Chemical co-ordination n integration by BNP

CHEMICAL CO-ORDINATION
AND INTEGRATION
By Biswanath prusty

Have you ever wondered how the various organs perform their respective functions
in harmony and at the appropriate time? The nervous system and the endocrine system
ensure that the body works in a controlled and coordinated manner. The nervous system
includes the brain, spinal cord, sense organs and nerves while the endocrine system operates
through certain chemicals called hormones which are produced by specialized glands and are
secreted directly into the blood. The nervous system works with the endocrine system to
communicate, integrate and coordinate the functions of various organs and systems in our
body.
Co-ordination of activities of different parts of the body of a multicellular organism
is an important part of life. The Nervous system and the Endocrine system bring such
coordination in the body.
The two Systems are integrated and control different vital activities of the body. The
endocrine glands secrete hormones. Hormones act as chemical messengers and the co-
ordination achieved by them is called chemical co-ordination.
The nervous system and the endocrine system work together as a team to control
and coordinate all our activities such as our physical actions, our thinking processes and our
emotional behaviour.

Two major coordinating systems of the body are Exocrine and endocrine systems.
• Exocrine system consists of all those glands of the body which possess a duct for the
delivery of their secretions to the target organs. These glands are called Exocrine glands.
E.g. Sweat glands, salivary glands, tear glands.
• Endocrine system consists of all those ductless glands of the body which release their
secretions directly into the blood stream. These glands are called Endocrine glands. E.g.
Pituitary gland, pineal gland, thyroid gland, adrenal glands, parathyroid, thymus, pancreas
and gonads.
A study of endocrine glands and their secretions is called Endocrinology.
• Endocrine glands are also called ductless glands and their secretions are called Hormones.
Hormones are chemical messengers that are transported by blood or (lymph) from the
endocrine glands to the cells or organs, on which they act, called Target cells or organs.
Increase in secretion from an endocrine gland than normal is called hyper secretion.
Decrease in secretion from an endocrine gland than normal is called hypo secretion.
Both these conditions result in disorders.

❖ It includes endocrine glands and their
secretions (hormones).
❖ Hormones are non-nutrient chemicals that
act as intercellular messengers and are
produced in trace amounts.
• Hormones play an important role in control,
coordination and regulation of the
functioning of tissues, organs and systems
in the body. Well harmonized mechanisms
regulate the release of very precise
quantities of hormones to achieve optimal
functioning of the human body.
• The endocrine system is responsible for the
chemical coordination in our body.
ENDOCRINE SYSTEM

ENDO
CRINE
GLAN
DS
Hypothalamus
Pituitary
Pineal
Thyroid
Parathyroid
Thymus
Adrenal
Pancreas
Gonads
HUMAN ENDOCRINE SYSTEM

• Neurosecretory cells (nuclei) of
hypothalamus secrete the
following types of hormones:
• Releasing hormones
• Inhibiting hormones
• Oxytocin & vasopressin
HUMAN ENDOCRINE SYSTEM 1. HYPOTHALAMUS

• Releasing hormones: Stimulate
secretion of pituitary hormones. E.g.
gonadotropin releasing hormone (GnRH)
stimulates release of gonadotrophins from
pituitary.
• Inhibiting hormones: Inhibit secretion
of pituitary hormones. E.g. Somatostatin
inhibits release of growth hormone from
pituitary.
• Oxytocin & vasopressin: These are
transported axonally and stored in
pituitary.
HUMAN ENDOCRINE SYSTEM 1. HYPOTHALAMUS

