Water in the body is in two compartments

intracellular (ICF)

extracellular (ECF)

plasma of the blood

interstitial fluid – that bathes the cells

includes lymph, CSF, joint fluids, tears, etc.

To survive you need to maintain a normal volume and composition of both fluid areas

Since you are a living, dynamic organism, materials move between these areas

Homeostasis must be maintained no matter what you eat, drink, or do throughout your day

pH of fluids is also critical

can be nonelectrolytes

their bonds prevent dissociation = no electrically charged chemicals are created when they dissolve in water

Ex. glucose, lipids, urea

solutes can be electrolytes

these DO dissociate into ions in water

remember ions have a charge

because of the charge = they conduct electricity

Ex. sodium chloride, acids and bases, some proteins

each electrolyte dissociates into at least TWO ions

all of those ions contribute to the solute load and water will move down its gradient to equalize out

so electrolytes play a big part in causing fluid shifts in the body

the main electrolyte outside cells (interstitial fluid) is sodium

the main electrolyte inside cells is potassium

sodium-potassium pumps keep this fairly stable

play a big part in body’s reactions

but proteins, and some lipids are the largest by mass 

pressure keep fluids on the move

water can move easily BUT – not all solutes can do that

can’t pass through a membrane because of size or charge or need for a transport protein

nutrients and respiratory gases move usually in one direction, down their gradient

the blood plasma links you to the ‘outside’ world

lung, kidney, GI tract, are always exchang

– (solvent) the amount of water you gain each day should be equal to what you lose

digestive system is main way to gain

kidneys are main route for water loss

fluids move based on ionic concentrations

(important solutes)

gain through foods and lose through urine, sweat, feces

need to balance input and output

acid-base balance

hydrogen ion gain is precisely offset by their loss

many acids are generated during normal operations

kidneys are a major exporter of hydrogen

lungs also play a role by excreting carbon dioxide to regulate hydrogen ions

your intake and output are closely regulated

thirst is the main mechanism to prompt intake

hypothalamus

you do make a small amount of water in reactions internally

some you can’t help - insensible

feces

lungs

sweat

kidneys release about 60% of your water loss

maintain the correct amount of solutes in the blood to maintain the correct amount of water

your homeostatic mechanisms monitor and adjust changes in the plasma and CSF – not the individual cellular cytosol

so extracellular fluids are monitored – NOT intracellular

you have no receptors to detect how many liters of water or grams of sodium you contain

but receptors do monitor plasma volume and osmotic concentration

cells do not move water by active transport – water moves passively

sometimes hormones can produce changes in behavior

Ex. angiotensin II or aldosterone make you feel thirsty

antidiuretic hormone (ADH)

aldosterone

natriuretic peptides (ANP)

the first two of the three interrelated processes (fluid balance and electrolyte balance) are managed by hormones

comes through which gland???

why does the brain secrete this (hypothalamus)

sensor cells monitor your osmotic concentration outside the cells

tiny changes are noted

some of the sensor cells secrete ADH

ADH will target the kidneys to save water back to the blood… BP goes ????

ADH will also target sensors for thirst

most sodium is taken back into the blood even if no aldosterone

if aldosterone is secreted = essentially all sodium is taken back into the blood

water follows - if it can

why is aldosterone secreted?

to keep blood volume UP by diminishing urinary output

main trigger = renin system from kidneys

adrenal cells can be directly stimulated by elevated potassium levels = then kidneys secrete K+

these come from cardiac muscle when they are stretched too far

why would they be stretched???

ADH is blocked, also aldosterone

kidneys let a lot of water go in the urine

BP????

similar to aldosterone

enhance sodium reabsorption

cortisol and hydrocortisol

promote reabsorption of sodium = edema

if you lose water

plasma volume decreases

electrolyte concentration gets concentrated – not because of adding too much solute, but losing too much water

if you change the amount of electrolytes

water will be excreted or retained  to keep this balanced

clinically the balance between the two must be identified and corrected

Ex. is the problem too much water or too little electrolytes?

