AsaMBasa

7/18/2019 AsaMBasa

1/88

Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Human Anatomy & Physiology, Sixth Edition

Elaine . !arieb

PowerPointLecture Slides prepared by Vince Austin, University of Kentucky

26

Fluid, Electrolyte, and Acid

!ase !alance

7/18/2019 AsaMBasa

2/88


Body Water Content

In"ants ha#e lo$ body "at, lo$ bone mass, and are

%&' or more $ater

(otal $ater content declines throughout li"e

)ealthy males are about *0' $ater+ healthy "emalesare around 0'

(his di""erence re"lects "emales-

)igher body "at

/maller amount o" seletal muscle

In old age, only about 4' o" body $eight is $ater

7/18/2019 AsaMBasa

3/88


Fluid Compartments

1ater occupies t$o main "luid compartments

Intracellular "luid IC3 5 about t$o thirds by #olume,contained in cells

E6tracellular "luid EC3 5 consists o" t$o majorsubdi#isions

Plasma 5 the "luid portion o" the blood

Interstitial "luid I3 5 "luid in spaces bet$een cells

7ther EC3 5 lymph, cerebrospinal "luid, eye humors,syno#ial "luid, serous "luid, and gastrointestinal

secretions

7/18/2019 AsaMBasa

4/88


Fluid Compartments

3igure 2*.8

7/18/2019 AsaMBasa

5/88


Composition of Body Fluids

1ater is the uni#ersal sol#ent

/olutes are broadly classi"ied into

Electrolytes 5 inorganic salts, all acids and bases,

and some proteinsonelectrolytes 5 e6amples include glucose, lipids,

creatinine, and urea

Electrolytes ha#e greater osmotic po$er thannonelectrolytes

1ater mo#es according to osmotic gradients

7/18/2019 AsaMBasa

6/88


Electrolyte Concentration

E6pressed in millie9ui#alents per liter mE9:;, ameasure o" the number o" electrical charges in oneliter o" solution

mE9:; < concentration o" ion in =mg:;>:the atomic$eight o" ion number o" electrical charges on oneion

3or single charged ions, 8 mE9 < 8 m7sm

3or bi#alent ions, 8 mE9 < 8:2 m7sm

7/18/2019 AsaMBasa

7/88Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Extracellular and Intracellular Fluids

Each "luid compartment o" the body has a distincti#e

pattern o" electrolytes

E6tracellular "luids are similar e6cept "or the highprotein content o" plasma

/odium is the chie" cation

Chloride is the major anion

Intracellular "luids ha#e lo$ sodium and chloride

Potassium is the chie" cation

Phosphate is the chie" anion

7/18/2019 AsaMBasa



/odium and potassium concentrations in e6tra? andintracellular "luids are nearly opposites

(his re"lects the acti#ity o" cellular @(P?dependentsodium?potassium pumps

Electrolytes determine the chemical and physicalreactions o" "luids

7/18/2019 AsaMBasa



Proteins, phospholipids, cholesterol, and neutral "atsaccount "or

A0' o" the mass o" solutes in plasma

*0' o" the mass o" solutes in interstitial "luid

A%' o" the mass o" solutes in the intracellularcompartment

7/18/2019 AsaMBasa

10/88


Electrolyte Composition of Body Fluids

3igure 2*.2

7/18/2019 AsaMBasa

11/88


Fluid o!ement Among Compartments

Compartmental e6change is regulated by osmoticand hydrostatic pressures

et leaage o" "luid "rom the blood is piced up by

lymphatic #essels and returned to the bloodstream

E6changes bet$een interstitial and intracellular"luids are comple6 due to the selecti#e permeability

o" the cellular membranes

($o?$ay $ater "lo$ is substantial

7/18/2019 AsaMBasa

12/88



Ion "lu6es are restricted and mo#e selecti#ely by

acti#e transport utrients, respiratory gases, and $astes mo#e

unidirectionally

Plasma is the only "luid that circulates throughoutthe body and lins e6ternal and internalen#ironments

7smolalities o" all body "luids are e9ual+ changes insolute concentrations are 9uicly "ollo$ed byosmotic changes

InterActive Physiology:

Fluid, Electrolyte, and Acid/Base Balance: Introduction to Body Fluids

P"A#P"A#

7/18/2019 AsaMBasa

13/88


Continuous ixing of Body Fluids

3igure 2*.&

7/18/2019 AsaMBasa

14/88


Water Balance and ECF $smolality

(o remain properly hydrated, $ater intae muste9ual $ater output

1ater intae sources

Ingested "luid *0' and solid "ood &0'

