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BIOSCIENCE(SHS 0022)

Chapter 5:ACID-BASE BALANCE

Ms. Mollie

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LEARNING OBJECTIVE

To describe:

Important definitions.

Conditions - Respiratory & Metabolic Organs involved & its process.

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INTRODUCTION

The body's balance between acidity andalkalinity is referred to as acid-basebalance. The acidity or alkalinity of any

solution, including blood, is indicated onthe pH scale.

Acid-base balance can be defined as

homeostasis of the body fluids at a normalarterial blood pH ranging between 7.37 and7.43

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Important definition

Acid

Any ionic molecular substance thatact as a proton donor

Sour tasting substance (like vinegar)

A chemical compound that can reactwith base to form a salt

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Important definition

Acidosis A dangerous condition where the blood

and body tissues are less alkaline (ormore acidic) than normal.

Alkalosis

Excessive alkalinity of the blood and bodytissue.

Alkalemia Abnormal blood alkalinity

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Base

Any ionic or molecular that can act as aproton acceptor.

A bitter-tasting substance and soapy feel

A chemical compound that can react with

an acid to form a salt.

Can also be called an alkali.

Bicarbonate a salt of carbonic acidproduced by neutralizing a hydrogen ion.

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Conditions

Respiratory acidosis

Metabolic acidosis

Respiratory alkalosis Metabolic alkalosis

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ACIDOSIS: Causes

Respiratory

Respiratorydepression

Pulmonarydisease

Metabolic

Diabeticketoacidosis

Kidney disease

Hyperchloremicacidosis

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ALKALOSIS: Causes

Respiratory

Hyperventilation

Metabolic

Vomiting

Retention of

bicarbonate

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How body pH is regulated?

Chemical buffers both within cells andbody fluids react immediately to regulatethe hydrogen ion and hydroxide ion

concentrations. Pulmonary system release CO2 in

respiration

Kidneys release HCO3 in urine

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Blood pH

The normal pH of arterial blood is 7.4

A person is considered to have acidosiswhen the pH is below this value, and tohave alkalosis when it rises above 7.4

The lower limit at which a person can live isabout pH 7.0 and the upper limit is 7.8.

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Blood pH

To prevent a change in the pH of the blood,body fluids including cytoplasm arebuffered.

A buffer is a chemical or a combination ofchemicals that can absorb either hydrogenions (H+) or hydroxide ions (OH-) andtherefore maintain a relatively constanthydrogen ion concentration.

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Buffers

Proteins are effective chemical buffersboth within cells and within blood.Hemoglobin is the most active protein

buffer within blood, and it absorbsexcess hydrogen ions when it is notcarrying oxygen.

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Buffers

There are two other types of chemicalbuffers in body fluids--the carbonatecarbonateand phosphatephosphate buffer systems.

The phosphate system (NaH2PO4and Na2HPO4) effectively buffers

urine and cytoplasm.

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Buffers

The carbonate system (a mixture ofcarbonic acid and sodiumbicarbonate) is present in both tissuefluid and blood.

The concentration of bufferingsubstances is regulated by the lungsand/or kidneys.

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Organs involved

Lung - respiration

Kidney urine production

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Role of lung

If the respiratory ion concentration of theblood remains high, the respiratory centerof the medulla oblongata is stimulated and

the breathing rate increases. As carbon dioxide is excreted the pH shifts

toward normal.

This respiratory regulation of the acid-basebalance is a physiological type of buffersystem that is an important to the chemicalsystems.

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Role of kidney

The kidneys are a powerfulmechanism by which the pH may beregulated.

The kidneys may form either an acidor alkaline urine, bringing the

hydrogen ion concentration backtoward normal.

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Role of kidney

When the kidneys form an acid urine,they excrete H+, and when thekidneys form an alkaline urine, they

excrete the bicarbonate ion.

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Effects of alkalosis

decreased myocardial contractility

arrhythmias decreased cerebral blood flow

confusion

neuromuscular excitability

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Effects of acidosis

Hyperventilation

Tachycardia Vasoconstriction