1. The document discusses the hormonal cascade system involving the hypothalamus. It begins with the hypothalamus secreting releasing hormones that stimulate the anterior pituitary gland. 2. The anterior pituitary gland then secretes additional hormones that target various endocrine glands like the thyroid, adrenals, ovaries and testes. These glands ultimately secrete hormones into the bloodstream. 3. There is amplification and negative feedback involved, with hormones from downstream glands inhibiting the previous steps in the pathway once sufficient amounts are present. The document then discusses the various endocrine glands and hormones they secrete.

1. SUBJECTIVE ASSIGNMENT - 2
Course Name : UGC - ACADEMIC WRITING
Name : K. VINOTH
Email : vinobiochem2345@gmail.com
Student ID : 1ec62c9cf35511e9ac22856977b3bf24

2. Mr. K. VINOTH., M.Sc., M.Phil.,
Assistant Professor
Department of Biochemistry
Islamiah College (Autonomous)
HORMONAL CASCADE SYSTEM
INVOLVING
HYPOTHALAMUS

3.  INTRODUCTION
 CLASSIFICATION OF CHEMICAL MESSENGERS
 STUDY OF HORMONES
 HORMONAL CASCADE SYSTEM
 ENDOCRINE GLANDS
 Hypothalamus
 Anterior pituitary gland
 Posterior pituitary gland
 Thyroid gland
 Parathyroid gland
 Pancreas
 Adrenal cortex
 Testes
 Ovaries
 HORMONES SECRETED BY OTHER ORGANS
 LOCAL HORMONES

4. INTRODUCTION
All the physiological activities of the body are regulated by two major systems:
1. Nervous system
2. Endocrine system.
These two systems interact with one another and regulate the body functions. This section deals with
endocrine system and Section 10 deals with nervous system. Endocrine system functions by secreting
some chemical substances called hormones.
CELL-TO-CELL SIGNALING
Cell-to-cell signaling refers to the transfer of information from one cell to another. It is also called cell
signalling or intercellular communication. The cells of the body communicate with each other through
some chemical substances called chemical messengers.
CHEMICAL MESSENGERS
Chemical messengers are the substances involved in cell signaling. These messengers are mainly secreted
from endocrine glands. Some chemical messengers are secreted by nerve endings and the cells of several
other tissues also.
All these chemical messengers carry the message (signal) from the signaling cells (controlling cells) to
the target cells. The messenger substances may be the hormones or hormonelike substances.

5. Classification of Chemical
Messengers
Generally the chemical messengers are classified into
two types:
1. Classical hormones secreted by endocrine
glands
2. Local hormones secreted from other tissues.
However, recently chemical messengers are classified
into four types:
1. Endocrine messengers
2. Paracrine messengers
3. Autocrine messengers
4. Neurocrine messengers

6. STUDY OF HORMONES
A hormone is usually studied as follows:
1. Source of secretion (gland as well as the cell that secretes the hormone)
2. Chemistry
3. Halflife
4. Synthesis and metabolism
5. Actions
6. Mode of action
7. Regulation of secretion
8. Applied physiology
i. Disorders due to hypersecretion of the hormone
ii. Disorders due to hyposecretion of the hormone.

7. Hormonal cascade system:
Hypothalamus to anterior pituitary to ultimate glands
 Signaling steps
 For many hormonal systems, pathway originates in brain using components that
innervate hypothalamus
 Hypothalamus responds by secreting specific releasing hormones (polypeptide
hormones)
 Releasing hormones transported through closed portal system to anterior pituitary; bind
to membrane receptors and cause secretion of specific anterior pituitary hormones
(polypeptide hormones)
 Anterior pituitary hormones enter bloodstream and bind receptors in ultimate glands
(such as thyroid gland, adrenal cortex, ovary, testes)
 Ultimate glands secrete hormones into bloodstream; hormones bind to receptors on
target tissues to generate systemic response

8.  Amplification of signal-
Amount and stability of
hormones increased at each step in
pathway
 Negative feedback-
Hormones inhibit previous
steps in pathway when sufficient
amounts are present
ENDOCRINE GLANDS