!etabolic $ater or $ater o" o6idation 80'

7/18/2019 AsaMBasa

15/88


Water Balance and ECF $smolality

1ater output

rine *0' and "eces 4' Insensible losses 2', s$eat '

Increases in plasma osmolality trigger thirst andrelease o" antidiuretic hormone @D)

7/18/2019 AsaMBasa

16/88


Water Inta%e and $utput

3igure 2*.4

7/18/2019 AsaMBasa

17/88


egulation of Water Inta%e

(he hypothalamic thirst center is stimulated

By a decline in plasma #olume o" 80'58' By increases in plasma osmolality o" 852'

ia baroreceptor input, angiotensin II, and otherstimuli

7/18/2019 AsaMBasa

18/88


egulation of Water Inta%e

(hirst is 9uenched as soon as $e begin to drin$ater

3eedbac signals that inhibit the thirst centersinclude

!oistening o" the mucosa o" the mouth and throat

@cti#ation o" stomach and intestinal stretchreceptors

7/18/2019 AsaMBasa

19/88


egulation of Water Inta%e' (hirst echanism

3igure 2*.

7/18/2019 AsaMBasa

20/88


egulation of Water $utput

7bligatory $ater losses include

Insensible $ater losses "rom lungs and sin

1ater that accompanies undigested "ood residues in

"eces 7bligatory $ater loss re"lects the "act that

Fidneys e6crete A00?8200 m7sm o" solutes tomaintain blood homeostasis

rine solutes must be "lushed out o" the body in$ater

7/18/2019 AsaMBasa

21/88


Influence and egulation of A)H

1ater reabsorption in collecting ducts is proportional

to @D) release ;o$ @D) le#els produce dilute urine and reduced

#olume o" body "luids

)igh @D) le#els produce concentrated urine

)ypothalamic osmoreceptors trigger or inhibit @D)release

3actors that speci"ically trigger @D) release includeprolonged "e#er+ e6cessi#e s$eating, #omiting, or

diarrhea+ se#ere blood loss+ and traumatic burns

7/18/2019 AsaMBasa

22/88

Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings 3igure 2*.*

echanisms and Conse*uences of A)H

elease

7/18/2019 AsaMBasa

23/88


)isorders of Water Balance' )ehydration

1ater loss e6ceeds $ater intae and the body is in

negati#e "luid balance Causes include hemorrhage, se#ere burns, prolonged

#omiting or diarrhea, pro"use s$eating, $aterdepri#ation, and diuretic abuse

/igns and symptoms cottonmouth, thirst, dry "lushedsin, and oliguria

Prolonged dehydration may lead to $eight loss, "e#er,and mental con"usion

7ther conse9uences include hypo#olemic shoc and

loss o" electrolytes

7/18/2019 AsaMBasa

24/88

Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings 3igure 2*.%a

)isorders of Water Balance' )ehydration

Excessi!e loss of H+$ from

ECF

+ -ECF osmotic

pressure risesCells lose H+$

to ECF .y

osmosis/ cells

shrin%

0a1 echanism of dehydration

7/18/2019 AsaMBasa

25/88


Genal insu""iciency or an e6traordinary amount o"$ater ingested 9uicly can lead to cellularo#erhydration, or $ater into6ication

EC3 is diluted 5 sodium content is normal bute6cess $ater is present

(he resulting hyponatremia promotes net osmosis

into tissue cells, causing s$elling (hese e#ents must be 9uicly re#ersed to pre#ent

se#ere metabolic disturbances, particularly in

neurons

)isorders of Water Balance'

Hypotonic Hydration

7/18/2019 AsaMBasa

26/88

Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings 3igure 2*.%b

)isorders of Water Balance'

