Download Chapter 20 powerpoint file

POWERPOINT® LECTURE SLIDE PRESENTATION
by LYNN CIALDELLA, MA, MBA, The University of Texas at Austin
Additional Text by J Padilla exclusively for physiology at ECC
UNIT 3
20
Integrative Physiology II:
Fluid and Electrolyte
Balance
HUMAN PHYSIOLOGY
AN INTEGRATED APPROACH
DEE UNGLAUB SILVERTHORN
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
FOURTH EDITION
Mass Balance in the Body
 Homeostasis requires that amounts
gained must be equal to that lost.
 Ion concentration- need proper
amounts of Na+, Cl-, K+, and Ca2+:
 nervous, cardiac& muscle functionimbalances cause problems with
membranes of cells that are excitable.
 Primarily replaced with thirst &
appetite and excreted in urine,
sweat, & feces
 pH balance- cells functions within a
pH range that is maintained by H+,
CO2, & HCO3–
 Fluid- water levels need to be
maintained, ingestion and urine
formation have largest impact.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Key factors for Homeostasis
 Na+ & H2O=
affect ECF
Osmolarity:
amounts of solutes
dissolved in
solution,
concentration and
permeability
influence direction
of osmosis which
changes the size of
cells
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Osmosis and Osmotic Pressure
Osmolarity describes
the number of
particles of
solution in a
quantity of
osmoles OsM per
liter
Osmolarity is
influence by fluid,
ion, & protein
levels.
Compensation
occurs via renal,
behavioral,
repiratory, and CV
responses
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 5-29
Water Balance in the Body
Water makes up 5060% of total body
weight.
Main entry way is
through food, most
lost in urine unless
there is excessive
sweating or diarrhea
Homeostasis
maintains water
balance unless there
is pathology or an
abnormal ingestion of
water.
Men have more water
© 2007 Pearson Education, Inc., publishing as Benjamin Cummings
thanCopyright
women
Figure 20-2
Water Balance
A model of the role of the kidneys in water balance
Kidneys cannot
add water, only
preserve it or get
rid of excess
amounts. Renal
filtration will stop
if there is a major
loss causing
extremely low
blood pressure
and blood volume
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-3
Fluid and Electrolyte Homeostasis
The body’s
integrated
response to
changes in blood
volume and blood
pressure
incorporate many
systems
Decreased blood
volume will result
in mechanisms
that increase
blood pressure
and volume, and
reduce water loss
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-1a
Fluid and Electrolyte Homeostasis
Increased blood
volume results
in the excretion
of salt and water
which eventually
reduces blood
pressure and
ECF/ICF
volumes.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-1b
Urine Concentration
Osmolarity changes
as filtrate flows
through the nephron.
Reabsorption is
controlled by kidney
tissue concentrations
as water
permeability and
diffusion of solutes
changes as needed.
Water and sodium
reabsorption alter
urine concentration.
Diuresis is the
removal of excess
water.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-4
Water Reabsorption
Vasopression or
antidiuretic
hormone causes
a graded effect
of forming
water pores on
collecting duct
cells. Thus
permeability is
increased and
more water is
retained making
urine more
concentrated.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-5a
Water Reabsorption
If
vasopressin
is absent
water will not
move out
through water
pores
(aquaporins)a
nd the urine
will be dilute.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-5b
Water Reabsorption
The mechanism of vasopressin action
on tubular cells of the nephron
Cross-section of
kidney tubule
Collecting
duct
lumen
Filtrate
300 mOsm
Medullary
interstitial
fluid
Collecting duct cell
Vasa
recta
600 mOsM
600 mOsM
700 mOsM
Second
2 messenger
signal
cAMP
1
Vasopressin
Vasopressin
receptor
1 Vasopressin
binds to membrane receptor.
2 Receptor activates
cAMP second
messenger system.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-6, steps 1–2
Water Reabsorption
Apical membrane water permeability increases
exponentially with water pores are added
Cross-section of
kidney tubule
Collecting
duct
lumen
Medullary
interstitial
fluid
Collecting duct cell
Vasa
recta
600 mOsM
Filtrate
300 mOsm
600 mOsM
700 mOsM
Storage vesicles
Second
2 messenger
signal
Exocytosis
of vesicles
3
Aquaporin-2
water pores
1
cAMP
Vasopressin
Vasopressin
receptor
1 Vasopressin
2 Receptor activates
3 Cell inserts AQP2
water pores into
binds to memcAMP second
apical membrane.
brane Copyright
receptor.© 2007 Pearson
messenger
system.
Education,
Inc., publishing as Benjamin
Cummings
Figure 20-6, steps 1–3
Water Reabsorption
Vassopressin is also called antidiuretic hormone- it causes
reabsortion of water (in turn increasing urine concentration
and decreasing volume).
