Maintaining Water-Salt/Acid-Base Balances and The Effects of Hormones Urinary System

Maintaining Maintaining Water-Salt/Acid-Base Water-Salt/Acid-Base

Balances Balances and and

The Effects of HormonesThe Effects of HormonesUrinary SystemUrinary System

Control of Blood CompositionControl of Blood Composition

Kidneys filter 150-180 liters of blood Kidneys filter 150-180 liters of blood plasma AND only produce 1-1.8 plasma AND only produce 1-1.8 liters of urine in 24 hoursliters of urine in 24 hours

Composition depends on 3 factorsComposition depends on 3 factors1.1. DietDiet

2.2. MetabolismMetabolism

3.3. Urine outputUrine output

Blood CompositionBlood Composition

Kidneys play an important role in Kidneys play an important role in keeping blood composition constantkeeping blood composition constant

1.1. Excretion of Nitrogen-containing Excretion of Nitrogen-containing wastes like urea, uric acid, and wastes like urea, uric acid, and creatininecreatinine

2.2. Maintain water and electrolyte balanceMaintain water and electrolyte balance

3.3. Ensure blood pH 7.35-7.45Ensure blood pH 7.35-7.45

Maintain water and electrolyte Maintain water and electrolyte balancebalance

Water accounts for 60% of body weight Water accounts for 60% of body weight in females and 50% in malesin females and 50% in males

Water locations in body:Water locations in body:1.1. 25 Liters in Intracellular Fluid – contained in 25 Liters in Intracellular Fluid – contained in

living cellsliving cells

2.2. 15 Liters in Extracellular Fluid – all body fluids 15 Liters in Extracellular Fluid – all body fluids outside of cellsoutside of cells

a.a. 12 Liters in Interstitial Fluid: Tissue Fluid, 12 Liters in Interstitial Fluid: Tissue Fluid, Cerebrospinal Fluid, Serous Fluid, humors of eye, Cerebrospinal Fluid, Serous Fluid, humors of eye, lymphlymph

b.b. 3 Liters in Blood Plasma3 Liters in Blood Plasma


Intake and Output Intake and Output of body water must of body water must be in balance for be in balance for body to remain body to remain hydrated.hydrated.


Type and amount of solutes (sodium, Type and amount of solutes (sodium, potassium, and calcium) in body potassium, and calcium) in body fluids are vital to overall body fluids are vital to overall body homeostasishomeostasis

Reabsorption of water and Reabsorption of water and electrolytes regulated by hormoneselectrolytes regulated by hormones

Falling blood Falling blood pressure from pressure from blood loss, excess blood loss, excess sweat, or low levels sweat, or low levels of sodium in blood of sodium in blood stimulate:stimulate:

This is done by two HORMONES:This is done by two HORMONES:1.1. ADH ADH

2.2. ALDOSTERONEALDOSTERONE

KIDNEYS REGULATE KIDNEYS REGULATE THE VOLUME OF BLOODTHE VOLUME OF BLOOD

ADH ADH (ANTIDIURETIC HORMONE)(ANTIDIURETIC HORMONE)

anti-"increased urine output“anti-"increased urine output“ released by pituitary glandreleased by pituitary gland promotes reabsorption of water from promotes reabsorption of water from

collecting duct and distal convoluted collecting duct and distal convoluted tubuletubule

How does ADH work?How does ADH work?

Cells in hypothalamus detect low HCells in hypothalamus detect low H22O O content of blood content of blood

ADH released into blood, by the ADH released into blood, by the hypothalamus and acts on distal hypothalamus and acts on distal convoluted tubule and collecting ductconvoluted tubule and collecting duct

MMore H2O reabsorbed, thus decreasing ore H2O reabsorbed, thus decreasing the volume of urine (and concentrating the volume of urine (and concentrating it)it)

SoSo, blood volume increases, blood volume increases As blood becomes more dilute, this is As blood becomes more dilute, this is

detected by the hypothalamus, ADH detected by the hypothalamus, ADH secretion stopsecretion stop

a negative feedback loopa negative feedback loop In some cases of high blood pressure, In some cases of high blood pressure,

DIURETIC DRUGS are prescribed DIURETIC DRUGS are prescribed which inhibit ADH secretion which inhibit ADH secretion

How does ADH work?How does ADH work?

