WSU BIOLOGY 251 - Acid Base balance (4 pages)

Previewing page 1 of 4 page document View the full content.
View Full Document

Acid Base balance

Previewing page 1 of actual document.

View the full content.
View Full Document
View Full Document

Acid Base balance


topic 23-Acid Base balance

Lecture number:
Lecture Note
Washington State University
Biology 251 - Introductory Human Physiology
Unformatted text preview:

BIO 251 1st Edition Lecture 23 Outline of Last Lecture I Input output of fluids ions a Balance concept b Types of input output II Fluid ion distribution in body a Fluid compartment within body b Ion distribution c Mvmt of water ions w I ECF d Regulation of fluid ion distrb III Regulation of ECF volume a Na balance b Mechanisms regulating Na in kidney c Control of Na reabsorption IV Regulation of ECF osmolarity a Purpose b How ECF effects ICF c Mechanisms of water reg Outline of Current Lecture I Background These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute a Acid b Base c Ph d Buffers II Chem buffer a Protein b Hb c phosphate III pulmonary ventilation IV kidney V acid base imbalances Current Lecture o o o o o Background Why regulate acid base balance Only a narrow pH range is compatible w life Effects of pH fluctuations Changes in muscles nerve excitability Acidosis too much H depresses CNS Alkalosis too little H causes overexcitability Change enzyme activities profoundly Influence K levels Acid chemistry review Acid is a hydrogen containing substance that dissociated in solution to produce Free H Anions neg charged ions Base chemistry review Base is substance that binds w free H removes it from solution pH review pH log 1 H Low pH high acid Every unit change in pH tenfold change in H b c it is a log scale Buffers review o o o o o o o o o o Mixture of several chemical compounds in solution that minimize pH changes when acid or base is added or removed from solution Chemical buffer systems are 1st line of defense against pH fluctuations Buffers respond within fractions of 2nd to changes in H Buffers pick up H rapidly but DO NOT eliminate from body not long term solutions HCO3 buffer Effective most important in body for buffering pH changes caused by anything other than CO2 generated acid b c HCO3 is produced from CO2 H HCO3 H2CO3 CO2 H20 Important buffering system Above reaction is almost always catalyzed in body by carbonic anhydrase When H is added from any source other than CO2 drives above reaction to right H ions are absorbed CO2 is produced When H falls above reaction is driven to left CO2 and water combine to produce H and HCO3Protein buffers Both acidic basic groups that can take up or give up H Most important in ICF where most proteins exist Hemoglobin acts as a buffer CO2 diffuses into blood capillaries it dissociates CO2 H2O H2CO3 H HCO3 Deoxy Hb has great affinity for binds free H capillaries In lungs reaction is reverse Hb gives up the H to bind to O2 H then binds w HCO3 to reform CO2 water Hb is important in buffering the blood Phosphate buffers Important buffer in ICF 2nd to proteins Only buffer found in urine Humans consume excess phosphate which is excreted Phosphates w I tubular system act as a buffer Pulmonary ventilation is 2nd line of defense against pH fluctuations Respiratory system responds to increases in arterial H w I few min When H increases ventilation rates increase Increase in ventilation rates results in more CO2 than usual being expired Leads to decrease in plasma H b c you eliminate CO2 you drive following reaction to left and get rid of H CO2 H2O H2CO3 H HCO3When H falls ventilation is reduced Causes build up of CO2 Drives reaction to right Causes increase in H Lungs rid body fluids of 100x more H than kidneys remove from non carbonic acid sources o o o o o o o o Person can always alter ventilation rates to change plasma acid base balance Respiratory system usually only returns pH 50 75 of normal b c pH gets closer to normal Less ventilation rates are influences Kidneys 3rd line of defense against pH fluctuations Slowest but most potent Can regulate Removal of H created by ANY source All non carbonic acids must be removed by kidney Carbonic acid also removed by kidneys Important in cases of respiratory pathologies Removal of HCO3 pH almost exactly Do all this by adjusting 3 substances H HCO3 bicarbonate NH3 ammonia Mechanism of regulation during acidosis High secretion of H into tubule H in tubular system buffered before excreted First combines w filtered HCO3 in tubular system to produce water until all HCO3 is used up Next H combines with filtered phosphate in tubule H2PO4 so produced is excreted in urine Once all phosphate in urine used up NH3 produced from amino acid glutamine combines w H NH4 excreted in urine HCO3 reabsorbed into plasma from tubule Mechanisms of regulation during alkalosis Rate of H via CO2 secretion reduced Rate of HCO3 filtration increased Plasma levels of HCO3 higher than normal under alkalosis b c not as much H for HCO3 to bind Result less H in urine more HCO3 in urine urine becomes alkaline Continues till acid base balance restored Acid Base Imbalances Overview Changes in pH reflected by changes in ratio of HCO3 to CO2 When ratio of HCO3 CO2 is less than 20 1 acidosis exists When ratio of HCO3 CO2 is greater than 20 1 alkalosis exist Concentration of HCO3 in ECF is 600 000x the concentration of H When CO2 produces

View Full Document

Access the best Study Guides, Lecture Notes and Practice Exams

Loading Unlocking...

Join to view Acid Base balance and access 3M+ class-specific study document.

We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Acid Base balance and access 3M+ class-specific study document.


By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?