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HOMEOSTASIS
2
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For proper metabolic
functions body requires all these conditions at particular level
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Why should the internal environment remain constant?
Let's take the example of temperature, the temperature of external environment
continuously change during the day but the enzymes work within a certain
range of temperature therefore, the living organisms must keep their internal
temperature within this range
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How body maintain homeostasis by feedback
mechanism
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(ii) Thermoregulation:
The maintenance of temperature within suitable limits where enzymes can
work optimally
(iii) Excretion:
The process where metabolic toxic waste or excess metabolic substances from
body i
...
2
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The CO2 produced in respiration utilized in photosynthesis
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At night plant only
perform respiration only CO2 is produced which is removed by the process of
diffusion through body surface
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2
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2 Removal of Extra Water
The plant store large amount of water this water can be removed from plant in
two ways i
...

(a) Transpiration
(b) Guttation

HOMEOSTASIS
Transpiration is the removal of water in the form of vapors from aerial part of
plant
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It only occurs at night when water pressure
is high in leaves and low temperature environment is present
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Plants produce some secondary products like latex, resin and gum
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Some plants produce
special types of gums for example Neem or keeker etc
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The coniferous plants
produce resins like material while the rubber plants produce latex which
removes from scare like openings
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2
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3
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Hydrophytes:
The plant which grow in fresh water; they live completely or partially n fresh
water so called totally or partially submerged plants
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·
 These plants do not contain roots or have poorly developed roots
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g water lily
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Halophytes:
They grow in sea marshes or in saltish water
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To move water from outside to
inside the plant develop following characters
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 Plants oppose salt to move outside from vacuole
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c
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They have developed root system which does not grow very deep
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d
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They grow in desert or steep slopes or
at high altitude
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HOMEOSTASIS
They have vertically growing deep root system to absorb proper amount of
water
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They have short sized leaves or leaves are modified into spines to reduce loss of
water by reducing the number of stomata
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g
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2
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According to their environment their cells require more
critical balance of water and solutes
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Osmoregulation in aquatic environment: The aquatic conditions are
classified on the basis of the concentration of salt present in it
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Animals osmoregulate differently in
both waters
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Osmoregulation in fresh water: Fresh water animals have hypertonic

conditions inside their body or cells so they always facing the problem of
flooding of H2O and loss of salts
...
Osmoregulation in marine animals
Usually marine animals have hypotonic conditions (low salt) inside the body
but some marine animals develop hypertonic (high salt) or isotonic (same salt
condition) by metabolism
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Actively get sea water and have
salt glands to increase the salt
and desalination

Eat food which contain
nitrogenous compound i
...
meat

These animals do not require
any activity to adjust their
internal osmotic condition
...
e
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Produce concentrated urine

iii
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Only arthropods, some molluscs reptiles, birds and
mammals can survive in this habitat
because:
 Their bodies are covered by exoskeleton or thick skin, which prevent loss
of water
...

 Some of them can produce water from fats catabolism with the help of
peroxisomes i
...
camel, kangaroos
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Excretion:
During metabolism living organisms catabolize protein and other nitrogen
containing compounds which produce some toxic nitrogenous compound
...
If these compound retain in the body and accumulate, they
can damage the cells or organs therefore they must be removed from the body
...

On the other hand plants metabolism is different from animal
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Carbohydrate is catabolized to produce CO2 and H2O
...
As autotrophs they
synthesize variety of compounds, so the waste products of one reaction are
utilized in other metabolic reactions as reactant and consumed
...
So the animals develop some
organs to filter the tissue fluid or blood
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Name of animal
Planaria
(Platyhelminthes)
Earthworm
(Annelids)
Cockroach
(Arthropod)
Vertebrate

Excretory
organs
Flame cells
(Protonephridia),
Excretory ducts
Metanephridia

Excretory
compound
Dilute urine
Dilute urine

Malphigian tubules Uric acid pellets
Kidneys

Source

Nh3, Urea, Uric
acid

Haemolymth
Blood

2
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The main organs which
involved in homeostasis are;
(i)
Skin: The skin is considered as the largest organ of the body,
basically functions as a protective organ as the first line of defense
but it also works efficiently as a homeostatic organ by maintaining
temperature, water and salt
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Maintenance of O2 and CO2 level, maintain rate of
respiration and continuous flow of energy
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4
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Structure of Human Skin
Human skin consists of three layers called epidermis, dermis and hypodermis
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This layer does not contain blood vessels
...

Dermis is the layer present between epidermis and hypodermis, it contains
many different structures i
...
nerves ending receptors to detect temperature
change, pain, pressure etc
...


HOMEOSTASIS
A network of arterioles is also present in the form of network, which are
involved in temperature regulation
...

Hypodermis is the inner most layer of skin containing fats which act as
insulation against loss of heat
...

2
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2
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e increase or decrease, and then Receptor send nerve impulse
to the brain
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If Body Temperature Start Rise;

(ii)

Production of sweat: The sweat gland starts to produce and secrete
sweat
...

Laying down of hairs: In hot condition, muscles which are attached

(iii)

Vasodilation: Arterioles found in the form of network in dermis, dilate

(i)

blood vessels near the surface of skin which allows more heat loss
...

In cold condition when body temperature starts decreasing;
(i)

(ii)
(iii)
(iv)

Erection of hairs: The muscles contract pulling the hairs upright and
trapping a layer of insulating air next to skin
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Vasocontraction: Narrowing of blood arteriole of dermis occur which
Decrease in sweat production: The sweat gland stops to produce
and secrete sweat, so it prevents from energy loss
...
It prevents loss through the
adipose tissue in hypodermis which works as an insulation layer
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4
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Role of lungs to keep the CO2 concentration low to certain level
Tissue/cells produce a large amount of CO2 during aerobic respiration
...
This reaction takes place
by an enzyme called carbonic anhydrase present in R
...
C
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The level of H+ in blood is
continuously monitored by special detectors (receptor) carotid bodies and aortic
bodies
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B
...
A
small amount of CO2 is also carried and dissolved in R
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C when the blood
reaches lungs these bicarbonate ions diffuse back into RBC where again
converted into carbonic acid then into CO2
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If the CO2 level increases in blood, pH of blood start increasing so that the
receptor sends a message to the control center which ultimately increases the
breathing rate to expel out the CO2 efficiently
...
4
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Role of kidney in controlling blood composition
Blood is
2O and
+
++
+
some solutes like Na , Cl , Ca , K etc
...
Liver
continuously produces urea and NH3 by breaking amino acid, we continuously
take different solute ions in our food like Na+, Ca++, K+ etc
...

2
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The kidneys lie above the waistline
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The renal artery, renal vein, nerve and ureter are connected to each kidney at
the hillus
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Urine passes through ureter to the urinary bladder
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A urethra: The urethra is a tube which comes out from the urinary bladder,
runs down and opens outside the body through urinary opening
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2
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1 Structure of a Kidney
Kidney is enclosed in a membrane called peritoneum
...
A longitudinal section of kidney shows three main parts: the cortex,
the medulla and the pelvis
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The medulla is the inner lighter portion of the kidney
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The medulla contains nephrons
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These are tiny kidney tubules where osmoregulation occurs
to produce urine
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Pelvis is a
funnel like space
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HOMEOSTASIS
2
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2 Structure of Nephron
Nephrons are the functional unit of kidney
...
Each nephron
consists of four main parts: The Bowmann's capsule, proximal convoluted
tubule, Loop of Henle, distal convoluted tubule
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Nephrons are surrounded by different blood vessels that are connected to the
renal artery and renal vein
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5
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Function of Nephron
The renal artary when enters into kidney, it divides into
millions of branches called afferent arteriole
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Each afferent arteriole further divides into numerous blood
capillaries in Bowmann's capsule with glomerulus and
collectively called Malpighian body or renal corpuscle

Blood leaving the glomerulus through afferent arteriole,
enters blood capillaries surrounding the nephron
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2
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4
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The liver stores surplus glucose of
food by converting it into glycogen and other food substances but it cannot
store the proteins
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The amino group (NH2) is removed from amino acid called deamination
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So the liver cells quickly convert
NH3 into less toxic substance urea
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A small amount of urea is also excreted in
sweat as well
...
e
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These are removed from body
with water and this mixture is called urine
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Two main processes are involved in the
formation of urine within nephron
...
It is of
two types:
(a) Ultrafiltration
(b) Selective filtration
(a) Ultra filtration
Ultrafiltration occurs at Malpighian body when the blood from afferent arteriole
enters into glomerulus located in Bowman's capsule
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Process of non-selective filtration is called ultrafiltration
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It requires some energy
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If this large amount of filtrate allowed passing out from the body as
urine, the body will dehydrate and death may occur
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(b) Selective reabsorption
Selective reabsorption occurs at Loop Of Henle and collecting duct with the
help of hormones
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e
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These solutes are reabsorbed

HOMEOSTASIS
via diffusion and active transport
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Most of the
water in the filtrate is reabsorbed by osmosis here
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Excess water, excess salts
and metabolic waste products such as urea, uric acid and creatinine pass out
of the collecting duct into the renal pelvis as a mixture called urine
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At the loop of Henle, some water is reabsorbed
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5
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Role of kidneys in osmoregulation
The water potential (capacity to loose water) of blood in the body has to be kept
constant because big and sudden change in the water potential of blood can
lead to serious problems e
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if plasma becomes very much dilute water will
enter the blood cells will swell and possibly burst
...
This control of water and salt content of the
body is known as osmoregulation
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Kidneys make sure that the concentration of blood stays more or
less constant
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6 DISORDERS OF KIDNEYS
Kidney Stone: A kidney stone is a solid mass that forms from the crystals of
calcium oxalate or Calcium Carbonate
...
These molecules separate from urine, precipitate in kidney
and deposit in the form of stone
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The little large size stone however damages the
kidney tissues; it may stick anywhere in urinary tract and cause renal failure
with pain
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The broken rudiments drain out from kidney with urine
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The large intake of water is the only measure to minimize the chances of
formation of stone in kidney
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It is mainly due to solute misbalance in blood and kidneys
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The amount of H2O is not regulated also
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(i) Kidney dialysis: Patient of kidney failure may get a kidney transplant
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If a donor is not available, the patient can be treated with dialysis
using a dialysis machine
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It helps to clean the patient's blood from metabolic waste products and toxics
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Each session lasts about 3-5 hours depending on the patient's body size and
medical condition

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