water balance

Urine Outputmore water in usually means more urine out

Increased water intake = increased urine outputDecreased water intake = decreased urine output

some liquids encourage increase urine excretion – diuretics

frequency of urination dependent on hormonal signals

Three Effects of Urine1. Osmotic Pressure

2. Blood Pressure

3. pH Balance

Osmotic Pressureosmotic pressure (osmolarity) –

water pressure due to presence of solutesThe more concentrated a

solution, the higher its osmotic pressure (osmolarity)

antidiuretic hormone (ADH) – regulates blood osmotic pressure through kidneysa short peptide hormone

Osmotic PressureWhat type of situation would

cause increased osmotic pressure of our blood/interstitial fluid?sweating / dehydration

causes increased ADH productionincrease water reabsorptiondilutes bloodconcentrates urine

COLLECTING DUCT OF THE

NEPHRON

NaCl

Urea

Water

INTERSTITIAL FLUID/BLOOD

osmoreceptors in hypothalamus detect increased osmotic pressure sends signals to pituitary gland

ADH produced in hypothalamus and is transported to the pituitary gland

Osmoreceptorsin hypothalamus

Drinking reducesblood osmolarity

to set point

H2O reab-sorption helpsprevent further

osmolarity increase

STIMULUS:The release of ADH istriggered when osmo-receptor cells in the

hypothalamus detect anincrease in the osmolarity

of the blood

Homeostasis:Blood osmolarity

Hypothalamus

ADH

Pituitarygland

Increasedpermeability

Thirst

Collecting duct

Distaltubule

Osmotic Pressureincreased osmotic

pressure

osmoreceptorspituitary gland; release ADH

decreased osmotic pressure

increased sensation of thirst

increased water reabsorption by kidney

ADH AnimationThe following animation will contain some terminology

not covered.

Animation

Blood Pressureblood pressure – increase

force of blood on blood vessels

aldosterone – hormone which increases Na+ reabsorption in kidneysincreased H2O in blood

increased blood pressure

Blood Pressure

aldosterone produced in adrenal gland, above kidney

Blood Pressure

Blood PressureWhat part of the kidney would be affected by low blood

pressure?glomerulus; high blood pressure needed for filtration

decreased blood pressure detected by juxtaglomerular apparatus (JGA)receptors next to

the glomerulus

Blood Pressurethe enzyme renin, is released

angiotensinogen angiotensinrenin

Blood Pressure

Two important functions of angiotensin:

1. causes blood vessel constriction

2. stimulates aldosterone release

Increased Na+

and H2O reab-sorption in

distal tubules

Homeostasis:Blood pressure,

volume

STIMULUS:The juxtaglomerular

apparatus (JGA) respondsto low blood volume or

blood pressure (such as dueto dehydration or loss of

blood)

Aldosterone

Adrenal gland

Angiotensin

Angiotensinogen

Reninproduction

Renin

Arterioleconstriction

Distal tubule

JGA

low blood pressure

juxtaglomerular apparatus

cells to release renin; produce

angiotensin

blood pressure increases

constrict blood vessels

induce aldosterone release;increase Na+ reabsorption

pH BalanceHow do living systems regulate the amount of acid /

base in their systems?

buffers – conjugate acid-base pairs

H3PO4 H2PO4- + H+

pH Balanceconversion of CO2 to other compounds help

regulate blood pH

H2O + CO2 H2CO3 HCO3- + H+

pH determined by the relative magnitudes of HCO3

- reabsorption and H+ secretion in the proximal and distal tubules

carbonic acid bicarbonate ion

H+

HCO3-

• If blood pH too low increase in H+ secretion (pH of urine gets lower, more acidic) increase in blood pH

• If blood pH too high increase in HCO3- reabsorption (pH of urine

increases) decrease in blood pH

Classwork/HomeworkSection 7.6 – Pg. 356 #1-8, 10