Hypotonic Hydration

Excessi!e H+$ enters

the ECF

+ ECF osmotic

pressure falls

- H+$ mo!es into

cells .y osmosis/

cells s2ell

0.1 echanism of hypotonic hydration

7/18/2019 AsaMBasa

27/88


)isorders of Water Balance' Edema

@typical accumulation o" "luid in the interstitial

space, leading to tissue s$elling Caused by anything that increases "lo$ o" "luids out

o" the bloodstream or hinders their return

3actors that accelerate "luid loss include

Increased blood pressure, capillary permeability

Incompetent #enous #al#es, localiHed blood #esselblocage

Congesti#e heart "ailure, hypertension, high blood

#olume

7/18/2019 AsaMBasa

28/88


Edema

)indered "luid return usually re"lects an imbalancein colloid osmotic pressures

)ypoproteinemia 5 lo$ le#els o" plasma proteins

3orces "luids out o" capillary beds at the arterialends

3luids "ail to return at the #enous ends Gesults "rom protein malnutrition, li#er disease, or

glomerulonephritis

7/18/2019 AsaMBasa

29/88


Edema

Bloced or surgically remo#ed lymph #essels

Cause leaed proteins to accumulate in interstitial

"luid E6ert increasing colloid osmotic pressure, $hich

dra$s "luid "rom the blood

Interstitial "luid accumulation results in lo$ bloodpressure and se#erely impaired circulation

El t l t B l

7/18/2019 AsaMBasa

30/88


Electrolyte Balance

Electrolytes are salts, acids, and bases, but

electrolyte balance usually re"ers only to salt balance

/alts are important "or

euromuscular e6citability

/ecretory acti#ity

!embrane permeability

Controlling "luid mo#ements

/alts enter the body by ingestion and are lost #iaperspiration, "eces, and urine

3 di i Fl id d El t l t B l

7/18/2019 AsaMBasa

31/88


3odium in Fluid and Electrolyte Balance

/odium holds a central position in "luid and

electrolyte balance

/odium salts

@ccount "or A0?A' o" all solutes in the EC3

Contribute 20 m7sm o" the total &00 m7sm EC3solute concentration

/odium is the single most abundant cation in theEC3

/odium is the only cation e6erting signi"icantosmotic pressure


7/18/2019 AsaMBasa

32/88



(he role o" sodium in controlling EC3 #olume and$ater distribution in the body is a result o"

/odium being the only cation to e6ert signi"icant

osmotic pressure

/odium ions leaing into cells and being pumpedout against their electrochemical gradient

/odium concentration in the EC3 normally remainsstable


7/18/2019 AsaMBasa

33/88



Changes in plasma sodium le#els a""ect

Plasma #olume, blood pressure IC3 and interstitial "luid #olumes

Genal acid?base control mechanisms are coupled tosodium ion transport

l ti f 3 di B l Ald t

7/18/2019 AsaMBasa

34/88


egulation of 3odium Balance' Aldosterone

/odium reabsorption *' o" sodium in "iltrate is reabsorbed in the

pro6imal tubules

2' is reclaimed in the loops o" )enle

1hen aldosterone le#els are high, all remaining aIis acti#ely reabsorbed

1ater "ollo$s sodium i" tubule permeability hasbeen increased $ith @D)


7/18/2019 AsaMBasa

35/88



(he renin?angiotensin mechanism triggers the

release o" aldosterone

(his is mediated by the ju6taglomerular apparatus,$hich releases renin in response to

/ympathetic ner#ous system stimulation

Decreased "iltrate osmolality

Decreased stretch due to decreased blood pressure

Genin catalyHes the production o" angiotensin II,$hich prompts aldosterone release


7/18/2019 AsaMBasa

36/88



@drenal cortical cells are directly stimulated torelease aldosterone by ele#ated FIle#els in the

EC3 @ldosterone brings about its e""ects diminished

urine output and increased blood #olume slo$ly


Fluid, Electrolyte and Acid/Base Balance: Water HomeostasisP"A#P"A#


7/18/2019 AsaMBasa

37/88



3igure 2*.

Cardio!ascular 3ystem Baroreceptors

7/18/2019 AsaMBasa

38/88



Baroreceptors alert the brain o" increases in blood#olume hence increased blood pressure

/ympathetic ner#ous system impulses to the

idneys decline

@""erent arterioles dilate

Jlomerular "iltration rate rises

/odium and $ater output increase


7/18/2019 AsaMBasa

39/88



(his phenomenon, called pressure diuresis,decreases blood pressure

Drops in systemic blood pressure lead to oppositeactions and systemic blood pressure increases

