The Mechanism of Osmoregulation

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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The Mechanism of Osmoregulation

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