Introduction to Physiology:
The Cell and
General Physiology
Sangar M. Osman
- The goal of physiology is to explain the physical and
chemical factors that are responsible for the origin, development, and progression of life.
- Physiology can be divided into viral physiology, bacterial
physiology, cellular physiology, plant physiology, human physiology, and many more subdivisions.
- In human physiology, we attempt to explain the specific
characteristics and mechanisms of the human body that make it a living being
- Physiology is considered to be the basis of medicine, a
high proportion of body disorders are basically physiological malfunctions
1.To provide students with the knowledge about the function
of different body systems and organs.
2.To make students understand the mechanisms of function
that operate in the living organism at all levels ranging from subcellular to the whole integrated body.
3.To provide students through out teaching programs with
necessary examples of clinical applications of dysfunction.
- Text book of medical physiology( Guyton &Hall) - Review of medical physiology( Ganong)
- Principles of anatomy & physiology - Essentials of medical Physiology
- Additional references: Medical websites e:g
Pubmed (https://www.ncbi.nlm.nih.gov/pubmed/) Google Scholar (https://scholar.google.com/)
1.Introduction
2.Cell and membrane Physiology 3.Physiology of the muscles
4.Physiology of the nerves
5.Autonomic nervous system physiology (ANS) 6.Central nervous system physiology (CNS) 7.Physiology of special senses
8.Physiology of blood 9.Endocrine Physiology
10.Cardiovascular system physiology (Heart and circulation) 11.Gastrointestinal physiology
12.Physiology of respiration
Introduction to Physiology:
The Cell and
1. Introduction to Physiology
2. Functional Organization of the Human Body and Control of the “Internal Environment”
3. The Cell and Its Functions
Physiology: the study of the functions of living things, how the human body works.
Physiology focus on mechanisms of action, cause and effect sequences of physical and chemical processes in the body
Why vs. How in Physiology
• Physiological process (what):
Shivering in response to cold • Why? Because shivering
generates heat, which warms the body
• How? Temperature sensitive nerve cells detect a decrease in body temperature, signal a region of the brain responsible for
temperature sensitivity, activates a nerve pathway that causes
Structure and Function
• The structure of the body
(Anatomy) are closely
related to the functions of
the body (Physiology)
• For example, over 300
million tiny air sacs in the
lungs contain thin walls
closely associated with
Functional Organization of the Human Body and Control of the “Internal Environment”
There is an exquisite structural organization of the human body, from the most microscopic (chemical to the body as a whole (organism):
• Chemical Level
• Cellular Level
• Tissues Level
• Organs Level
Chemical Level
Chemical Level: atoms and molecules make up the body
- Atoms: the smallest building blocks of matter, Example: oxygen, carbon, hydrogen, nitrogen
- Molecules: atoms combine to make later molecules
Cellular Level
Cellular Level: cells are the basic units of life
- Cells: the smallest unit capable of carrying out the basic processes
associated with life
Basic Cellular Functions
1. Obtaining food and oxygen
2. Performing chemical reactions
3. Eliminating carbon dioxide and other waste
4. Synthesizing proteins
5. Controlling exchange of materials in and out
6. Move materials throughout compartments
7. Sense and respond to environment
Cellular Specialization
In Humans, and other multicellular organisms cells perform specialized functions over and above their basic functions
- example: digestive glands use protein synthesis machinery within cells to produce digestive enzymes; specialized proteins to breakdown food
(function: protein synthesis)
- example: Kidney tubules regulate substances between the blood on one side of the cell, and the urine on the other side of the cell to selectively retain necessary substances in the blood and remove wastes
(function: controlling exchange)
- example: muscle cells are tightly packed with proteins that produce intracellular movement, generating tension
Tissue Level
•
Tissue Level
: tissues are group of cells with
specialized functions
•
Cells of similar structure and function combine to
form 4 main types of tissues
1- Epithelial Tissue
2- Connective Tissue
3- Muscle Tissue
Tissue Types
1- Epithelial Tissue
- Internal and external covering, form barriers and
boundaries
- Specialized for exchange of materials in/out of cells
2- Connective Tissue
- Connect, support and anchor body tissue
- Specialized for attaching and transporting materials
3- Muscle Tissue
- movement and contraction of organ, body
- specialized for movement of cellular components
4- Nervous Tissue
- Initiate and transmit electrical signals
Organ Level
• Organ level: a unit made up of several tissue types
• Epithelial, connective, muscle and nervous tissues combine to
form organs
• Example: the stomach:
- Lined with epithelial tissue that produce secretions and digestive enzymes, absorb nutrients, and protects against stomach contents
- Middle wall contains 3 layers of involuntary smooth muscle tissue
that contracts to mix, churn, and breakdown food
- Contain nervous tissue throughout its layer to respond to food entering the stomach, prepares the stomach for food entry, etc
Organ Systems Level
• Organ System Level: groups of organs are organized into body
systems as they interact for specific body functions
• Example: the circulatory system is made up of the blood, heart and
blood vessels
- Human Body System: 1. Circulatory System 2. Digestive System 3. Respiratory Systems 4. Urinary System
5. Skeletal System 6. Muscular System
7. Integumentary System 8. Immune System
9. Nervous System 10. Endocrine System
Organism Level
•
Organism level
: the
body systems are
packaged together into
a functional human
body
•
Body systems work
together to regulate the
body as a whole to
keep the organism
(you!) alive and well
•
The human body is
made up of living cells,
organized into
Q. Calculate total body water (TBW) for a 70 kg man
TBW = 60% of body weight
TBW = 60% X 70 = 42 L of water
Differences Between Extracellular and Intra cellular Fluids
- The extracellular fluid (internal environment) contains large amounts of sodium, chloride, and bicarbonate ions plus nutrients for the cells, such as oxygen, glucose, fatty acids, and amino
acids. It also contains carbon dioxide that is being transported from the cells to the lungs to be excreted, plus other cellular waste products that are being transported to the kidneys for excretion.
