Download Control and Coordination

CONTROL AND COORDINATION (HORMONES)
The nervous system and endocrine system
control the activities of our body. These systems
maintain homeostasis in the body. The endocrine
system consists of different glands situated in various
parts of body. The glands which do not posses special
ducts to carry their secretion to the site of action are
called as endocrine glands. These are also called as
ductless glands. The secretions of endocrine glands
are called hormones. The hormone acts on some
specific organs. These organs are called as target
organs. The hormones are carried to the target organs
through blood. The hormones are called as chemical
regulators or informational molecules. The hormones
are produced in minute quantities .They are destroyed
in liver or in the target organs.
Q. Mention common properties of hormones.
Ans:
1. Hormones are carried through blood all over the
body.
2. They are produced in organ called Endocrine
gland. They alter or stimulate the activity of Target
organs.
3. Hormones are generally bound to any specific
carrier protein. Only in such form they are
transported .
4. Hormones are produced in response to specific
stimulus.
5. They have a considerable high degree of target
specificity.
6.
The rate of secretion varies from low to high. It
depends upon the nature and intensity of
stimulus.
7.
The hormones generally affect the cellular
metabolism.
8.
Excessive secretion of hormones or deficiency
leads to any disorder.
Pituitary gland or Hypophysis:
It is small bean shaped endocrine gland. It is about
1cm in sagittal diameter (length) and 1.2 to1.5cm in
breath. It weighs about larger and enlarged during
pregnancy.
The pituitary is situated on the ventral side of the
brain just below the hypothalamus (or the floor of
Diencephalon. It is lodged in a small cavity called
Hypophyseal fossa or sella turcica present in the
Sphenoid bone of the cranium.
The Pituitary is connected to the Hypothalamus by a
stalk of nervous tissue. The region where stalk is
attached to Hypothalamus is a swollen median part
called Median eminence. The stalk is often called as
infundibulum. Hypophysis can be differentiated into
two parts viz. Adenohypophysis (Anterior lobe of
pitutory gland) and Neurohypophysis (posterior lobe
of pitutory gland)
The pituitary is a compound body with double origin.
The anterior pituitary is formed by an out pushing
(Rathke’s pouch) from the dorsal part the buccal
cavity.
The posterior part is formed from the funnel like
downgrowth
of
the
Hypothalamus
called
infundibulum. Thus the anterior and posterior parts
correspond to the epithelial and neural regions
respectively. They fuse with each other.
The connection / contact of Rathke’s pouch for the
buccal cavity vanishes. Thus the pitutory gland is
established. The pitutory gland is thus derived entirely
from the ectoderm.
hormones secreted by the neurosecretary cells of the
hypothalamic nuclei.
(Rathke’s pouch – Buccal ectoderm) Down growth of
neural tube – Neural plate ectoderm. The
adenohypophysis as well as the neuro hypophysis is
ectodermal in origin in nature.
Hormones secreted by Pars distilis (i.e. anterior
pitutory) of the Adenohypophysis.
Adenohypophysis can be differentiated in three parts
viz. Pars tuberalis, pars distilis and pars intermedia.
The anterior part is called as Adenohypophysis and
posterior part is called as Neurohypophysis.
2 Thyrotropin or thyrotrophic hormone or TSH i.e.
thyroid stimulating hormone
Adenohypophysis – It consists of reticular connective
tissue along with epithelial cells (also called
parenchyma). It is differentiated into 3 regions viz.Pars
distalis,Pars tuberalis and Pars intermedia. Of these,
the Pars distalis is the most prominent. In this part
blood sinusoids are present forming a rich network.
Also epithelial cells are found around the sinusoids.
These cells are secretary in nature. They secrete
hormones
The pars distalis is made up of loose chords of
epitheloid secretary cells.The masses of epitheloid
tissues are surrounded by reticular connective tissue
containing blood capillaries.
The Neurohypophysis is also called as the posterior
lobe of the pituitary gland. It is about 25% of the total
pituitary gland. It is made up of large spindle-shaped
cells called Pituicytes.There are blood capillaries and
nerve fibres around the pituicytes. But the pituicytes
are non-secretory in nature.In Hypothalamus,there
are two groups of neurosecretory cells called as supraoptic and para-ventricular nuclei. They are secretory in
nature.
