Nitrogen
1.5%
Elemental composition
of the human body
Molecular composition
of the human body
Tissue Level of Organization
• Tissue level
– Cells of similar shape and specialized function
• Four major tissue types
– Muscle
• Specialized for contracting and generating tension
– Nervous
• Specialized in impulse production and transmission
– Connective
• Specialized for connecting and supporting
– Epithelial
• Specialized for surface lining and exchange
Levels of Organization: Tissue
_____tissue
_____tissue
_____tissue
_____tissue
• Cells with similar
functions grouped into
the 4 primary tissues
• Tissue:
•
•
•
•
Organ system of the body
A group of cells with similar structure and function plus the
extracellular substances located between them is a tissue. The many tissues
that make up the body are classified into four primary tissue types:
Epithelial,
Connective,
Muscle, and
Nervous.
Organ: Organs are composed of two or more tissue types that together
perform one or more common functions. The skin
 Stomach
 Eye
 And heart are examples of organs.
 Organ System:




An organ system is a group of organs classified as a unit because of a common function
or set of functions. In this text the body is considered to have 11 major organ systems:
Integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic,
respiratory, digestive, urinary, and reproductive
Body Systems
Body Systems
The Organism
• Collection of
body systems
working together
to maintain life.
• Strive to
maintain an
internal balance
–Homeostasis
oxygen-review.com
HOMEOSTASIS
• The process through which a nearly
stable
internal
environment
is
maintained in the body so that cellular
functions can proceed at maximum
efficiency.
– 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
BASIC CELL FUNTIONS
• Sensing and responding to changes in surrounding
environment
• Control exchange of materials between cell and its
surrounding environment
– Obtain nutrients and oxygen from surrounding
environment
– Eliminate carbon dioxide and other wastes to
surrounding environment
• Perform chemical reactions that provide energy for the cell
• Synthesize needed cellular components
BODY COMPOSITION
• In average young adult male:
Body composition
% of body weight
Protein, & related substances
18%
Fat
15%
Mineral
7%
Water
60%
BODY FLUIDS
• Body cells are in contained
in watery internal
environment through which
life-sustaining 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
BODY FLUIDS
Water content in body is divided into 2 compartments:
Fluid Compartments
 60% of body weight
Extracellular
fluid
( 1/3)
Intracellular
fluid
( 2/3)
 20% of body wt
 40% of body wt
 33% of TBW
Plasma
 25% of ECF
 5% of body wt
Interstitial
fluid
75% of ECF
 15% of body wt
 67% of TBW
Transcellular
fluid
CSF
Intraocular
Pleural
Peritoneal
Pericardial
Synovial
Digestive
secretions
How to calculate total body water (TBW)?
Q. Calculate TBW for a 70 kg man.
TBW = 60% of body weight
TBW = 60% X 70 = 42 L of water
HOMEOSTASIS
Differences between ECF & ICF
ICF
ECF
Cations:
Anions:
Na+ (142mmol/L)
K+ (4.2)
Mg2+ (0.8)
Cl- (108)
HCO3- (24)
Cations:
Na+ (14)
K+ (140)
Mg2+ (20)
Anions:
Cl- (4)
HCO3- (10)
Phosphate ions
Nutrients:
O2, glucose, fatty acids, &
amino acids.
Wastes:
CO2, Urea, uric acid,
excess water, & ions.
Nutrients:
High concentrations of proteins.
MAINTENANCE OF HOMEOSTASIS
• Homeostasis involves dynamic mechanisms that detect and
respond to deviations in physiological variables from their
“set point” values by initiating effector responses that
restore the variables to the optimal physiological range.
• Two systems that maintain homeostasis are: Nervous system
& Endocrine system
MAINTENANCE OF 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
Factors controlled through Homeostasis
Factors homeostatically regulated include
• Concentration of nutrient molecules
• Concentration of water, salt, and other electrolytes
• Concentration of waste products
• Concentration of O2 = 100mmHg and CO2 = 40
mmHg
• pH = 7.35
• Blood volume 4-6 L and pressure 120/80
• Temperature = 37o C
Control of Homeostasis
• Homeostasis is continually being
disrupted by
– External stimuli
• heat, cold, lack of oxygen,
pathogens, toxins
– Internal stimuli
• Body temperature
• Blood pressure
• Concentration of water, glucose,
salts, oxygen, etc.
• Physical and psychological
distresses
• Disruptions can be mild to severe
• If homeostasis is not maintained, death
may result
Control of Homeostasis
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 (natural) 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
Feedback Loops: Types
• Negative feedback loop
– Original stimulus reversed
– Most feedback systems in the body are negative
– Used for conditions that need frequent adjustment
• Positive feedback loop
– Original stimulus intensified (increased)
– Seen during normal childbirth
Feedback Loop: 3 Main Components
Negative feed back loop consists of:
• Receptor
structures that monitor a
controlled condition and
detect changes
• Control center
sets the normal range, receives
input from the receptor and
sends output when changes
are needed
• Effector
– receives directions from
the control center
– produces a response
that restores the
controlled condition
Negative Feedback Loops in the Body
• Negative feedback loops are very common in the human
body.
• Negative feedback loops are excellent mechanisms of
controlling parameters and allow for the “fine-tuning” of
physiological processes, such as blood glucose,
oxygenation level and blood pressure.
• A negative feedback loop tends to bring a system back
to equilibrium…
Negative Feedback Loop
Negative Feedback Loop
Homeostasis - Negative Feedback Loop
Blood glucose
concentrations rise after
a sugary meal (the
stimulus), the hormone
insulin is released and it
speeds up the transport
of glucose out of the
blood and into selected
tissues (the response),
so blood glucose
concentrations decrease
(thus decreasing the
original stimulus).
Homeostasis of Blood Pressure
• Baroreceptors in walls of
blood vessels detect an
increase in BP
• Brain receives input and
signals blood vessels and
heart
• Blood vessels dilate, HR
decreases
• BP decreases
Positive Feedback Loops in the Body
• Positive feedback loops are rare in the human body.
• A positive feedback loop tends to push a system away
from equilibrium.
• Examples:
Stomach’s digestion of protein, and Childbirth
• The classic example of a positive feedback loop in the
body is the action of oxytocin during labor…
Positive Feedback during childbirth
• Stretch receptors in walls of uterus send signals to the brain
• Brain induces release of hormone (oxytocin) into
bloodstream
• Uterine smooth muscle contracts more forcefully
• More stretch, more hormone, more contraction etc.
• Cycle ends with birth of the baby & decrease in stretch
Positive Feedback:
Blood clotting
Unit 1 Introduction Homeostasis
1.
2.
3.
4.
5.
6.
7.
Define Physiology? Who is the father of modern biology?
Define Homeostasis?
Give any two examples of homeostasis?
What is feedback system? Name the types of feedback system?
Write about the components of Homeostatic mechanism?
What is negative feedback mechanism?
How is blood pressure regulated taking into account the negative
feedback mechanism?
8. How is body temperature controlled taking into account the
negative feedback mechanism?
9. What is positive feedback mechanism? Give example of positive
feedback mechanism?
10. What is the mechanism of cooling body in summer?
11.What is the mechanism of warming body in winter?
12.How does body controls high and low blood sugar?