Ch. 7 Homeostasis of Body Fluids Flashcards
What are the types of body fluids
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.
why is osmotic pressure not long lasting usually
Water moves easily through plasma membranes // osmotic concentration b/w Intra and extracellular fluid
how is fluid gained in the body (2)
o Water taken as liquid or food
o Metabolic water (water formed as a product of cellular respiration)
how is fluid lost from the body (4)
o Kidneys,
o Alimentary canal,
o Surface of lungs,
o Skin
What are the four organs involved in excretion
lungs sweat glands alimentary canal kidneys
how are the lungs excretory organs
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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
how are the sweat gland excretory organs
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(directly linked to temperature regulation)
o water containing by-products of metabolism (salts, urea, lactic acid
how are the alimentary canal excretory organ
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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)
how are the kidney excretory organs
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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)
What are the 4 steps of the nephron in excretion
- Blood enters glomerulus
- Filtration: High blood pressure forces water and small dissolved molecules out of blood and in capsule (not large molecules)
- 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
- Secretion: materials needed to be removed from body= secreted into kidney from peritubular capillaries
During reabsorption, what processes of absorption occur at each part of the nephron
a. Reabsorption in PCT and LoH= osmosis
b. Reabsorption in DCT and collecting= active reabsorption
What hormone is released to control water loss and what does it do
level of active reabsorption controlled by antidiuretic hormone (ADH)
where is ADH produced
hypothalamus and released from posterior lobe
what does ADH control
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
What are the 6 feedback steps involving loss of water
- concentration of water decrease (osmo pressure increase)
- osmoecptors in hypo are stimulated
- posterior stimulated to release ADH
- permeabiliy increase
- increase water reabsorbed
- water concentration increase, osmo decrease
What does aldosterone do in terms of water loss
- 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
how is aldosterone involved in blood pressure
- increasing water reabsorption (increase aldo)= increased blood volume > increase b.p
what mechanism is involved in regulating water intake
thirst mechanism
what causes great water loss
- strenuous activity= water loss high (sweat, urine, faeces, exhaled breath)
after strenuous activity, what occurs to the movement of blood plasma
- 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
What are the six feedback steps of the thirst mechanism
- water concentration decreases, osmo pressure increase, mouth dry
- osmorecptors in thirst centre in hypo detect
- feels thirsty
- responds by drinking
- water drunk absorbed into blood
- water leaves blood and into cells
define dehydration
excessive loss of water and accompanying salts from the body; results when the body loses more fluid than it takes i
symptoms of dehydration
o severe thirst
o low b.p.
o dizziness
o headache
Define water intoxication
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caused by drinking too much water when the amount of salts (and other electrolytes in the body) is low