The nerve fibers arising from these nuclei enter the
neurohypophysis. The hormones secreted by these
hypothalamic nuclei are stored in the axon terminals
of the nerve fibers. ( in the enlarged bodies called as
Herring bodies.)Thus the neurohypophysis does not
have a secretary role of its own. But it only stores the
1 Growth hormone (GH) or somatotropin or STH i.e.
somatotrophic hormone
3 Adrenocorticotrophic
Adrenocorticotropin.
hormones
(ACTH)
or
4 Prolactin
5 Gonadotropins or Gonadotrophic hormones
a) FSH or follicle stimulating hormone
b) LH or Luteinizing hormone.
Pars intermedia –
MSH i.e. Melanocyte stimulating hormone
Pars nervosa
Pitressin or Vasopressin or Antidiuretic hormone ADH
Pitocin or Oxytocin
Coherin
Hormones secreted by Pars distalis i.e.
anterior pituitary.
1. Growth hormone(GH) somatotrophic hormone or
somatotropin or STH
This hormone is necessary for the normal growth of
the body. The growth of the body is under the control
of the hereditary factors (genes) and the diet. But this
hormone
is also essential for growth. This hormone stimulates
the body growth by retention of the proteins and
calcium .It also enhances (increases) the synthesis and
deposition of the proteins in the tissues.Hence there is
low excretion of nitrogen. This leads to growth and
elongation of the bones by absorption of calcium from
blood.It brings about proportionate growth of the
muscles and visceral organs.
GH is regulated by the hypothalamic hormones i.e. the
hormones secreted by the hypothalamus. These are as
follows-
It promotes protein synthesis, lipolysis in adipose
tissue to release more fatty acids Throughout the life
the GH is essential for replenishment of the tissues
and therefore for the recovery of ‘wear and tear’.
b) Growth hormone inhibitory hormone – (GHIH).
( a ) Deficiency of GH in early age i.e. in infants and
children stops the growth of long bones. The child
attains the height only about 2.5 to 3 ft. Such a
condition is called pituitory dwarfism. The intelligence
of such persons is normal only the physical and sexual
growth is retarded.The pituitary dwarfs are of 2 types
viz. Lorain dwarfs and Frolich dwarfs.
The midgets in circus are Lorain dwarfs. They are just
physically retarded but mentally normal.
a) Growth hormone releasing hormone (GHRH).
This hormone stimulates the pitutory to secrete GH
This Growth hormone inhibiting hormone is also
called as somatostasin. The Growth hormone
inhibiting hormone inhibits the pituitary secretion of
GH.
2. Thyrotrophic hormone ( TTH ):
(Thyroid stimulating hormone TSH or Thyrotropin)
This hormone stimulates the growth and activity of
thyroid gland. Thus it stimulates the follicles of the
thyroid gland to take up the Iodine from blood and to
utilize it for the production of the T3 and T4 hormones
i.e. the thyroid hormones.
The Frolich dwarfs are mentally as well as physically
retarded.
The secretion of TSH by the anterior pituitary is under
the control of the Thyrotropin releasing hormone
(TRH) of the hypothalamus.
(b) Hyposecretion of GH in adults leads to Simmond’s
disease.it is characterized by early senescence or
ageing.
3.
Adrenocorticotrophic
Adrenocorticotropin
( b ) Over secretion of GH from childhood to maturity
leads to a condition called pitutory gigantism or
gigantism. In such cases the bones and the muscles
undergo elongation and growth tremendously due to
which the person attains the height more than 7ft. it
looks as a giant hence the name gigantism or
gigantism.
( c ) Over secretion of GH after adolescence
(adulthood) leads to abnormal enlargement of the
jaws and the bones of the hands and feet. The
eyebrow ridges become more prominent giving a
gorilla like appearance.Such person has no giant
structure. These persons may be mentally retarded.
This condition is called Acromegaly. The secretion of
hormone
(ACTH)
or
This hormone stimulates the cortical region of the
adrenal gland, to produce and secrete the cortical
hormone. The adrenal cortical hormones are often
called as corticoids.
The mineralocorticoids are concerned with mineral
metabolism i.e. Na-K metabolism. Therefore it is
related with the fluid and electrolyte balance. The
glucocorticoids are related with the metabolism of
carbohydrates and fats. The sex corticoids stimulate
the development of external sex characters of male
type.
The secretion of ACTH by the anterior pitutory is
under the control of a hormone called Corticotrophin
releasing hormone (CRH) by the hypothalamus.
