olumide adeola pidan, Olumide pidan

2. Homeostasis
The Interstitial Fluid is the environment of the cells, and life
depends on the constancy of this internal sea.
Homeostatic Mechanisms : Maintain within a narrow range.
 Tonicity
 Volume
 Specific ion concentration
Defence of Tonicity –(280-295mOsm/L)
 Vasopressin secretion
Increased Osmolality of ECF
 Thirst Mechanism
Thirst Increased
Vasopressin Secretion
Increased
Water Intake Water Retention
Dilution of ECF
Inhibitor
y

3. Homeostasis
Defence of Volume:
 ECF Na+ - Most important
 Renin-Angiotensin-
Aldosterone System
 Vasopressin Secretion:
Volume stimuli override
osmotic regulation
 ANP & BNP
Angiotensinogen
Renin
Angiotensin I
ACE
Angiotensin II
Adrenal
Cortex
Brain
Thirst
Aldosterone Vasopressin
Kidney
Na Retention
Water
Retention
Blood Vessel
Vasoconstriction

4. Homeostasis
Defence of Specific Ionic Concentration:
 Glucose
 Na+ & K+
 Ca++ - Mainly by Parathyroid & Calcitonin
 Mg++ - Incompletely understood mechanisms
Also dependent on H+ ion
pH is maintained within a narrow range.

5. Acid Base Equilibrium
What is Acid Base Equilibrium About?
Buffers
? Fixed
Cation?
Base Excess/
Deficit? Anion
Gap?

6. Acid Base Equilibrium
Acid Base Equilibrium is all about
Maintenance of H+ ion concentration of
the ECF.
Source of H+ ion in Body:
CO2 from
metabolism
H+ load from
AA
metabolism
Strenuous Exercise Lactic
Acid
Diabetic
KA
Ingestion of
NH4Cl, CaCl2
Failure of Kidneys to
Excrete PO4--, SO4--
12500 mEq/d
50 - 100 mEq/d

7. Some Basic Chemistry
Definitions:
Arrhenius:
 Acid: H+ Donor in Solution
 Base: OH- donor in Solution
Browsted and Lowry:
 Acid: Proton Donor
 Base: Proton Acceptor
H20 can be both

8. Some Basic Chemistry
Simple Rule of Thumb:
Acid Higher conc. Of H+ ion
Base  Lower conc. Of H+ ion
Strong Acid/Base  Dissociates completely and irreversibly
Weak Acid/Base  Dissociates partially and reversibly
Strong Electrolyte: Dissociates completely in solution at
physiological pH
Eg: NaCl, KCl
Weak Electrolyte: Dissociates incompletely in solution at
physiological pH
Eg: CO2 – HCO3
- System, Proteins

9. Some Basic Chemistry
pH (Puissant of Hydrogen):
Negative logarithm of H+ ion concentration to the base of 10
Why pH?
 Normal H+ ion conc: 0.00004meq/L or 40nEq/L or 4x10-9
mol/L
 pH converts to decimal numbers & takes away negative
sign.
 Normal pH: 7.35-7.45
 Normal H+ Conc: 0.00002mEq/L – 0.0001 mEq/L

10. Some Basic Chemistry
Pitfalls: Non-linear Negative Logarithmic scale
 pH Decreases as [H+] increases.
 Each unit change in pH from 7 represents 10 fold change in
H+ ion conc.
 Eg: At pH 4, there are 10 times as much H+ than at pH 5, & 100 times
as at pH 6
 Same numeric change in different portions of the pH scale
implies vastly different nanomolar change in H+ ions
 Eg: pH 56 => 100 times greater change in ionic conc than when pH
7 8
 Body H+ ion conc is not as tightly controlled as the other ion,
though the pH scale implies so.