/ince sodium ion concentration determines "luid

#olume, baroreceptors can be #ie$ed as KsodiumreceptorsL

aintenance of Blood Pressure Homeostasis

7/18/2019 AsaMBasa

40/88

Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings 3igure 2*.A

aintenance of Blood Pressure Homeostasis

Atrial 4atriuretic Peptide 0A4P1

7/18/2019 AsaMBasa

41/88


Atrial 4atriuretic Peptide 0A4P1

Geduces blood pressure and blood #olume by

inhibiting E#ents that promote #asoconstriction

aand $ater retention

Is released in the heart atria as a response to stretchele#ated blood pressure

)as potent diuretic and natriuretic e""ects Promotes e6cretion o" sodium and $ater

Inhibits angiotensin II production

echanisms and Conse*uences of A4P

7/18/2019 AsaMBasa

42/88

Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings 3igure 2*.80

echanisms and Conse*uences of A4P

elease

Influence of $ther Hormones on 3odium

7/18/2019 AsaMBasa

43/88


Estrogens

Enhance aCl reabsorption by renal tubules

!ay cause $ater retention during menstrual cycles

@re responsible "or edema during pregnancy


Balance


7/18/2019 AsaMBasa

44/88


Progesterone

Decreases sodium reabsorption

@cts as a diuretic, promoting sodium and $ater loss

Jlucocorticoids 5 enhance reabsorption o" sodiumand promote edema


Balance

egulation of Potassium Balance

7/18/2019 AsaMBasa

45/88



Gelati#e IC3?EC3 potassium ion concentrationa""ects a cell-s resting membrane potential

E6cessi#e EC3 potassium decreases membranepotential

(oo little Fcauses hyperpolariHation andnonresponsi#eness


7/18/2019 AsaMBasa

46/88



)yperalemia and hypoalemia can Disrupt electrical conduction in the heart

;ead to sudden death

)ydrogen ions shi"t in and out o" cells

;eads to corresponding shi"ts in potassium in the

opposite direction

Inter"eres $ith acti#ity o" e6citable cells

egulatory 3ite' Cortical Collecting )ucts

7/18/2019 AsaMBasa

47/88


egulatory 3ite' Cortical Collecting )ucts

;ess than 8' o" "iltered Fis lost to urine regardlesso" need

Fbalance is controlled in the cortical collectingducts by changing the amount o" potassium secretedinto "iltrate

E6cessi#e Fis e6creted o#er basal le#els by corticalcollecting ducts

1hen F

le#els are lo$, the amount o" secretion ande6cretion is ept to a minimum

(ype @ intercalated cells can reabsorb some Fle"t inthe "iltrate

Influence of Plasma Potassium Concentration

7/18/2019 AsaMBasa

48/88


Influence of Plasma Potassium Concentration

)igh FI content o" EC3 "a#ors principal cells to

secrete FI

;o$ FIor accelerated FI loss depresses its secretionby the collecting ducts

Influence of Aldosterone

7/18/2019 AsaMBasa

49/88


Influence of Aldosterone

@ldosterone stimulates potassium ion secretion byprincipal cells

In cortical collecting ducts, "or each aIreabsorbed,a FIis secreted

Increased FIin the EC3 around the adrenal corte6causes

Gelease o" aldosterone

Potassium secretion

Potassium controls its o$n EC3 concentration #ia"eedbac regulation o" aldosterone release

egulation of Calcium

7/18/2019 AsaMBasa

50/88



Ionic calcium in EC3 is important "or

Blood clotting

Cell membrane permeability

/ecretory beha#ior

)ypocalcemia

Increases e6citability

Causes muscle tetany


7/18/2019 AsaMBasa

51/88



)ypercalcemia

Inhibits neurons and muscle cells

!ay cause heart arrhythmias

Calcium balance is controlled by parathyroid

hormone P() and calcitonin

egulation of Calcium and Phosphate

7/18/2019 AsaMBasa

52/88



P() promotes increase in calcium le#els by

targeting

Bones 5 P() acti#ates osteoclasts to brea do$nbone matri6

/mall intestine 5 P() enhances intestinalabsorption o" calcium

Fidneys 5 P() enhances calcium reabsorption and

decreases phosphate reabsorption

Calcium reabsorption and phosphate e6cretion gohand in hand


7/18/2019 AsaMBasa

53/88



3iltered phosphate is acti#ely reabsorbed in thepro6imal tubules

In the absence o" P(), phosphate reabsorption isregulated by its transport ma6imum and e6cesses aree6creted in urine

)igh or normal EC3 calcium le#els inhibit P()secretion

Gelease o" calcium "rom bone is inhibited

;arger amounts o" calcium are lost in "eces andurine

!ore phosphate is retained

Influence of Calcitonin

7/18/2019 AsaMBasa

54/88


Influence of Calcitonin

Geleased in response to rising blood calcium le#els

Calcitonin is a P() antagonist, but its contributionto calcium and phosphate homeostasis is minor tonegligible


