ATE Physiology 1, L1

the term “milieu interieur” was created by

Claude Bernard

the expression "milieu intérieur" refers to

stable internal conditions maintained by living organisms

components of homeostasis

isovolemia, isoionia, isotonia, isohydria

homeostasis is

the process by which living organisms regulate and maintain a stable internal environment

isovolemia

constant volume

isoionia

constant ion composition

isotonia

constant osmotic pressure

isohydira

constant pH

the interstital space resembles

ancient oceans

an anatomical space is not the same as a compartment

flickering clusters of water molecules

dynamic, short-lived groupings of water molecules that constantly form and break hydrogen bonds with each other

flickering clusters of water molecules are positioned in

quaternary order

water penetrates dividing membranes in the

flickering cluster form

water in the body acts as a

solvent; medium for reactions

water in the body also acts as a

source of osmotic forces

another function of the water in the body is

forming compartments

Water content of blood

90%

Water content of liver, muscle, brain

70-75%

Water content of bone

25%

Water content of fat

10%

Barriers separating compartments (2 types)

cell membranes and capillary walls

the cell membrane is

permeable for water without restriction, but selective for other substances

the capillary walls

retain colloids, permeable for other substances

Parts of the membrane determining transport:

lipid bilayer, complex proteins

what are the complex proteins determining transport through membranes

receptors, enzymes, carriers, channels

types of transport through membranes

passive transport and active transport

types of passive transport require

no ATP

types of passive transport

simple and facilitated diffusion

facilited diffsion

a type of passive transport in which substances move down their concentration gradient with the help of membrane proteins

types of active transport

from direct energy source and from indirect energy source

primary active transport moves substances

against their gradients

Primary active transport (direct use of ATP)

transport protein (pump) uses ATP hydrolysis to move ions/molecules against their gradient

secondary active transport

does not directly use ATP, but depends on gradients created by primary active transport

direction of solutes involved in secondary active transport

either both in the same direction or in opposite directions

Total body Water (TBW)

Extracellular compartment (2/3)+ Intracellular compartment (1/3)

How much is the tbw /bwkg?

600-650 ml/bwkg

parts of the EC body fluid

intravasal, (in the circul.) interstitial in the tissues

the EC compartment has subcompartments

intravascular, interstitial, transcellular

transcellular subcompartment

separated from the other compartments of the body by epithelial cell layers!!!

examples of transcellular subcompartments

synovial fluid, aqueous humour, glandular discharges, content of the urinary bladder, gastrointestinal tract

measuring the EC compartment by the dilution principle

quickly and slowly equilibrating spaces

quickly equilibrating space

substance flow is fast, it equilibrates within the 0.5 -1 hour

examples of quickly equilibrating spaces

blood plasma, interstitium of soft tissues, lymph

slowly equilibrating space

uniform distribution develops only 8-10 hours later

examples of slowly equilibrating spaces

bone, transcellular space

the intracellular compartment is considered to be

uniform

Stewart Dilution Principle

a method used in physiology to measure the volume of a fluid compartment in the body

Stewart-principle in living organisms

In the living organism the concentration of the indicator decreases constantly

Why does the C decrease contantly in a living organism

permeates barrieres, metabolized, excreted by the kidney, lung or the skin

Stewart-principle in living organisms

indicator concentration should be calculated at administration

When does the indicator start to get eliminated?

immediately after administration

substances used for the assessment of total body water

³H₂O, ²H₂O antipirin, urea, tiourea

exsiccation

desiccation till constant mass at a temperature of 105 ºC

assessing body density

weigh the mass, quantify volume, calculate density (m/V)

densities of some tissues

bone: 1.56, soft tissue: 1.06, fat: 0.94

What is the constant water content of lean body mass?

73% water content

What is the constant water content of fat?

10% water content

calculating density: suitable for estimating the

composition of the body (fat content)

TOBEC (Total Body Electrical Conductance)

measures the fat content of the body with high precision

fat content can be measured by

measuring density experimentally, or calculating it from TBW%

substances used for the uantification of the EC compartment

diffuse across capillary walls, but cannot cross cell membranes

example substances used for the uantification of the EC compartment

inulin, mannitol, sacharose

EC space – Stewart-principle

3 types of distributions; fast, slow and late distribution

EC space – Stewart-principle: Fast distribution:

shows the volume of the soft tissues

EC space – Stewart-principle: Slow distribution:

shows the volume of the soft plus the fibrous tissues

EC space – Stewart-principle: Late distribution:

shows the volume of bone, fibrous and soft tissues