Cross-section of
kidney tubule
Collecting
duct
lumen
Medullary
interstitial
fluid
Collecting duct cell
600 mOsM
Filtrate
300 mOsm
H2O
H2O
Vasa
recta
H2O
600 mOsM
H2O
4
700 mOsM
Storage vesicles
Second
2 messenger
signal
Exocytosis
of vesicles
3 Aquaporin-2
water pores
1
cAMP
Vasopressin
Vasopressin
receptor
1 Vasopressin
2 Receptor activates
3 Cell inserts AQP2
binds to memcAMP second
water pores into
Education,
Inc., publishing as apical
Benjamin
Cummings
brane Copyright
receptor.© 2007 Pearson
messenger
system.
membrane.
4 Water is absorbed
by osmosis into
the blood.
Figure
20-6, steps 1–4
Factors Affecting Vasopressin Release
Three stimuli
control
vasopressin but
the most potent is
blood osmolarity
above 280mOsM.
The higher the
osmolarity, the
more vasopressin
released by
posterior pituitary.
Osmoreceptors
also trigger thrist
centers in
hypothalamus
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-7
Water Balance
Countercurrent
exchange in the
medulla of the
kidney. Descending
limb is permeable to
water while the
ascendig limb is
permeable to ions.
25% of all Na+ and
K+ reabsorption
happens in ascending
limb; resulting in
dilute urine. Water
amounts can be
changed again at
distal tubule and
collecting duct.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-10
Fluid and Electrolyte Balance
 Vasa recta removes water- blood
runs in opposite direction as filtrate,
water moves in according to the
concentration gradient
 Close anatomical association of the
loop of Henle and the vasa rectathis allows for water to move out of
the tubule and into the blood without
dilution the interstitial fluid in the
medulla.
 Urea increase the osmolarity of the
medullary interstitium- transporter
proteins move urea into the medulla to
increase osmolarity of the interstitial
fluid creating a gradient to move
water out without affecting the
movement of other ions (Na+ & K+)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Sodium Balance
Homeostatic
responses to salt
ingestion show the
integrated effects
on sodium, water,
and blood
pressure. Without
salt appetite [salt]
would increase
and tissue cells
.would shrink.
Thus vasopressin
and thirst is
activated.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-12
Sodium Balance
Aldosterone action in principle cells- targets
cells of the distal convoluted tubule and collecting
duct.
Interstitial
fluid
P cell of distal nephron
Lumen
of distal
tubule
Transcription
2
mRNA
Blood
Aldosterone
1
Aldosterone
receptor
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
1 Aldosterone
combines with a
cytoplasmic
receptor.
2 Hormone-receptor
complex initiates
transcription in
the nucleus.
Figure 20-13, steps 1–2
Sodium Balance
Existing channels are called the leak proteins
that allow for a rapid movement of ions
Interstitial
fluid
P cell of distal nephron
Lumen
of distal
tubule
3 Translation and
protein synthesis
New
channels
Transcription
2
mRNA
Blood
Aldosterone
1
Aldosterone
receptor
2 Hormone-receptor
complex initiates
transcription in
the nucleus.
ATP
3 New protein
channels
and pumps
are made.
ATP
4 Aldosteroneinduced
proteins modify
existing proteins.
New pumps
4
Proteins modulate
existing channels
and pumps.
1 Aldosterone
combines with a
cytoplasmic
receptor.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-13, steps 1–4
Sodium Balance
Aldosterone causes K+ secretion and sodium reabsorption.
A secondary effect is that water follows sodium.
Interstitial
fluid
P cell of distal nephron
Lumen
of distal
tubule
3 Translation and
protein synthesis
New
channels
K+
secreted
K+
Transcription
2
mRNA
Aldosterone
1
Aldosterone
receptor
Na+
2 Hormone-receptor
complex initiates
transcription in
the nucleus.
ATP
ATP
4 Aldosteroneinduced
proteins modify
existing proteins.
New pumps
4
Proteins modulate
existing channels
and pumps.
1 Aldosterone
combines with a
cytoplasmic
receptor.
3 New protein
channels
and pumps
are made.
K+
5
Na+
reabsorbed
Blood
K+
Na+
Na+
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
5 Result is increased
Na+ reabsorption
and K+ secretion.
Figure 20-13, steps 1–5
Sodium Balance
Decreased blood
pressure
stimulates renin
secretion.
Granular cells
can be activated
to release renin
by three factors:
drop in blood
pressure, a signal
from the kidneys,
or increased
sympathetic
activity.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-15
Sodium Balance
The reninangiotensinaldosterone pathway(RAAS). Renin is an
enzyme that assist in
ANG II formation.
ANGII activates
several mechanisms
that ultimately
increase blood
pressure and volume
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-14
Sodium Balance
Action of natriuretic
peptides- cause
sodium loss through
urine (natriuresis) and
act as RAAS
antagonist. They are
released when
myocardial cells
stretch too much or
during heart failure
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-16
Potassium Balance
 Regulatory mechanisms keep plasma potassium in narrow range
(3.5-5meq/L)
 Aldosterone is released in response to excess levels, it increases
permeability at distal nephron so K is moved into the urine while
sodium is reabsorbed
 Hypokalemia (K+ levels below 3)
 In ECF levels are low, K+ leaves the cell, and resting membrane
potential is more negative (hyperpolaized)= stronger stimulus
 Muscle weakness and failure of respiratory muscles and the heart due
to hyperpolarized neurons.
