Chemical Coordination and Integration: Endocrine System
activities in humans
Use the neurons to
transmit the signal
Signal transmission is
Effect is localized
Use the circulatory
system to transmit the
Signal transmission is
Effect is widespread
Nervous System vs Endocrine System
Endocrine glands are called
They secrete hormones.
Hormones are non-nutrient
chemicals act as intercellular
They are produced in trace
Location - Below the thalamus &
just above the brainstem
It synthesizes and secretes certain
These hormones regulate the
synthesis and secretion of pituitary
Two types of hormones are
produced by hypothalamus:
A marble-sized gland at the
base of the brain
Location - in the bony
cavity called sella tursica.
Controlled by the
hypothalamus or other
neural mechanisms and
therefore the middle man.
Divided anatomically into:
Hormone Target(s) Function
GH All cells in
Stimulates growth and repair. Hyper-secretion of GH
leads to Gigantism and low secretion of GH results
stunted growth called Dwarfism.
TSH Thyroid Stimulates the thyroid gland to secrete the hormone
thyroxine (T4) and triiodothyronine (T3). It regulates
the body's metabolic activities.
ACTH Adrenals Stimulates the adrenal gland to produce
PRL Breasts Stimulates the growth of the mammary glands and
formation of milk.
LH and FSH are called gonadotrophins as stimulate
LH stimulates the synthesis and secretion of
hormones called androgens from testis.
Stimulates the ovaries to produce oestrogen and
Stimulates growth and development of the
ovarian follicles in females.
Stimulate the production and release of
melanin which regulates pigmentation of the
Stimulates a vigorous contraction of uterus
at the time of child birth, and milk ejection
from the mammary gland.
Stimulates reabsorption of water and
electrolytes by the distal tubules and reduces
loss of water through urine (Diuresis).
The pineal gland is reddish-gray and about
the size of a grain of rice in humans.
Location - on the dorsal side of forebrain.
Hormone – Melatonin
Function - It affects the modulation of
sleep patterns in the circadian rhythms
and seasonal functions.
It helps in maintaining the body
It influences metabolism, pigmentation,
the menstrual cycle as well as our defense
Location - Thyroid is a
gland located at the base
of the neck below the
Composition - It is
composed of two lobes
located on either side of
The thyroid gland is
composed of follicles and
Each thyroid follicle is
composed of follicular
cells, enclosing a cavity.
Regulation of the basal metabolic rate.
Control the metabolism of carbohydrates,
proteins and fats.
Maintenance of water and
Secrete thyrocalcitonin (TCT) which
regulates the blood calcium levels.
Support the process of red blood
Hypothyroidism is a
condition characterized by
abnormally low thyroid
Hyperthyroidism is a
condition in which the
thyroid gland produces and
secretes excessive amounts
of thyroid hormones,
and/or thyroxine (T4).
Location - Two pairs of
parathyroid glands located
behind the outer wings of the
It secrete a peptide hormone
called parathyroid hormone
The secretion of PTH is
regulated by the circulating
levels of calcium ions.
Function - PTH regulates the
amounts of calcium,
phosphorus and magnesium in
the bones and blood.
It increases the blood Ca2+
levels and maintain calcium
balance in the body.
Location - Dorsal side of the
heart and the aorta
Role - Plays an important role in
the development of the immune
Role ofThymosin :
Provide cell-mediated immunity
Promote production of antibodies
to provide humoral immunity
o Thymus is degenerated in old
Location - anterior
part of each kidney
Composed of two
types of tissues:
Source : http://robbwolf.com/2012/04/09/real-deal-adrenal-fatigue/
Adrenal medulla releases the catecholamines:
i)Adrenaline or Epinephrine
ii)Noradrenaline or Norepinephrine
These hormones are released in stressful
situations, hence called emergency hormones or
hormones of Fight or Flight.
These hormones increase the heart beat,
alertness, pupilary dilation, piloerection (raising of
hairs), sweating etc.
Adrenal cortex divided into three layers:
Function of Adrenal Medulla and Cortex
The pancreas is a
flattened organ lies in
the abdomen, posterior
and slightly inferior to
It is a composite gland
and acts as both exocrine
and endocrine gland.
Histologically, it consists
of islets of Langerhans
and acini cells.
Location - Present in the scrotal sac (outside abdomen) of male.
Testis performs dual functions as a primary sex organ as well as an
Composed of seminiferous tubules and interstitial
The Leydig cells or interstitial cells produce a
hormones called androgens mainly testosterone.
During puberty, testosterone helps to bring about the
following physical changes that turn a boy into an
Increase in muscle mass and strength, and increase in
Growth of facial and pubic hair,
Deepening of the voice, male hair patterns,
Sperm production (spermatogenesis)
Location -A pair of ovaries located in the abdomen of female.
It is the primary female sex organ which produces one ovum
during each menstrual cycle.
It produces two groups of steroid hormones :
Estrogen and Progesterone.
Estrogen is synthesised and secreted by ovarian follicles.
It is responsible for development of growing ovarian follicles, the
appearance of female secondary sex characteristics at puberty such
as high pitch of voice, development of mammary gland.
Progesterone is secreted by corpus luteum.
It regulates female sexual behaviour.
It prepares the uterus for pregnancy, and the mammary glands for
Progesterone supports pregnancy.
Atrial wall of heart secretes peptide hormone atrial
natriuretic factor (ANF), which decreases blood pressure.
Juxtaglomerular cells of kidney produce a peptide hormone
erythropoietin which stimulates erythropoiesis
(formation of RBC).
Gastro-intestinal tract secrete four major peptide hormones:
Gastric inhibitory peptide (GIP).
Gastrin acts on the gastric glands and stimulates the secretion
of hydrochloric acid and pepsinogen.
Secretin acts on the exocrine pancreas and stimulates
secretion of water and bicarbonate ions.
Cholecystokinin (CCK) acts on both pancreas and gall
bladder and stimulates the secretion of pancreatic enzymes
and bile juice, respectively.
Gastric Inhibitory Peptide (GIP) inhibits gastric
secretion and motility.