PHYSIOLOGY


Physiology


Introduction to Physiology


Physiology ( /ˌfɪziˈɒlədʒi/) is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system.



Human physiology



Human physiology is the science of the mechanical, physical, and biochemical functions of humans in good health, their organs, and the cells of which they are composed. The principal level of focus of physiology is at the level of organs and systems within systems. Much of the foundation of knowledge in human physiology was provided by animal experimentation. Physiology is closely related to anatomy; anatomy is the study of form, and physiology is the study of function.

Due to the frequent connection between form and function, physiology

and anatomy are intrinsically linked and are studied in tandem as part of a medical curriculum.

The study of human physiology dates back to at least 420 B.C. and the time of Hippocrates, the father of medicine. Physiology was first recognized in the early 1960s.



The critical thinking of Aristotle and his emphasis on the relationship between structure and function marked the beginning of physiology in Ancient Greece, while Claudius Galenus (c. 126-199 A.D.), known as Galen, was the first to use experiments to probe the function of the body. Galen was the founder of experimental physiology. The medical world moved on from Galenism only with the appearance of Andreas Vesalius and William Harvey.



*



Man and his Environment


Physiology is a science which analyses the body organ functions & their interactions with the environment .

Goals include :
1. organization of the body & body systems
2. transport across the cell membrane
3. body fluids & fluids exchange
4. problem presentation
5. structure & functions of the nephron
6. acid-base balance
7. homeostasis
8. structure & functions of the neuron
9. autonomic nervous system
10. basal metabolic rate
11. body temperature
12. problem discussion


                                                                                1)

     A) Levels of structural organization

1. CELLS : are made up of molecules
2. TISSUE : consists of similar types of cells
3. ORGAN : made up of different types of tissues
4. SYSTEM : consists of different organs that work closely together



                 B) Body systems

1. Integumentary  system :
a) forms the external body covering.
b) composed of the :
i) skin  ii) sweat glands   iii) oil glands  iv) hair
and  v) nails.
c) protects deep tissues from injury.
d) synthesizes vitamin D.


2. Skeletal system :
a) composed of :
i) bone  ii) cartilage  iii) ligaments.
b) protects & supports body organs.
c) provides the framework for muscles.
d) site of blood cell formation.
e) stores minerals.


3. Muscular system :
a) composed of muscles & tendons.
b) allows locomotion & facial expression.
c) maintains posture.
d) produces heat.


4. Nervous system :
a) composed of brain, spinal cord, & nerves.
b) is the fast-acting control system of the body.
c) responds to stimuli by activating muscles and glands.


5. Endocrine system :
a) composed of glands ( pituitary, thyroid, adrenal… etc.).
b) glands secrete chemicals (hormones) which change cellular activities.
c) acts along with the nervous system to control body functions.


6. Cardiovascular system :  
a) composed of the heart & blood vessels.
b) the heart pumps blood.
c) the blood vessels transport blood throughout the body.


7. Lymphatic system :
a) composed of : red bone marrow, thymus, spleen, lymph nodes, & lymphatic vessels.
b) picks up fluid leaked from blood vessels & returns it to the blood.
c) disposes of debris in the lymphatic stream.
d) houses white blood cells involved with immunity.


8. Respiratory system :
a) composed of : the nasal cavity, pharynx, larynx, trachea, bronchi, & lungs.
b) keeps blood supplied with oxygen & removes carbon dioxide.


9. Digestive system :
a) composed of : oral cavity, esophagus, stomach, small intestine, large intestine, rectum, anus, & liver.
b) breaks down food into absorbable units that enter the blood.
c) eliminates indigestible foodstuffs as feces.


10. Urinary system :
a) composed of : kidneys, ureters, urinary bladder, & urethra.
b) eliminates nitrogenous wastes from the body.
c) regulates water, electrolytes, & pH balance of the blood.


11. Male reproductive system :
a) composed of : prostate gland, penis, testes, scrotum, & ductus deferens.
b) main function is the production of offspring.
c) testes produce sperms & male sex hormones.
d) ducts & glands deliver sperms into the female reproductive tract.


12. Female reproductive system :
a) composed of : mammary glands, ovaries, uterine tubes, uterus, & vagina.
b) main function is production of offspring.
c) ovaries produce eggs (ova) & female sex hormones.
d) remaining structures serve as sites for fertilization & development of the fetus.
e) mammary glands produce milk to nourish the newborn.

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Man and his Environment
contd



C)  Organ systems interrelationship

1. The integumentary system protects the body from the external environment.
2. Digestive & respiratory systems in contact with the external environment, take in nutrients & oxygen.
3. nutrients & oxygen are distributed by the blood.
4. metabolic wastes are eliminated by the urinary & respiratory systems.


