Download CLASS-X BIOLOGY EPISODE

CLASS-X
BIOLOGY
EPISODE-2
STATE SYLLABUS
COORDINATION – 2
CHEMICAL COORDINATION IN ANIMALS
Endocrine glands
The human body internally has a number of glands. Glands secrete digestive
juice, some may secrete hormones and some destroy or produce blood cells.
The glands are broadly of two types. They are 1) Endocrine and
2) Exocrine glands.
Most of the glands that secrete digestive juices are exocrine. The endocrine
glands secrete substances known as HORMONES.
What is endocrine system?
The endocrine system is defined as a system of duct less glands. The glands do
not have ducts of their own. The secretions of these glands are directly poured
into the blood to be supplied to target organ or organs.
What are the secretions of endocrine glands and what is their function?
The secretions of the endocrine glands are known as HORMONES.
What is the important function of these glands?
. Homeostasis is achieved by the nervous system and endocrine system. A
steady state functioning of the body adjusting to external stress is Homeostasis
Hormones produced in the endocrine glands work with the nervous system and
control and coordinate the activities of the body.e should note that Hormones do
not work independently.
What are the characteristics of hormones?
The characteristics are
1). Hormones are chemical regulators secreted according to environmental
changes both in or outside the body. They are information molecules. The target
organ or organs are intitiated or inhibited in their function. They are like catalysts.
2). The glands are at different locations and their target organ or organs are
different.
3). The chemical nature of hormones could be proteins or amino-acid derivatives
or steroids.
4). Due to low molecular weight they can easily diffuse into the cells.
5). Their actions are more effective in small concentrations.
1
Hence they are produced in small quantities.
6). Abnormal production of hormones can result in serious consequences to the
body.
7). An endocrine gland may even act on other endocrine gland and control its
function.
How many endocrine glands are there in a Human body? Where are they
located? What are their secretions? And what of the target organs for each of
these glands?
The principle endocrine glands in our body are
1). Pituitary
2). Thyroid
3). Parathyroid
4). Adrenal
5). Ovary
6). Testes
7). Pancreas.
Let us now study each gland.
Pituitary:- Pituitary gland is located in the brain. It is a small pea-shaped gland
hanging from the base of brain. See the image…….
This image shows the location and structure of pituitary gland.
2
This image shows the location of pituitary gland in the brain
Pituitary gland is called the “Ma ster gland” as it produces a number of hormones
which control the hormones of other endocrine glands.
Is Pituitary gland controlled in its function?
The secretions of hypothalamus to which pituitary is attached controls it. It
receives messages from brain in the form of releasing factors or neurosecretions.
What is the structure of Pituitary?
Pituitary gland has three lobes. The anterior lobe, the posterior lobe and an
intermediate lobe.
The image shows the three lobes of the gland
3
The anterior lobe produces six hormones. They are
1.Growth hormone(GH)
2.Thyroid stimulating hormone(TSH).
3.Adreno cortico Tropic hormone (ACTH).
4.Follicle stimulating hormone(FSH).
5.Luteinising hormone(LH).
6.Protaction.
The posterior lobe produces two hormones. They are
1.Vasopresine or Antidiuretic hormone(ADH).
2.Oxytocin.
Let us now examine the function of each hormone.
Anterior lobe of Pituitary Hormones and their function
1.GH or Growth hormone:a new born baby grown in a adult. How does this growth occur? What stimulates
growth?
The hormone produced in the anterior lobe of Pituitary known as somatotrophic
or growth hormone. It stimulates growth and cell metabolism.
Have you heard about very tall persons above 6’ .5” or about very short persons
about 3’ in height.
The over production or deficiency of GH causes this condition
Deficiency of GH in the early growing ages causes the condition known as
Dwarfism. These persons are very start and have stunted growth.
Over production leads to Gigantism as you can see in the image.
X 4
These persons grow to abnormal heights.
Another condition known as Acromegaly is the result of hypersecretion of GH
after a person attains adoscence i.e., after puberty. In this condition the bones of
lower jaw and limbs become abnormally long. But this person does not attain a
giant structure.
