Dr Yogesh Singh dryogeshsinghaiimsyahoocoin M 9997265620 Homeostasis Def maintenance of the constancy of the internal environment of the body Internal environment ID: 928152
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Slide1
Introduction to Physiology
Dr Yogesh Singh
dryogeshsinghaiims@yahoo.co.in
M: 9997265620
Slide2Homeostasis
Def. –
maintenance of the constancy of the internal environment of the body.
Internal environment –
milieu
interieur
extracellular fluid which includes interstitial fluid.
Slide3Simple diffusion -
Movement of molecules from higher concentration to lower concentration till equilibrium is reached
Slide4Diffusion
can takes place through:
Lipid bilayer
Lipid soluble substances-
O2,Co2,alcohol,
steriods
etcLipid insoluble – water (through spaces bet lipid mol) urea, sugar (less or no permeability) iii) Electrolytes – impermeable – charge on fatty acid chain
- Hydrated forms are larger
Slide5Factors affecting rate of diffusion
Lipid solubility
Molecular size & wt.
Temperature
Thickness of membrane
Surface area
Concentration gradientPressure gradientElectrical gradient
Molecular
Membrane related
Gradients
Slide6Fick’s law of diffusion –
Q
α
─ ─ ─ ─
Δ
C
∙
P∙A
MW∙ ΔX
Q = net rate of diffusionΔC = conc. gradient of a substanceP = permeability of membrane to the sub.A
= surface area of a membraneMW = molecular wt. of sub.ΔX = thickness or distance
Imp.
Slide7Two big jump in the tree of LIFE
Movement
Multicellularity
Slide8Volume and composition of this fluid should be maintained constant (within narrow limits) in spite of changes in external environment for the normal function of cell.
Failure of homeostasis leads to disease
Slide9Some regulating systems and their functions –
Resp. system - CO
2
content
Liver and pancreas – glucose
Kidney – conc. of ions
CVS – blood flow and temp regulationNervous and endocrine systems regulate the function of other systems
Slide10Composition of ECF is same all over the body because of constant mixing of interstitial fluid and blood and circulation of blood
Slide11Foundation steps for the movement
Mass and Newton law of motion
Self generated movement (Intention and will )
Slide12Role of dual nature of
Charge
Slide13Na
+
30
Pr - 30
Na
+
30Cl -30
Na+ 30
Pr - 30Na+ 30Cl - 15Cl - 15
Na+ 45Pr - 30
Na+ 15Cl - 15Cl - 15
ABNa+ 40
Pr - 30Na+ 20Cl - 20 Cl - 10
conc. Gradient for Cl -
electrical gradientConc. gradient
electrical gradientMore –vity in A
Slide14Gibbs – Donnan Equilibrium
Explains difference in the conc. of
diffusible ions
in two compartments separated by semi permeable membrane, when one compartment contains non diffusible ions
Na
+
Cl -Pr -ABNa +Cl
-
Proteins are non diffusible anions in AConc. Of Na + is more in A as compared to B
Slide15Explaination
–
1) All the solutions are electrically neutral.
( total no. of anions = total no. of cations ) 2) Product of diffusible cations and an anions in both the compartment is equal.
( Na+A x Cl-A = Na+B x Cl-B ) Applied – In ICF conc. of diffusible K+ is more because of presence of non diffusible Pr -
and PO4 -
Slide16Diffusion potential or Equilibrium potential - E
Potential generated across the cell membrane in the presence of
non diffusible
ions in one compartment.
Magnitude of potential developed can be calculated by Nernst equation.
Slide17Equilibrium potential or diffusion potential (E)
=
+
61 log ------------
Conc. inside
Conc. outsideE
K = - 94 mVENa = + 61 mVECl = - 90 mVGoldmann-Hodgkin,s equation =- 61 log --------------------------------------CNai.PNa + CKi.PNa + C
Clo.PClo
CNao.PNa + CKo.PNa + CClo.PCli Nernst equation -
Slide18The role of permeability and RMP
Cell membrane
Lipid bilayer
Lipid soluble substance can freely pass though the cell membrane
Slide19Thought question???
Does lipid soluble substance pass through the gap between two lipid molecule or it pass through the lipid itself?
Slide20Transport of charge ions across cell membrane
Need for special carrier or channel or transporter
Sodium channel
Slide21Thought question
Size of sodium channel
Approximate number of sodium channel in typical cell
Carrying capacity of sodium channelNumber of transported molecule in unit timeDuty cycle duration
Slide22Body fluid compartments-
60% of body wt.(70kg.) – 42 lits.
ICF-2/3 -28lits
2
lits
in RBC
ECF – 1/3 – 14 lits
Interstitial fluid -11 lits. 3/4
Plasma -3lits -5% 1/5
Transcellular -1-2 lits
7% of fluid in intravascular compartment
Slide2362% of body wt in males and 52 % in females
72% of lean body mass (adipose free)
body wt is 70kg in man
body water is 42 lits.
28 lits ( 2/3) ICF – 2 lits - intravascular
14 lits. (1/3) ECF – 3 lits - intravascular
Body fluids
Slide24Measurement of body fluid compartments-
indicator dilution technique –
Criteria for ideal dye –
Dye should get uniformly diluted only in the compartment whose whose volume is to be measured
Body fluids
Slide25Dye should be
nontoxic
,
should not change fluid volume,
should not be metabolized, altered
or excreted in significant amount
should be able to estimate easily
Body fluids
Slide26Two spaces are calculated indirectly –
- Intracellular fluid compartment
( TBW – ECF)
- Extravascular fluid compartment
(ECF - plasma vol.)
Body fluids
Slide27Example
Inulin for ECF – 100 mg inulin injected
After 30 min. inulin conc in blood – 0.75 mg /dl
25 mg excreted in urine during 30 mins.
ECF vol = 100 – 25 / 0.75 = 10000 ml
= 10 lits.
Body fluids
Slide28Substances used
–
TBW
–
D
2
O, tritiated H2O, aminopyrineECF – Na thiosulphate, sucrose, mannitol,Intravascular fluid – Plasma vol. - Evan’s blue, T1824 , 131I2 Hematocrit
Osmolarity of ECF = 290 mOsm / lit
Body fluids
Slide29Control
system
OR
Regulating system
Slide30Limitations
–
- age
Undamped oscillations due to long dead time and more gain of system
– overcorrection
e.g. Chyene Stoke’s breathing, clonus during deep reflexes
Slide31Body fluid compartments-
60% of body wt.(70kg.) – 42 lits.
ICF-2/3 -28lits
2
lits
in RBC
ECF – 1/3 – 14 lits
Interstitial fluid -11 lits. 3/4
Plasma -3lits -5% 1/5
Transcellular -1-2 lits
7% of fluid in intravascular compartment