1. Keseimbangan Cairan
Tubuh & Elektrolit
Departemen Fisiologi
Fak. Kedokteran USU

2. Total Cairan Tubuh
 Infant mempunyai kandungan lemak, tulang
lebih rendah & sedangkan kandungan air
sebesar 73% atau lebih
 Total cairan tubuh berkurang seiring
pertambahan usia
 Pria sekitar 60% berat badan; Wanita sekitar
50% berat badan
 Hal ini disebabkan karena pada wanita:
 Kandungan lemak lebih tinggi
 Otot rangka lebih sedikit
 Pada usia tua, kandungan air sekitar 45%

3. Fluid Compartments
 Water occupies two main fluid compartments
 Intracellular fluid (ICF) – about two thirds by
volume, contained in cells
 Extracellular fluid (ECF) – consists of two major
subdivisions
 Plasma – the fluid portion of the blood
 Interstitial fluid (IF) – fluid in spaces between cells
 Other ECF – lymph, cerebrospinal fluid, eye
humors, synovial fluid, serous fluid, and
gastrointestinal secretions

5. Electrolyte Composition of Body Fluids
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 26.2

6. Beberapa mekanisme
sehingga suatu zat dapat
melewati membran
1. Difusi
2. Difusi yang dipermudah
3. Osmosis
4. Endositosis dan eksositosis, dan
5. Epithelial transport

8. Difusi Yang Dipermudah
 Transport Aktif
 Transport Aktif Primer Pompa
Natrium-Kalium
 Transport Aktif Primer Pompa
Kalsium
 Transport Aktif Sekunder:
Kotransport Natrium pada Glukosa
dan Asam Amino

9. Transport Aktif
 Saat membran sel menggerakkan molekul
zat untuk mendaki melawan gradien
konsentrasi (atau mendaki melawan arus
listrik atau melawan gradien tekanan,)
maka proses ini disebut transport aktif.
 Memerlukan energi
 Transport aktif primer: dalam bentuk ATP
 Transport aktif sekunder: gradien
konsentrasi ion natrium

10. Osmosis
Keadaan
pergerakan
netto air yang
disebabkan
karena adanya
pebedaan
konsentrasi
disebut
osmosis

11. Endositosis dan
Eksositosis
 Endositosis merupakan suatu mekanisme
dimana membran meliputi (membungkus)
bahan – bahan yang penting atau cairan
ekstraseluler dan isinya.
 Dua bentuk dasar dari endositosis adalah
pinositosis dan fagositosis.

12. Cerebrospinal Fluid
 Kapasitas Cerebral cavitiy sekitar 1600-1700
mililiter  150 ml merupakan cerebrospinal
fluid, sisanya otak dan medulla spinalis
 Cerebrospinal fluid tersebut terdapat pada
ventricle otak, cisterna dan subarachnoid
space antara otak & medulla spinalis

13.  Fungsi utama
CSF sebagai
bantalan otak,
keduanya
memiliki
gravitasi yg
hampir sama

14. Blood–Cerebrospinal Fluid
and
Blood-Brain Barriers
 Terdapat antara darah & CSF & cairan otak
 Barriers antara choroid plexus dan membran
kapiler jaringan semua area parenkhim otak
kecuali sebagian hipothalamus, kelenjar
pineal, area postrema yang mana pada
daerah ini bahan-bahan (substans) jaringan
lebih mudah berdifusi ke jaringan

15. Pembentukan
 CSF dibentuk dengan kecepatan 500ml per hari.
 2/3 dari CSF berasal dari plexus choroideus
pada ventrikel 4, terutama pada 2 ventrikel
bagian lateral
 Sebagian CSF merupakan hasil sekresi
ependymal seluruh permukaan ventrikel dan
membran arachnoid, dan sebagian berasal dari
otak sendiri melalui bagian perivascular
sekeliling pembuluh darah yang melewati otak

16. Aliran CSF
 Melalui choroid plexuses dan kemudian melalui
sistem cerebrospinal. Cairan yang disekresikan
di lateral ventricles mula-mula menuju third
ventricle; kemudian setelah bertambah mengalir
kebawah menuju aqueduct of Sylvi sampai fourth
ventricle, tempat cairan bertambah.
 Akhirnya cairan keluar melalui 3 lubang kecil ; 2
foramen Luschka sebelah lateral dan sebuah
midline foramen Magendie, memasuki cisterna
magna, (ruangan cairan yang berada di
belakang medulla dan antar acerebellum).
Cisterna magna merupakan lanjutan ruangan
subarachnoid yang berada di sekeliling otak dan
medulla spinalis

17.  Hampir seluruh CSF kemudian mengalir dari
cisterna magna melalui ruang subarachnoid
sekeliling cerebrum. CSF mengalir melalui
arachnoidal villi menuju sinus venous sagittal
dan sinuses venous yang lain. Dan CSF
dikosongkan menuju aliran vena melalui pori-
pori vili ini

