Chapter 6.1 - Regulation of the composition of body fluids

Question 1

Water makes up a large proportion of the human body.

% in different groups include:

Answer 1

WATER IN 
INFANTS = 75%
ADULT MALE = 60%
ADULT FEMALES = 50%
OLD AGE = 45%

Question 2

How is the distribution of body fluids (water) in a 70Kg male?

Answer 2

WATER CONTENT = 60%
- APPROX 42 L OF WATER

BRAIN - 80-85%
TEETH - 8-10%
LUNGS - 75-80%
HEART - 75-80%
BONES - 20-25%
LIVER - 70-75%
KIDNEYS - 80-85%
BLOOD -50%
MUSCLES - 70-75%
SKIN - 70-75%

Question 3

What is the intracellular fluid?

Answer 3

The fluid inside the cell is called intracellular fluid or CYTOSOL

Question 4

What is extracellular fluid?

Answer 4

FLUID OUTSIDE THE CELLS IS KNOWN AS EXTRACELLULAR FLIUD

• includes tissue fluid and blood plasma

Question 5

Extracellular fluid includes what?

Answer 5

1. INTRAVASCULAR - Blood plasma located within the blood vessels
2. INTERSTITIAL, INTERCELLULAR/TISSUE FLUID - fluid between the cells
3. TRANSCELLULAR FLUID - fluid in specific body regions
   - fluid in the brain, spinal cord, eyes and joints, and surrounding the hearts.

Question 6

Explain the breakdown of fluid in the body:

Answer 6

if Total Volume = 42 L (60% of body weight)
then
1. Intracellular fluid compartment = 28L

2. Extracellular Fluid compartment = 14 L
   - –1. Intravascular fluid (plasma) = 3 L
   - –2. Intersitial Fluid = 10.5 L
   - –3. Trancellular fluid = 0.5L

Question 7

Type of body fluid.
The proportion of total body fluid.
Components of the body fluid.

Answer 7

1. Intracellular fluid
   2/3 of total body water
   fluid inside the cell - cytosol
2. Extracellular fluid
   1/3 of total body water
   fluid outside cells

• 1. PLASMA (intravascular fluid)
     approx 1/4 of extracellular fluid
     the fluid part of the blood
• 2 and 3 Interstitial and transcellular fluid
  approx 3/4 of extracellular fluid
  Lymph, CSF, synovial joint fluids, fluids in eyes and ears, fluid in the chest and abdominal cavities, around heart, fluids in the alimentary canal, kidney filtrate.

Question 8

How do materials get exchanged between fluids?

Answer 8

• different body fluids are NOT ISOLATED FROM ONE ANOTHER
• there is CONTINUOUS EXCHANGE OF MATERIALS BETWEEN THEM

EG. plasma is separated from the interstitial fluid by thin walls of the capillaries
- there is a relatively free exchange of materials between the 2.

however, dissolved materials that are large molecules, such as proteins of the plasma, tend to remain within the blood vessels as they are too large to move through the capillary walls.

Question 9

What is osmotic concentration?

Answer 9

The concentration of solutes: aka osmolarity

Question 10

What is Osmotic pressure?

Answer 10

The tendency of a solution to take in the (water) pure solvent.

Question 11

What is an osmoreceptor?

Answer 11

A receptor sensitive to osmotic pressure of body fluids.

Question 12

How does osmotic pressure and osmotic concentration relate?

Answer 12

Water travels easily through plasma membranes, so any difference in osmotic concentration between the intracellular fluid and the extracellular fluid does not last very long.

The greater difference in osmotic concentrations between 2 solutions, the greater the osmotic pressure.

Question 13

What is metabolic water?

Answer 13

Water formed as a by-product of cellular respiration

Question 14

How is most body fluid is obtained? AND AMOUNT

Answer 14

2500mL/DAY

1. Taken in as liquid/ DRINKING (1600mL)
2. Contained in food that is eaten (700mL)
3. Metabolic water (200mL)

Question 15

How is water lost from the body?