ALCOHOL also inhibits ADH secretion ALCOHOL also inhibits ADH secretion Drinking alcohol therefore causes Drinking alcohol therefore causes

increased urination ---> dehydration increased urination ---> dehydration ---> HANGOVER---> HANGOVER

Beer and alcohol cannot quench your Beer and alcohol cannot quench your thirst! You will urinate more liquid thirst! You will urinate more liquid than you take in and the body than you take in and the body becomes even more dehydrated than becomes even more dehydrated than before.before.

The content of water in your body is The content of water in your body is normally about 50%.normally about 50%.

ALDOSTERONE ALDOSTERONE

This is a hormone released by the This is a hormone released by the ADRENAL GLANDSADRENAL GLANDS

Aldosterone acts on the kidney to Aldosterone acts on the kidney to RETAIN Na+ (& water) and EXCRETE RETAIN Na+ (& water) and EXCRETE K+. K+.

Remember from last classRemember from last class [Na+] in the blood is important to the [Na+] in the blood is important to the

kidneys’ ability to reabsorb Hkidneys’ ability to reabsorb H22OO

Concentration of sodium in blood, in Concentration of sodium in blood, in turn, regulates secretion of turn, regulates secretion of aldosterone aldosterone

another another negative feedbacknegative feedback loop loop If Na+ in blood too low, too little HIf Na+ in blood too low, too little H22O O

is reabsorbed, results in is reabsorbed, results in HYPOTENSIONHYPOTENSION

If Na+ in blood too high, results in If Na+ in blood too high, results in HYPERTENSION HYPERTENSION

ALDOSTERONE ALDOSTERONE

Fall blood pressure stimulates:Fall blood pressure stimulates:

Hypothalamus, which stimulates Hypothalamus, which stimulates posterior pituitary to release ADH posterior pituitary to release ADH (antidiuretic hormone)(antidiuretic hormone) ADH causes less water loss in urine SO ADH causes less water loss in urine SO

blood volume increases and blood blood volume increases and blood pressure risespressure rises

Adrenal Cortex which releases Adrenal Cortex which releases AldosteroneAldosterone Aldosterone stimulates kidney tubules to Aldosterone stimulates kidney tubules to

reabsorb more sodium ions (salt)reabsorb more sodium ions (salt) WATER FOLLOWS SALTWATER FOLLOWS SALT So if water follows salt, less water will be So if water follows salt, less water will be

lost in urine, blood volume increases and lost in urine, blood volume increases and blood pressure risesblood pressure rises


Kidney to release ReninKidney to release Renin Renin leads to the formation of Renin leads to the formation of

angiotensin II in the bloodangiotensin II in the blood Angiotensin II causes smooth muscle of Angiotensin II causes smooth muscle of

blood vessels to constrict which increase blood vessels to constrict which increase blood pressureblood pressure


KIDNEYS AND BLOOD pHKIDNEYS AND BLOOD pH Kidneys help maintain blood pH. Kidneys help maintain blood pH.

However, so do the lungs (respiratory However, so do the lungs (respiratory system). system). You may recall that COYou may recall that CO22 is is released released from the from the

lungs when you lungs when you exhaleexhale.. H+ + HCOH+ + HCO33- ↔ H- ↔ H22COCO33 ↔ H ↔ H22O + COO + CO22

Based on the acidity of the blood, Based on the acidity of the blood, chemoreceptors either stimulate or chemoreceptors either stimulate or depress breathing. depress breathing. If, for example, your blood is slightly alkaline, If, for example, your blood is slightly alkaline,

will your depth of breathing rate increase or will your depth of breathing rate increase or decrease? ANSWER: IT WILL DECREASE.decrease? ANSWER: IT WILL DECREASE.

The kidneys, too, rid the body of The kidneys, too, rid the body of acidic and basic wastes. acidic and basic wastes.