Fluid, Electrolyte, and Acid/Base Balance: Electrolyte HomeostasisP"A#P"A#

egulation of Anions

7/18/2019 AsaMBasa

55/88


egulation of Anions

Chloride is the major anion accompanying sodiumin the EC3

AA' o" chloride is reabsorbed under normal p)

conditions

1hen acidosis occurs, "e$er chloride ions arereabsorbed

7ther anions ha#e transport ma6imums and e6cessesare e6creted in urine

Acid5Base Balance

7/18/2019 AsaMBasa

56/88


Acid Base Balance

ormal p) o" body "luids

@rterial blood is %.4

enous blood and interstitial "luid is %.&

Intracellular "luid is %.0

@lalosis or alalemia 5 arterial blood p) rises

abo#e %.4 @cidosis or acidemia 5 arterial p) drops belo$ %.&

physiological acidosis

3ources of Hydrogen Ions

7/18/2019 AsaMBasa

57/88


3ources of Hydrogen Ions

!ost hydrogen ions originate "rom cellular

metabolism Breado$n o" phosphorus?containing proteins

releases phosphoric acid into the EC3

@naerobic respiration o" glucose produces lacticacid

3at metabolism yields organic acids and etonebodies

(ransporting carbon dio6ide as bicarbonate releaseshydrogen ions

Hydrogen Ion egulation

7/18/2019 AsaMBasa

58/88


Hydrogen Ion egulation

Concentration o" hydrogen ions is regulatedse9uentially by

Chemical bu""er systems 5 act $ithin seconds

(he respiratory center in the brain stem 5 acts$ithin 8?& minutes

Genal mechanisms 5 re9uire hours to days to e""ectp) changes

Chemical Buffer 3ystems

7/18/2019 AsaMBasa

59/88



/trong acids 5 all their )I

is dissociated completelyin $ater

1ea acids 5 dissociate partially in $ater and are

e""icient at pre#enting p) changes

/trong bases 5 dissociate easily in $ater and 9uiclytie up )I

1ea bases 5 accept )Imore slo$ly e.g., )C7&M

and )&


7/18/2019 AsaMBasa

60/88


C e ca u e 3yste s

7ne or t$o molecules that act to resist p) changes

$hen strong acid or base is added

(hree major chemical bu""er systems

Bicarbonate bu""er system

Phosphate bu""er system

Protein bu""er system @ny dri"ts in p) are resisted by the entire chemical

bu""ering system

Bicar.onate Buffer 3ystem

7/18/2019 AsaMBasa

61/88


y

@ mi6ture o" carbonic acid )2C7& and its salt,sodium bicarbonate a)C7& potassium or

magnesium bicarbonates $or as $ell

I" strong acid is added

)ydrogen ions released combine $ith thebicarbonate ions and "orm carbonic acid a $ea

acid

(he p) o" the solution decreases only slightly

Bicar.onate Buffer 3ystem

7/18/2019 AsaMBasa

62/88


y

I" strong base is added

It reacts $ith the carbonic acid to "orm sodiumbicarbonate a $ea base

(he p) o" the solution rises only slightly

(his system is the only important EC3 bu""er

Phosphate Buffer 3ystem

7/18/2019 AsaMBasa

63/88


p y

early identical to the bicarbonate system

Its components are

/odium salts o" dihydrogen phosphate )2P74M, a$ea acid

!onohydrogen phosphate )P742M, a $ea base

(his system is an e""ecti#e bu""er in urine andintracellular "luid

Protein Buffer 3ystem

7/18/2019 AsaMBasa

64/88


y

Plasma and intracellular proteins are the body-s mostplenti"ul and po$er"ul bu""ers

/ome amino acids o" proteins ha#e

3ree organic acid groups $ea acids

Jroups that act as $ea bases e.g., amino groups

@mphoteric molecules are protein molecules thatcan "unction as both a $ea acid and a $ea base

Physiological Buffer 3ystems

7/18/2019 AsaMBasa

65/88


y g y

(he respiratory system regulation o" acid?basebalance is a physiological bu""ering system

