HOMEOSTASIS
What is homeostasis? What are the processes
involved in Homeostasis?
HOMEOSTASIS
Homeostasis
may be defined as the maintenance of the internal conditions of body at
equilibrium, despite changes in the external environment.
For
example, the core temperature of human body remains at about 37°C despite
fluctuations in the surrounding air temperature.
PROCESSES OF HOMEOSTASIS
The
following are some process of homeostasis.
1. Osmoregulation
It is the maintenance of the amounts of water and salts in
body fluids (i.e. blood and tissue fluids).
2. Thermoregulation
The maintenance of internal body temperature is called
thermoregulation.
3. Excretion
In this process, the metabolic wastes are eliminated from
body to maintain the internal conditions at equilibrium.
|
HOMEOSTASIS IN ANIMALS |
How does the removal of extra water take
place in plants?
METHODS OF REMOVAL OF
WATER (IN PLANTS)
There
are two methods of removal of extra water in plants, which are:
a. Transpiration
b. Guttation
TRANSPIRATION
It
is the removal of excess water in the form of vapors from the aerial parts of
plant which occurs only in the daytime.
GUTTATION
Guttation
is the removal of water in the form of liquid through special pores called
hydathodes is called Guttation. It occurs in night time only.
Name the types of plants on the basis of
their habitats.
TYPES OF PLANTS ON THE
BASIS OF HABITAT
On
the basis of habitat or conditions of water and salt, there are four different
types of plants.
i.
Hydrophytes
ii.
Halophytes
iii.
Mesophytes
iv.
Xerophytes
What are the characteristic features of
Hydrophytes?
HYDROPHYTES
Hydrophytes
are the plants which live completely or partially submerged in freshwater.
The
characteristic features of Hydrophytes are:
·
They
don’t have roots.
·
They
may have thin and spongy tissues in leaves and stems.
·
They
have developed mechanisms for the removal of extra water from their cells.
·
They
have broad leaves with a large number of stomata on their upper surfaces.
·
The
most common example of such plants is water lily, hydrilla etc.
What are the characteristic features of Halophytes?
HALOPHYTES
Halophytes
live in sea waters and are adapted to salty environments. Salts enter in the
bodies of such plants due to their higher concentration in sea water which is
not suitable.
The
characteristic features of Hydrophytes are:
·
Halophytes
have salt glands where plant store salts by taking it through active transport.
·
Plants
oppose salt to move outside from vacuole.
·
Example
includes:
What are the characteristic features of Xerophytes?
XEROPHYTES
Such
plants live in dry environments where quantity is very low. They grow in desert
or at high altitude. To conserve water, they have adapted following features:
·
They
possess thick, waxy cuticle over their epidermis to reduce water loss from internal
tissues.
·
They have less number of stomata to reduce the
rate of transpiration.
·
Such
plants have deep roots to absorb maximum water from soil.
·
Some
xerophytes have special parenchyma cells in stems or roots in which they store
large quantities of water.
·
Cacti
(Singular Cactus) are the common examples of such plants.
What are the characteristic features of Mesophytes?
MESOPHYTES
Mesophytes
are the plants that grow in moderate water containing soil. They have following
features:
·
They
have well developed root system which does not grow very deep.
·
They
have moderate sized leaves.
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HOMEOSTASIS IN ANIMALS |
Describe Osmoregulation in aquatic
environment.
OSMOREGULATION IN
AQUATIC ENVIRONMENT
The
aquatic conditions are classified on the basis of salt concentration present in
it.
i.
The
water which contains very low amount of salt is called fresh water.
ii.
The
water which contains very high amount of salt is called marine water.
Osmoregulation
in fresh water
Fresh
animals have hypertonic conditions inside their body or cells so they always
face the problem of flooding of water and loss of salts.
Such
animals are further categorized on the basis of cell.
Unicellular
organisms
Such
animals pump out excess water via contractile vacuole.
For
instance; Amoeba, Paramecium etc.
Multicellular
organisms
Such
organisms pump out excess water by producing dilute urine.
Osmoregulation
in marine animals
Marine
animals have hypotonic conditions inside the body but some marine animals
develop hypertonic or isotonic by metabolism.
On
the basis of salts, there are following three types of fishes.
|
Bony fish |
Cartilaginous fish |
Osmoconformer |
|
Have
low salt inside their bodies |
Have
high salt by storing urea inside |
Have
equal amount of salt |
|
Contain
salt glands |
Eat
food that contain nitrogenous compounds |
No
particular activity to adjust internal environment. |
Describe Osmoregulation in terrestrial
animals.
Osmoregulation
in terrestrial animals
It
is the harshest environment for living organisms because of direct exposure of
heat, excess loss of water occurs that results in dehydration. Following are
the species that can bear such habitat:
·
Arthropods
·
Molluscs
·
Reptiles
·
Birds
·
Mammals
Aforementioned
species can survive the terrestrial habitats because:
·
Bodies
are covered by exoskeleton
·
They
conserve water by reabsorption in kidneys and rectum
·
Continuously
water drinking and consumption of watery foods.
Define Excretion.
EXCRETION
The
removal of nitrogenous wastes from the body is called excretion.
During
metabolism, living organisms catabolize protein and other nitrogen containing compounds
which produce nitrogenous wastes. The removal of this waste is called
excretion.
Name the excretory organs, excretory
compounds and sources of following organisms.
|
Organism |
Excretory organ |
Excretory compound |
Source |
|
Planaria (Platyhelminthes) |
Flame cells (Protonephridia), Excretory ducts. |
Dilute urine |
Tissue fluid |
|
Earthworms (Annelids) |
Metanephridia |
Dilute urine |
Coelomic fluid |
|
Cockroach (Arthropod) |
Malpighian tubule |
Uric acid pellets |
Haemolymph |
|
Vertebrate |
Kidneys |
NH3, urea,
uric acid |
Blood |
HOMEOSTASIS IN MAN
Name the organs involved in homeostasis.
The
main organs which involved in homeostasis are:
a. Skin
b. Lungs
c. Kidneys
What is skin? Describe the functions of
skin.
SKIN
Skin
is considered as the largest organ of the body. It consists of two layers i.e.
epidermis and dermis. Epidermis is the outer protective layer without blood
vessels while dermis is the inner layer containing blood vessels, sensory nerve
endings, sweat and oil glands, hairs and fat cells. It is considered as the
first line of defense because:
·
Skin
performs important role in the regulation of body temperature.
·
Skin
helps in providing cooling effect when sweat is produced by sweat glands and
excess body heat escapes through evaporation.
·
Metabolic
wastes such as excess water, salts, urea and uric acid are also removed in
sweat.
Q. Describe the structure of Skin.
STRUCTURE
Human
skin consists of three layers called epidermis, dermis and hypodermis.
Epidermis
·
Epidermis
is the outer layer of skin made up of keratin protein.
·
It
does not contain blood vessels.
·
It
prevents water loss from the body.
Dermis
It
is the intermediate layer between epidermis and hypodermis. Dermis is
responsible to maintain the following functions.
·
It
contains many different structures i.e. nerve endings receptors to detect
temperature change, pain, pressure etc.
·
Dermis
is also responsible to secrete sweat.
·
It
contains hair follicles and sebaceous glands which secrete oily sebum.
·
It
is responsible to maintain temperature.
Hypodermis
It
is the most inner layer of the skin that contains fats and act as insulating
agent to prevent loss of heat.
It
also stores energy.
Describe the role of skin in regulation of
body temperature.
ROLE OF SKIN IN
REGULATING BODY TEMPERATURE
The
skin is responsible to maintain the body temperature by feedback mechanism. When
the receptor in skin detects change in temperature from mean point (37oC)
i.e. increase or decrease the receptor send nerve impulse to the brain to
regulate the body temperature.
IF BODY TEMPERATURE
RISES
If
body temperature rises following changes occurs.
·
Sweat
production
·
Laying
down of hairs
·
Vasodilation
SWEAT PRODUCTION
The
sweat accumulates at the surface of skin which evaporates with heat energy to
cool down the body temperature.
LAYING DOWN OF HAIR
In
hot environment, the muscles which are attached with the hair relax which
allows hair to lie flat against the surface of the skin.
VASODILATION
Arterioles
dilates (became wide) which increase the flow of blood as well as it brings the
blood vessels near the surface of the skin which allow more heat loss.
IF BODY TEMPERATURE
DECREASES
If
body temperature decreases, following changes takes place:
·
Erection
of hairs,
·
Vasoconstriction,
·
Decrease
sweats production.
ERECTION OF HAIRS
The
muscles contract pulling the hairs upright and trapping a layer of insulating
air next to the skin to maintain the body temperature.
VASOCONSTRICTION
Narrowing
of blood arterioles of dermis occur which reduces the blood flow in capillaries
of skin so less heat is lost.
DECREASE SWEAT
PRODUCTION
The
sweat gland stops to produce and secrete sweat, so it prevent from energy loss.
Describe the role of Lungs to keep CO2 concentration
low.
ROLE OF CO2
During
aerobic respiration, a large amount of CO2 is produced by the cells.
When the blood passes from these cells, the CO2 diffuses into the
blood via capillaries where it reacts with water to form carbonic acid in the
presence of carbonic anhydrase, present in RBCs.
