1. ENDOCRINE SYSTEM 1
R. Kalliecharan

2. Hormonal Effects
Hormones regulate :
1) Homeostasis– chemical comp and
volume
2) Metabolic Activities
3) Growth and Development
4) Reproduction
5) Immune System
6) Smooth and Cardiac Muscles

3. Location of Glands
• 1) Specific Hormones affect Specfic
TARGET Cells by binding to `
Specific RECEPTORS
• For e.g. TSH binds to receptors on
surface of Thyroid Follicular cells but not
to Adrenals
• Receptors are constantly synthesized
and broken down

4. Hormone Transport
Circulating Hormones ( Endocrine
secretion) - hormones in blood act on
distant target cell e.g. LH or ACTH
Paracrine secretion – act within short
distance e.g. Gastrin H of G-cells in
pylorus act on parietal cells of
fundic glands
Juxtacrine secretion-- act at very short
distance e.g. somatostatin inhibits
insulin
Autocrine secretion-act on themselves
e.g. interleukin-2

6. Mechanism of Hormone
Action
• 1) Steroid and Thyroid Hormones—
activation of intracellular
receptor
• 2) Protein Hormones—activation of
plasma membrane –1st messenger –
adenyl cyclase activation followed
by 2 nd messenger (c AMP )

7. Pituitary Gland (Hypophysis)
• Location: Sella Turcica of Sphenoid bone
• Gland is attached to Hypothalamus by
infundibulum
• Lobes:1) Adenohypophysis- oral ectoderm
and (2) Neurohypophysis-neural ectoderm
• 1)Adeno—consists of pars distalis (Ant
pit) , pars tuberalis and pars intermedia
• 2)Neuro—consists of pars nervosa (Post
pit) , infundibular stem and median
eminence

9. Pars nervosa

11. Hypophyseal Portal System
• 1) Hypothalamus secretes releasing and
inhibiting hormones into primary capillary
plexus (pcp) at Med Eminence
• 2) Int Carotid A—superior hypophyseal
artery---PCP---hypophyseal portal veins ---
secondary CP in pars distalis— hormones
go out via Ant hypophyseal veins

14. Ant Pit (pars distalis)
• 1) Cells are ÷ into chromophils and
chromophobes
• Chromophils are ÷ into acidophils
and basophils
• 2) Acidophils and secretions :
a) somatotrophs → GH (somatotropin)
b) mammotrophs → prolactin

16. • 3) Basophils and secretions
a) thyrotrophs → TSH
b) corticotrophs → ACTH, LPH, MSH,
endorphins and enkephalins
c) gonadotrophs → LH and FSH
4) Chromophobes → no cytoplasmic
staining

18. Hypothalamic Regulation of
Pars Distalis
• Hypothalamus secretes Releasing and
Inhibiting Hormones
• TRH--- ↑ TSH --- ↑ T 4 + T 3
• CRH--- ↑ ACTH--- ↑ glucocorticoids
(Adrenals)
• GnRH--- ↑ FSH--- ovary (↑ estrogens) ,
-- Sertoli cells (↑ABP and inhibin)
• --↑ LH maturation,ovulation, and
corpus luteum
• --Leydig cells (↑ testosterone )

19. Hypothalamic Regulation
of Pars Distalis
GRH(SRH)---↑GH--- ↑Somatomedin C
•
• Somatostatin---↓ GH
PRH--- ↑ Prolactin--- ↑ milk secretion
•
PIH (dopamine)--- ↓ Prolactin
•

21. Cont.
• Pars Tuberalis--- some cells secrete
FSH and LH
• Pars Intermedia---Area is
rudimentary in Humans

22. Negative Feedback System
• Hypothalamus(CRH)->AntPit(↑ACTH)
↑ ↓
•
• ¦ Adrenal cortex(↑cortisol)
↓
• ¦
---------------------------------- ↓
•

23. ++
Target
Target Tissue Tissue
TSH
T3& T4

25. Neurohypophysis
• Pars nervosa (post pit)---has no secretory
cells. It has pituicytes and
unmyelinated axons of
neurosecretory neurons.
• Herring bodies contain hormones. These
are Oxytocin from paraventricular N.-
uterine m
• And ADH (vasopressin )from supraoptic N
• -- increases water permeability of kidneys