This document provides an overview of the endocrine system and how it coordinates and regulates various bodily functions through the secretion of hormones. It describes the major endocrine glands like the hypothalamus, pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, gonads, and others. It also discusses the characteristics, classifications, functions, and mechanisms of action of different hormones. Disorders that can occur due to hormonal imbalances are also mentioned.

1. CHEMICAL COORDINATION AND
INTEGRATION
Class 11 - CBSE

2. Endocrine system – Chemical coordination system – Endocrine glands & hormones
Controlled by nervous system – neuro-endocrine system
Endocrine gland
• Secrete hormones
• Ductless glands
Hormone – Ernest H. Starling (1905)
• Secretin – first hormone discovered
• Insulin – first hormone isolated by Banting & McLeod
• Produced by endocrine gland
• Non-nutrient chemicals
• Intercellular messengers
• Produced in trace amount
• Provide coordination
Characteristics of hormones
• Low molecular weight
• Effective in low conc.
• Don’t provide energy
• Accelerate or inhibit
• Produced in inactive form
• Excess or deficiency cause disorder
Classification of hormones
• 4 categories
• Amino acid derivative
• Peptide hormone
• Protein/Polypeptide hormone
• Steroid hormone

3. Amino acid derived
hormone
Peptide hormone Protein hormone Steroid hormone
• Epinephrine(Adren
aline)
• Norepinephrine
(Noradrenaline)
• Thyroxine
• Oxytocin
• Vasopressin
(composed of
peptides)
• Somatotropic
• Thyrotropic
• Gonadotropic
• Insulin
• Glucagon
• Parathromone
• Human chorionic
gonadotropin
• Relaxin
• Estradiol
• Progesterone

4. Human Endocrine System

5. Hypothalamus
• Supreme commander
• Basal part of diencephalon
• Contain neurosecretory cells called nuclei
• Produce hormones
• Regulate pituitary hormones
Releasing hormone
(stimulate pituitary)
• Gonadotrophin
releasing hormone
(release
gonadotrophins)
Inhibiting hormone
(Inhibit pituitary)
• Somatostatin
(inhibit the release
of growth hormone)
Types of hormones secreted by hypothalamus

6. Pituitary Gland / Hypophysis
• Located in sella turcica
• 0.5 gm, 1 cm diameter
• Attached to brain by infundibulum
• 2 lobes
• Anterior (Adenohypophysis) –
hormone from hypothalamus
reach thro’ portal circulatory
system
• Posterior (Neurohypophysis) –
under the direct neural regulation
of hypothalamus
Pars distalis –
Anterior pituitary
Pars intermedia
• Growth hormone (GH),
• Prolactin (PRL),
• Thyroid stimulating hormone (TSH),
• Adrenocorticotrophic hormone
(ACTH),
• Luteinizing hormone (LH) and
• Follicle stimulating hormone (FSH).
Melanocyte
stimulating hormone
(MSH)
Pars nervosa –
Posterior pituitary Oxytocin
Vasopressin (synthesized
by hypothalamus and
transported to pituitary
Gonadotropins –
not in childhood

7. Pituitary Hormone Functions
Growth Hormone (GH)
Peptide
Growth and metabolism (Dwarfism – deficiency, Gigantism – over
secretion, after adolescence – Acromegaly)
Prolactin (PRL)/Luteotropic Hormone
- protein
stimulates milk secretion after the child birth (parturition) in females
Thyroid stimulating hormone
(TSH)- glycoprotein
Stimulate thyroid to secrete T3 and T4 (Thyroxine)
Adrenocorticotrophic hormone
(ACTH)- peptide
Stimulate adrenal cortex – glucocorticoids & mineralocorticoids
Luteinizing hormone (LH)/ Interstitial
cell stimulating hormone) -
glycoprotein
In male – testosterone by testis
In female – maturation of ovarian follicle, ovulation, corpus luteum
Follicle stimulating hormone (FSH)
-glycoprotein
Regulates gonads – In male – spermatogenesis
In female – maturation of graffian follicles
Melanocyte stimulating hormone
(MSH)
Acts on melanocytes - pigmentation of the skin
Oxytocin - peptide vigorous contraction of the uterus, ejection of milk
Vasopressin –peptide – acts on kidney –
reduce diuresis
reabsorption of water & electrolytes by distal tubules of nephron -
antidiuretic hormone (ADH)- deficiency – Diabetes insipidus