4. Prolactin – It is not secreted in males.It is secreted
in females in the three months of pregnancy ( 3 rd
trimester ) and after the after the birth of the child for
about a year. This is also called as lactogenic hormone.
It initiates and maintains the secretion of milk by the
mammary glands in mothers. Thus it is necessary for
initiation and maintaining lactation. The presence of
this hormone in blood reduces the changes of
pregnancy so long as mother is feeding her baby.
5. Gonadrotropins /Gonadotrophic hormones
As the names indicate, these hormones primarily act
upon the gonads. There are two types of
gonadotrophic hormones
FSH – Follicle stimulating hormone
LH – Luteinizing hormone
FSH--- In male, the FSH also brings about descent of
testes into scrotum just before the birth or after the
birth. It stimulates the testis in males to develop the
seminiferous tubules. It also stimulates the germinal
epithelium of the seminiferous tubules to produce a
large number of the spermatogonia. FSH also helps in
the production of the sperms. Thus the FSH basically
induces the cell divisions and differentiation.
In female, FSH stimulates the germinal epithelium of
the ovary to produce the follicles.Therefore stages
upto the double-layered follicles are formed in the
ovary before the birth. It stimulates the developing
follicles to undergo development of the Primary
oocyte and further the secondary oocyte. Further the
FSH stimulates follicular cells to secrete the female sex
hormone called estrogen. The FSH also stimulates the
follicular cells to divide more . FSH is also responsible
for arrest of menstruation at the end of menstrual
phase. It also brings about regeneration of uterine
endometrium after this phase. The development of
Mature follicle also takes place in the ovary.
Luteinizing hormone (LH) – This hormone stimulates
the ovaries for the maturation of ovarian follicle (
Graafian follicle). The ovulation i.e. discharge of ovum
from the ovary is also brought about by this hormone.
After the ovulation this hormone stimulates the
follicular cells to undergo luteinization which finally
forms corpus luteum. This is a temporary endocrine
gland which secretes another sex hormone called
progesterone. The secretion of progesterone takes
place under the control of LH. In males LH is called as
interstitial cells stimulating hormone (ICSH). This
hormone stimulates the interstitial cells of Leydig
which are found in the connective tissue of the testis.
These cells secrete the male sex hormone called
testosterone. Thus if the pitutory gland is removed
(hypophysectomised) then the gonads of the person
fail to develop. The secretion of this hormone is under
the control of Gonadotropin Releasing hormone
(GnRH) of the hypothalamus.
The posterior pituitory is also secretary in
nature but the hormones are not actually synthesized
by the pituicytes. The pituicytes present in the Pars
nervosa are non secretary but the hypothalamic
nucleus consists of neuro-secretory cells. These cells
synthesize the hormones. The axons of these
neurosecretory cells pass through the hypophysial
stalk. These axons terminate in pars nervosa. The
hormone
Produced by the hypothalamic nuclei are stored in
the axon terminals (Herring bodies) of these
neurosecretary cells. The axon terminals lie in the pars
nervosa hence it appears that the pars nervosa
secretes the hormones. There are two hormones
secreted by pars nervosaAntidiuretic hormone (ADH) or Vasopressin or
pitressin
Oxytocin or pitocin
Coherin
Pitressin or Vasopressin-This hormone is useful to the
person in maintaining or conserving water in the body.
Whenever there is adequate quantity of water in
blood, the osmotic pressure of the blood increases.
This may be also due to loss of water from the body
through perspiration, etc. the increased osmotic
pressure stimulates the hypothalamic nuclei to
secrete Vasopressin. This hormone acts upon the
distal convoluted tubules and collecting tubules of the
kidney due to which reabsorption of water increases.
Thus the volume of urine decreases. It is because of
this activity vasopressin is also called as Antidiuretic
hormone ( ADH ) Failure of this hormone leads to
reduced renal reabsorption of water. Hence large
volume of hypotonic i.e. dilute urine is formed. This
condition is called as Diabetes insipidus. But in this
disorder no glucose is eliminated in urine.
Pitressin or vasopressin also increases the arterial
blood pressure because it makes the arteries to
constrict. Failure of this hormone leads to reduced
renal reabsorption of water. Hence large volume of
hypotonic i.e. dilute urine is formed. This condition is
called as Diabetes insipidus. But in this disorder no
glucose is eliminated in urine.
