Download Chapter 27 Reproductive Endocrinology

Chapter 26 Fluids, Electrolytes , Acid-Base
fluid homeostasis
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maintain osmotic equilibrium of all body fluids
maintain fluid volume
maintain cell volume
maintain electrolyte levels
maintain optimum pH
integration of systems
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renal
cardiovascular
respiratory
neural
endocrine
behaviors
Water
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50 – 75 % of body weight
~ 42 L
universal solvent
ICF = intracellular fluid
~ 28L
ECF = extracellular fluid
~ 14 L
• blood
• tissue fluid
• lymph vessels
• meninges
• joints
plasma ~ 5L
interstitial
lymph
CSF
synovial fluid
water flow
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continuous exchange between ECF’s and ICF
same osmolarity
285 – 300 mOsm / L
water movement :
osmosis
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towards high particle concentration
any change in solute concentration leads to water flow
filtration
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any pressure gradient leads to water flow
mass balance
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water intake = water output
1o intake
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also
1o output
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also
= beverages
food
metabolic water
= urine
sweat
respiratory
~ 2.5 L
obligatory water loss
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insensible water loss
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skin
feces
sensible water loss
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~ 900 ml / day
respiratory
~ 500 ml / day
amt urine to get solutes out of the body
additional water loss
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varied urine volume
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where?
to balance intake
to correct blood volume (BP)
regulation of water volumes
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hypothalamus :
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osmoreceptors
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thirst
water conservation
• affects rate of ADH release
water intake
renal :
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RAAS
renin-angiotensin-aldosterone system
• stim by:
 blood volume , low BP
Δ ~ blood volume
GFR
need more water ?
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need more water
too much water
hypothalamus
hypothalamus
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thirst
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thirst
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ADH
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ADH
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kidney
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kidney
renin
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renin
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GFR
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GFR
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disorders
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dehydration
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hemorrhage
vomiting, diarrhea
skin
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sweat , burns
hypotonic hydration
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extreme intake
renal insufficiency
edema
solutes
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electrolytes
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non-electrolytes
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glucose
proteins
lipids
dissociate into ions
Electrolytes
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molecules that dissociate in water
+ ions
=
cations
- ions
=
anions
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functions:
osmolarity
acid – base balance
tissue / organ functions
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mEq/L
=
milliequivalent per liter
electric charges / L
= moles x electric charge
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1 mEq/L
=
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Na+ sodium
ECF
nerve, muscle
osmolarity
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K+
ICF
nerve, muscle
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Ca++ calcium
bones, teeth
nerve (NT release)
muscle contraction
cardiac conduction
blood clotting
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Mg++ magnesium
bone
ATP
1 mOsm
cations
potassium
anions
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Cl
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HCO3- bicarbonate
buffer system
CO2 transport
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HPO4-- phosphate
ICF
bones, teeth
DNA, RNA, ATP
phosphate buffer
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proteins -
buffers
plasma osmolarity
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chloride
ECF
HCl
sodium
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most abundant cation in ECF
mostly NaCl and NaHCO3
142 mEq/L
accounts for most osmolarity of plasma and ECF
primary molecule in movement of water
primary in movement of many ions
no Na receptors have been found
regulation tied to
osmolarity
blood pressure (volume)
what’s wrong with a little sodium ?
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daily Na intake would raise Osm to 305-310 mOSm
cells shrink
increased blood volume / BP
nerve depolarization
sodium regulation
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kidney reabsorbs 90% Na w/o hormonal control
aldosterone
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increases Na reabsorption
stim:
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ANP
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water intake
low BP
sympathetic
hi K
via renin-angiotensin
renin
decreases Na reabsorption
inhibits aldosterone , renin
lowers osm
sodium regulation – part 2
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estrogen
 Na rebsorb
like aldosterone
“retain water”
progesterone blocks aldosterone
Na excreted
 Na and water reabsorption
hi cortisol
edema
potassium
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main cation ICF
affects resting membrane potential
esp. neurons, muscles, heart
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any change in K+ affects nerves, muscles, heart:
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10-15 % lost in urine regardless of body’s need
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aldosterone
high K+ in ECF
cells depolarize
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low K in ECF
hyperpolarize
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hyperpolarize
low pH (hi H )
potassium regulation
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 K+ secreted
 K+ in ECF / plasma
renin-angiotensin
stim:
Addison’s
hyperkalemia
diuretics
possible hyperkalemia
water (intake) hypokalemia
calcium
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functions
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hypocalcemia
tetany
hypercalcemia
inhibits neurons
( Na permeability)
calcium regulation
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blood levels important, not bone levels
renal constant PCT reabsorption
PTH parathyroid hormone
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bone
 Ca to blood
small intestine
 Ca absorption
kidney
 reabsorption (DCT)
 blood Ca
calcitonin
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 blood Ca
 Ca deposition to bone
anions
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Cl
follows Na
exchanged for HCO3-
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HCO3-
amount varies to control pH
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Acid – Base , pH
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pH = parts hydrogen
acid increases H+
base decreases H
+
eg. HCl ; -COOH
eg. NaOH ; NaHCO3
in blood :
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increased pH
alkalosis > 7.45
decreased pH
ICF
acidosis < 7.35
7.0
the pH problem
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pH ~ free H ions
most bodily functions are affected by pH changes !
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protein functions (3D shape depends on H bonds)
enzymes
Na+ and K+ concentrations
pH extremes
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< 7.0
CNS depressed
> 7.8
CNS overexcited
respiratory arrest
coma, death
convulsions
the body produces acids
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amino acids
fatty acids
keto acids
lactic acid
H+ from gastric HCl
CO2 is the largest source of acid (H+)
acid – base homeostasis
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buffer systems
fastest
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respiratory mechanisms
slower
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renal mechanism
slowest (several hours)
weak, short term
(few minutes)
stronger
75% effective
strongest
buffer systems
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buffer
=
weak acid or weak base
buffer system =
weak acid + weak base
 weak acid
strong acid + buffer
strong acid + weak base  weak acid + salt
 weak base
strong base + buffer
strong base + weak acid  weak base + water
3 buffer systems
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bicarbonate system
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phosphate system
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protein system
• blood and ECF
• kidney , ICF
• ICF
bicarbonate buffer system
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bicarbonate ion
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weak acid
carbonic acid
H2CO3
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weak base
sodium bicarbonate
NaHCO3
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HCO3-
strong acid + weak base
HCl
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NaHCO3  H2CO3 + NaCl
strong base + weak acid
NaOH
 weak acid + salt
 weak base + water
H2CO3  NaHCO3 + H2O
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constant source of HCO3-
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all cells produce HCO3alkaline reserve
CO2 + H2O

