Ch. 7 Homeostasis of Body Fluids

Question 1

What are the types of body fluids

Answer 1

o Intracellular Fluid: Fluid inside cell- the cytosol
o Extracellular Fluid: Fluid outside cell
♣ Plasma: Fluid part of blood
♣ Intercellular fluid: Lymph, CSF, synovial fluid, fluid in joints etc.

Question 2

why is osmotic pressure not long lasting usually

Answer 2

Water moves easily through plasma membranes // osmotic concentration b/w Intra and extracellular fluid

Question 3

how is fluid gained in the body (2)

Answer 3

o Water taken as liquid or food

o Metabolic water (water formed as a product of cellular respiration)

Question 4

how is fluid lost from the body (4)

Answer 4

o Kidneys,
o Alimentary canal,
o Surface of lungs,
o Skin

Question 5

What are the four organs involved in excretion

Answer 5

lungs sweat glands alimentary canal kidneys

Question 6

how are the lungs excretory organs

Answer 6

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Excretion of CO2 (cannot be regulated) o	Water + CO2 produced during respiration, cannot use CO2 // carried in blood to lungs o	Water also lost from lungs through water vapour as we exhale

Question 7

how are the sweat gland excretory organs

Answer 7

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(directly linked to temperature regulation)

o water containing by-products of metabolism (salts, urea, lactic acid

Question 8

how are the alimentary canal excretory organ

Answer 8

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Excrete bile pigments (cannot be regulated) o	Bile pigments (breakdown of haemoglobin) entered canal in bile, leave with faeces o	Faeces not considered excretory as undigested food (not produced by cells)

Question 9

how are the kidney excretory organs

Answer 9

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principal excretory organ (60% of water loss) o	Responsible for maintain constant concentration of materials in body fluids o	Important waste removed= urea (produced by liver during protein breakdown)

Question 10

What are the 4 steps of the nephron in excretion

Answer 10

1. Blood enters glomerulus
2. Filtration: High blood pressure forces water and small dissolved molecules out of blood and in capsule (not large molecules)
3. Reabsorption: 90% of water and other useful substances are reabsorbed into peritubular capillaries as filtrate passes through proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct
4. Secretion: materials needed to be removed from body= secreted into kidney from peritubular capillaries

Question 11

During reabsorption, what processes of absorption occur at each part of the nephron

Answer 11

a. Reabsorption in PCT and LoH= osmosis

b. Reabsorption in DCT and collecting= active reabsorption

Question 12

What hormone is released to control water loss and what does it do

Answer 12

level of active reabsorption controlled by antidiuretic hormone (ADH)

Question 13

where is ADH produced

Answer 13

hypothalamus and released from posterior lobe

Question 14

what does ADH control

Answer 14

o permeability of walls of DCT + L.o.H
♣ High level of ADH > tubules very permeable to water
Outward flow > reduces volume > increase concentration of material remaining
♣ Low level of ADH > tubules not very permeable to water
Fluid in tubules > volume not reduced > fairly dilute

Question 15

What are the 6 feedback steps involving loss of water

Answer 15

1. concentration of water decrease (osmo pressure increase)
2. osmoecptors in hypo are stimulated
3. posterior stimulated to release ADH
4. permeabiliy increase
5. increase water reabsorbed
6. water concentration increase, osmo decrease

Question 16

What does aldosterone do in terms of water loss

Answer 16

• Secreted by adrenal cortex, (salt retaining hormone)
  o acts on kidney tubules to increase Na reabsorbed into bloodstream and increase K excreted in urine
  o Water= also reabsorbed with Na, // aldosterone= role in regulating water content

Question 17

how is aldosterone involved in blood pressure

Answer 17

• increasing water reabsorption (increase aldo)= increased blood volume > increase b.p

Question 18

what mechanism is involved in regulating water intake

Answer 18

thirst mechanism

Question 19

what causes great water loss

Answer 19

• strenuous activity= water loss high (sweat, urine, faeces, exhaled breath)

Question 20

after strenuous activity, what occurs to the movement of blood plasma

Answer 20

• plasma = lower water content + more concentrated // higher osmotic pressure
  o = water moves from intercellular fluid into plasma by osmosis
  o = intercellular fluid more concentrated and water diffused out of cells > cells start shrinking form dehydration

Question 21

What are the six feedback steps of the thirst mechanism

Answer 21

1. water concentration decreases, osmo pressure increase, mouth dry
2. osmorecptors in thirst centre in hypo detect
3. feels thirsty
4. responds by drinking
5. water drunk absorbed into blood
6. water leaves blood and into cells

Question 22

define dehydration

Answer 22

excessive loss of water and accompanying salts from the body; results when the body loses more fluid than it takes i

Question 23

symptoms of dehydration

Answer 23

o severe thirst
o low b.p.
o dizziness
o headache

Question 24

Define water intoxication

Answer 24

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caused by drinking too much water when the amount of salts (and other electrolytes in the body) is low