(here is a re#ersible e9uilibrium bet$een

Dissol#ed carbon dio6ide and $ater

Carbonic acid and the hydrogen and bicarbonate

ions

C72 )27)2C7&)I )C7&M

Physiological Buffer 3ystems

7/18/2019 AsaMBasa

66/88


y g y

During carbon dio6ide unloading, hydrogen ions areincorporated into $ater

1hen hypercapnia or rising plasma )Ioccurs

Deeper and more rapid breathing e6pels more

carbon dio6ide )ydrogen ion concentration is reduced

@lalosis causes slo$er, more shallo$ breathing,

causing )I

to increase Gespiratory system impairment causes acid?base

imbalance respiratory acidosis or respiratoryalalosis

enal echanisms of Acid5Base Balance

7/18/2019 AsaMBasa

67/88


Chemical bu""ers can tie up e6cess acids or bases,

but they cannot eliminate them "rom the body

(he lungs can eliminate carbonic acid byeliminating carbon dio6ide

7nly the idneys can rid the body o" metabolic acidsphosphoric, uric, and lactic acids and etones and

pre#ent metabolic acidosis (he ultimate acid?base regulatory organs are the

idneys


7/18/2019 AsaMBasa

68/88


(he most important renal mechanisms "or regulatingacid?base balance are

Conser#ing reabsorbing or generating ne$

bicarbonate ions

E6creting bicarbonate ions

;osing a bicarbonate ion is the same as gaining ahydrogen ion+ reabsorbing a bicarbonate ion is thesame as losing a hydrogen ion


7/18/2019 AsaMBasa

69/88


)ydrogen ionsecretion occurs in the PC( and in

type @ intercalated cells

)ydrogen ions come "rom the dissociation o"carbonic acid

ea.sorption of Bicar.onate

7/18/2019 AsaMBasa

70/88


Carbon dio6ide combines $ith $ater in tubule cells,

"orming carbonic acid

Carbonic acid splits into hydrogen ions andbicarbonate ions

3or each hydrogen ion secreted, a sodium ion and abicarbonate ion are reabsorbed by the PC( cells

/ecreted hydrogen ions "orm carbonic acid+ thus,bicarbonate disappears "rom "iltrate at the same ratethat it enters the peritubular capillary blood

ea.sorption of Bicar.onate

7/18/2019 AsaMBasa

71/88


Carbonic acid

"ormed in "iltratedissociates torelease carbondio6ide and $ater

Carbon dio6idethen di""uses into

tubule cells, $hereit acts to trigger"urther hydrogenion secretion

3igure 2*.82

6enerating 4e2 Bicar.onate Ions

7/18/2019 AsaMBasa

72/88


($o mechanisms carried out by type @ intercalatedcells generate ne$ bicarbonate ions

Both in#ol#e renal e6cretion o" acid #ia secretionand e6cretion o" hydrogen ions or ammonium ions)4I

Hydrogen Ion Excretion

7/18/2019 AsaMBasa

73/88


Dietary hydrogen ions must be counteracted by

generating ne$ bicarbonate (he e6creted hydrogen ions must bind to bu""ers in

the urine phosphate bu""er system

Intercalated cells acti#ely secrete hydrogen ions intourine, $hich is bu""ered and e6creted

Bicarbonate generated is

!o#ed into the interstitial space #ia a cotransportsystem

Passi#ely mo#ed into the peritubular capillary blood

Hydrogen Ion Excretion

7/18/2019 AsaMBasa

74/88


In response to

acidosis

Fidneys generatebicarbonate ions

and add them tothe blood

@n e9ual amount

o" hydrogen ionsare added to theurine

3igure 2*.8&

Ammonium Ion Excretion

7/18/2019 AsaMBasa

75/88


(his method uses ammonium ionsproduced by themetabolism o" glutamine in PC( cells

Each glutamine metaboliHed produces t$oammonium ions and t$o bicarbonate ions

Bicarbonate mo#es to the blood and ammonium ionsare e6creted in urine

Ammonium Ion Excretion

7/18/2019 AsaMBasa

76/88

Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings3igure 2*.84

Bicar.onate Ion 3ecretion

7/18/2019 AsaMBasa

77/88


1hen the body is in alalosis, type B intercalated

cells

E6hibit bicarbonate ion secretion

Geclaim hydrogen ions and acidi"y the blood (he mechanism is the opposite o" type @ intercalated

cells and the bicarbonate ion reabsorption process

E#en during alalosis, the nephrons and collectingducts e6crete "e$er bicarbonate ions than theyconser#e

espiratory Acidosis and Al%alosis

7/18/2019 AsaMBasa

78/88


Gesult "rom "ailure o" the respiratory system tobalance p)