 Hyperkalemia (K+ levels above 6)
 In ECF levels are high, more K+ enters the cell, thus depolarizing it
but then less able to repolarize thus LESS excitable
 Can lead to cardiac arrhythmias
 K+ irregularities include kidney disease, diarrhea, and diuretics
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Behavioral Mechanisms
Drinking water and eating salt is the only
way the body obtains these substances,
therefore individuals who cannot do this
must be assisted.
 Drinking replaces fluid loss – when
body osmolarity raises above
280mOsM hypothalmic osomreceptors
trigger thrist. Oropharynx receptors are
stimulated by cold drink and signal
thirst quench
 Low sodium stimulates salt appetite –
the hypothalamus also has centers for
salt appetite which trigger a response
when osmolarity is low.
 Avoidance behaviors help prevent
dehydration
 Desert animals avoid the heat
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Disturbances in Volume and Osmolarity
In each situation
compensantion
mechanism aim to
bring conditions to
normal, in some
cases there is
incomplete
compenstation.
Notice how most
imbalances are due
to what is ingested
or loss in excess
amounts
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-17
Severe Dehydration Compensation
 Condition: low ECF volume, low blood pressure,
high osmolarity
 Compensation Mechanisms
 Cardiovascular Responses- increase cardiac output &
vasoconstriction to increase blood pressure.
Vasoconstriction reduces GFR activating granular cells
to release renin
 Angiotensin II- produce after renin release that
activates RAAS pathway to trigger thirst, vasopressin
release, and vasoconstrion. (aldosterone is not release
as it would increase osmolarity)
 Vassopressin- increase water reabsorption to reduce
loss in urine
 Thrist/ IV-replacement of loss fluids and lowering of
osmolarity
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Acid-Base Balance
 Normal plasma pH is 7.38–7.42- also resembles the pH inside
cells, its optimum for proper protein & enzyme function
 H+ concentration is closely regulated- slight pH changes indicate
a 10-fold increase/decrease in [H+] which can have damaging
effects on protein structure & function.
 Abnormal pH affects the nervous system- H+ imbalances cause
K+ imbalances because transporter protein in kidneys moves H+
and K+ in antiport fashion
 Acidosis: neurons become less excitable and CNS depression
patients can fall into a coma or have respiratory failure
 Alkalosis: hyperexcitable- numbness, tingling, muscle twitches,
severe cases lead to paralysis of respiratory muscles
 pH disturbances- induced by an imbalance of H+ input/output
 Compensation by buffers, ventilation, or renal regulation
 Greatest source is CO2 level changes induced by metabolic or
respiratory factors
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Acid-Base Balance
Hydrogen balance in the body is quickly compensated by
ventilation and slowly compensated by renal regulation.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-19
Acid and Base Input
Acid
 Organic acids – acids produced by the body during metabolism or
ingested molecules that realease H+ (acidic fruits, amino acids, fatty
acids)
 Under extraordinary conditions – produce more H+ than the body
can normally get rid off and cause pathological effects
 Metabolic organic acid production can increase Ketoacids –
strong acids produced when fats & proteins are metabolized
 Diabetes – metabolism disorder causes ketoacid formation
 Accumulation of CO2 - can occur as a result of anaerobic
respiration, increased metabolism, or decreased ventilation
 Acid production - CO2 combines with water rapidly to make an
acid and drop pH. Respiratory system gets rid of 75% of a
Base Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
pH Disturbances
The reflex pathway for respiratory compensation of metabolic acidosis
responds to shifts in H+ & CO2 based on the law of mass action.
CO2 + H2O == H2CO3 == H+ HCO3 .
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-20
pH Homeostasis
 Buffers moderate changes in pH- cannot prevent changes,
they absorb/release H+
 Cellular proteins, phosphate ions, and hemoglobin- serve as
intracellular buffers
 Ventilation
 Rapid- quickly gets rid of CO2 by increasing breathing rate
 75% of disturbances- are cleared by ventilation thanks to
the central and peripheral chemoreceptors that sense
changes in [H+]
 Renal regulation- uses ammonia and phosphate buffers in
addition to
 Directly excreting or reabsorbing H+
 Indirectly by change in the rate at which HCO3– buffer is
reabsorbed or excreted
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
pH Disturbances
Overview of renal
compensation for
acidosis. The nephron
takes care of the 25%
of compensation the
lungs can’t handle.
They excrete H+ by
trapping it in ammonia
and phosphate ions.
They also make
HCO3
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-21
Intercalated Cells
Role of intercalated cells in acidosis and alkalosis – these are located in
between principal cells of the distal tubule and have high amounts of
carbonic anhydrase. Movement occurs via H+-ATPase and H+-K+-ATPase
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 20-23
Acid-Base Balance
Respiratory system
increases CO2 during
hypoventilation and
decreases it during
hyperventilation.
When metabolism
causes a disturbance
respiratory keeps CO2
levels normal but pH
changes because
buffer levels drop.
Mass balance shifts
equation to left or
right
CO2 + H2O == H2CO3 == H+ HCO3 .
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings