CHEMICAL CONTROL AND

INTEGRATION

Topics:
v Introduction
v Endocrine system and
hormones
v Human endocrine system
v The hypothalamus
v The pituitary gland
v The pineal gland
v Thyroid gland
v Parathyroid gland
v Thymus
v Adrenal gland
v Pancreas
v Testis
v Ovary
v Hormones of : heart , kidney
and gastrointestinal tract
v Mechanism of hormone action
v Summary
v Bibliography
 INTRODUCTION
One of the important differences between
living and non-living things is that the living
things are capable of actively responding to
changes in their environment. These
environmental changes act as stimuli which
bring about a definite response from the
organism.
Proper coordination of the different parts of
the body is essential for proper
responsiveness. If all the cells in the body
respond in the same way to a particular
stimulus, the organism could have elicited
only a few responses. Running, for example,
needs certain muscle fibres to contract and
certain other muscle fibres to relax at the
same time. The liver has to provide additional
materials to be oxidised in order to generate
extra energy. The cells need extra amounts of
oxygen for their metabolism which generates
additional amounts of carbon dioxide to be
breathed out. Thus, for a concerted activity or
response to be elicited there is a need for
coordination of the functions of the various
organ systems, organs, tissues and cells.

Apart from the need for coordination of the

functions of various systems in the body to
fulfill the needs of day-to-day life, there is
need for coordination of processes like
development, growth and differentiation in
an organism. In short, all activities of an
organism involve coordinated functioning of
various organs and organ systems which
enable it to respond to various external and
internal stimuli. The functions of individual
cells, tissues and organ systems in one part of
the body are related to the activities of the
other parts of the body and this requires a
form of communication among them.
Animals in general, have two different, but
related systems of internal communication: (1)
a somewhat slower system called the
endocrine system and (2) a very fast acting
nervous system. The nervous system
consisting of specialised cells called neurons,
conducts electrochemical impulses from one
part of the body to another. These impulses
are generally of brief duration and the
nervous responses are usually brief. The
endocrine system consists of specialised
glands called endocrine glands which secrete
the chemical substances called hormones. The
hormones released into the blood stream or
other body fluids reach every cell through the
circulatory system and elicit a response in
distantly located organs and tissues of the
organism. Usually the response to a hormonal
stimulus is a change in the metabolism of cells
and these changes may persist for long
periods of time.
 ENDOCRINE SYSTEM AND
HORMONES
Endocrine glands are glands of the endocrine
system that secrete their products, hormones,
directly into the blood rather than through a
duct. The major glands of the endocrine
system include the pineal gland, pituitary
gland, pancreas, ovaries, testes, thyroid
gland, parathyroid gland, hypothalamus and
adrenal glands. The hypothalamus and
pituitary gland are neuroendocrine organs.
Endocrine glands lack ducts and are hence
called ductless glands .
Their secretions are called as hormones.
Hormones are non -nutrient chemicals which
act as intercellular messengers and are
produced in trace amounts.
Hormones are our body's chemical
messengers. They travel in your bloodstream
to tissues or organs. They work slowly, over
time, and affect many different processes,
including:
Growth and development
Metabolism - how your body gets energy
from the foods you eat
Sexual function
Reproduction
Mood
 HUMAN ENDOCRINE SYSTEM
The endocrine glands and hormone
producing diffused tissues/cells located in
different parts of our body constitute the
endocrine system

The endocrine system is a chemical messenger

system consisting of hormones, the group of
glands of an organism that carry those
hormones directly into the circulatory system
to be secreted to distant target organs, and
the feedback loops of homeostasis that the
hormones drive. In humans, the major
endocrine glands are the thyroid gland and
the adrenal glands. In vertebrates, the
hypothalamus is the neural control centre for
all endocrine systems. The field of study
dealing with the endocrine system and its
disorders is endocrinology, a branch of
internal medicine

Main glands of the endocrine system. Note

that the thymus is no longer considered part
of the endocrine system, as it does not
produce hormones.
1.THE HYPOTHALAMUS
The hypothalamus is the basal part of
diencephalon, forebrain and it regulates a
wide spectrum of body functions. The
hypothalamus is a portion of the brain that
contains a number of small nuclei with a
variety of functions. One of the most
important functions of the hypothalamus is to
link the nervous system to the endocrine
system via the pituitary gland.

The hypothalamus is responsible for the

regulation of certain metabolic processes and
other activities of the autonomic nervous
system. It synthesises and secretes certain
neurohormones, called releasing hormones
or hypothalamic hormones, and these in turn
stimulate or inhibit the secretion of hormones
from the pituitary gland.

The hypothalamus controls body

temperature, hunger, important aspects of
parenting and attachment behaviours, thirst,
fatigue, sleep, and circadian rhythms.The
hormones produced by the hypothalamus
are of two types, the releasing hormones
(which stimulate secretion of pituitary
hormones) and the inhibiting hormones
(which inhibits the secretions of pituitary
hormones ).For example a hypothalamic
hormone called Gonadotrophin releasing
hormone(GnRH)stimulates the pituitary
synthesis and release of gonadotrophins.
On the other hand, somatostatin from the
hypothalamus inhibits from the
hypothalamus inhibits the release of growth
hormone from the pituitary.
2.THE PITUITARY GLAND
The pituitary gland is a tiny organ, the size of
a pea, found at the base of the brain. As the
“master gland” of the body, it produces
many hormones that travel throughout the
body, directing certain processes or
stimulating other glands to produce other
hormones.

The pituitary gland makes or stores many

different hormones. The following hormones
are made in the anterior (front part) of the
pituitary gland:
Prolactin - stimulates breast milk production
after childbirth. It also affects sex hormone
levels from ovaries in women and from
testes (testicles) in men, as well as fertility
Growth hormone (GH) - stimulates growth
in childhood and is important for maintaining
a healthy body composition and well-being
in adults. In adults, GH is important for
maintaining muscle mass and bone mass. It
also affects fat distribution in the body.
Adrenocorticotropin (ACTH) - stimulates the
production of cortisol by the adrenal glands—
small glands that sit on top of the kidneys.
Cortisol, a "stress hormone," is vital to our
survival. It helps maintain blood pressure
and blood glucose (sugar) levels, and is
produced in larger amounts when we’re
under stress—especially after illness or injury.
Thyroid-stimulating hormone (TSH) -
stimulates the thyroid gland to produce
thyroid hormones, which regulate the body's
metabolism, energy balance, growth, and
nervous system activity
Luteinizing hormone (LH) - stimulates
testosterone production in men and egg
release (ovulation) in women
Follicle-stimulating hormone (FSH) - promotes
sperm production in men and stimulates the
ovaries to produce estrogen and develop
eggs in women. LH and FSH work together to
enable normal function of the ovaries and
testes
The following hormones are stored in the
posterior (back part) of the pituitary gland:
Antidiuretic hormone (ADH) - also called
vasopressin, regulates water balance in the
body. It conserves body water by reducing
the amount of water lost in urine
Oxytocin – causes milk to flow from the
breasts in breastfeeding women, and may
also help labor to progress.

Pituitary Tumors
The most frequent type of pituitary disorder
is a pituitary gland tumor. These tumors are
fairly common in adults. They are not brain
tumors and are almost always benign (that
is, not cancer). In fact, cancerous tumors of
this sort are extremely rare.
There are two types of tumors—secretory
and non-secretory. Secretory tumors produce
too much of a hormone normally made by
the pituitary, and non-secretory tumors do
not. Both types of tumors can cause problems
if they are large and interfere with normal
function of the pituitary gland and/or nearby
structures in the brain.
The problems caused by pituitary tumors fall
into three general categories:
Hyper-secretion - too much of any hormone
in the body is caused by a secretory pituitary
tumor
Hypo-secretion- too little of any hormone in
the body can be caused by a large pituitary
tumor, which interferes with the pituitary
gland’s ability to produce hormones.
Hypo-secretion:can also result from surgery
or radiation of a tumor
Tumor mass effects - as a pituitary tumor
grows and presses against the pituitary
gland or other areas in the brain, it may
cause headaches, vision problems, or other
health effects
Injuries, certain medications, bleeding inside
or close to the pituitary, and other conditions
can also affect the pituitary gland. Loss of
normal pituitary function also can occur after
major head trauma.
3.THE PINEAL GLAND
The pineal gland is situated in the middle of
the human brain and is the major site of the
body's melatonin production.
The pineal gland is located deep in the brain
in an area called the epithalamus, where the
two halves of the brain join. In humans, this
is situated in the middle of the brain; it sits in
a groove just above the thalamus, which is
an area that co-ordinates a variety of
functions related to our senses. The pineal
gland contains high levels of calcium and can
be used by radiographers to mark the
middle of the brain in X-ray images.
The pineal gland is best known for the
secretion of the hormone melatonin, which is
released into the blood and possibly also
into the brain fluid, known as cerebrospinal
fluid. The body's daily (circadian) clock
controls the production of pineal melatonin,
so melatonin is commonly used in human
research to understand the body's biological
time. There is a rhythm to the biology of the
pineal gland. It varies with changes in day
length and this is why the pineal gland is
sometimes referred to as both an endocrine
clock and an endocrine calendar.
Melatonin secreted by the pineal gland is an
important part of the body's circadian timing
system and can synchronize daily rhythms.
There is considerable research that shows
that without the pineal gland and its
secretion of melatonin, animals are unable to
adapt physiologically to seasonal changes.
4.THYROID GLAND
The thyroid gland is an endocrine gland in
your neck. It makes two hormones that are
secreted into the blood: thyroxine (T4) and
triiodothyronine (T3). These hormones are
necessary for all the cells in your body to
work normally.

Thyroid disorders are very common and tend

mainly to occur in women, although anybody
- men, teenagers, children and babies, too -
can be affected. About one in 20 people has
some kind of thyroid disorder, which may be
temporary or permanent.

The thyroid gland lies in the front of your

neck in a position just below your Adam’s
apple. It is made up of two lobes - the right
lobe and the left lobe, each about the size of
a plum cut in half - and these two lobes are
joined by a small bridge of thyroid tissue
called the isthmus. The two lobes lie on either
side of your wind-pipe.

Function
The thyroid makes two hormones that it
secretes into the blood stream. One is called
thyroxine; this hormone contains four atoms
of iodine and is often called T4. The other is
called triiodothyronine, which contains three
atoms of iodine and is often called T3. In the
cells and tissues of the body the T4 is
converted to T3. It is the T3, derived from T4 or
secreted as T3 from the thyroid gland, which
is biologically active and influences the
activity of all the cells and tissues of your
body.
Hormones function:

The T4, or rather the T3 derived from it, and

the T3 secreted directly by the thyroid gland
influence the metabolism of your body cells.
In other words, it regulates the speed with
which your body cells work. If too much of
the thyroid hormones are secreted, the body
cells work faster than normal, and you have
hyperthyroidism. If you become
hyperthyroid because of too much secretion
of the hormones from the thyroid gland, the
increased activity of your body cells or body
organs may lead, for example, to a
quickening of your heart rate or increased
activity of your intestine so that you have
frequent bowel motions or even diarrhea.On
the other hand if too little of the thyroid
hormones are produced (known as
hypothyroidism), the cells and organs of your
body slow down. If you become
hypothyroid, your heart rate, for example,
may be slower than normal and your
intestines work sluggishly, so you become
constipated.
Thyroid disorders:
1.Hypothyroidism (under-active thyroid) - not
enough thyroxine is produced for the body’s
needs.
2.Hyperthyroidism (overactive thyroid) - too
much thyroxine is produced for the body’s
needs.
Hypothyroidism is the most common
disorder.
Controlling of thyroid gland:
There has to be some sort of mechanism that
regulates very carefully the amount of T4 and
T3 secreted by your thyroid gland so that the
right - the normal - amounts are
manufactured and delivered into the blood
stream. The mechanism is very similar to that
which regulates the central heating in a
house where there is a thermostat in, say, the
living room, which is set to a particular
temperature and which activates the gas- or
oil-fired furnace, or boiler that heats the hot
water. In the case of the thyroid the
‘thermostat’ consists of a little gland, called
the pituitary gland that lies underneath your
brain in your skull. The pituitary senses the
level of thyroid hormones in your blood
stream, just as the thermostat in your living
room senses the temperature. Under normal
circumstances, if the level drops just a little
below normal, the pituitary reacts by
secreting a hormone called the thyroid
stimulating hormone, also known as TSH,
and this hormone activates the thyroid gland
to put out more T4 and T3.
Conversely, when the thyroid hormone levels
rise above normal the ‘thermostat’ senses
this and the pituitary stops secreting TSH so
that the thyroid gland stops working so hard
and the secretion of T4 and T3 is reduced.
5.PARATHYROID GLAND