8. Pineal Gland
• Located between cerebral hemispheres
• Protrudes from roof of 3rd ventricle
• Secrete Melatonin
• Regulate diurnal rhythm
• Sleep-wake cycle
• Body temperature
• Metabolism
• Pigmentation
• Menstrual cycle
• Immune system

9. Thyroid Gland
Largest endocrine gland, store hormone
Anterior to thyroid cartilage
Bilobed, connected by isthmus
Contains thyroid follicles made of cubical epithelium
Filled with colloid, iodine essential for synthesis
Contains follicular & parafollicular cells C cells
Thyroxine/T4 Triiodothyronine/T3 Calcitonin
• Thyroglobulin (glycoprotein) –
precursor for T3 (less, active) & T4
• Contain iodine atoms
• Stimulate metabolic activity
• Increase oxygen consumption
(except brain, lungs, testes, retina)
• When Calcium level is
high- Calcitonin is
secreted
• Suppress the release of
Ca from bones

10. Hyperthyroidism Hypothyroidism
Over secretion of thyroid hormone
– Graves disease/Exophthalmic
goitre
- produce antibodies like TSH
- Negative feedback control is lost
- Symptoms
- Eyeball protrusion
- Weight loss
- Increased body temp.
- Rapid heart beat
- Nervousness
- Tremor
- Restlessness
Cretinism-deficiency during infancy
Symptoms – slow body & mental growth, low heart
rate, BP, Pot belly, pigeon chest, protruding tongue
Myxodema – deficiency in adult
Puffy appearance, laziness, slow heart beat, low
body temp., reproductive failure.
Simple goitre/Endemic goitre – iodine deficiency in
diet
Enlargement of thyroid gland with Cretinism &
Myxodema
Hashimoto’s disease –all thyroid functions are
impaired
Autoimmune disease – thyroid gland is destroyed
Disorders of thyroid gland

11. Parathyroid Glands
Consist of 4 separate
glands on the posterior
surface of thyroid gland
- 2 types of cells
- Chief cells –
parathormone or
Collip’s hormone
(precursor-
preprohormone) –
regulate Ca,
Phosphate balance
- Oxyphil cells
- PTH opposes the
effect of Calcitonin
Release of Parathormone
increase blood Ca
Ca released from bones
increase Ca absorption in
digestive tract
Reduce loss of Ca in urine
Hyposecretion Hypersecretion
• Deficiency of PTH
• Decrease of Ca level in blood
• Convolusions, cramps
• Parathyroid
tetany/hypocalcemic tetany
• Excess PTH
• More Ca drawn from bones
• Demineralization
• Osteoporosis

12. Thymus/Hassall’s corpuscles
• lobular structure
• between lungs, behind sternum on the ventral side of aorta
• development of the immune system
• secretes the peptide hormones called thymosins
• differentiation of T-lymphocytes production of
antibodies
cell-mediated immunity Humoral immunity
• Thymus is degenerated in old individuals
• Causing decreased production of thymosins

13. Adrenal Glands
• Paired conical, yellowish structure on top of Kidneys
• External adrenal cortex, Internal adrenal medulla
Adrenalin
e/Epineph
rine
Noradrenaline/
Norepinephrin
e
Catecholamines/ Emergency
hormones
Fight or Flight hormones
• Secreted in response to stress
• Increase alertness
• Pupillary dilation
• Piloerection
• Sweating
• Increase heart beat
• Heart contraction increases
• Increase of respiration rate
• Stimulate glycogen breakdown
• Increased blood glucose level
• Stimulate lipid and protein
breakdown
Zona reticularis (inner layer),
zona fasciculata (middle
layer) zona glomerulosa
(outer layer)
Secretes corticoids
Glucocorticoids
Involved in carbohydrate metabolism
• stimulate gluconeogenesis
• lipolysis and proteolysis
• inhibit cellular uptake
• Inhibit utilisation of amino acids
• Eg. Cortisol
• produces anti-inflammatory
reactions
• suppresses immune response
• stimulates RBC production
Mineralocorticoids
regulate the balance of water
and electrolytes
Eg. Aldosterone
• Acts on renal tubules
• stimulates the reabsorption of Na+
and water
• excretion of K+ and phosphate
ions
• Maintain electrolytes, body fluid
volume, osmotic pressure and
Androgenic steroids - growth of axial hair, pubic hair and facial hair during
puberty