It is located on floor of diencephalon and has neurosecretory cells which produce neurohormones. Some of them are poured into
adenohypophysis (anterior and intermediate pituitary) through hypophyseal portal system while two hormones (oxytocin and
ADH) are directly taken by nerve cells into neurohypophysis (posterior pituitary) by infundibulum.
Hormones poured in adeno hypophysis function as releasing or inhibiting hormones They are peptide in nature.
Names and major function of peptide hormones presented below,
• Thyrotropin Releasing Hormone (TRH)
Stimulates anterior pituitary to secrete thyrotropin or thyroid stimulating hormone.
• Adrenocorticotropin Releasing Hormone (ACTH)
Stimulates anterior pituitary to secrete adrenocorticotropin hormone.
• Gonadotropin Releasing Hormone (GnRH)
Stimulates secretion of gonadotropins by adenohypophysis which are of two type FSH and LH.
• Somatotropin Releasing Hormone or Growth Hormone Releasing Hormone (SRH or GHRH)
Stimulates production of growth hormone or somatotrophic hormone by anterior pituitary.
• Somatostatin or Growth Hormone Inhibiting Hormone (GHIH)
It inhibits adenohypophysis to secrete growth hormone.
• Prolactin Releasing Hormone (PRH)
The anterior pituitary is stimulated to secrete prolactin.
• Prolactin Inhibiting Hormone (PIH)
The hypothalamic hormone stops synthesis of PRH by anterior pituitary. Hormone prolactin is under predominant inhibitory
control through Neurotransmitter dopamine
• Melanocyte Stimulating Hormone Releasing Hormone (mSH - RH)
The releasing hormone induces intermediate pituitary to secrete mSH
• Melanocyte Stimulating Hormone Inhibiting Hormone (mSH-IH)
The inhibiting hormone stops synthesis of mSH.

• It is located in a bony cavity called sella tursica / hypophyseal fossa.
• It is attached to hypothalamus by a stalk / infundibulum.
• It is called master gland due to it regulate most of the endocrine gland.
HUMAN ENDOCRINE SYSTEM 2. PITUITARY GLAND

Parts of Pituitary
Adenohypophysis
(anterior
pituitary)
Pars
distalis
Pars
intermedia
Neurohypophysis
(posterior
pituitary)
Pars
tuberalis

It produces the following hormones:
1. Somatotropin or Growth hormone (GH)
(STH).
2. Prolactin (PRL).
3. Thyroid stimulating hormone (TSH).
4. Adrenocorticotrophic hormone (ACTH).
5. Follicle stimulating hormone (FSH).
6. Luteinizing hormone (LH) (ICSH).
i. Pars distalis (Anterior pituitary)

1. Somatotropin or Growth
hormone (GH)
For body growth, protein, fat and carbohydrate
metabolism.
• Over-secretion/Hypersecretion of this hormone
during the period of skeletal growth causes
Gigantism (abnormal growth) characterized by
excessive growth of bones, with the
enlargement of internal organs.
• Hyposecretion of GH causes Dwarfism (stunted
growth).
Dwarfism and Gigantism

1. Somatotropin or Growth
hormone (GH)
• Over-secretion of GH in adults (mainly
in middle age) causes Acromegaly
(severe disfigurement especially of
face). It leads to serious complications
and premature death Here, the bones
become abnormally thick.
• Early diagnosis of the disease is difficult.
It may be undetected for many years.
Acromegaly

2. Prolactin (PRL): Regulates growth of mammary
glands and milk production.
3. Thyroid stimulating hormone (TSH): Stimulates
secretion of thyroid hormones from thyroid
gland.
4. Adrenocorticotrophic hormone (ACTH): Stimulates the
synthesis and secretion of steroid hormones
(glucocorticoids) from adrenal cortex. It increases the
concentration of cholesterol and steroid with in the
gland and increases the output of steroid hormones,
especially cortisol. Hyposecretion causes acute psoriasis
and dermatitis. Hypersecretion causes cushing diseases
like obesity, skin pigmentation, excessive hair,
demineralization of bone.
Mammary gland Thyroid gland

5.Follicle stimulating hormone
(FSH)
• Stimulates gonadal activity.
• In males, FSH & androgens regulate
sperm formation (spermatogenesis).
• In females, FSH stimulates the
growth and development of the
ovarian follicles.

6. Luteinizing hormone (LH) or
interstitial cell stimulating
hormone (ICSH)
• Stimulate gonadal activity.
• In males, it stimulates the synthesis
and secretion of androgens from
testis.
• In females, it induces ovulation and
maintains the corpus luteum.