Nephrons vary the amount of H+ and Nephrons vary the amount of H+ and NHNH33 that they excrete and the that they excrete and the amount of HCOamount of HCO33- and Na+ they - and Na+ they reabsorb in order to keep the pH reabsorb in order to keep the pH levels normal.levels normal.

KIDNEYS AND BLOOD pHKIDNEYS AND BLOOD pH

If blood acidic, more H+ and ammonia If blood acidic, more H+ and ammonia (NH3) are excreted, and more sodium (NH3) are excreted, and more sodium bicarbonate is reabsorbed. bicarbonate is reabsorbed.

Sodium bicarbonate neutralizes acid:Sodium bicarbonate neutralizes acid: Na+HCONa+HCO33- + HOH --> H- + HOH --> H22COCO3 3 + NaOH (strong + NaOH (strong

base)base)


If blood alkaline, less H+ If blood alkaline, less H+ excreted, less Na+ and excreted, less Na+ and HCO3- reabsorbedHCO3- reabsorbed

Reabsorption and excretion of Reabsorption and excretion of ions (e.g. K+, Mg++) by ions (e.g. K+, Mg++) by kidneys also maintains proper kidneys also maintains proper ELECTROLYTE BALANCE of ELECTROLYTE BALANCE of blood.blood.


Ensuring proper blood pHEnsuring proper blood pH

Blood pH must be Blood pH must be 7.35-7.457.35-7.45

Alkalosis: blood pH Alkalosis: blood pH above 7.45above 7.45

Acidosis: blood pH Acidosis: blood pH below 7.35below 7.35

Several pH Several pH controlling systemscontrolling systems

pH control systempH control system

Blood BufferBlood Buffer First line of defense in resisting pH First line of defense in resisting pH

changeschanges Chemical buffers that act to prevent Chemical buffers that act to prevent

dramatic changes in hydrogen ion dramatic changes in hydrogen ion concentration when a strong acid or concentration when a strong acid or strong base is addedstrong base is added

pH control systempH control system Respiratory Respiratory

controlscontrols When COWhen CO22 enters enters

blood from tissue blood from tissue cells, it is converted cells, it is converted to carbonic acidto carbonic acid

Modify blood pH by Modify blood pH by retaining COretaining CO22 (decrease pH) or by (decrease pH) or by eliminating more eliminating more COCO22 from blood from blood (increase blood pH)(increase blood pH)

Renal MechanismRenal Mechanism Only system that can remove metabolic Only system that can remove metabolic

acids and bases from the bodyacids and bases from the body Kidneys act slowly to change pH (hours Kidneys act slowly to change pH (hours

to days to regulate)to days to regulate) pH of urine can vary from 4.5 to 8.0 pH of urine can vary from 4.5 to 8.0

pH control systempH control system

KIDNEY PROBLEMSKIDNEY PROBLEMS

Kidney functions are vital to Kidney functions are vital to homeostasis; homeostasis; problems can be life-problems can be life-threateningthreatening

Infections can be detected with Infections can be detected with URINALYSIS - look for blood cells and URINALYSIS - look for blood cells and proteins in urine. proteins in urine.

NORMAL URINE NEVER HAS BLOOD NORMAL URINE NEVER HAS BLOOD PROTEIN OR BLOOD CELLS IN IT. IT PROTEIN OR BLOOD CELLS IN IT. IT SHOULD ALSO NOT CONTAIN MORE SHOULD ALSO NOT CONTAIN MORE THAN TRACE AMOUNTS OF GLUCOSETHAN TRACE AMOUNTS OF GLUCOSE

If water and salts retained, causes If water and salts retained, causes fluid accumulation in body tissues, fluid accumulation in body tissues, plus ionic imbalances (leads to plus ionic imbalances (leads to problems in including loss of problems in including loss of consciousness and heart failure). consciousness and heart failure). This condition is called EDEMA.This condition is called EDEMA.

KIDNEY PROBLEMSKIDNEY PROBLEMS

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Maintaining Water-Salt/Acid-Base Balances and The Effects of Hormones Urinary System