The parathyroid glands are four tiny glands,

located in the neck, that control the body’s
calcium levels. Each gland is about the size of
a grain of rice (weighs approximately 30
milligrams and is 3-4 millimeters in diameter).
The parathyroids produce a hormone called
parathyroid hormone (PTH). PTH raises the
blood calcium level by:

breaking down the bone (where most of the

body’s calcium is stored) and causing calcium
release
increasing the body’s ability to absorb
calcium from food
increasing the kidney’s ability to hold on to
calcium that would otherwise be lost in the
urine.
Normal parathyroid glands work like the
thermostat in your home to keep blood
calcium levels in a very tightly controlled
range. When the blood calcium level is too
low, PTH is released to bring the calcium
level back up to normal. When the calcium
level is normal or gets a little too high,
normal parathyroids will stop releasing PTH.
Proper calcium balance is crucial to the
normal functioning of the heart, nervous
system, kidneys, and bones. The parathyroid
glands are important in tightly controlling
calcium levels in the bloodstream. Because of
this, calcium levels are generally very stable.
This is important to ensure the nervous
system and the body’s muscles can work
properly, and also that bones remain strong.
The main target organs where parathyroid
hormone exerts its effects are the bones and
the kidneys. When calcium levels are low,
parathyroid hormone is released by the
parathyroid glands into the blood and
causes the bones to release calcium and
increase levels in the bloodstream.

6.THYMUS
The thymus is an organ that is secretory in
pre-pubescence, which earns its status as a
gland. The thymus gland has an important
role in immune function. One of its main
secretions is the hormone thymosin.
Thymosin stimulates the maturation of T cells,
which are derivatives of the white blood cells
that circulate our system. T cells “kill” or are
cytotoxic to damaged cells. The damaged
cells may be cancerous cells that have lost
the ability to stop proliferating, or even cells
infected with viruses. T cells will be able to
bind the T receptor on the target cell’s
surface that will initiate its eventual death.
The T cell’s cytotoxicity comes from the
cytokines it produces.