Oxytocin
This is another hormone actually secreted by the
hypothalamic nuclei. This hormone is useful in the
ejection of the milk from the mammary glands. Hence
oxytocin is also called as milk ejection hormone.
Oxytocin is secreted due to the sucking of the breast
by an infant (new born child). It is also secreted due to
the distension of the uterus by fully formed foetus.
The oxytocin contracts the smooth muscles of the
uterus (also mammary glands). It thus helps in child
birth. Hence oxytocin is also called as birth hormone.
In males, it is essential to bring about the ejaculation
of semen at the end of coitus.
It is supposed to induce prolonged rhythmic
integrated contractions of the jejunum.
Feed back mechanism/ feed back control/feedback
regulation
Hypothalamus
TRH (Thyrotropin Releasing hormone) 
Anterior pituitary
TSH (thyroid stimulating hormone)

Thyroid gland

Thyroxine
Feed back mechanism is a self regulatory mechanism.
It is due to this mechanism he regulation of the
hormones by different endocrine glands takes place.
e.g. the Hypothalamus secretes TRH whenever the
concentration of Thyroxine in blood is poor. TRH then
stimulates the Anterior pituitary to release TSH.
The TSH acts upon thyroid gland to release thyroxine
in the blood. The increased level of thyroxine in the
blood inhibits the TRH secretion by the hypothalamus.
Hence the TSH secretion by the anterior pituitary is
stopped. Further in absence of TSH the secretion of
the thyroxine is stopped
Again if the concentration of thyroxine
becomes lower the hypothalamus is stimulated to
release TRH. It ultimately leads to thyroxine secretion
as mentioned earlier.
Coherin
Intermediate lobe (Pars intermedia)
This lobe is vestigial in human beings. Hence the name
of hormone Melanocyte stimulating hormone (MSH).
Its presence in human being is doubtful. This
hormone affects the pigment cells i.e. the
Melanocytes present in the skin. The MSH stimulates
the Melanocyte for the synthesis of the black pigment
called melanin. This hormone darkens the skin of the
lower vertebrates.
Thyroid gland:
Thyroid gland is a soft labile gland. It is usually 30 gms
in weight. It enlarges to certain extent during
pregnancy. It is more or less H- shaped / Butterfly
shaped gland. It is situated in neck region. It is found
to be attached to the anterior surface of larynx. It
covers the lower end of larynx and upper end of
trachea. The thyroid gland is differentiated into two
lobes. The lobes are connected with each other by a
band of connective tissue called isthmus.
Histological structure of thyroid gland:
The thyroid gland is differentiated into two conical
lobes. Each lobe is covered by a thick connective
tissue sheath called as capsule. From the capsule a
number of septa/ trabeculae arise. The septa thus
divide thyroid lobe into a number of polyhedral
lobules.
In each lobule, the connective tissue is present which
is called as the intralobular connective tissue. In this
tissue blood vessels, lymph vessels, nerve fibers,
thyroid follicles and Para-follicular cells are situated.
This tissue is often called as the interfollicular
connective tissue.
The thyroid gland is generally spherical or ovoid.
Therefore in this section they appear circular or oval.
Each follicle is lined by follicular cells. These cells are
generally cuboidal in shape. They may become
columnar during their hyperactivity or thin squamous
like indicating their less activity (hypo activity). The
follicular cells have prominent nuclei and granular
cytoplasm. There are secretary granules in cytoplasm.
Therefore it appears granular. They also have well
developed endoplasmic reticulum (ER) and Golgi
complex(GC). The follicular cells secrete the hormones
called T3 and T4.
There are Para follicular cells or C cells around the
follicles, in inter follicular connective tissue. These
cells secrete a hormone called Calcitonin /
Thyrocalcitonin / TCT.
In each follicle there is a cavity or lumen. It is
filled with a gelatinous amber colored substance
called colloid.
It is amber colored due to the presence of iodine in
colloid. The thyroid hormone (T3 and T4) can not be
stored in pure form. They are combined with a protein
globulin thus forming thyroglobulin molecules. The
thyroglobulin is stored as colloid in the lumen. As per
the
necessity, thyroglobulin
molecules are
pinocytosed by follicular cells. Thyroglobulin is split to
release thyroid hormone. The thyroid hormone is thus
released into the interfollicular connective tissue and
further in blood vessels.