H2CO3
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H+ + HCO+phosphate buffer system
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weak acid
sodium dihydrogen phosphate
weak base
sodium monohydrogen phosphate Na2HPO4
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strong acid + weak base  weak acid + salt
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strong base + weak acid  weak base + water
HCl
NaOH
+ Na2HPO4
 Na H2PO4 + NaCl
+ Na H2PO4  Na2HPO4 + H2O
Na H2PO4
long term
protein buffer system
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amino acid
= weak acid and a weak base
• amino group
= weak base
NH2
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• carboxyl
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= weak acid
COOH
eg. Hemoglobin
respiratory mechanism
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respiratory rate affects pH
by changing concentration of CO2 in blood
stimulus:
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H+ concentration affects carotid/aortic chemoreceptors
CO2 concentration affects medulla
compensates for metabolic causes of pH imbalance
ventilation corrects blood pH
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CO2 + H2O
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 rate   CO2   pH
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–  CO2 + H2O
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H2CO3

+
-
H + HCO3
 H2CO3  H+ + HCO3-
 rate   CO2   pH
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 CO2 + H2O
 H2CO3  H+ + HCO3-
 respiratory rate
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causes
 blood pH
to  blood pH
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? respiratory rate
to  blood pH
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? respiratory rate
renal mechanism
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“ultimate acid-base regulatory organ”
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H+ and HCO3- secretion / reabsorption
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wide range of urine pH
can buffer any pH imbalance
lactic acid
uric acid
ketones
CO2
bases
HCO3- reabsorption affects blood pH
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HCO3- filtered in glomerulus
constantly reabsorbed to blood
to raise blood pH
 HCO3- reabsorption
to lower blood pH
 HCO3- reabsorption
new HCO3- from CO2 or glutamine
acid-base imbalances
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respiratory
caused by respiratory problem
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respiratory acidosis
poor CO2 exchange
respiratory disease
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respiratory alkalosis
hyperventilation
metabolic
caused by non-respiratory problem
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metabolic acidosis
diarrhea
lactic acid (exercise)
ketosis (diabetes)
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metabolic alkalosis
antacids
constipation
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kidney diseases
usually acidosis
pH compensations
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respiratory mechanism
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will compensate for metabolic and renal causes
can’t compensate for respiratory causes
to  blood pH
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? respiratory rate
to  blood pH
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? respiratory rate
renal mechanism
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will compensate for metabolic and respiratory causes
can’t compensate for renal causes
to  blood pH
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? HCO3- reabsorption
to  blood pH
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? HCO3- reabsorption