• In human, it is almost merged with
pars distalis.
• It produces Melanocyte stimulating
hormone (MSH).
• MSH acts on melanocytes to regulate
skin pigmentation.
ii. Pars Intermedia

• It stores Oxytocin & Vasopressin (hormones of
hypothalamus).
• The neurohypophysis Is formed by the posterior lobe of
pituitary gland. Its cells are called pituicytes.
Oxytocin
• Contracts the smooth muscles.
• In females, it stimulates contraction of uterus at the time
of child birth, and milk ejection from the mammary gland.
Vasopressin or ADH
• It increases reabsorption of water in kidneys resulting in
the decrease in the rate of urine production.
• It reduces heart rate and helps in micturition.
• Hyposecretion of this hormone causes diabetes insipidus.
(Neuro-
hypophysis)
b. Neurohypophysis (posterior pituitary)

Thyroid gland
The thyroid gland is situated in the neck in front of the larynx and
trachea at the level of the 5th, 6th and 7th cervical and 1st thoracic
vertebrae. It is a highly vascular gland that weighs about 25 g and is
surrounded by a fibrous capsule. It resembles a butterfly in shape,
consisting of two lobes, one on either side of the thyroid cartilage
and upper cartilaginous rings of the trachea. The lobes are joined by
a narrow isthmus, lying in front of the trachea.
The lobes are roughly cone-shaped, about 5 cm long and 3 cm wide.
The thyroid gland sits in the throat region, just below the larynx,
served by large arteries with many branches and a dense network of
capillaries.
It’s a butterflies shaped largest endocrine gland.
The hormones it secretes, travel in the bloodstream throughout
the body to:
Increase metabolism
Regulate glucose use
Protein synthesis
Nervous system development.
It also releases Calcitonin, which helps maintain blood calcium
homeostasis by causing calcium to be removed from the blood and
deposited into bones when blood (calcium) levels are too high.

It consists of two lobes which are connected by an isthmus.
The microscopic structure of the thyroid gland shows thyroid
follicles filled with a homogenous material called colloid.
Small amount of loose connective tissue from stroma of the gland.
Beside containing blood capillaries, the stroma contain small
cluster of specialized parafollicular cell.
Thyroid hormones are produced by the secretory cells lining the
follicle and stored in the colloid until needed. So each follicle
accumulates a storage form of the circulating thyroid.

When the thyroid gland becomes overactive and produces more
thyroid hormone than is necessary for optimal functioning, the
condition is called Hyperthyroidism.
When the thyroid gland becomes underactive and produces less
thyroid hormone than is necessary, the condition is called
Hypothyroidism.
Cretinism is a condition of severely stunted physical and mental
growth due to untreated congenital deficiency of thyroid hormone
(hypothyroidism) or from prolonged nutritional deficiency of iodine.
Goiter is a disease of the thyroid gland characterized by an
enlargement of the gland, visible externally as a swelling on the front
of the neck. Simple goitre is caused by a deficiency of iodine in the
diet. (Fig. 23.11)
Functions of Thyroid Hormones:
• Increases the metabolic rate of the body and enhance heat
production and maintain BMR (basal metabolic rate).
• Promote growth of body tissues and mental faculties.
• Stimulates body differentiation.

PARATHYROID GLANDS
There are four small parathyroid glands, two embedded in the posterior
surface of each lobe of the thyroid gland. They are surrounded by fine
connective tissue capsules. The cells forming the glands are spherical in
shape and are arranged in columns with channels containing blood
between them.
Function
The parathyroid glands secrete parathyroid hormone (PTH,
parathormone). Secretion is regulated by the blood level of calcium.
When this falls, secretion of PTH is increased and vice versa. The main
function of PTH is to increase the blood calcium level when it is low.
This is achieved by indirectly increasing the amount of calcium absorbed
from the small intestine and reabsorbed from the renal tubules. If these
sources provide inadequate supplies then PTH stimulates osteoclasts
(bone-destroying cells) and resorption of calcium from bones.
Parathormone and calcitonin from the thyroid gland act in a
complementary manner to maintain blood
calcium levels within the normal range. This is needed for:
• muscle contraction
• blood clotting
• nerve impulse transmission.