Role of Calcitonin / TCT
Calcitonin / thyrocalcitonin is secreted by the Para
follicular cells or C- cells especially when they are
stimulated due to hypercalcemia.
Hypercalcemia means high plasma Ca++. The Para
follicular cells are stimulated when they receive blood
having more Ca++. As a response they secrete the
calcitonin. The calcitonin helps to reduce the plasma
Ca++ and PO4-- by the following activities.
1. Absorption of Ca++ and PO4--by the intestinal
epithelial lining is temporarily arrested.
2. Reabsorption of Ca++ and PO4--from the PCT of
nephron is temporarily arrested.
Thus they are released into urine and further
excreted.
Thyroxin
is
essential
metamorphosis.
3. The liberation of Ca++ and PO4-- from bones and
cartilage is temporally arrested. These attempts helps
to maintain low Ca++ in plasma.
(If more thyroxin is injected or administered to the
tadpoles, they undergo metamorphosis rapidly due to
which they are converted into tiny frogs.)
Thyroid follicular hormones
On the contrary, if no thyroxine is produced
then they fail to undergo metamorphosis and remain
in the same larval stage. Such a phenomenon is called
as Neotany e.g. Axolotl larva of salamander.
As mentioned earlier, the follicular cells of thyroid
secrete T3 and T4. T3 means triiodo thyronine and T4
means the Tetra- iodo thyronine or thyroxin.
These are the iodinated derivatives of the
amino acid called Tyrosine.
The absorption of iodine from blood into follicular
cells takes place under the effect of TSH of
hypophysis. Also the iodination of tyrosine takes place
under the effect of TSH.
The T3 is produced in fewer amounts than T4 but T3 is
found to be at least 5 times more active or potent
than T4 .
Roles of T3 and T4
1. The T3 and T4 increase the basal metabolic
rate(BMR) therefore the rate of utilization of oxygen
by the cells increases.
2. T3 and T4 increase the rate of protein synthesis as
well as synthesis of amino acids.
3. T3 and T4 also play very significant role in
carbohydrate metabolism. They stimulate the  cells
of Islet of Langerhans. Therefore more insulin is
secreted. Hence the glucose is absorbed by the liver
cells. Also the glucose metabolism is increased. The
absorption of glucose by the intestinal epithelial lining
increases. In liver it is converted to glycogen.
4. T3 and T4 increases fat degradation. Therefore
cholesterol level of blood increases.
5. T3 and T4 stimulate the sympathetic nerve. Thus
the heart rate, breathing rate etc increases.
6.
in
Amphibians
for
Initially the tadpoles are herbivorous. They consume
the leaves of the aquatic plants. Therefore they get
iodine in the diet. The iodine is utilized to produce
thyroxin. The thyroxin is further utilized for
metamorphosis. Later on after production of sufficient
thyroxin, the tadpole becomes carnivorous.)
Hypothyroidism - Insufficient production of T3 and T4
leads to a disorder called hypothyroidism. The T3 and
T4 are not produced in such a person to the required
level.Hypothyroidism in children leads to Cretinism.
Hypothyroidism in adult leads to Myxedema.
Cretinism Hypothyroidism in children leads to
disorder called Cretinism. Such child is called as Cretin.
The peculiar features of a cretin are as follows1.It is due to improper metabolism, the growth of the
body (physical growth) is retarded. (Stunted) so the
cretin is physically dwarf. The height of such a child
reaches maximum up to 3 to 3.5 ft.
Also the cretins are mentally retarded.
2. More fat is deposited over the chest leading to
Pigeon chest and over the abdomen resulting into pot
belly.
3. As less fat is metabolized, energy production is also
reduced. Hence the cretin is less energetic.
4. The cretin exhibit lack of initiation and lack of
alertness. Also the cretin is less active and sluggish.
5. It is due to the same reason the body temp. In
found to be very low.
6. In such a child, due to less stimulation of the
sympathetic nerves and less demand for oxygen, the
heart rate, respiratory rate and breathing rate are
found to be low.
7. The cretin has expressionless face.
8. The tongue enlarges and protrudes out of the
mouth cavity.
9. The blood pressure of such a child is low.
10. Comparatively body weight is more.
Myxedema
Hypothyroidism is deficiency of T3 and T4. In adults it
leads to Myxedema
The characteristic features of Myxedema are as
follows.
More fat is deposited allover the body leading to
puffness.