Despite the thymus’ essential role in immune

health, the thymus gland is not active during
our entire lifetime. In fact, it is only active
until puberty and becomes non-functional in
adulthood. But its actions are instrumental in
preventing the body from having an
autoimmune response, which is when the
immune system cannot distinguish between
itself and foreign agents. Chronic periods of
fever, fatigue, and malaise mark the lives of
patients with autoimmune diseases.
Therefore, the thymus gland is closely tied to
the lymphatic system as it is the body’s
natural defense network. The network of
vessels and tissues that make up the
lymphatic system make it possible for the
body to expel or “drain” toxins and waste
from the body
The thymus is a soft organ located behind the
breastbone and between the lungs. In
relation to the organs in the human body, the
thymus is a two-lobed structure that lies
almost on top of the heart and traces up
along the trachea. The thymus gland is more
or less triangular in shape and has two lobes
that are encased in a fibrous exterior. Its
thymic lobes are an opaque pink, and the
most superficial layer is named the cortex.
When the thymus is sliced for a histology
study, it will reveal a deeper layer called the
medulla. If the human chest were divided
into four regions, the thymus would be
located right in the center of the upper
quadrants with both clavicles beside it.
7.ADRENAL GLAND
The adrenal glands are small structures
attached to the top of each kidney.
The human body has two adrenal glands
that release chemicals called hormones into
the bloodstream. These hormones affect
many parts of the human body. The human
body has two adrenal glands and one sits on
top of each kidney. Each adrenal gland
weighs 4–5 g in an adult. Adrenals are first
detected at 6 weeks' gestation.They are also
known as Suprarenal gland.
Each adrenal gland is composed of two
distinct parts: the outer part called the
adrenal cortex and the inner adrenal
medulla. The adrenal glands secrete different
hormones which act as 'chemical
messengers'. These hormones travel in the
bloodstream and act on various body tissues
to enable them to function correctly. All
adrenocortical hormones are steroid
compounds made from cholesterol.
The adrenal cortex produces three
hormones:

•Mineralocorticoids: the most important of

which is aldosterone. This hormone helps to
maintain the body’s salt and water levels
which, in turn, regulates blood pressure.
Without aldosterone, the kidney loses
excessive amounts of salt (sodium) and,
consequently, water, leading to severe
dehydration and low blood pressure.
•Glucocorticoids: predominantly cortisol. This
hormone is involved in the response to illness
and also helps to regulate body metabolism.
Cortisol stimulates glucose production
helping the body to free up the necessary
ingredients from storage (fat and muscle) to
make glucose. Cortisol also has significant
anti-inflammatory effects.
•Adrenal androgens: male sex hormones
mainly dehydroepiandrosterone (DHEA) and
testosterone. All have weak effects, but play
a role in early development of the male sex
organs in childhood, and female body hair
during puberty.
Adrenocorticotropic hormone (ACTH),
secreted by the anterior pituitary gland,
primarily affects release of glucocorticoids
and adrenal androgens by the adrenal gland
and, to a much lesser extent, also stimulates
aldosterone release.
The adrenal medulla produces
catecholamines:
Catecholamines include adrenaline,
noradrenaline and small amounts of
dopamine – these hormones are responsible
for all the physiological characteristics of the
stress response, the so called 'fight or flight'
response.
8.PANCREAS
The pancreas is a long flattened gland
located deep in the belly (abdomen). Because
the pancreas isn’t seen or felt in our day to
day lives, most people don't know as much
about the pancreas as they do about other
parts of their bodies. The pancreas is,
however, a vital part of the digestive system
and a critical controller of blood sugar levels.

The pancreas carries out two important roles:

It makes digestive juices, which consist of

powerful enzymes. These are released into
the small bowel after meals to break down
and digest food.
It makes hormones that control blood
glucose levels.
The pancreas produces hormones in its
'endocrine' cells. These cells are gathered in
clusters known as islets of Langerhans and
monitor what is happening in the blood. They
then can release hormones directly into the
blood when necessary. In particular, they
sense when sugar (glucose) levels in the
blood rise, and as soon as this happens the
cells produce hormones, particularly insulin.
Insulin then helps the body to lower blood
glucose levels and 'store' the sugar away in
fat, muscle, liver and other body tissues
where it can be used for energy when
required.

The pancreas is very close to the stomach. As

soon as food is eaten, the pancreas releases
digestive enzymes into the bowel to break
food down. As the food is digested, and
nutrient levels in the blood rise, the pancreas
produces insulin to help the body store the
glucose (energy) away. Between meals, the
pancreas does not produce insulin and this
allows the body to gradually release stores
of energy back into the blood as they are
needed.
Glucose levels remain very stable in the
blood at all times to ensure that the body has
a steady supply of energy. This energy is
needed for metabolism, exercise and, in
particular, to fuel the parts of the brain that
'run' on glucose. This makes sure that the
body doesn't starve between meals.
PANCREATIC DISORDER:
When the cells that make insulin either stop
working altogether, or become inefficient
and do not make enough insulin, this causes
diabetes mellitus. Type 1 diabetes mellitus is
caused when the body's immune system
attacks its own cells in the islets of
Langerhans, meaning that these cells cannot
produce insulin. Type 2 diabetes mellitus is a
metabolic disorder where the body is no
longer able to produce or respond to insulin.

