Introduction To
Physiology
Dr. Robert Mbelwa
0715832005
0785675676
drrobertmbelwa@gmail
12-Mar-16
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Learning Objectives
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Define physiology and its various specialties
Identify the major levels of organization in
organisms .
Identify the 11 organ systems of the body and
their major components.
Explain the concept of homeostasis, including
both positive and negative feedback.
Physiology

The term physiology is derived
from the Greek word
PHYSIOLOGICOS
– PHYSIS – Nature; LOGOS – Study

Inquiry to Nature
– Physiology is the study of normal
function and phenomenon of
living things
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Physiology

Aims at Describing, Explaining and
Understanding
– How living things work or function;
– The intricate control system and
regulatory mechanisms
» How and why plants grow?
» What makes bacteria divide
» How do fish obtain and use oxygen
» How is food digested
» What makes the heart beat
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Interrelation With
Other Specialties

In order to discover how living
things work
– We need to know the actual structure
of the body
» The bones, muscles and their
attachments, nerves different organs
and their location (ie. Gross
anatomy)

The physiologist can then explain,
for example how a limb moves
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Interrelation With
Other Specialties

Limb moves because
– Particular set of muscles contract

But this is not the end of story
– Further questions arise
» Why? And how? Do the muscles contract

To answer these questions, the
physiologist must know
– The structure of the muscle (Histology)
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Interrelation With
Other Specialties
– What is happening at the cellular
level (ie Biochemistry)

There is an inter-relationship
between the biological
sciences
– In order to understand
physiology one needs to have
knowledge of a number of other
biological sciences
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Branches of Physiology

Several branches of physiology
according to the different types
of living things
– Physiology of plants, birds,
insects, fish, mammals ; of which
human physiology is of special
interest for Health Sciences
Specialties
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Branches of Physiology

Human physiology can be
further subdivided
– according to the different
systems
»circulation, respiration,
muscles, digestion,
reproduction, nervous
system, endocrine system
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Comparative physiology

Studied in a variety of species
– emphasis on how a particular organ or
system function in different species
– Most of the knowledge about human
physiology originated from
experimentation on different animals.
–    
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For the purpose of your
course

You will be concerned with
Human physiology
– During the first & second
semesters you will be taught
Basic & an aspect of clinical
Physiology

The course will be offered in
ten modules
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Basic Physiology
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Semester 1
– Covers modules 1-7
– Fluid and circulation
» The cell and its immediate internal
environment, Body fluids,
homeostasis
» Blood
» The excitable tissue
» The cardiovascular system
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Basic Physiology
– Metabolism and excretory systems
» The Respiratory system
» The renal system
» The Digestive system

Semester 2
– Modules covered 8-10
» Reproduction
» Neuroendocrine system
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The Endocrine system
The nervous system
– Sensory, motor, autonomic and special
senses
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Method of Teaching
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Mainly Lectures
– Provide only the backbone information
– They are intended to stimulate and guide the
students into a more detailed private study on
the topics covered
Practical
– Actual practical or practical demonstration
Others
Seminars, tutorials, student’s presentations
– Intended to help the individuals to
» revise materials covered
» Cover new avenues related to what has
already been covered
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Recommended Textbooks

Textbook of Medical Physiology, by
Arthur C. Guyton, 10th edition

Review of Medical Physiology,
by
William F. Ganong, 20th edition

Physiology , by Berne, Robert &Mathew
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Recommended Textbooks

Others
– Human Physiology, the Mechanisms of body
Function; by Vander, Sherman,& Luciano. 6th edition
– Essentials of Medical Physiology, by Johnson,
Leonard R. 2nd edition
– Physiology, NMS, by Bullock, Boyles, Wang. 3rd
edition
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Others Sources
– There are several books on systemic
physiology
» Respiratory physiology
» Cardiovascular physiology, etc
– From the Internet
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Assessment
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Continuous assessment tests
– Mainly at the end of module
– End of Semester university
examination
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Mode of examination
– Mixture of multiple choices Questions,
matching items & short answers,
essays
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Organization
of the
human body
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Levels of structural
organization

The human
body exhibits 6
levels of
structural
complexity :
1.
2.
3.
4.
5.
6.
Chemical
Cellular
Tissue
Organs
System Level
Organismic
Level
Levels of Structural Organization
cont’d
1- Chemical level


the simplest level
of structural
ladder
At this level atoms
combine to form
molecules such as
water, sugar, &
proteins
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Levels of Structural Organization
cont’d
2- Cellular level
 the smallest
functional/livin
g units of living
things .
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Levels of Structural Organization
cont’d
3- Tissue level

groups of similar
cells that have a
common function
(4 basic types)
a. Epithelium
b. Muscle
c. Connective
tissue
d. nerve
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Levels of Structural Organization
cont’d

4- Organ level,
an organ is a
structure
composed of 2
or more tissue
types that
performs a
specific
function .
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
Organ level consists of two or
more types of
primary tissues
that function
together to
perform a
particular function
or functions
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– 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
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Levels of Structural Organization
cont’d

5- Organ System
is a group of
organs that work
together to
accomplish a
common purpose
– each organ has
its own job to do

sometimes an
organ is part of
more than one
system
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Levels of Structural Organization
cont’d