The
carbonic acid dissociates into H+ and HCO3-
ions. Most of the bicarbonates diffuse out from RBCs to blood plasma. A small
amount of CO2 is also carried and dissolved in RBCs when the blood
reaches lungs these bicarbonates diffuses back into RBCs where again converted
into carbonic acid then into CO2. The CO2 diffuses into
alveoli where from it is expelled out when breathing.
Name the organs that composed the human
urinary system.
HUMAN URINARY SYSTEM
The
human Urinary system is composed of the following organs.
·
A
pair of kidneys,
·
A
pair of ureter,
·
A
urinary bladder,
·
A
urethra.
Describe the structure of Kidney.
STRUCTURE OF KIDNEY
Kidney is enclosed in a membrane called
peritoneum, surrounded by peritoneal membrane which is filled with peritoneal
fluid.
The
longitudinal section of kidney shows three main parts which are cortex, medulla
and the pelvis.
·
Cortex
is the outer part which is covered and protected by a fibrous capsule.
·
Medulla
is the inner portion which contains the conical projection i.e. renal pyramids;
the human Kidneys contain 12-16 pyramids. It also contains Nephrons which are
tiny kidney tubules where Osmoregulation occurs to produce urine.
·
The
kidneys are connected to the ureter at pelvis. It is the enlarged portion of
ureter inside the kidney.
Describe the structure of Nephron.
STRUCTURE OF NEPHRON
Each
kidney contains more than one million nephrons, which are microscopic urinary
tubules.
Each
nephron consists of four main parts:
i.
The
Bowman’s capsule,
ii.
Proximal
convoluted tubule,
iii.
Loop
of Henle,
iv.
Distal
convoluted tubule.
The
renal artery has many branches called afferent arterioles inside kidneys. Blood
enters into the renal artery goes through the arterioles. Afferent arterioles
are collectively known as glomerulus, when enters into Bowman’s capsule.
Glomerulus
and Bowman’s capsule is collectively called as Malpighian tubule.
Blood
leaves the glomerulus through efferent arteriole. The surrounding blood
capillaries of loop of Henle form a branch called renal vein.
Describe the formation of urea in kidneys.
UREA FORMATION
Formation
of urea takes place within the liver cells. The amino group (NH2) is
removed from amino acid as the excessive amino acids cannot be broken down by
liver itself, this process is called deamination. This NH2 group is
converted into ammonia (NH3) which is very poisonous. So the liver
cells quickly convert NH3 into urea, which is less toxic.
This
urea is carried by blood to kidneys and excretes out in the form of urine.
What is urine?
URINE
Excess
mineral salt and nitrogenous waste products i.e. urea, creatinine and uric acid
are removed from body with water and this mixture is called urine.
Describe the process of urine formation in
man.
Two
main processes which are involved in the formation of urine are:
i.
Filtration
ii.
Re-absorption
FILTRATION
It
is the process of taking out material from blood. It is of two types:
(a)
Ultra
filtration (b) Selective filtration
Ultra
filtration
Ultra
filtration occurs at Malpighian body when the blood from afferent arteriole
enters into glomerulus located in Bowman's capsule. Most of the blood plasma is
forced out of the glomerulus blood capillaries into Bowman's capsule without
any selection. Process of non-selective filtration is called ultra filtration.
Selective
filtration
Selective
filtration occurs at proximal and distal convoluted tubule when blood flows
into peritubular capillaries, the remaining amount of urea filter out from
blood by active transport. It requires some energy.
REABSORPTION
To
prevent the loss of huge amount of water and useful salts, nephron reabsorbs
useful substances and excessive water into the blood stream by:
a.
Non
selective reabsorption
b.
Selective
reabsorption
NON SELECTIUVE
REABSORPTION
It
occurs at distal and proximal convulated tubules without any secretions.
SELECTIVE REABSORPTION
It
occurs at loop of Henle and collecting duct by the help of hormones (ADH) and
(PTH).
What do you know about kidney stones?
KIDNEY STONES
A
solid mass that forms from the crystals of calcium oxalate or Calcium Carbonate
is called kidney stone.
These
molecules separate from urine, precipitate in kidney and deposit in the form of
stone.
·
If
the stones are not hard, they can be passed out via urine.
·
The
little large size stone however damages the kidney tissues, it may stuck
anywhere in urinary tract and cause renal failure with pain.
MANAGEMENT
·
Lithotripsy
What is kidney failure?
KIDNEY FAILURE
When
the kidney stops working, it is called kidney failure.
CAUSES
·
Low
water and fibers intake
·
Disbalance
of solute
MANAGEMENT
·
Dialysis
·
Transplantation
Describe the mechanism of kidney dialysis.
DIALYSIS