Some women also get diabetes temporarily

when they are pregnant. This is called
gestational diabetes. There are other rarer
forms of diabetes, some of which are
inherited. In addition, people will get
diabetes if their pancreas is taken away
surgically or damaged (for instance by
severe pancreatitis).

Very rarely, patients develop growths

(tumours) of the cells that make up the islets
of Langerhans. These may be benign tumors,
where a particular kind of cell multiplies and
makes large quantities of its hormone
whether it is needed or not. For example, if
the tumor is made of insulin-producing cells,
it is called an insulinoma. This is where too
much insulin is produced when it is not
required. This also happens with glucagon-
producing cells, or a glucagonoma, which
produces too much glucagon. These and
other hormone-producing tumors in the
pancreas are very rare, but endocrinology
specialists have important parts to play in
diagnosing patients with these tumors and
contributing to their management and
treatment.
The digestive cells of the pancreas can be
involved in the condition known as
pancreatitis. This is a very painful and serious
condition caused by digestive enzymes
'leaking' into the pancreas itself and
damaging the delicate tissues in and around
it.
It is also possible for a tumor to develop in
the part of the pancreas that produces the
digestive juices that are released into the
bowel. This condition is called pancreatic
cancer.
9.TESTIS
Testis, plural testes, also called testicle, in
animals, the organ that produces sperm, the
male reproductive cell, and androgens, the
male hormones. In humans the testes occur
as a pair of oval-shaped organs. They are
contained within the scrotal sac, which is
located directly behind the penis and in front
of the anus. In humans each testis weighs
about 25 grams (0.875 ounce) and is 4–5 cm
(1.6–2.0 inches) long and 2–3 cm (0.8–1.2 inches)
in diameter. Each is covered by a fibrous
capsule called the tunica albuginea and is
divided by partitions of fibrous tissue from
the tunica albuginea into 200 to 400 wedge-
shaped sections, or lobes.

Within each lobe are 3 to 10 coiled tubules,

called seminiferous tubules, which produce
the sperm cells. The partitions between the
lobes and the seminiferous tubules both
converge in one area near the anal side of
each testis to form what is called the
mediastinum testis. The main function of the
testes is producing and storing sperm.
They’re also crucial for creating testosterone
and other male hormones called androgens.
Testes get their ovular shape from tissues
known as lobules. Lobules are made up of
coiled tubes surrounded by dense connective
tissues. Seminiferous tubules are coiled tubes
that make up most of each testis. The cells
and tissues in the tubules are responsible for
spermatogenesis, which is the process of
creating sperm.

These tubules are lined with a layer of tissue

called the epithelium. This layer is made up
of Sertoli cells that aid in the production of
hormones that generate sperm. Among the
Sertoli cells are spermatogenic cells that
divide and become spermatozoa, or sperm
cells.
The tissues next to the tubules are called
Leydig cells. These cells produce male
hormones, such as testosterone and other
androgens.
10.OVARY
The ovaries produce and release eggs
(oocytes) into the female reproductive tract
at the mid-point of each menstrual cycle.
They also produce the female hormones
estrogen and progesterone.

The ovaries form part of the female

reproductive system. Each woman has two
ovaries. They are oval in shape, about four
centimeters long and lie on either side of the
womb (uterus) against the wall of the pelvis
in a region known as the ovarian fossa. They
are held in place by ligaments attached to
the womb but are not directly attached to the
rest of the female reproductive tract, e.g. the
fallopian tubes.