Which organs…(4)

Answer 15

1. KIDNEYS - URINE ( 1500mL)
2. SKIN (500mL)
3. SURFACE OF LUNGS (300mL)
4. ALIMENTARY CANAL - FAECES (200mL)

Question 16

Define Excretion

Answer 16

Removal of the wastes of metabolism from the body

Question 17

Why is excretion important?

Answer 17

Many WASTES FROM METABOLISIMIS TOXIC and would be harmful to health if allowed to accumulate in the body fluids.

EVERY CELL PRODUCES waste products, so their removal before they reach harmful concentrations is extremely important.

Question 18

How are the lungs involved in excretion? can water loss be regulated?

Answer 18

Excretes carbon dioxide

Carbon dioxide and water are produced by all body cells during cellular respiration.

• body can not use CO2 and it is carried in the blood until it reaches the lungs, where it is excreted
• some water also lost in the FORM OF WATER VAPOUR AS WE EXHALE.
• water loss cannot be regulated

Question 19

How are the sweat glands in the skin involved in excretion? can water loss be regulated?

Answer 19

Skin secretes water-containing by-products of metabolism such as salts, urea, and lactic acid.

loss of water (sweat) is directly linked to temp. regulation.

Question 20

How is the alimentary canal involved in excretion?

can water loss be regulated?

Answer 20

The A canal passes out BILE PIGMENTS that entered the SMALL INST. with the BILE.

These pigments are the breakdown products of haemoglobin from RBCs.

They leave the body with Faeces.

The bulk of the faeces is composed of undigested food materials.

These are not considered to be excretory products, as they have not been produced by the cells.

• water loss cannot be regulated

Question 21

How are the kidneys involved in excretion? can water loss be regulated?

Answer 21

Principal excretory organs

responsible for maintaining a constant cont. of materials in the body fluids.

one of the important wastes removed by the kidneys is urea, which is produced in the liver during the breakdown of proteins.

water loss can be regulated by the kidneys to achieve constant cont. of dissolved subts. in the body fluids.

Question 22

What are kidneys?
Location?
role?

Answer 22

What? Pair of reddish-brown organs, 11cm long

Location? Abdomen on either side of the vertebral column,

• at about the level of the lowest ribs,
• attached to the rear wall of the abdominal cavity.
• due to the presence of the liver, the right kidney is usually slightly lower than the left.
• embedded in, and held in position by a mass of fatty tissue.

role- 60% of water lost from the body is excreted by the kidneys as urine.

• excretory organ
• regulation of the composition of body fluids.

Question 23

What is the structure of the urinary system?

Answer 23

1. Kidney - organ that produces urine
2. Renal Vein - takes blood away from the kidney
3. Renal artery - takes blood away from the heart to the kidney
4. Ureter - a tube leaving the kidneys draining with urine, away from it.
5. Bladder - a muscular reservoir/ bag that holds the urine until it passed out of the body

via peristalsis

6. Urethra - a tube from the bladder that opens to the outside, and empties the bladder.

Question 24

Define nephron. how many? function?

Answer 24

A functional unit in the kidney.

the kidney contains 1.2 million microscopic units

nephrons carry out the kidney’s role in excretion and water regulation.

Question 25

Label a nephron

Answer 25

9 items of importance

Question 26

Explain the process of producing urine. 1. Glomerular filtration 2. Selective reabsorption 3. Secretion

Answer 26

Glomerular Filtration 1. Blood enters the glomerulus, under high pressure 2. fluid (water) and small dissolved molecules is forced out of the blood into Bowman’s capsule - filtration 3. large molecules and blood cells are retained in the blood 4. FILTRATE IS collected by the Glomerular capsule ``` Selective Reabsorption The filtrate passes through the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct. Water and other useful subts. are REABSORBED into PERITUBULAR CAPILLARIES. • water • sodium ions • chloride ions • amino acids • glucose. - diffusion ``` Active Secretion - Secretion refers to the movement of substances from the blood in the peritubular capillaries into the tubule. - Substances such as hydrogen ions, potassium ions and certain drugs are secreted into the urine. Urine Production - water and dissolved substances that remain make up the urine. - urine is carried by collecting ducts to the ureter and then to the bladder.