20. Teori Pembentukan CSF
 Sekresi CSF oleh plexus choroideus
merupakan active transport sodium ions
melalui epithelial cells yang berada di bagian
luar plexus.
 Ion sodium menarik ion chlorida. Kedua ion
in meningkatkan konsentrasi sodium chloride
di CSF yang mana kemudian segera
menyebabkan osmosis air

21.  Glukosamemasuki CSF dan ion potassium
dan bicarbonate keluar CSF menuju kapiler

22. Susunan CSF
 Karakteristik CSF sebagai berikut: Tekanan
osmotik, kira-kira sama dengan plasma,
konsentrasi ion , juga kira-kira sama dengan
plasma; ion chlorida sekitar 15 per cent Lebih
besar dari plasma; ion potassium, kira-kira 40
per cent lebih sedikit; dan glucosa, sekitar 30
per cent lebih sedikit

23. Water Intake and Output
Figure 26.4
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

24. Acid-Base Balance
 Normal pH of body fluids
 Arterial blood is 7.4
 Venous blood and interstitial fluid is 7.35
 Intracellular fluid is 7.0
 Alkalosis or alkalemia – arterial blood pH rises
above 7.45
 Acidosis or acidemia – arterial pH drops below 7.35
(physiological acidosis)
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

25. Regulation of Water Intake: Thirst Mechanism
Figure 26.5
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26. Mechanisms and Consequences of ADH
Release
Figure 26.6
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27. Regulation of Sodium Balance: Aldosterone
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 26.8

28. Mechanisms and Consequences of ANP
Release
Figure 26.10
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29. Disorders of Water Balance: Dehydration
 Water loss exceeds water intake and the body is in
negative fluid balance
 Causes include: hemorrhage, severe burns,
prolonged vomiting or diarrhea, profuse sweating,
water deprivation, and diuretic abuse
 Signs and symptoms: cottonmouth, thirst, dry
flushed skin, and oliguria
 Prolonged dehydration may lead to weight loss,
fever, and mental confusion
 Other consequences include hypovolemic shock and
loss of electrolytes
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

30. Disorders of Water Balance: Dehydration
1 Excessive loss of H2O from 2 ECF osmotic 3 Cells lose H2O
ECF pressure rises to ECF by
osmosis; cells
shrink
(a) Mechanism of dehydration
Figure 26.7a
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

31. Disorders of Water Balance:
Hypotonic Hydration
 Renal insufficiency or an extraordinary amount of
water ingested quickly can lead to cellular
overhydration, or water intoxication
 ECF is diluted – sodium content is normal but
excess water is present
 The resulting hyponatremia promotes net osmosis
into tissue cells, causing swelling
 These events must be quickly reversed to prevent
severe metabolic disturbances, particularly in
neurons
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

32. Disorders of Water Balance:
Hypotonic Hydration
1 2 ECF osmotic 3 H2O moves into
Excessive H2O enters
the ECF pressure falls cells by osmosis;
cells swell
(b) Mechanism of hypotonic hydration
Figure 26.7b
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

33. Disorders of Water Balance: Edema
 Atypical accumulation of fluid in the interstitial
space, leading to tissue swelling
 Caused by anything that increases flow of fluids out
of the bloodstream or hinders their return
 Factors that accelerate fluid loss include:
 Increased blood pressure, capillary permeability
 Incompetent venous valves, localized blood vessel
blockage
 Congestive heart failure, hypertension, high blood
volume
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

34. Edema
 Hindered fluid return usually reflects an imbalance
in colloid osmotic pressures
 Hypoproteinemia – low levels of plasma proteins
 Forces fluids out of capillary beds at the arterial
ends
 Fluids fail to return at the venous ends
 Results from protein malnutrition, liver disease, or
glomerulonephritis, sindroma nefrotik
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

35. Edema
 Blocked (or surgically removed) lymph vessels:
 Cause leaked proteins to accumulate in interstitial
fluid
 Exert increasing colloid osmotic pressure, which
draws fluid from the blood
 Interstitial fluid accumulation results in low blood
pressure and severely impaired circulation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

36. Caused by excess water loss
Hypernatremia or overall sodium excess
Excess salt intake, hypertonic
solutions, excess
(Na > 145, aldosterone,diabetes insipidus,
sp gravity < increased water loss, water
deprivation
1.010) S&S: thirst, dry, flushed skin,
dry, stick tongue and mucous
membranes
Occur s with net loss of sodium or net
water excess
Hyponatremia Kidney disease with salt wasting,
adrenal insufficiency, GI losses,
(Na < 135, increased sweating, diuretics, SIADH
S&S: personality change, postural
hypotension, postural dizziness, abd
sp gravity > cramping, diarrhea, tachycardia,
1.030 convulsions and coma

37. Regulation of Potassium Balance
 Hyperkalemia and hypokalemia can:
 Disrupt electrical conduction in the heart
 Lead to sudden death
 Hydrogen ions shift in and out of cells
 Leads to corresponding shifts in potassium in the
opposite direction
 Interferes with activity of excitable cells
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