                         D)  The cell
The cell is the basic living unit of the body.
Cells bind to each other & aggregate to form tissues; tissues aggregate to form organs; organs aggregate to form systems; systems ultimately aggregate to form the body.
Cells bind to each other via membrane junctions.
The human body contains about 100 trillion cells.
Each type of cells is adapted to perform particular functions, e.g. RBCs (bags containing hemoglobin) transport oxygen from lungs to tissues.


Membrane junctions :
Are of two types :
1. tight junction : which is impermeable & encircles the cell.
2. gap junction : is a nexus that allows chemical substances to pass b/w cells.



Basic characteristics of cells :
1. in all cells, oxygen combines with breakdown products of lipids, CHO, & proteins to release energy.
2. the waste products of all cells are delivered out into the surrounding fluids.
3. all cells are able to replicate.


Organization of the cell :

: The cell is made up of two major parts
1. cytoplasm : which is separated from the surrounding fluid by a cell membrane.
2. nucleus : which is separated from the cytoplasm by a nuclear membrane.
The different substances that form the cells
are collectively called the protoplasm which is
: composed mainly of :

1. water
Which is the principal fluid medium of the cell ,
& is present in most cells in a concentration of ~
70 – 80% (except fat cells).

2. Ions :
Are necessary for some cellular control mechanisms, e.g. ions acting across the cell
membrane are responsible for transmission of electrical impulses in nerve & muscle cells
The most important ions in the cell are :
K+ , Mg2+ , Po43 , So4 -, Hco3- , Na+ , Cl- , & Ca2+ .

3. Proteins :
Constitute 10 – 20% of total cell mass.
: Cell proteins are usually divided into two types
a) structural proteins (microtubules)
b) globular proteins (enzymes)

4. Lipids :
Constitute 2% of the total cell mass.
The most important lipids in most cells are phospholipids & cholesterol.

5. (Carbohydrates (CHO
Structurally have little functions.
Constitute one of the major sources of energy for cellular activities.




Cell structure & functions


Cell structure & functions

The cell is not merely a bag of fluids, enzymes, & chemicals, but also contains highly physically organized structures many of them are called organelles.
These organelles are important for cells to performing their functions; for instance, without mitochondria more than 95% of cell
energy supply would cease immediately

: Cell membrane
Separates the cell from surrounding .
(Is a thin elastic structure only 7.5 – 10 nms thick (nanometers
Consists primarily of a bilayer of phospholipids molecules & proteins. 1/10TH of the phospho-lipid molecules are glycolipids
Most of cell organelles are also covered by membranes.

: The lipid bilayer
The phosphate ends face water inside, & outside the cells are soluble in water (hydrophilic).
(The fatty acid tails imbedded in the center of the membrane, facing each other, are soluble In fats (hydrophobic


The hydrophobic layer of the membrane prevents the passage of water & water- soluble substances such as ions, glucose, & urea. It allows the passage of fat-soluble substances such as oxygen, carbon dioxide, & alcohol.
Cholesterol dissolves in the lipid bilayer of the Membrane & helps to determine the degree of membrane permeability to water-soluble constituents of body fluid.

The proteins :
Two types of proteins exist in cell membranes :
a) Peripheral proteins: i) do not penetrate cell membrane. ii) are attached to the inside or outside surface of the membrane. iii) Act as enzymes, receptors, or antigens.

b) integral proteins :
i large protein molecules that penetrate the whole thickness of the membrane.
ii form channels & carriers via which water-soluble substances are transported.
iii most of the integral proteins are glyco-proteins (CHO).

CHO :
Often coat the entire outside of the cell membrane (glycocalyx).
Most of integral proteins are glycoproteins, & 1/10TH of the phospholipid molecules are glycolipids.



The cytoplasm

Material between plasma membrane and nucleus

: Cytosol
.Largely water with dissolved proteins,salt, suger and other soluble substanses
:Cytoplasmic organelles
Metabolic machinary of the cell

:Specialized cellular compartments
:Membranous (!
mitochondria _ peroxisomes _ lysosomes _ endoplasmic reticulum and golgi apparatus


Nonmembranous (!!
Cytoskeleton*centerioles and ribosomes
: Mitochondria
The power house of the cell-
Without it most of the cellular function will cease -
Coverd with doube membranes -
Provide with the most cell ATP via aerobic cellular respiration -
Contain their own DNA and RNA therefore are able to replicate -
Vary in number and size from cell to another according to the metabolic needs

(Endoplasmic reticulum(ER
Interconnected tubes and parallel membranous enclosing cisternae connect with nuclear membrane 2varitetes rough ER and smooth ER

Granular rough ER
External surface studded with ribosome's manufactures all secreted proteins
Responsible for the synthesis of integral membrane proteins and phospholipids for cell membranes

Ribosome
Granules containing protein r RNA -
Site of protein synthesis -
Free ribosomes synthesize soluble proteins -
Membrane -bound ribosome synthesize proteins to be incorporated into membranes -

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