Such person exhibit low metabolic rate therefore the
energy production is less. They suffer from weakness.
As less energy is produced there body temperature is
found to be low.
required quantity of thyroid hormone. So the blood
contains less T3 andT4. When the hypothalamus
receives such blood, it gets stimulated. It then releases
TRH (Thyrotropin releasing hormone) the TRH then
stimulates the hypophysis (Adenohypophysis) to
secrete more TSH. The TSH further acts upon thyroid
follicles and stimulates them. As a response follicular
cells enlarge and become columnar. Also overall the
thyroid gland enlarges (Goiter). The thyroid follicular
cells fail to produce required amount ofT3 and T4 as
there is shortage of the raw material (i.e.
iodine.)Therefore the disorder is called as iodine
deficiency Goiter. It may result into cretinism or
Myxedema as per the age of person.
Hyperthyroidism- Grave’s disease or Ex-ophthalmic
goiter
Over secretion or excessive secretion of thyroid
hormone (T3 &T4) results into Graves’s disease or
Exophthalmic Goiter. The ill effects are as follows
The basal metabolic rate (BMR) increases
tremendously. Therefore body proteins are utilized. It
results in weight loss.
It is due to more metabolism of fat and protein
extreme thinning of the body results (emaciation)
Their heart rate is less. Breathing rate is also less.
More fat is metabolized so more energy is produced
therefore the person becomes overactive. It results
into restlessness, sleeplessness (insomnia) as well as
nervousness.
Reproductive failure is also seen. Their BP is also less.
The BP increases due to rise in cholesterol level.
Iodine deficiency Goiter / simple Goiter:
Since more energy is produced body temperature
increases sweating is observed ever during winter at
the surface of palms and soles of feet
They are sluggish and exhibit lack of alertness.
Goiter means enlargement / enlarged thyroid gland. It
results due to dietary deficiency of iodine. Generally in
mountain regions, the superficial iodine rich soil is
eroded during raining. Therefore it is not incorporated
into the vegetables. Consumption of such vegetables
for a prolonged period leads to deficiency of iodine in
blood. Therefore thyroid gland fails to produce the
Due to excessive stimulation of sympathetic nerves,
the heart rate increases. The breathing rate also
increases the oxygen consumption by the body also
increases
Muscle tremor develops
The feed back mechanism fails. Therefore the follicles
are more stimulated by TSH they enlarge resulting into
enlarged thyroid gland. It is called goiter. The follicular
cells become columnar and hyperactive.
2. Also the Thymosins promote production of
Antibodies thereby providing Humoral immunity.
Therefore the Thymosins are important in
development of immune system. In aged people,
the thymus gland undergoes degeneration. Hence
they suffer from weakening of immunity.
A fibrous tissue develops behind the eyeballs. It leads
to protrusion of eyeball (exophthalmos) i.e.
Exophthalmic Goiter.
Adrenal gland (Supra-renal gland)
Parathyroid gland
Location- Attached to the kidneys on the dorsal side.
Location- On the backside of the thyroid gland.
Appearance- They appear pyramid shaped.
Appearance- in the form of 2 pairs of spherical lobes.
Adrenal gland can be differentiated into 2
parts viz. Adrenal cortex and Adrenal medulla.
Role- secretes the hormone Parathormone ( PTH)
Role of PTH Increases the level of Ca++ in plasma by
the following ways--1. Reabsorption of the Ca++ by the PCT of the renal
tubule. Therefore less excretion of Ca++ alongwith
urine.
2. Decalcification of bones and cartilages.
3. More absorption of Ca++ by the lining of intestine.
Therefore PTH is Hypercalcemic hormone. It is
antagonistic to TCT
Adrenal cortex can be further differentiated
into 3 regions such as Zona Glomerulosa ( outer), Zona
Fasciculata( middle) and Zona Reticularis ( inner).
Adrenal cortex secretes 3 types of corticoids
such as Mineralo corticoids, Glucocorticoids and sex
corticoids of male type.
Mineralocorticoids --- These are the hormones
which control electrolyte metabolism.( Na+- K+ )
metabolism and water balance. One of the
mineralocorticoids is Aldosterone.
( Thyrocalcitonin) of the thyroid gland.
Role of Aldosterone --Thymus gland
1. Increases renal reabsorption of Na+.
Location- On the dorsal side of the heart and the
aorta.
2. Increases renal reabsorption of water.
Appearance as lobules.