38. Regulation of Calcium
 Ionic calcium in ECF is important for:
 Blood clotting
 Cell membrane permeability
 Secretory behavior
 Hypocalcemia:
 Increases excitability
 Causes muscle tetany
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

39. Regulation of Calcium
 Hypercalcemia:
 Inhibits neurons and muscle cells
 May cause heart arrhythmias
 Calcium balance is controlled by parathyroid
hormone (PTH) and calcitonin
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40. Regulation of Calcium and Phosphate
 PTH promotes increase in calcium levels by
targeting:
 Bones – PTH activates osteoclasts to break down
bone matrix
 Small intestine – PTH enhances intestinal
absorption of calcium
 Kidneys – PTH enhances calcium reabsorption and
decreases phosphate reabsorption
 Calcium reabsorption and phosphate excretion go
hand in hand
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41. Influence of Calcitonin
 Released in response to rising blood calcium levels
 Calcitonin is a PTH antagonist, but its contribution
to calcium and phosphate homeostasis is minor to
negligible
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42. Acid-Base Balance
 Normal pH of body fluids
 Arterial blood is 7.4
 Venous blood and interstitial fluid is 7.35
 Intracellular fluid is 7.0
 Alkalosis or alkalemia – arterial blood pH rises
above 7.45
 Acidosis or acidemia – arterial pH drops below 7.35
(physiological acidosis)
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

43. Hydrogen Ion Regulation
 Concentration of hydrogen ions is regulated
sequentially by:
 Chemical buffer systems – act within seconds
 The respiratory center in the brain stem – acts
within 1-3 minutes
 Renal mechanisms – require hours to days to effect
pH changes
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44. Respiratory Acidosis and Alkalosis
 Result from failure of the respiratory system to
balance pH
 PCO2 is the single most important indicator of
respiratory inadequacy
 PCO2 levels
 Normal PCO2 fluctuates between 35 and 45 mm Hg
 Values above 45 mm Hg signal respiratory acidosis
 Values below 35 mm Hg indicate respiratory
alkalosis
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45. Respiratory Acidosis and Alkalosis
 Respiratory acidosis is the most common cause of
acid-base imbalance
 Occurs when a person breathes shallowly, or gas
exchange is hampered by diseases such as
pneumonia, cystic fibrosis, or emphysema,
impaired activity of diaphragm muscle and
impaired respiratory control in the brain stem
 Respiratory alkalosis is a common result of
hyperventilation and is caused by low level of
oxygen in the plasma, meningitis, head injury and
anxiety
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46. Metabolic Acidosis
 All pH imbalances except those caused by abnormal
blood carbon dioxide levels
 Metabolic acid-base imbalance – bicarbonate ion
levels above or below normal (22-26 mEq/L)
 Metabolic acidosis is the second most common
cause of acid-base imbalance
 Typical causes are ingestion of too much alcohol
and excessive loss of bicarbonate ions,such as
diarrhea, and excessive vomitting
 Other causes include accumulation of lactic acid,
shock, ketosis in diabetic crisis, starvation, and
kidney failure,high extracellular K+
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47. Metabolic Alkalosis
 Rising blood pH and bicarbonate levels indicate
metabolic alkalosis
 Typical causes are:
 Vomiting of the acid contents of the stomach
 Hypokalemia
 Intake of excess base (e.g., from antacids)
 Constipation, in which excessive bicarbonate is
reabsorbed
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48. Respiratory and Renal Compensations
 Acid-base imbalance due to inadequacy of a
physiological buffer system is compensated for by
the other system
 The respiratory system will attempt to correct
metabolic acid-base imbalances
 The kidneys will work to correct imbalances caused
by respiratory disease
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49. Respiratory Compensation
 In metabolic acidosis:
 The rate and depth of breathing are elevated
 Blood pH is below 7.35 and bicarbonate level is
low
 As carbon dioxide is eliminated by the respiratory
system, PCO2 falls below normal
 In respiratory acidosis, the respiratory rate is often
depressed and is the immediate cause of the acidosis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

50. Respiratory Compensation
 In metabolic alkalosis:
 Compensation exhibits slow, shallow breathing,
allowing carbon dioxide to accumulate in the blood
 Correction is revealed by:
 High pH (over 7.45) and elevated bicarbonate ion
levels
 Rising PCO2
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51. Renal Compensation
 To correct respiratory acid-base imbalance, renal
mechanisms are stepped up
 Acidosis has high PCO2 and high bicarbonate levels
 The high PCO2 is the cause of acidosis
 The high bicarbonate levels indicate the kidneys are
retaining bicarbonate to offset the acidosis
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52. Renal Compensation
 Alkalosis has Low PCO2 and high pH
 The kidneys eliminate bicarbonate from the body
by failing to reclaim it or by actively secreting it
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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings