Introduction to medical physiology

G. Ogweno

Basics

Calor, dolor, rubor and tumor

A basic way in which the body reacts to infection, irritation or other injury, the key feature being redness, warmth, swelling and pain. Inflammation is now recognized as a type of nonspecific immune response

)

Aulus Cornelius Celsus

De medicina, c. A.D. 25

The discipline

Physiology:knowledge of nature; function of body;grk natural phylosophy

• Physis-nature

• Logos-discourse

• Knowledge of mechanism of life at organ, tissue, cellular and molecular levels

• Contribution of organ -system to homeostasis

What is physiology?

• Dynamic study of life

• Describes “vital” functions of living organs, cells, molecules

• Branches: medical, comparative,

• Evolved disciplines: biochemistry, biophysics, neurosciences, molecular genetics, molecular biology, cell biology

Physiological genomics

• Functional genomics: understanding roles of genes play in physiology

• Link between cells, molecules genes and functions

• Polymorphisms and group effects on population=gene variants

Methods of study

• Hypothesis formation• Accurate observations• Experimentation• Methodical documentation• Quantitative approach to analytical experimentation• Establishment of identity of

fact:perception(observation),inference,comparison (logic), testimony(authority)

• Begin by accepting nothing on trust from any source whatsoever, by questioning everything and forming our own conclusions

Colligative properties of molecules

Property dependent on number of solute molecules present and not their characteristics:

• Lowering of vapor pressure

• Elevation of boiling point

• Depression of freezing point

• Osmotic pressure

Units of concentration of solutes• Moles:gram molecular weight=Avogadro’s number• Equivalent:applies to electrical/charged particles;1 eq=1 mol of

ionized substance divided by its valence• Gram equivalent: wt chemically equivalent to 8.0g of oxygen• Normality: no. of gram equivalent in 1 L• pH=-log H+ conc• Osmoles: gram molecular weight of substance divided by number of

freely moving particles that each molecule liberates in solution=osmotically active particles

• 1 osm=1 mole of solution depressing freezing point of water by 1.86ºC

• Osmolarity=number of osmoles per lit of solution, affected by temp and vol

• Osmolality=osmoles/Kg solvent, indepent of temp& vol

Fluids:descriptive terms

• Mixture:two or more components intermixed• Solution:homogenous mixture of components

e.g gases, lig, solid• Solvent: present in greatest amount, dissolving

medium• Solute: present in smaller amount• True solution:gases,lig,solids dissolved in

water,usually transparent; solutes(individual atoms& molecules) not visible to naked eye, don’t settle out, don’t scatter light ,path of beam of light invisible

contd

• Colloids: emulsions or heterogenous mixture that often appear translucent or milky; solutes larger than soln but don’t settle out, scatter ligth;visible path of light; undergo sol (fluid)-gel(solid) transformation reversible

• Suspension: heterogenous mixture with large, often visible solutes that tend to settle out e.g mixture of sand and water, blood

• Azeotrope: mixture which vaporizes into the same proportions as the volume concentration of the components in solution e.g alcohol in water 96%; lowers its vp, less volatile, bp is raised

Solutes and water movement

• Diffusion:tendency of molecules or ions to scatter evenly throughout the environment by kinetic energy and random; along or down concentration gradient. Speed influenced by molecular size and temperature

• Osmosis:movement of solvent molecules e.g water into a region predominanlty higher solutes to which membrane impermeable; tendency of migration of solvent to region of greater solutes; depends on membrane types, solutes

• Osmotic pressure: force counteracting water movement• Tonicity: ability of solution to change the shape or tone of

cells by altering their internal water volume;osmolality of solution relative to plasma, how it affects cell volume(conc&permeability)

Body fluids

Ideal solution: • O.p=nCRT/v• 1 Mole solute depressefreezing point of 1

Kg by 1.86ºCNormal plasma: • O.P=7.3 atmos• 280-300 mOsm/L• Freezing point=-0.54ºC

Avoiding The Final

Meltdown