The ovaries have two main reproductive

functions in the body. They produce oocytes
(eggs) for fertilization and they produce the
reproductive hormones, estrogen and
progesterone. The function of the ovaries is
controlled by gonadotrophin-releasing
hormone released from nerve cells in the
hypothalamus which send their messages to
the pituitary gland to produce luteinizing
hormone and follicle stimulating hormone.
These are carried in the bloodstream to
control the menstrual cycle.
The ovaries release an egg (oocyte) at the
midway point of each menstrual cycle.
Usually, only a single oocyte from one ovary
is released during each menstrual cycle, with
each ovary taking an alternate turn in
releasing an egg. A female baby is born with
all the eggs that she will ever have.This is
estimated to be around two million, but by
the time a girl reaches puberty, this number
has decreased to about 400,000 eggs stored in
her ovaries. From puberty to the menopause,
only about 400–500 eggs will reach maturity,
be released from the ovary (in a process
called ovulation) and be capable of being
fertilized in the fallopian tubes/uterine
tube/oviduct of the female reproductive tract.

The ovarian phases of a 28-day menstrual

cycle. Ovulation occurs mid-cycle.
The ovarian phases of a 28-day menstrual
cycle. Ovulation occurs mid-cycle.

In the ovary, all eggs are initially enclosed in

a single layer of cells known as a follicle,
which supports the egg. Over time, these
eggs begin to mature so that one is released
from the ovary in each menstrual cycle. As
the eggs mature, the cells in the follicle
rapidly divide and the follicle becomes
progressively larger. Many follicles lose the
ability to function during this process, which
can take several months, but one dominates
in each menstrual cycle and the egg it
contains is released at ovulation.
The major hormones secreted by the ovaries
are estrogen and progesterone, both
important hormones in the menstrual cycle.
Estrogen production dominates in the first
half of the menstrual cycle before ovulation,
and progesterone production dominates
during the second half of the menstrual cycle
when the corpus lutetum has formed. Both
hormones are important in preparing the
lining of the womb for pregnancy and the
implantation of a fertilized egg, or embryo.
11.HORMONES OF:
•heart
•kidney
•gastrointestinal tract
HEART:

Atrial natriuretic factor (ANF) also called

atrial natriuretic peptide (ANP), is a peptide
hormone which is secreted by cardiac cells of
the body. Heart cells of atrial walls release
this hormone to regulate the blood volume
and arterial blood pressure. The atrial
natriuretic factor is a potential vasodilator
viz. it dilates the blood vessels to reduce the
pressure. In response to the high blood
pressure, cardiac cells secrete Atrial
natriuretic factor which leads to
vasodilatation (dilation of the blood vessels)
and thus, decreases the blood pressure.
KIDNEY:

Erythropoietin (EPO), is another peptide

hormone secreted by a non-endocrine tissue,
kidney. It is also known as hemopoietin.
Erythropoietin secreted by the
juxtaglomerular cells of the kidney which
functions by triggering the RBC production in
the bone marrow, especially when the
oxygen level in the blood reduces. The
formation of RBC is called erythropoiesis.
GASTROINTESTINAL TRACT:
Gastrin, secretin, cholecystokinin (CCK) and
gastric inhibitory peptide (GIP) are four
peptide hormones secreted by endocrine
cells of the gastrointestinal tract (GIT). These
hormones help in the digestion by
stimulating the secretion of different
enzymes and gastric juices.

Gastrin: This stimulates the release of HCl

and pepsinogen for digestion by acting on
the gastric glands.
Secretin: Secretin stimulates the exocrine
portion of the pancreas for the secretion of
water and bicarbonate ions.
Cholecystokinin: CCK stimulates the secretion
of pancreatic enzymes and bile by the
pancreas and gallbladder respectively.
Gastric inhibitory peptide: As the name
suggests, it has an inhibitory action on gastric
glands and thus inhibits the gastric secretion.
Growth factors which help in normal growth
and repairing of tissues are also a non-
endocrine tissue secretion.
MECHANISM OF HORMONE
ACTION
Hormones produce their effects on target
tissues by binding to receptor proteins
present in the target tissues.