remember that water follows solutes

if the osmotic concentration of your fluids outside the cell gets too much, the cell will lose water – shrivel

reverse is true

these pressures allow movement of liquids

across membranes (pericardial, peritoneal)

between blood and CSF

between compartments of the eye

between compartments of inner ear

the extracellular and intracellular fluids are pretty much in osmotic balance

most of the movement is within the extracellular compartment – between blood and tissue fluid

when more water leaves than you gain

if electrolytes are retained = osmotic concentration of the ECF rises

so water leaves cells to balance out the solutes

ADH, renin, the feeling of thirst work to return the shift back into the cells

sodium, K, phosphate, calcium, magnesium, chloride

these affect water balance and cell functions

imbalance between gains and losses of sodium  - common problem

potassium imbalance are less common – more dangerous

THE MAJORITY OF SODIUM IS FOUND OUTSIDE THE CELL 

remember that sodium is the central player in maintaining homeostasis of body fluids

sodium bicarbonate and sodium chloride are the two main compounds

even if you take in too much sodium, the concentration in the ECF remains stable

water just moves through the compartments to find a balance

ALDOSTERONE is the main player in managing the kidneys regulation of salt and water

THIS IS FOUND INSIDE CELLS – INTRACELLULAR

sodium potassium pumps maintain this

needed for resting membrane potential

too little causes nonresponsiveness

too little or too much disrupts electrical conduction in the heart = sudden death

plays a part in buffering pH in and out of the cell

usually potassium just needs to be excreted

limited ability to save it

most abundant mineral in body

tightly regulated

used in nerves, muscles, clotting, mitosis, cofactors

stored in bones when an excess is eaten

removed from bones when diet does not supply enough

parathyroid tumors may result in too little or too much parathyroid hormone produ

declining plasma levels of calcium directly stimulate the parathyroid glands

parathyroid hormone (PTH) is released

it targets….

bones – activates osteoclasts

small intestine to enhance absorption of calcium

kidneys increase reabsorption by the tubules

remember the hydrogen bond – weak, but abundant in living systems

most biochemical reactions are influenced by those bonds

so the fluid environment of your body’s reactions must be regulated with respect to H+

blood pH is 7.4, venous blood and interstitial fluid is 7.35

above 7.45 = alkalosis

below 7.35 in arteries = acidosis (physiologic)

technically above neutral and still basic, but considered ‘acidic’ in the body

most hydrogen ions in your body are from reactions - not what you ingest

not really from drinking orange juice

aerobic respiration of glucose

carbon dioxide  and water are products

carbonic acid is produced

fermentation of glucose = lactic ACID

breakdown of nucleic acids

dismantling of sulfur-containing amino acids

phosphoric and sulfuric acids from phosphate–containing foods  FIXED ACIDS

kidneys eliminate

lactic acid, ketone bodies are ORGANIC ACIDS

these are metabolized quickly – do not really accumulate

VOLATILE ACIDS – carbonic acid – breaks down quickly and leaves the body

proteins have amino acids with positive and negative groups that take up or release hydrogens

mostly done with those ‘R’ groups

plasma proteins do this, as do protein fibers and dissolved amino acids

hemoglobin is a buffer in RBCs

phosphate buffer system – important in kidney

bicarbonate buffer system - …….

because you generate lots of carbon dioxide  - the carbonic acid-bicarbonate buffer system is key

where does carbon dioxide come from????

most is converted to carbonic acid, which then dissociates into a hydrogen ion and bicarbonate

this prevents changes in pH caused by organic and fixed acids in the ECF

so this is a system that works outside cells – except for the RBCs

CO2 + H2O          H2CO3      H+  +  HCO3-

carbonic acid quickly dissociates into a hydrogen proton and the bicarbonate ion

adding hydrogen protons doesn’t make a pH change because the bicarbonate captures them

carbonic acid is made and quickly changes into carbon dioxide and water

carbon dioxide is breathed out

this depends on a good functioning respiratory system

an immediate way to buffer your acids

so adding hydrogen ions =

they combine with bicarbonate to make carbonic acid

this dissociates into carbon dioxide and water

you lose the carbon dioxide from the lungs

so a strong fixed or organic acid is changed into a volatile acid and blown off

reaction can go other way – but rare occurrence

chemoreceptors sense carbon dioxide in the blood and are stimulated

leads to an increase in respiratory rate

scenario- healthy person

carbon dioxide leaves at the rate it is created in cells

to keep all in equilibrium carbonic acid gives up hydrogen which becomes part of the water molecule and carbon dioxide leaves

breathing will change to keep the pH in balance

chemoreceptors sense carbon dioxide in the blood and are stimulated

leads to an increase in respiratory rate

scenario- healthy person

carbon dioxide leaves at the rate it is created in cells

to keep all in equilibrium carbonic acid gives up hydrogen which becomes part of the water molecule and carbon dioxide leaves