Question 27

Where does each process in the kidneys' nephron occur?

Answer 27

Filtration - glomerulus Reabsorption - Proximal convoluted tubule, ascending/descending limbs, the loop of Henle, collecting duct Secretion - Descending limb, loop of Henle urine - collecting duct

Question 28

What happens when excess water is lost in the body?

Answer 28

water loss is balanced by water intake due to strenuous activity or extreme heat water loss can be quite high As water is lost - 1. PLASMA BECOMES MORE CONCENTRATED, hence HIGHER OSMOTIC PRESSURE 2. therefore WATER MOVES from INTERSTITIAL FLUID INTO PLASMA VIA OSMOSIS 3. This makes Interstitial fluid more concentrated, and therefore water diffuses out of the cells, so CELLS START TO SHRINK FROM DEHYDRATION. 4. OSMORECEPTORS in HYPOTHALAMUS detect INCREASE IN OSMOTIC PRESSURE. 5. NO. OF RESPONSES TRIGGERED to trigger water content hence lower pressure.

Question 29

What depends on the Volume and Composition of urine produced?

Answer 29

The volume and Composition of urine produced by kidneys depend on how much water there is in the body fluids. A large volume of water is consumed, then you will produce a large volume of DILUTE URINE. if dehydrated, not drinking enough water - Produce a smaller volume of CONCENTRATED URINE.

Question 30

How much water is being reabsorbed? where and how?

Answer 30

- 99% OF WATER FILTERED THROUGH GLOMERULI Oof kidneys is REABSORBED. - THIS OCCURS THROUGH THE WALLS OF THE KIDNEY TUBULES ALONG THE ENTIRE LENGTH. 1. REABSORPTION occurring at PROXIMAL CONVULTED TUBULE, and LOOP OF HENLE IS VIA OSMOSIS. 2. REABSORPTPN AT THE DISTAL CONVOLUTED TUBULE AND COLLECTING DUCT IS ACTIVE REABSORPTION.

Question 31

What is ANTIDIURETIC HORMONE?

Answer 31

ANTIDIURETIC HORMONE (ADH) - A hormone produced by the HYPOTHALAMUS and RELEASED by the POSTERIOR LOBE OF PIT. GLAND, THAT STIMULATES THE KIDNEYS TO REMOVE WATER FROM URINE, THUS REDUCING URINE PRODUCTION: aka vasopressin

Question 32

How does ADH affect the reabsorption of water and urine formation?

Answer 32

The permeability of the walls of the distal convoluted tubule and collecting duct are controlled by the ADH. INCREASED REABSORPTION - when Cont. of ADH in the blood is HIGH - tubules are very permeable to water and thus water is able to LEAVE the tubule and enter the surrounding capillary network. - OUTWARD FLOW OF WATER FROM THE FLUID WITHIN TUBULES REDUCES ITS VOLUME, HENCE INCREASES CONT. OF MATERIALS REMAINING. DECREASE IN REABSORPTION - cont of ADH LOW, LESS PERMEABLE, LITTLE WATER ABSORBED INTO BLOOD PLASMA, URINE IS DILUTE, VOLUME NOT REDUCED TO ANY SIG. EXTENT.

Question 33

ADH CONTROLLING WATER IN FEEDBACK PROCESS.

Answer 33

STIMULUS: Osmotic pressure of the blood is HIGH, due to DECREASE OF WATER IN BLOOD (via excessive sweating) RECEPTOR: OSMORECEPTOR IN HYPOTHALAMUS, detected high osmotic pressure of blood. MODULATOR: Hypothalamus stimulates the posterior lobe of pit. gland to RELEASE ADH. EFFECTOR: ADH is carried all over the body by the BLOOD, AND AFFECTS TARGET ORGANS WHICH NEPHRON TUBULES IN KIDNEY. - PERMEABILITY OF DISTAL CONVOLUTED TUBULE AND COLLECTING DUCT INCREASED. RESPONSE: MORE WATER IS REABSORPED INTO BLOOD PLASMA FROM DISTAL CONVOLUTED TUBULE. FEEDBACK: Reabsorption of water increases the amount of water in blood plasma, OSMOTIC PRESSURE DECREASED. - adjustment has eliminated or reduced og. stimulus - NEGATIVE FEEDBACK.