On the basis of chemical nature,

hormones are divided into:
•.Peptide, polypeptide & protein hormones:
Insulin, Glucagon, Pituitary hormones,
Hypothalamic hormones.
•.Steroids: Cortisol, Testosterone,
Progesterone, Estrogen.
•.Iodothyronines: Thyroid hormones.
•Amino acid derivatives: Epinephrine.
Mode of Hormone Action:
Non-steroid hormones: They are amino
acid, peptides & protein hormones. As they
are water soluble & lipid insoluble, they
cannot pass through the cell membrane. So,
they act through second messengers.
Steroid hormones: They are lipid soluble, and
can pass through the cell membrane. So they
directly enter the cell. The only exception
being Thyroid hormones that are amine
derivatives but are lipid soluble.
Non-steroid Hormone Action:
These hormones produce their effect on
target tissues by binding to the receptors.
Receptors are protein molecules, specific for
a hormone.
These are extra cellular or surface receptors,
i.e., present in the cell membrane.
These hormones/ first messenger as they
cannot enter the target cell produces Second
Messengers with the help of receptors, that
regulate cell metabolism.
The second messengers are Cyclic AMP, Ca2+,
IP3 (Inositol triphosphate).
Present in the cell membrane are the
receptors, G-protein & Adenyl cyclase. The G-
proteins are associated with GDP (Guanosine
diphosphate).
The hormone forms a complex with the
receptor protein, causing a change in shape
due to which it comes in contact with G-
protein. It interacts with G-protein changing
GDP to GTP.
The G-protein now activates Adenyl cyclase
that converts ATP to Cyclic AMP (Adenosine
monophosphate).
The Cyclic AMP activates the Kinase enzyme
which triggers intracellular biochemical
changes like enzyme activation, secretion,
ion channel changes etc. These biochemical
changes result in physiological &
developmental effects.
Hormones are required in very small
amounts as a single activated molecule
produces a lot of Cyclic AMP, this is known as
Signal Amplification.
Steroid Hormone Action:
These hormones diffuse through the cell
membrane of the target cell. They either the
cytoplasm or they directly enter the nucleus.
Their receptors are intracellular.
They form a complex with the receptors.
These complexes bind to the chromosomes
and activate certain genes, thus affecting
transcription of mRNA and translation of
proteins. These proteins promote metabolic
reactions in the cell.
Actions of these hormones are slower but
they last longer.
 SUMMARY
•The hormones are chemical substances
provide chemical co-ordination, integration
and regulation in human body.
•They regulate metabolism, growth and
development of our organs.
•The pituitary gland is divided into three
major parts called as pars distalis, pars
intermedia and pars nervosa.
•The pituitary hormones regulate the growth
and development of somatic tissues and
activities of peripheral endocrine gland.
•The hormone thyrocalcitonin regulates the
calcium levels in our blood.
•Hormone thymosin play a major role in
differentiation of T-lymphocytes, which
provide cell mediated immunity.
•Adrenal medulla secretes epinephrine and
norepinephrine that increase alertness,
sweating, heartrate, cardiac output, strength
of contraction, proteolysis and lipolysis.
•Glucagon stimulates glycogenolysis and
gluconeogenesis resulting in hyperglycemia.
•The testes secrete androgens, stimulate the
development, maturation and functions of
male accessory organs.
•The ovary secretes estrogen and
progesterone.
•The gastrointestinal tract secretes gastrin,
secretin, cholecystokinin and gastric
inhibitory peptide.
 BIBLIOGRAPHY
Ø Rajkumarbiologyweebly.com
Ø Wikipedia.org
Ø Gradestack.com
Ø Excellup.com
Ø Scribd.com
Ø Courseslumenlearning.com
Ø Biologydicussion.com
Ø Ramneetkaur.com
Ø Byjus.com
Ø Endocrineweb.com
Ø Yourhormonesinfo.com
Ø Everydayhealth.com