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7/30/2019 The Mechanism of Osmoregulation
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THE MECHANISM OF
OSMOREGULATION
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OSMOREGULATION
Is the maintenance of the osmotic pressure in theblood.
Controlled by negative feedback involving the
control of water & mineral salts in the distaltubule & the collecting duct.
When the osmotic pressure in the body is high,due to little intake of water, excessive sweating or
ingestion of a large amount of salty food, theosmoreceptors in the hypothalamus isstimulated.
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Nerve impulses are generated & sent to:
the pituitary gland to stimulate it to increase the
production ofantidiuretic hormone (ADH) and the adrenal gland to reduce the production of
aldosterone transported to the kidneys.
ADH increase the permeability of the walls of thedistal convoluted tubules & the collecting duct to
reabsorbed water into the blood by osmosis.
Aldosterone causes a reduction in the absorption
in the absorption of sodium chloride.
A small volume of concentration urine is
therefore produced.
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When the osmotic pressure in the body is low
and there is too much of water in the body,ADH production is decreased & aldosterone
production is increased.
The distal convoluted tubules & collectingduct become less permeable to water &
sodium chloride is not reabsorbed.
A large volume of diluted urine is produced.
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Normal blood osmotic
pressure or correct waterpotential
Normal blood osmotic
pressurre or correct water
potential
ADH increases: Distal covoluted tubules & collecting
duct more permeable to water, causing the medulla
to absorb more water from the collecting ducts
Aldosterone decreases: More sodium chloride is
discharged
The urine produced is concentrated.
ADH decrease: Distal covoluted tubules & collecting
duct less permeable to water, causing the medulla to
absorb less water from the collecting ducts
Aldosterone increases: More sodium chloride is
absorbed
A large volume of diluted urine is produced.
ncrease
increas
Decrease
Decrease
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The Consequences of Impaired Kidney
Function
Kidney impairment is caused by poisons, kidney
diseases, high blood pressure or high blood
glucose level
Prolonged impairment results in kidney failure.
Kidney failure occurs when the nephrons are
destroyed.
Wastes products in the blood must not beallowed to accumulate as they become toxic at
the higher concentration.
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These wastes products can be removed by amachine which functions as an artificialkidney.
The machines separate the solute moleculesbased on their rate of diffusion across asemipermeable membrane. The process iscalled haemodialysis.
Patients can also choose to go through kidneytransplant.
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During haemodialysis:
the patient blood which is drawn from anartery,
is channelled into a dialysing tubing which is
semipermeable in nature,and placed into a dialysis fluid.
The dialysis fluid contains
a carefully regulated amount of dissolvedmineral salts and glucose, with a compositionsimilar to that in the blood plasma (minus thenitrogenous contents)
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A concentration gradient is set up and
nitrogenous wastes, excess mineral salts andother toxins diffuse from patients blood intothe dialysis fluid.
After a few hours,
the clean filtered blood is returned to thepatient through a vein in the same arm.
The dialysis fluid is changed regularly to
remove the wastes substances & to maintainthe diffusion gradient between the patientsblood & the dialysis fluid
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Kidney failure patients have to go through
haemodialysis for the rest of their lives.
Kidney transplant involves the replacement of
the impaired kidney with a donor kidney.
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The Regulation of Blood Sugar
(Glucose) Level
When the blood glucose level exceeds the normal
level, the B-celss in the islets of Langerhans found in
the pancreas secretes a hormone, insulininto the
blood.
Insulin converts any excess glucose into insoluble
glycogen, which is then stored in the liver & muscles.
The glucose level in the blood would then decreasethereby return returning the glucose level in the
blood to its normal level
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When the blood glucose level falls below thenormal level, the -cells of the islets of
Langerhans in the pancreas secrete another
hormone, glucagon into the blood,
which converts glycogen back to glucose,
thereby raising & returning the glucose level
in blood to its normal level
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Normal blood glucose level
(norm)
Normal blood glucose level
(norm)
Glucose Glycogen
Glucose Glycogen
Rise
Rises
Falls
Falls
insulin
glucagon
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The Regulation of Body Temperature
Regulated by balancing the heat produce fromthe metabolism inside the body against the
heat lost from the body.
S ti
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Normal Body Temperature Normal Body Temperatur
Sweating
Vasodilation
Relaxtion of the erector muscles
Reduced metabolic rate
No shiveringIncreased heat through convection, conduction &
radiation
No sweating
VasoconstrictionContractionn of the erector muscles
Increased metabolic rate
Shivering
Decreased heat through convection, conduction &
radiation
increase
increase
Decrease
Decrease
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Practising a Healthy Lifestyle
Drug abuse is the taking of drugs excessively, notunder a doctors prescription.
Drug abuse can cause high blood pressure, heartproblems, damage to liver and weaken the
immune system. Drug can also cause brain damage & mental
problem
Alcohol is depressant.
Excessive consumption of alcohol producesvomiting & breathing difficulties. The brainbecomes anaesthetised & the person becomesunconscious or coma.
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