THYMUS GLAND
The thymus gland is located in the upper
part of the thorax near the heart. It is a soft
pinkish, bilobed mass of lymphoid tissue. It
is a prominent gland at the time of birth but
it gradually atrophies in the adult.
Hassall's corpuscles are spherical or oval
bodies present in thymus. They are
phagocytic in function.
Thymus secretes a hormone, thymosin
which stimulates the development and
differentiation of T-cells/ T-lymphocyte,
thereby increasing immunity.

ADRENAL (SUPRARENAL) GLANDS
There are two adrenal glands, Each one situated on the upper pole of each kidney enclosed
within the renal fascia. They are about 4 cm long and 3 cm thick.
The arterial blood supply to the glands is by branches from the abdominal aorta and renal
arteries.
The glands are composed of two parts which have different structures and functions. The outer
part is the cortex and the inner part the medulla. The adrenal cortex is essential to life but the
medulla is not.
Adrenal cortex
The adrenal cortex produces three groups of steroid hormones from cholesterol. They are
collectively called adrenocorticocoids (corticosteroids, corticoids). They are:
• glucocorticoids
• mineralocorticoids
• sex hormones (androgens).
The hormones in each group have different characteristic actions but due to their structural
similarity their actions may overlap.

A. Glucocorticoids
Cortisol and corticosterone are the main glucocorticoids. They are essential for life. Their secretion is stimulated by
Adrenocorticotrophic hormone from the anterior pituitary and by stress.
Glucocorticoids have widespread effects on body system. The main functions include the regulation of carbohydrate
metabolism, formation and storage of glycogen, promotion of sodium and water reabsorption from the renal tubules.
They are released during allergic reactions and are secreted by zona fasiculata, middle Zone of adrenal cortex.
B. Mineralocorticoids
Aldosterone is the main mineralocorticoid. It is secreted by zona glomerulosa, outer zone of adrenal cortex.
Its functions are associated with maintenance of the electrolyte balance in the body.
The amount of Aldosterone produced is influenced by the sodium level in blood. If there is a fall in the sodium blood level,
more aldosterone is secreted and more sodium is reabsorbed.
C. Sexcorticoids (androgen)
Zona reticularis is the inner zone which secretes sexcorticoids. They are associated with deposition ot protein in muscles and
retention of nitrogen.
The hormones are secreted as DHEA (Dehydroxy epiandrosterone), which is precursor of both testosterone and estrogens.
Adrenal medulla
The medulla is completely surrounded by the cortex. It develops from nervous tissue in the
embryo and is part of the sympathetic division of the autonomic nervous system. It is stimulated
by its extensive sympathetic nerve supply to produce the hormones adrenaline and nor
adrenaline.

Adrenaline and noradrenaline
Noradrenaline is the postganglionic neurotransmitter of the sympathetic division of the autonomic nervous system. Adrenaline and
some noradrenaline are released into the blood from the adrenal medulla during stimulation of the sympathetic nervous system. They
are structurally very similar and this explains their similar effects. Together they potentiate the fight or flight response after initial
sympathetic stimulation by:
• increasing heart rate
• increasing blood pressure
• diverting blood to essential organs including the heart, brain and skeletal muscles by dilating their blood vessels and constricting
those of less essential organs, such as the skin
• increasing metabolic rate
• dilating the pupils.
Adrenaline has a greater effect on the heart and metabolic processes whereas noradrenaline has more influence on blood vessels.
Hyposecretion of glucocorticoids i.e. Inadequate secretion of cortisol causes diminished gluconeogenesis, low blood glucose,
muscle weakness and pallor.
Hypersecretion of mineralocorticoids i.e. excess aldosterone affects kidney function, causing excessive reabsorption of sodium
chloride and water causing hypertension, and excessive excretion of potassium causing hypokalemia, which leads to cardiac
arrhythmia and muscle weakness.
Hyposecretion of mineralocorticoids: Hypoaldosteronism results in failure of kidneys to regulate sodium, potassium and water
excretion, leading to deficiency of blood sodium and potassium, excessive dehydration, low blood volume and low blood pressure.
Addison's disease is due to the hypo secretion of all adrenal cortex hormones. There is electrolyte upset.
Hypersecretion of sexcorticoids: Virilism is due to excessive secretion of sex corticoids caused by adrenal tumour which resuits in
appearance of male secondary characters in females, like male voice, beard moustaches.

PANCREATIC ISLETS
The cells which make up the pancreatic islets (islets of Langerhans) are found in clusters irregularly
distributed throughout the substance of the pancreas. Unlike the exocrine pancreas, which produces
pancreatic juice, there are no ducts leading from the clusters of islet cells.
Pancreatic hormones are secreted directly into the bloodstream and circulate throughout the body.
There are four main types of cells in the pancreatic islets:
• α(alpha) cells that secrete glucagon (15%)
• β(beta) cells that secrete insulin (65%)
• ƃ (delta) cells that secrete somatostatin (5%)
• F-cells constitute about 15% of islets and produce somastostatin.

Glucagon stimulates the liver to convert stored glycogen into glucose in the blood. Level of
Glucagon is controlled by feedback mechanism in accordance with the level of glucose in the
blood.
When the blood sugar rises, the secretion of glucagon is suppressed and when it drops the
secretion of glucagon is stimulated.
Glucagon is also called an 'anti-insulin' hormone.
Insulin
is antagonistic to glucagon.
Insulin regulates the level of glucose in the blood by feedback mechanism.
When the blood sugar level drops, the secretion of insulin is suppressed. When the blood sugar
level increases, the secretion of insulin is stimulated.
It promotes protein. synthesis in tissue from amino acids and reduces catabolism of proteins. It is
an anabolic hormone.
It increases the synthesis of tat in the adipose tissue from fatty acids and reduces the breakdown
and oxidation of fat.
Somatostatin suppresses the release of hormones from the pancreas and digestive tract.
Pancreatic polypeptide inhibits the release of digestive secretion of the pancreas the most
common endocrine disorder of the pancreas is the diabetes mellitus (hyperglycemia).

Gonads (Ovarles and Testes)
Gonads are the organs that produce gametes, sperm in males and oocytes in females.
Gonads also secrete hormones.
1. Ovaries
Ovaries are paired oval bodies which are located in the female pelvic cavity.
Hormones produced by Ovaries include:
(1) Estrogen and progesterone
Estradiol and estrone are two estrogens. These female sex hormones, along with FSH and LH from the anterior pituitary
perform following functions:
• They regulate female reproductive cycle. Maintain pregnancy.
• Prepare mammary glands for lactation.
• Promote development and maintenance of female secondary sex characteristics.
(2) Relaxin
During pregnancy, ovaries and placenta produce a hormone relaxin. It increases the flexibility of pubis symphysis during
pregnancy and helps to dilate uterine cervix during labour and delivery.
(3) Inhibin
This hormone released from ovaries inhibits the secretion of FSH from anterior pituitarv.
2. Testis
The male gonads, the testis are oval glands that lie in the scrotum.
Male sex hormones or androgens are produced by testis.
They are secreted by leydig cells or interstitial cells found in the connective tissue around seminiferous tubules.

Androgen's are steroid hormones produced under control of ICSH (LH) of pituitary gland with maximum
activity of puberty.
Two Common androgens are testosterone and androsterone.
Dihydrosterone is the active form of testosterone.
Functions of Testosterone:
• Testosterone stimulates the descent of testes before birth.
• It regulates production of sperm.
• It stimulates the development and maintenance of male secondary sex characteristics.
Pineal Gland
It is a stalked small rounded gland named so after its resemblance with pine cone. Pineal gland is found
behind the anterior choroid plexus. Its weight is about 150 mg.
The gland is richly vascularized.
Unlike lower animals, human pineal gland is devoid of light sensitive cells.
The gland functions as biological clock. It has pineal and glial cells.
The gland secretes two biogenic amine hormones.
Serotonin: It constricts (vasoconstriction) blood vessels at a place of injury.
Melatonin: the hormone develop pale skin color in amphibians. Its release is governed by diurnal dark-
light cycle. Light inhibits melatonin secretion. Melatonin concentration is maximum in midnight and
minimum during noon. The hormone control sleep, mood, ovarian cycle, puberty, and opposes FSH & LH
hormones.

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