14. Pancreas
• composite gland
• both exocrine and endocrine gland
• Endocrine - ‘Islets of Langerhans’
• 1 to 2 million Islets of Langerhans
• types of cells - -cells and -cells
Glucagon -
hyperglycemic
hormone
• peptide hormone
• acts on hepatocytes
• stimulates
glycogenolysis
• increased blood
sugar
(hyperglycemia)
• reduces the cellular
glucose uptake
Insulin
• peptide hormone
• acts on hepatocytes & adipocytes
• enhances cellular glucose
• uptake & utilization
• movement of glucose from blood
to hepatocytes and adipocytes
• decreased blood glucose levels
(hypoglycemia)
• stimulates conversion of glucose
to glycogen (glycogenesis)
• Prolonged hyperglycemia leads to
a complex disorder called diabetes
mellitus
• loss of glucose through urine
• formation of ketone bodies
• treated with insulin therapy

15. Testis
pair of testis - scrotal sac – In Male
seminiferous
tubules and
stromal or
interstitial tissue
Leydig cells
or interstitial
cells
Androgens- testosterone
• regulate development, maturation and
functions of the male accessory sex organs
like epididymis, vas deferens, seminal
vesicles, prostate gland, urethra
• stimulate muscular growth, growth of facial
and axillary hair, aggressiveness, low pitch
of voice
• Stimulate spermatogenesis (formation of
spermatozoa)
• act on CNS, influence male sexual
behaviour (libido)
• produce anabolic (synthetic) effects on
protein and carbohydrate metabolism

16. Ovary
pair of ovaries – in Female
Estrogen
• stimulation of growth &
activities of female
secondary sex organs
• development of
growing ovarian
follicles
• female secondary sex
characters
• mammary gland
• Regulate female sexual
behaviour
Progesterone
• Supports Pregnancy
• acts on mammary
glands
• stimulates the
formation of milk alveoli
• milk secretion
corpus
luteum

17. HORMONES OF HEART, KIDNEY AND GASTROINTESTINAL
TRACT
Atrial wall of heart Atrial natriuretic factor (ANF) – peptide hormone
• decreases blood pressure
• When BP is increased
• ANF is secreted
• dilation of the blood vessels
• reduces the blood pressure
Juxtaglomerular cells
of kidney
Erythropoietin - peptide hormone
• stimulates erythropoiesis (formation of RBC)
Endocrine cells in
gastro-intestinal tract
Gastrin - acts on the gastric glands, stimulates the secretion of HCl and pepsinogen
Secretin - acts on the exocrine pancreas, stimulates secretion of water and bicarbonate
ions
Cholecystokinin (CCK) - acts on pancreas and gall bladder, stimulates the secretion of
pancreatic enzymes and bile juice
Gastric inhibitory peptide (GIP)- inhibits gastric secretion & motility
Non-endocrine
tissues
Growth factors - normal growth of tissues & repairing/regeneration

18. Hormone
Hormones bind to hormone receptors located in the target tissues only – receptors – specific
1 hormone = 1 receptor
• On cell membrane - membrane-bound
receptors
• inside the target cell - intracellular receptors/nuclear receptors
• hormone-receptor complex – binding of hormone to its
receptor
Type of hormone Examples
peptide, polypeptide, protein
hormones
insulin, glucagon, pituitary hormones, hypothalamic hormones
steroids cortisol, testosterone, estradiol and progesterone
iodothyronines thyroid hormones
amino-acid derivatives epinephrine

19. Mechanism of Hormone Action
Intracellular receptors
• Steroid & Thyroid hormones
• Lipophilic
• Can easily pass plasma membrane
• Act thro’ intracellular receptors in
cytosol/ nucleus
• Hormone-receptor complex binds
to hormone responsive element
(HRE) on DNA
• Cause increased expression of
specific genes
• Tissue growth and differentiation

20. Mechanism of Hormone Action
Extracellular receptors
• Protein/peptide hormones
• Hormone bind to cell surface
receptors
• Stimulate release of second
messengers (e.g., cyclic
AMP, IP3, Ca++ etc)
• regulate cellular
metabolism