Introduction to Physiology

• • Is the study of function in living matter

  This field of Physiology can be divided into:

  1. Viral physiology

  2. Bacterial physiology

  3. Cellular physiology

  4. Plant physiology

  5. Human physiology

  • Human Physiology - we explain the

  specific characteristics and mechanisms of

  the human body that make it a living being
• Cell


  The basic unit of the body, and each organ is an aggregate of many different cells held together by intercellular supporting structures
• Basic characteristics of cells

  • Oxygen combines with carbohydrates, fat and protein to release the energy needed for cell function
  • All cells have the ability to reproduce and whenever cell are destroyed, one or another of the remaining cells divide again and again until the appropriate number is replenished
  • The general mechanisms for changing nutrients into energy are basically the same in all cells
  • All cells deliver the end-products of their chemical reactions into the surrounding fluids
• HOMEOSTASIS

  • means maintenance of static, or constant condition in the

  environment.

  • All organs and tissues of the body perform functions that help to

  maintain these constant conditions.

  The Extracellular Fluid-The Internal Environment

  • 60% of human body is fluid. This is made up of:

  • Intracellular Fluid - this is the fluid found inside the cell which

  constitute most of the 40% of the total body fluid.

  • Extracellular Fluid - this is found in the spaces outside the

  cells, and is in constant motion throughout the body.
• Three main components of Homeostasis: Receptor, control center, Effector
• Homeostasis


  Functions of
• Extracellular Fluid Transport System

  • Transports nutrients (Circulatory System)
  • Moves fluid between blood capillaries and cells
• Origin of Nutrients in the Extracellular Fluid

  1. Respiratory System transports nutrients (O2) to tissues

  2. Gastrointestinal Tract absorbs nutrients into extracellular fluid

  3. Liver detoxifies and stores substances

  4. Musculoskeletal System provides locomotion
• 3. Removal of Metabolic End-Products

  A.Removal of Carbon Dioxide by the Lungs

  • blood picks up oxygen in the lungs, carbon

  dioxide is released from the blood into the alveoli,

  and the respiratory movement of air into and out

  of the alveoli carries the carbon dioxide to the

  atmosphere.

  B.The Kidneys

  •removes different end products of metabolism and

  excess of ions and water that might have

  accumulated in the extracellular fluid.
• Regulation of Body Functions

  1. The Nervous System - muscular and secretory

  activities

  B. The Hormones System - for metabolic function

  5. Reproduction - maintain static conditions by

  generating new beings to take the place of ones

  that are dying.
• Extraction of Energy from Nutrients (Mitochondria)

  • The principal substances from which cell extracts energy

  are Oxygen and one or more of the foodstuffs -

  Carbohydrates, Fats and Protein.

  7. Locomotion or Movements by the cells

  A.Ameboid locomotion - means the movements of an

  entire cell in relation to its surroundings, such as

  movement of WBC.

  B.Ciliary movements - the whiplike movement of cilia on

  the surface of the cells.

  • Occurs in:

  1. Respiratory airways

  2. Uterine tubes
• O2+Carbon=Glucose

  O2+Protein=Fatty acids
• The Cell and its function

  Organization of the Cell

  • A typical cell has two major

  parts namely:

  1. Nucleus - separated from

  the cytoplasm by the

  nuclear membrane

  B. Cytoplasm - separated

  from the surrounding fluids

  by the cell membrane
• Women have 28 trillion of cells

  Men=36 trillion

  17 trillion for yrs old
• Chemical composition


  Water - the principal medium

  of cell which is about 70 to

  80%. It provides transport of

  substances from one part of

  the cell to another.

  2. Electrolytes - provides

  inorganic chemicals for

  cellular reactions and for the

  operation of same cellular

  control mechanisms.

  • Potassium

  • Magnesium

  • Phosphates

  • Sulfate

  • Bicarbonate

  • Chloride (small quantities)

  • Calcium (small quantities)
• Proteins - the most abundant substance next to water, it

  constitutes 10 to 20% of the cell mass.

  • Two types:

  1. Structural Proteins (Fibrillar ) - provides the contractile

  mechanisms of all muscles.

  B. Global Proteins (mainly enzymes)

  C. Other type: nucleoproteins of the nucleus that contain

  DNA which contains the Genes.
• Lipids - the most important lipids are phospholipids and

  cholesterol which constitutes 2% of the total cell mass.

  Some cells contain large quantities of triglycerides, also

  called Neutral Fats.

  5. Carbohydrates - most human cell do not maintain large

  stores of carbohydrates, usually averaging 1% of the total

  mass.
• Physical structures of the cell

  The cell contains highly organized physical structures called

  Organelles.

  Cell Membrane (7.5 - 10 nm)

  2. Endoplasmic Reticulum

  1. Granular Endoplasmic Reticulum - functions for the

  synthesis of proteins in the cells ( Studded with

  ribosomes )

  B. Agranular Endoplasmic Reticulum or Smooth -

  functions for the synthesis of lipids substances.
• Ribosomes - granular particles attached to the outer

  surfaces of the endoplasmic reticulum and functions for the

  synthesis of proteins.

  4. Golgi Apparatus - functions in association with

  endoplasmic reticulum in the formation of lysosomes

  (secretory vesicles)

  5. Lysosomes - provides the intracellular digestive system.

  • It allows the cell to digest and remove unwanted

  substances and structures such as damaged or foreign

  structures like bacteria.

  • It produce Hydrolases, the enzyme that digest proteins,

  nucleic acid, mucopolysaccharides, lipids and glycogen.
• Peroxisomes – physically similar to lysosomes but

  they are formed by the smooth endoplasmic reticulum.