10. Endocrine
Gland
Hormone Primary Hormone Function
Hypothalamus Corticotropin- releasing
hormone (CRH)
Gonadotropin-releasing
hormone (GnRH)
Thyrotropin-releasing
hormone (TRH)
Growth hormone-releasing
hormone(GHRH)
Somatostatin
Dopamine
Stimulates the pituitary to release
adrenocorticotropic hormone (ACTH)
Stimulates the pituitary to release
luteinizing hormone (LH) and follicle-
stimulating hormone (FSH)
Stimulates the pituitary to release thyroid-
stimulating hormone (TSH)
Stimulates the release of growth hormone
(GH) from the pituitary
Inhibits the release of GH from the
pituitary
Inhibits the release of prolactin from the
pituitary

11. Endocrine Gland Hormone Primary Hormone Function
Anterior pituitary gland Adrenocorticotropic
hormone (ACTH)
Luteinizing hormone
(LH)
Follicle stimulating
hormone (FSH)
Thyroid stimulating
hormone (TSH)
Growth hormone
(GH)
Prolactin
Stimulates the release of hormones from
the adrenal cortex
In women, stimulates the production of sex
hormones (i.e.,estrogens) in the ovaries as
well as during ovulation; in men, stimulates
testosterone production in the testes
In women, stimulates follicle development;
in men, stimulates sperm production
Stimulates the release of thyroid hormone
Promotes the body’s growth and
development
Controls milk production (i.e., lactation)

12. Endocrine Gland Hormone Primary Hormone
Function
Posterior pituitary gland # Vasopressin
Oxytocin
Helps control the body’s water
and electrolyte levels
Promotes uterine contraction
during labor and activates
milk ejection in nursing
women
#These hormones are produced in the hypothalamus but stored in and released from the posterior pituitary
gland.

13. Endocrine Gland Hormone Primary Hormone Function
Thyroid gland Thyroid hormone (i.e., thyroxine
[T4] and triiodothyronine [T3])
Calcitonin
Controls metabolic processes in
all cells
Helps control calcium metabolism
(i.e., lowers calcium
levels in the blood)
Parathyroid gland Parathyroid hormone (PTH) Helps control calcium metabolism
(i.e., increases calcium levels in
the blood)

14. Endocrine Gland Hormone Primary Hormone Function
Pancreas Insulin
Glucagon
Helps control carbohydrate metabolism
(i.e., lowers blood sugar levels)
Helps control carbohydrate metabolism
(i.e., increases blood sugar levels)
Adrenal cortex Cortisol
Aldosterone
Helps control carbohydrate, protein,
and lipid metabolism; protects against
stress
Helps control the body’s water and
electrolyte regulation

15. Endocrine Gland Hormone Primary Hormone Function
Testes Testosterone Stimulates development of the
male reproductive organs, sperm
production, and protein anabolism
Ovaries Estrogen (produced by the
follicle)
Progesterone (produced by
the corpus luteum)
Stimulates development of the
female reproductive organs
Prepares uterus for pregnancy and
mammary glands for lactation

16. Hormones secreted by other organs
Pineal gland Melatonin
Thymus 1. Thymosin
2. Thymin
Kidney 1. Erythropoietin
2. Thrombopoietin
3. Renin
4. 1,25dihydroxycholecalciferol (calcitriol)
5. Prostaglandins
Heart 1. Atrial natriuretic peptide
2. Brain natriuretic peptide
3. Ctype natriuretic peptide
Placenta 1. Human chorionic gonadotropin (HCG)
2. Human chorionic somatomammotropin
3. Estrogen
4. Progesterone

17. Local hormones
Local hormones are the substances which act on the same area of their secretion or in
immediate neighborhood. The endocrine hormones are secreted in one place but execute their
actions on some other remote place.
Local hormones are usually released in an inactive form and are activated by some conditions
or substances.
Classification of Local Hormones
Local hormones are classified into two types:
I Hormones synthesized in tissues
II Hormones synthesized in blood

18. I Local hormones synthesized in the tissues are:
1. Prostaglandins and related substances
 Prostaglandins
 Thromboxanes
 Prostacyclin
 Leukotrienes
 Lipoxins
2. Other local hormones synthesized in tissues.
 Acetylcholine
 Serotonin
 Histamine
 Substance P
 Heparin
 Leptin
 Gastrointestinal hormones

19. II LOCAL HORMONES PRODUCED IN BLOOD
Local hormones produced in the blood are:
 Serotonin
 Angiotensinogen
 Kinins.