2)Thyroid stimulating Hormone (TSH) : Thyroid secretes thyroxin. The thyroid
stimulating hormone stimulates the thyroid gland to produce thyroxin. The
producing TSH by pituitary is controlled by Hypothalamus.
Hypersecretion of TSH causes thyroid atrophy.
The image shows the Thyroid Gland.
3). Adreno Cortico tropic Hormone(ACTH):ACTH stimulates the adrenal glands present on kidneys to stimulate the
production of glucocorticord and mineralocorticord hormones.
4). Follicle stimulating Hormone(FSH):The FSH stimulates the growth of graffian follidem female. In male it controls the
formation of sperms.
5
5). Luteinising Hormone(LH):- In females LH stimulates ovulation formation of
corpus leuteum and its hormones.
In male it is called Insterstitial cell stimulating hormone which is responsible for
testosterone secretion.
The secretion of the above hormones starts from Puberty. These hormones are
called Gonadotropins as their stimulating affect is on gonads.
6). Prolactin:- Prolactin is mainly responsible for enlargement of breasts in a
female during pregnancy. After the delivery of the baby this hormone control the
production of milk from mammary glands.
We have seen the six hormones secreted by the anterior lobe of pituitary. Let us
now study the two hormones secreted by the posterior lobe.
The posterior lobe of pituitary secretes
1.Vasopressin or antidiuretic hormone (ADH).
2.Oxytonin.
What are the functions of there hormones?
1). Vasopressin or ADH:Vasopressin is also called Anti diuretic hormone as it is a water retaining
hormone in the body. It maintains the electrolyte balance in the body. In
conditions of dehydration the body becomes deficient of water and the patient is
administred a large amount of electrolytes.
You must have heard of a product names “EL ECTROL”. This powder is mixed in
water and given to the patient for consumption. This liquid
replenishes the electrolytes lost by the body due to dedydration.
Deficiency of ADH lead to Diabetis insipidus due to which a person may urinate
frequently and cause excesssive thirst.
A patient tends to produce less urine when vasopressin is secreted in quantities
larger than normal.
III Intermediate lobe:- Let us now see another important structure in pituitary. An
intermediate lobe is present between the anterior and posterior lobes. It secretes
Melanocyte stimulating Hormone(MSH). This hormone stimulates the production
of a black pigment known as melanin in the skin. The pigment melanin is
responsible for the colour of the skin. It varies in the amount of its presence in
different people
6
Melanine
of different races and hence the variations in the skin colour of different races.
Example:- African – Dark skin or black skin.
Asian – Brown skin a wheatish colour.
Caucasian – High coloured skin generally referred as white skin.
Mongoloid- Like the Chinese
See the images and observe the ccolour of skin.
African
Caucasian
Indian
Mongoloid
Even intra racial variations exist to high degree of hues in skin colouras evident
from the image
7
Oxytocin:- 1).Causes contraction of uterus during child birth.
2).Controls secretion of breast milk during lactation.
This hormone is also called Birth hormone due to the above two functions.
In addition to endocrine glands the gastro-intestinal system also produces some
hormones.
Gastro intestinal mucosa present in stomach produces hormones called
GASTRIN, SECRETIN and CHOLECYSTOKININ.
The functions of which were studied in the process of digestion.
Gastrin stimulates production of gastric juice.
Secretin stimulates pancreas to produce pancreatic juice and stimulates the gall
bladder of the liver to release bile.
Control of Hormonal secretion:An endocrine gland produces hormones when it is stimulated. If gland is not
stimulated it does not produce a hormone. Thus the control is very simple.
What are Pheromones?
Pheromones are chemical substances secreted by organisms. The pheromones
are secreted by exocrine glands and released into the environment. They act as
chemical signals to other members of the species.
Let us see some examples?
One of the example is the method of population control in Honey bees.
The queen bee produces pheromones. The worker bee licks these pheromones
and spread it to other bees. This prevents maturation of their ovaries and
controls over crowding.
An ant which encounter a stressful situation produces pheromones alerting other
ants about the stressful situation.
Honey Bee
Ants
Thi image gives us a broad idea of pituitary secretions
8
9