PC72is the single most important indicator o"

respiratory inade9uacy

PC72 le#els

ormal PC72 "luctuates bet$een & and 4 mm )g

alues abo#e 4 mm )g signal respiratory acidosis

alues belo$ & mm )g indicate respiratoryalalosis

espiratory Acidosis and Al%alosis

7/18/2019 AsaMBasa

79/88


Gespiratory acidosis is the most common cause o"acid?base imbalance

7ccurs $hen a person breathes shallo$ly, or gase6change is hampered by diseases such aspneumonia, cystic "ibrosis, or emphysema

Gespiratory alalosis is a common result o"hyper#entilation

eta.olic Acidosis

7/18/2019 AsaMBasa

80/88


@ll p) imbalances e6cept those caused by abnormalblood carbon dio6ide le#els

!etabolic acid?base imbalance 5 bicarbonate ionle#els abo#e or belo$ normal 22?2* mE9:;

!etabolic acidosis is the second most commoncause o" acid?base imbalance

(ypical causes are ingestion o" too much alcohol

and e6cessi#e loss o" bicarbonate ions 7ther causes include accumulation o" lactic acid,

shoc, etosis in diabetic crisis, star#ation, andidney "ailure

eta.olic Al%alosis

7/18/2019 AsaMBasa

81/88


Gising blood p) and bicarbonate le#els indicatemetabolic alalosis

(ypical causes are

omiting o" the acid contents o" the stomach

Intae o" e6cess base e.g., "rom antacids

Constipation, in $hich e6cessi#e bicarbonate isreabsorbed

espiratory and enal Compensations

7/18/2019 AsaMBasa

82/88


@cid?base imbalance due to inade9uacy o" aphysiological bu""er system is compensated "or bythe other system

(he respiratory system $ill attempt to correctmetabolic acid?base imbalances

(he idneys $ill $or to correct imbalances causedby respiratory disease

espiratory Compensation

7/18/2019 AsaMBasa

83/88


In metabolic acidosis

(he rate and depth o" breathing are ele#ated

Blood p) is belo$ %.& and bicarbonate le#el is

lo$

@s carbon dio6ide is eliminated by the respiratorysystem, PC72"alls belo$ normal

In respiratory acidosis, the respiratory rate is o"tendepressed and is the immediate cause o" the acidosis

espiratory Compensation

7/18/2019 AsaMBasa

84/88


In metabolic alalosis

Compensation e6hibits slo$, shallo$ breathing,allo$ing carbon dio6ide to accumulate in the blood

Correction is re#ealed by

)igh p) o#er %.4 and ele#ated bicarbonate ion

le#els

Gising PC72

enal Compensation

7/18/2019 AsaMBasa

85/88


(o correct respiratory acid?base imbalance, renalmechanisms are stepped up

@cidosis has high PC72and high bicarbonate le#els

(he high PC72is the cause o" acidosis

(he high bicarbonate le#els indicate the idneys areretaining bicarbonate to o""set the acidosis

enal Compensation

7/18/2019 AsaMBasa

86/88


@lalosis has ;o$ PC72and high p)

(he idneys eliminate bicarbonate "rom the bodyby "ailing to reclaim it or by acti#ely secreting it


Fluid, Electrolyte, and Acid/Base Balance: Acid/Base HomeostasisP"A#P"A#

)e!elopmental Aspects

7/18/2019 AsaMBasa

87/88


1ater content o" the body is greatest at birth %0?

0' and declines until adulthood, $hen it is about'

@t puberty, se6ual di""erences in body $ater content

arise as males de#elop greater muscle mass )omeostatic mechanisms slo$ do$n $ith age

Elders may be unresponsi#e to thirst clues and are at

ris o" dehydration

(he #ery young and the #ery old are the most "re9uent#ictims o" "luid, acid?base, and electrolyte imbalances

Pro.lems 2ith Fluid, Electrolyte, and Acid5Base

Balance

7/18/2019 AsaMBasa

88/88

7ccur in the young, re"lecting

;o$ residual lung #olume

)igh rate o" "luid intae and output

)igh metabolic rate yielding more metabolic $astes

)igh rate o" insensible $ater loss

Ine""iciency o" idneys in in"ants

Balance

Documents

AsaMBasa