- The intracellular fluid differs significantly from the extracellular fluid; for example, it contains large amounts of potassium,
magnesium, and phosphate ions instead of the sodium and chloride ions found in the extracellular fluid.
- Special mechanisms for transporting ions through the cell
“Homeostatic” Mechanisms of the Major Functional Systems
Homeostasis
• The ability to maintain stable internal conditions despite changes in the internal or external
environment
- Example: temperature, fluid level, nutrient levels, chemical composition
• This is done from the cellular to body systems level in order to achieve steady state , a small range of internal conditions balanced within the body as a whole
• Homeostasis is a dynamic process of continued, fine-tuning and adjustments to maintain the internal conditions of the body in response to continued
External, Internal and Cellular Environments
• In a complete organism, like the human body, with multiple layers of cells, not every cell has contact with the external
environment; these cells they rely on exchange and regulation with the internal environment
• External environment: surrounding environment in which an organism lives
- example; sensation and exchange by the skin, intake of food to mouth
• Internal environment: fluid and materials surrounding cells within the body
- extracellular fluid (ECF)
-example: blood, interstitial fluid surrounding a cell
Factors Regulated
• Homeostatically Regulated Factors:
1. Nutrients
2. Gases (oxygen and carbon dioxide)
3. Waste products (urea, nitrogenous waste)
4. pH
Homeostatic Control
•
Homeostatic Control Systems
: functionally
interconnected network of body systems that
operate to maintain a given factor in the internal
environment
• Must be able to:
1. Detect deviations from “normal” or desired steady
state level
2. Integrate this information with other relevant
information
Homeostatic Components
•
Homeostatic Control Systems:
body
components maintaining a given factor for the
internal environment
•
Factor/Variable
: temperature, pH, nutrient
level, etc. needed by the body
•
Sensor
: detects change in factor
•
Integrator
: receives sensory information and
brings it together with other information,
decides how to respond
•
Effector
: cell, tissue, organ that changes
Feedback vs. Feedforward Responses
•
Feedback
: a response made after an initial change
has been detected
• 2 types:
1. Negative Feedback
2. Positive Feedback
Negative Feedback
• Negative Feedback: change in a factor triggers a response in the opposite direction; stabilizing, corrective, opposing change - increase relative to steady state? Negative feedback
response=decrease
- decrease relative to steady state? Negative feedback response=increase
• Example:
• Homeostatic Control System: Heating and Air System • Factor: room temperature in your home
• Setpoint: your desired setting (75 °F), i.e. steady state • Sensor: detects room temperature
• Integrator: thermostats adjusts the furnace on/off to keep temp within 75 ± 2 °F
Positive Feedback
• Positive Feedback: change in a factor triggers a response in the same direction; amplifying change, destabilizing, domino effect • RARE, few examples
- increase relative to steady state? positive feedback response=increase more
- decrease relative to steady state? positive feedback response=decrease more
• Example:
• Homeostatic Control System: Birth (parturition) • Factor: contractions of uterus to push baby out
• Setpoint: max pressure for removal of baby from uterus • Sensor: detects uterine pressure increase, cervical stretch
• Integrator: nervous system senses uterine contraction, sends signals to pituitary
• Effector: pituitary releases oxytocin to increase uterine contractions, stretch cervix
POSITIVE FEEDBACK
In some instances the body uses positive feedback to its advantage
Physiologic usefulness:
Blood clotting
When a blood vessel is ruptured and a clot begins to form, multiple enzymes called clotting factors are activated within the clot itself. Some of these enzymes act on other inactivated
POSITIVE FEEDBACK (VICIOUS CIRCLE)
Positive feedback does not lead to stability but to instability and, in some cases, can cause death
Example:
Excessive bleeding decrease BP
Decreased BP affects cardiac perfusion
Cardiac contractility
Cardiac output decrease
More decrease in BP and More deterioration in heart function
Disruptions of Homeostasis
• The body maintains a range of each factor in order to prevent illness, disease and death:
- Optimal range- where body functions most efficiently - Range of tolerance- can still function, but not optimal - Minimum or Maximum set point for steady state
Negative Feedback: Regulation of Blood Pressure
• External or internal stimulus increase BP – Baroreceptors (pressure sensitive
receptors)
• Detect higher BP
• Send nerve impulses to brain for interpretation
• Here these impulses inhibit the vasomotor center, which in turn decreases the number of impulses transmitted from the vasomotor center through the sympathetic nervous
system to the heart and blood vessels. • Vasodilatation
Learning outcomes
- The overall organization of the body
- The means by which the different parts of the body operate in harmony
- The body is actually a social order of about 100 trillion cells
organized into different functional structures, some of which are called organs
- Each functional structure contributes its share to the maintenance of homeostatic conditions in the extracellular fluid, which is called the
internal environment. As long as normal conditions are maintained in this internal environment, the cells of the body continue to live and