Role- secretes
Thymosins.
the
peptide
hormones
called
3. Increases renal excretion of K+ and PO4-- .
4. Maintains body fluid volume.
5. Maintains osmotic pressure and blood pressure.
Role of Thymosins--1. Essential in differentiation of T lymphocytes. These
cells produce cell mediated immunity.
Role of Glucocorticoids—One of them is Cortisol
which is predominant.
1.
Controls carbohydrate metabolism.
2.
Increase in total quantity of electrolytes (Na+ and
Cl-) in ECF i.e. extra cellular fluid. Therefore there
is increase in quantity of ECF.
3.
More retention of water in ECF.
Maintains cardio-vascular system and kidney
functions.
4.
Alkalosis and Polydypsia ( more thirst).
5.
Increased BP.
6.
Involved in anti-inflammatory reactions and
suppresses immune response.
6.
Muscle paralysis.
7.
Stimulates RBCs production.
Hormones of Adrenal medulla--- It secretes 2
hormones viz. Adrenaline
2.
Increases Gluconeogenesis.
3.
Increases Proteolysis and Lipolysis.
4.
Inhibits cellular uptake and utilization of amino
acids.
5.
Role of Male sex-corticoids
(Androgenic corticoids)
1.
Growth of hair in the armpits.
2.
Growth of pubic hair and facial hair during
puberty. ( secondary sex characters).
( Epinephrine) and Nor-adrenaline ( Nor-epinephrine).
These are also called as emergency hormones or
hormones of fight-flight-fright.They are secreted in
stress condition. They are also called as
Catacholamines.
Roles of the adrenal medullary hormones----1.
Increase alertness.
Addison's disease---
2.
Increase papillary dilation.
1.
Hyposecretion or deficiency of Cortisteroids
results into Addison's disease.
3.
Piloerection i.e. hair erection.
2.
Generalized weakness.
4.
Increase sweating.
3.
Weight loss.
5.
Increase heart rate ( Tachycardia).
4.
Low body temperature.
6.
Increase the rate of breathing and respiration.
5.
Low BP and low pulse rate.
7.
Increase the strength of heart.
6.
Acidosis.
8.
Breakdown of Glycogen , Lipids and Proteins.
7.
Feeble heart action.
9.
Increase in blood glucose level.
8.
More loss of Na+ and Cl- in urine.
9.
Impaired kidney function and kidney failure.
Pancreas – Dual gland (Mixed gland) or Exo-endocrine
gland:
Cushing’s syndrome
Exocrine portion – Acini of Pancreas
1.
Endocrine portion – Islets of Langerhans
Hypersecretion of corticosteroids results into
Cushing’s syndrome.
Islets of Langerhans – Made up of 3 types of cells viz
 ,  and  cells.
 - cells – (A cells) secrete Glucagon. It reduces the
absorption of Glucose by liver cells.
There is
breakdown of Glycogen into glucone. Therefore Blood
Glucose level increases (Hyperglycemia). Hence it is
described as Hyperglycemic hormone.
It stimulates Gluconeogenesis (glycogenolysis). It
reduces uptake of glucose by cells and its utilization.
 -cells - (B cells) secrete Insulin. It is antagonistic to

Prolonged and extreme condition of Diabetes
Mellitus results into formation of Ketone bodies
and their excretion in urine (Ketosis leading to
Ketonuria).
Hormones of GIT (Gastro Intestinal Trait) – The
endocrine cells present in the wall of stomach secrete
the hormones such as Gastrin, Secretin,
Cholecystokinin, Pancreaozymin, Gastric Inhibitory
Peptide (GIP).
Gastrin stimulates the gastric gland cells to secrete
Gastric enzymes.
Glucagon. It stimulates liver cells (hepatocytes) and
adipocytes for cellular uptake of Glucone and its
Secretin stimulates the intestinal glands to secrete
intestinal juice.
utilization. Therefore Glucose from blood decreases
(Hypoglycemia).
Cholecystokinin stimulates for the contraction of Gall
bladder to push the bile into intestine.
It also stimulates for glycogenosis (conversion of
Glucose into Glycogen).
Pancreaozymin stimulates the pancreate acids to
secrete Pancreatic juice. The GIP – inhibits gastric
secretion and motility.
There is always a balanced secretion of Insulin and
Glucagon. Therefore blood glucose level is maintained
constant.