breathing will change to keep the pH in balance

the kidneys also can also respond to a change in H+ and HCO3-

they secrete or reabsorb hydrogen or bicarbonate ions 

happens in PCT, DCT, CD

buffers in the filtrate absorb hydrogen

next segment concerns acid-base IMBALANCES

normally acid-base is maintained by those buffers – homeostasis

a major shift in the pH of body fluids may be life threatening – 

two varieties of this back-up which also tries to correct pH shifts - 

RESPIRATORY     and         METABOLIC

acidosis – too much acids or loss of bases = too many hydrogen ions

alkalosis – loss of acids or accumulation of bases

next segment concerns acid-base IMBALANCES

normally acid-base is maintained by those buffers – homeostasis

a major shift in the pH of body fluids may be life threatening – 

two varieties of this back-up which also tries to correct pH shifts - 

RESPIRATORY     and         METABOLIC

acidosis – too much acids or loss of bases = too many hydrogen ions

alkalosis – loss of acids or accumulation of bases

drives equation to the right

your excess carbon dioxide combines with water to make carbonic acid

this is a weak acid and immediately pops apart to form H+ and HCO3-

continuing to do this accumulates lots of hydrogen ions  = acidic fluid

happens in decreased ability to rid of carbon dioxide

so too much carbon dioxide in the blood can occur from not breathing it out as in emphysema, or a brain injury

there is no longer a balance of oxygen going in and carbon dioxide leaving

if breathing rate cannot be increased, or blood supply to lungs is inadequate = pH will continue to drop

life-threatening result is ACUTE RESPIRATORY ACIDOSIS

Ex. cardiac arrest or drowning

so too much carbon dioxide in the blood can occur from not breathing it out as in emphysema, or a brain injury

there is no longer a balance of oxygen going in and carbon dioxide leaving

if breathing rate cannot be increased, or blood supply to lungs is inadequate = pH will continue to drop

life-threatening result is ACUTE RESPIRATORY ACIDOSIS

Ex. cardiac arrest or drowning

too much carbon dioxide in blood

triggers receptors in brain

change breathing rate to faster as body tries to compensate

may not be possible if airways are plugged

this blows off more carbon dioxide (if possible)

acid levels diminish

so respiratory acidosis is caused by hypoventilation

this increases carbon dioxide in the blood

it combines with the water in the plasma

carbonic acid is created

this unstable acid pops apart as two pieces  = hydrogen (H+)

bicarbonate ion (HCO3-)

so blowing off too much carbon dioxide results in less carbon dioxide in the blood

this is respiratory alkalosis

to try to compensate your respiratory rate will automatically slow

and the kidneys will save hydrogen ions 

so blowing off too much carbon dioxide results in less carbon dioxide in the blood

this is respiratory alkalosis

to try to compensate your respiratory rate will automatically slow

and the kidneys will save hydrogen ions 

There are other ways to tip the balance of acids and bases in your body – out of homeostasis

Some examples are… 

starvation

drinking too much alcohol

taking too many antacids

vomiting

diarrhea

next slides look at METABOLIC IMBALANCES

too much acid build up or loss of too much bicarbonate = 

will reflect eventually in the blood plasma

again the carbonic acid equation shows the result

blood pH will become more acidic and the lungs will compensate

respiratory rate goes up

kidneys will also excrete hydrogen ions

vomiting or tipping the normally low pH in the stomach to much high (basic)

Ex. Tums

loss of too much hydrogen ions = drives the equation forward

breathing slows to save carbon dioxide which then makes carbonic acid and that contributes hydrogen ions back to blood and tissues

this brings the pH away from so basic

so respiratory and kidney function (normally -urinate out the H+) will try to adjust

So…in metabolic acidosis – breathing is also increased

And ….in metabolic alkalosis – slow shallow breathing

kidneys – will lose or retain sodium bicarbonate or hydrogen ions

try respiratory acidosis

hypoventilation = increasing carbon dioxide and hydrogen  and carbonic acid in blood

what does this do to serum pH???

which will the kidney excrete to  increase the serum pH??

try metabolic alkalosis

prolonged vomiting = loss of hydrogen ions

what happens to serum pH????

does breathing go up or down???

then what happens to the pH levels in the system???