Question 34

What is ALDOSTERONE?

Answer 34

A hormone that acts on the kidney to REDUCE the amount of SODIUM in the URINE and INCREASE the amount of POTASSIUM AKA SALT RETAINING HORMONE, SECRETED BY ADRENAL CORTEX REGULATION OF WATER OUPUT.

Question 35

Why does the adrenal cortex release Aldosterone?

Answer 35

in response to a 1. DECREASE Cont. of SODIUM IONS 2. DECREASE BLOOD VOLUME 3. DECREASE BLOOD PRESSURE 4. INCREASE CONT. OF K IONS IN BLOOD

Question 36

How does Aldosterone have a role in regulating the water content in the body?

Answer 36

Acts on the DISTAL CONVOLUTED TUBULES AND COLLECTING DUCT. TO INCREASE AMOUNT OF Na ions reabsorbed into the bloodstream, and K ion secreted in the URINE. achieves VIA ACTIVE TRANSPORT USING Na -K pump. - every 3 Na ions, reabsorbed, 2 K ions secreted. - thus there is a net movement of ions into the blood and subsequent transport of water into the blood via osmosis. therefore aldosterone has a role in regulating the water content in the body.

Question 37

Define Thirst Centre.

Answer 37

The part of the brain that regulates the feeling of thirst: located in the hypothalamus - promotes a person to drink water - the fluid is absorbed across the wall of the alimentary canal into the blood, decreasing osmotic pressure

Question 38

Thirst response in a stimulus-response feedback loop

Answer 38

STIMULUS: Water lost from various fluids, reduction in plasma volume, and an INCREASE IN OSMOTIC CONT. of the extracellular fluid. RECEPTOR: OSMORECEPTORS in the THIRST CENTRE IN THE HYPOTHALAMUS detects RISING OSMOTIC CONT. - other stimuli as dry mouth also is involved MODULATOR: Stimulation of the thirst centre in the hypothalamus makes a person FEEL THIRSTY EFFECTOR: CONSCIOUS FEELING OF THIRST MAKES PERSON TO DRINK RESPONSE: FLUID CONSUMED IS ABSORBED FROM ALIMENTARY CANAL INTO BLOOD PLASMA FEEDBACK: BLOOD CIRCULATES through the body, enable interstitial fluid and intercellular fluid to return to OSMOTIC CONT. - after drink, the thirst centre no longer stimulated and the desire to take in water ceases.

Question 39

WHAT HAPPENS TO ANY excess fluid in IN EXTRACELLULAR FLUID

Answer 39

``` CONSUMPTION BLOODSTREAM INTRACELLULAR FLUID LYMP BLOODSTREAM ``` any excess fluid in IN EXTRACELLULAR FLUID IS COLLECTED BY LYMPH SYSTEM AND RETURNED TO BLOOD VIA LYMPH VESSELS THAT JOIN IN THE UPPER CHEST

Question 40

Explain Dehydration

Answer 40

Excessive loss of water and accompanying salts from the body: results when the body loses more fluid than it takes in symptoms noticeable when a person lost 2% normal body water lost via sweating, vomiting, or diarrhea elderly people can suffer due to thirst reflex becomes less effective symptoms - severe thirst, low blood pressure, dizziness, and headache if conditions remain untreated patient becomes delirious, loses consciousness, and dies.

Question 41

Explain water intoxication

Answer 41

A potentially life-threatening condition caused by drinking too much water when the amount of salt + other electrolytes in the body is low. body fluids become diluted, cells take in extra water via osmosis commonly caused by long bouts of intensive exercise during which electrolytes are not replenished and large amounts of water are consumed (without any salts) treatment - electrolyte water symptoms - lightheadedness, headache, vomiting, and collapse.