Hormones of the Heart –
ANF – Atrial Natriuretic Factor
 -Cells - (Delta cells) – Secrete Somatostatin.
decreases Glucagon and Insulin secretion.
Diabetes Mellitus –

Takes place due to deficiency of Insulin

Blood Glucose level increases (Hyperglycemia)

Appearance of glucose in urine (Glucasuria)
It
The wall of atrium of heat secretes ANF (Atrial
Natriuretic Factor).
This hormone is secreted when there is increase in
Blood Pressure.
Effect – It causes dilation of blood vessels. Therefore,
the BP reduces. It causes increased Na+ excretion.
Also it causes increased excretion of water in urine.
Therefore, the blood volume reduces. Also the BP
decreases.
secretes usually the progesterone, but it also secretes
Relaxin at the time of parturation.
Hormones of Kidney – Erythropoietin.
The Estrogen –
The JG complex of kidney secretes the hormone called
(1)
Erythropoietin. It is a peptide hormone. It stimulates
the bone marrow for production of RBCs.
It is necessary for the growth of reproductive
organs like ovaries, oviducts, uterus and vagina.
(2)
It is necessary for the development of secondary
sexual characters like high pitch voice,
development of mammary glands, broadening of
pelvis, pubic hairs and depositing of
subcutaneous fat to give rise to feminine
appearance.
(3)
It is also necessary to regulate female sexual
behaviour.
Hormones of the Gonads – Testes and Ovaries are the
male and female gonads respectively.
Testes – The Interstitial cells of Leydig secrete the
androgens. One of them is predominant. It is
testosterone. They are all steroids.
Role of Androgens –
(1) Regulates and stimulates the development,
maturation and functions of male reproductive
system. It acts upon the seminiferous tubules,
epididymis, vasa-deferentia, seminal vesicles, prostate
gland, urethra etc.
(2) Also the endrogens are essential for the formation
of secondary sex characters in male. They include
development of pubic hair, facial hair, hair in the
armpits, masculine development, low pitch voice,
aggressiveness, etc.
Corpus Luteum – secretes Progesterone. It maintains
the pregnancy. It also acts on the mammary glands
and stimulate them for milk secretion.
Hormones of Hypothalamus –
There are several groups of neurosecretory cells in the
hypothalamus. They secrete neurohormones like CRH
(Corticotropin Releasing Hormone) for controlling the
ACTH secretion.
TSH RF – Thyroid Stimulating Hormone Releasing
Factor.
(3) They are also necessary for spermatogenesis.
FSH RF (FSHRH) – Follicular Stimulating Hormone
Releasing Factors
Ovary – The ovaries are the female gonads. The
follicular cells secrete estrogen. The corpusluteum
GHRF – Growth Hormone Releasing Factor.
GHIF – Growth Hormone Inhibiting Factor
PRIF – Prolactin Release Inhibiting Factor
(i)
The hormone normally does not enter the target
cell. It generates the second messengers like
cyclic AMP, Ca++ or IP3 (Inositol triphosphate),
etc.
(ii)
The second messenger further regulates the
cellular metabolism.
MSHRF – Melanocyte Stimulating Hormone Releasing
Factor.
MSH RF – Melanocyte Stimulating Hormone Release
Inhibiting Factor.Etc.
Also it secretes the hormones like Vasopressin (ADH),
Oxytocin (Pitocin) and Coherin
Explain the Mechanism of action of hormone.
Ans:
(1)
Hormones act on specific tissues and/or organs.
Such tissues and/or organs are regarded as
Target tissues or target organs.
(2)
The cells of Target tissues have specific binding
sites which are regarded as receptor sites.
(3)
The hormone receptors are generally present at
the surface of cell membrane also called as the
Membrane Bound Receptors. They may be
present inside the cell
(4)
When the hormone molecule binds with the
receptor molecule, it forms a hormone-receptor
complex.
(5)
The receptor is specific for a particular hormone.
(6)
The formation of such a complex leads to certain
biochemical changes in the target tissue.
(7)
Thus the hormone regulates the
metabolism and physiological functions.
tissue
(iii) The steroid hormones and Thyroxine interact
with intracellular receptors. So they regulate the
gene expression or chromosome function.
(iv) When the receptor is intracellular and within the
nucleus, the hormone receptor complex is
formed inside the nucleus. It then interacts with
the genome thereby resulting into changes in
physiological and developmental functions.