  • Contain Oxidases, which combines with hydrogen

  ions to form hydrogen peroxided (H.Os).

  • Most alcohol that a person drinks is detoxified by

  peroxisomes in the liver.

  7. Mitochondria - the "Powerhouses" of the cell.

  • It is composed of two lipid bilayer-protein membranes,

  outer and inner. 95% of ATP is produced here.
• Nucleus - the control center of the cell, it controls

  the chemical reactions that occur in the cell and

  reproduction of the cell.

  •It contains DNA in large quantities

  9. Nucleoli - contains large amount of Ribonucleic

  Acid and proteins found in the ribosomes.

  10. Microfilaments and Microtubular Structures in

  the Cell - act as Cytoskeleton, providing rigid

  physical structures for certain parts of the cell.

  11.Secretory Vesicles
• Functional system of the cell

  Ingestion by the cell (Endocytosis ) Two types:

  • Pinocytosis (Invagination) small particles with fluid

  Steps:

  1. molecules of protein attach to the membrane

  2. surface properties of the membrane change in a way that the entire

  pit invaginates inward

  3. the pits borders close are the attachment proteins and extracellular

  fluid

  4. Invaginated portion of membrane breaks away from the surface of

  the cell forming Pinocytic Vesicles
• Phagocytosis (Evagination)


  Ingestion of large particles such as bacteria, cells or portions of degenerating tissues
• Digestion of Foreign Substances in the Cell

  Immediately after a pinocytic or phagocytic vesicles appear inside a cell, lysosomes release hydrolases and begins hydrolysis of these vesicles
• Synthesis and Formation of Cellular Structures by Endoplasmic Reticulum and the Golgi Apparatus


  1. Formation of proteins by the Granular Endoplasmic Reticulum

  2. Synthesis of lipids by smooth endoplasmic reticulum

  3. Processing and formation of intracellular vesicles by the Golgi Apparatus
• Transport through cell membrane

  The fluid inside the cells of the body, called Intracellular Fluid, is different

  from that outside the cells, called Extracellular Fluid.

  The extracellular fluid includes both:

  1. Interstitial Fluid - that circulates in the spaces between the cells.

  B. Blood Plasma Fluid - that mixes freely with the interstitial fluid

  through the capillary walls.

  It is the extracellular fluid that supplies the cells with nutrition and other

  substances needed for cellular function. Before the cell can utilize these

  substance, they must be transported through the cell membrane.
• The Control center of the body


  The human body has thousands of

  control systems in it.

  Example of Control System are:

  1. Regulation of oxygen and carbon

  dioxide concentrations in the

  extracellular fluid.

  B. Regulation of arterial pressure
• Characteristics of Control System

  1. Negative Feedback Nature of Control System - this consist

  of a series of changes that return the factor toward a certain

  mean value, thus maintaining homeostasis.

  B. Positive Feedback - Vicious Circles; this does not lead to

  stability but to instability and often to death.

  • Useful: blood clotting (extravascular), childbirth (contraction

  of uterus), generation of nerve signals

  C. Adaptive Control System - feed forward and control
• Transport through the cell membrane

  Occurs by one or two basic processes: Diffusion/Passive Transport or Active Transport
• Diffusion or Passive Transport


  Random molecular movement of substances either opening the membrane or in combination with a carrier protein caused by kinetic motion of matter
• Active Transport


  Movement of ions or other substances across the membrane in combination with a carrier protein but additionally against an energy gradient, from low to high concentration, requiring chemical energy
• Diffusion Through the Cell Membrane

  Diffusion through the cell membrane is divided into two

  separate subprocesses namely:

  1. Simple Diffusion - means the molecular kinetic

  movement of molecules or ions through a membrane

  opening without the necessity or binding with carrier

  proteins in the membrane

  2. Facilitated Diffusion - means the interaction of the

  molecules or ions with a carrier protein that aids its

  passage through the membrane, by binding chemically

  with fit and shuttling it through the membrane in this form.
• Pathways of simple Diffusion Through Cell Membrane

  Diffusion through the lipid Bilayers

  1. Diffusion of lipid Soluble Substances

  • Lipid soluble substances can pass through the lipid

  bilayer rapidly

  • examples: oxygen, nitrogen, carbon dioxide, alcohol

  B. Transport of water and other lipid-insoluble

  molecules

  • examples: water (highly insoluble in lipid membrane)

  • it has great kinetic energy and has small molecules,

  thereby can penetrate rapidly through the lipid

  portion
• Pathways of simple Diffusion Through Cell Membrane

  Diffusion through the lipid Bilayers

  1. Diffusion of lipid Soluble Substances

  • Lipid soluble substances can pass through the lipid

  bilayer rapidly

  • examples: oxygen, nitrogen, carbon dioxide, alcohol

  B. Transport of water and other lipid-insoluble

  molecules

  • examples: water (highly insoluble in lipid membrane)

  • it has great kinetic energy and has small molecules,

  thereby can penetrate rapidly through the lipid

  portion
• Lipid bilayer


  This layer is impermeable to ions such as sodium, potassium because of the electrical charge which impedes their movement
• Causes of ion impermeability

  1. Electrical charge of these ions causes water to bond within forming hydrated ions which are very large to penetrate the lipid layer

  2. The electrical charge of the ion interacts with the changes of lipid bilayer
• Protein channels


  • They are selectively permeable to certain substances
• Sodium Channels


  Negatively-charged channels, 0.3 x 0.5 nm in size
• Potassium Channels


  Not negatively charged but can allow ions to pass through because their hydrated form are smaller than sodium, 0.3 x 0.3 nm in size
• Channels


  • Can be opened or closed by gates
  • Gates provide a means of controlling the permeability of one channel