6- organismic level
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Comprises of one
living individual
represents the
highest level of
structural
organization
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
consists of 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
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summary
Body systems:The human body
has 11 systems
Integumentary system
2. Nervous system
3. Skeletal system
4. Endocrine system
5. Muscular system
6. Cardiovascular system
7. Lymphatic system
8. Urinary system
9. Respiratory system
10. Digestive system
11. Reproductive system
1.
Homeostasis
&
Feedback systems for
controlling body functions
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Homeostasis
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Describes the body’s ability to maintain
relatively stable internal conditions
even though the outside world is
continuously changing
The literal translation of homeostasis is
“unchanging,”( homeo= the same,
stasis = standing still which is not
true).
Homeostasis cont’d
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The term does not really mean a static,
or unchanging, state.
Rather, it indicates a dynamic state of
equilibrium, or a balance, in which
internal conditions vary, but always
within relatively narrow limits.
In general, the body is in homeostasis
when its needs are adequately met and
it is functioning smoothly.
Homeostasis is essential for survival
and function of all cells
If homeostasis is not maintained, death
may result
Control of Homeostasis
Homeostasis cont’d
•Two general points within
homeostasis
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Autoregulation or intrinsic regulation –
results when cell, organ or system adjusts
its activity automatically.
Extrinsic regulation - results from activity of
nervous system or endocrine system
Homeostatic Control
Mechanisms
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Communication within the body is
essential for homeostasis.
Communication is accomplished chiefly
by the nervous and endocrine systems
which use neural electrical impulses or
blood borne hormones, respectively, as
information carriers.
Regardless of the factor being
regulated(the variable)all homeostatic
control mechanisms have at least three
interdependent components .
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Homeostatic Control
Mechanisms
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
The first component, the receptor, is
some type of sensor that monitors the
environment and responds to changes,
called stimuli, by sending information
(input) to
the second component, the control
center. Input flows from the receptor to
the control center along the so-called
afferent pathway. The control center,
analyzes the input it receives and then
determines the appropriate response or
course of action.
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Homeostatic Control
Mechanisms
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The third component, the effector,
provides the means of response (output)
to the stimulus. Information flows from
the control center to the effector along
the efferent pathway.
The results of the response then feed
back to influence the stimulus, either
depressing it (negative feedback) so that
the whole control mechanism is shut off
or enhancing it (positive feedback) so
that the reaction continues at an even
faster rate.
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•Components of homeostatic control
mechanisms
 Homeostatic
control
mechanisms are TWO:
– Negative feedback mechanisms – the net
effect of the response to the stimulus is
the shut off of the original stimulus or to
reduce its intensity I,e the original
stimulus is reversed
» E.g. – body temp, blood chemical levels
– Positive feedback mechanisms – tend to
increase the original disturbance
(stimulus) and push the variable farther
from its original value i.e original stimulus
is intensified
» E.g. – ovulation, blood clotting, birth
Negative Feedback Mechanisms

Most homeostatic control mechanisms are
negative feedback mechanisms. In these
systems, the output shuts off the original
stimulus or reduces its intensity. These
mechanisms cause the variable to change
in a direction opposite to that of the
initial change, returning it to its “ideal”
value; thus the name “negative” feedback
mechanisms
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Negative Feedback Loop
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Negative Feedback Loop
A good example of a nonbiological negative feedback
system
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is a home heating system connected to a
temperature-sensing thermostat .
If the thermostat is set at 20°C (68°F),
the heating system (effector) is triggered
ON when the house temperature drops
below that setting.
As the furnace produces heat and warms
the air, the temperature rises, and when
it reaches 20°C or slightly higher, the
thermostat triggers the furnace OFF.
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Example continued

This process results in a cycling of
“furnace-ON” and “furnace-OFF” so that
the temperature in the house stays very
near the desired temperature of 20°C.
Your body “thermostat,” located in a part
of your brain called the hypothalamus,
operates in a similar fashion.
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Negative Feedback: The Control of
Body Temperature
Homeostasis of Blood
Pressure
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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

Some of the variables that need to be
regulated by negativeback mechanisms
include
– Body temperature ,blood volume,heart
rate,blood pressure,the rate and depth
of breathing, and blood levels of
oxygen, carbon dioxide, minerals.
.etc
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Positive Feedback Mechanisms

In positive feedback mechanisms, the
result or response enhances the original
stimulus so that the activity (output) is
accelerated. This feedback mechanism is
“positive” because the change that occurs
proceeds in the same direction as the
initial disturbance, causing the variable to
deviate further and further from its
original value or range.
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Positive feedback cont’d

In contrast to negative feedback controls,
which maintain many physiological
functions or keep blood chemicals within
narrow ranges
 positive feedback mechanisms usually control
infrequent events that do not require
continuous adjustments

However, TWO familiar examples of their
use as homeostatic mechanisms are the
enhancement of labor contractions during
birth and blood clotting.
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Positive Feedback: Blood Clotting
•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
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
Homeostatic Imbalance
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Homeostasis is so important that most
disease can be regarded as a result of its
disturbance, a condition called
homeostatic imbalance.
As we age, our body’s control systems
become less efficient, and our internal
environment becomes less and less
stable. These events increase our risk for
illness and produce the changes we
associate with aging
Examples of homeostatic imbalance are
provided throughout this course to
enhance understanding of normal
physiological mechanisms.
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Final word

Hard work is the only cure for
hard life

I wish you all the best in your
academic pursuit

You will all make it
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