ENDORINE SYSTEM

1

• ENDORINE SYSTEM
• The endocrine system is one of the two
  coordinating and integrating systems of the body,
  the other being the nervous system. It acts
  through chemical messengers (hormones) carried in
  the circulation.
• 1. Endocrine Control Mechanisms
• Nervous and Endocrine Systems Function Together
  to Promote Homeostasis
• nervous system endocrine system
• neuroendocrine system

2
(No Transcript)
3

• B. Hormones
• Definition
• A hormone can be defined as a chemical substance
  which is synthesized and secreted by a specific
  cell type, is transported in the circulation and
  at very low concentrations elicits a specific
  response in distant target tissues
• Differences of endocrine, paracrine and autocrine
  mechanisms
• Classification
• peptide hormones, e.g. growth hormone, insulin
• steroid hormones, e.g. aldosterone, testosterone
• amino acid derivatives, e.g. thyroxine and
  adrenaline

4

• Hormone synthesis and secretion
• synthesis of peptide hormones follow the same way
  as protein synthesis
• Precursors ? proteolytic cleavage ? peptide
  hormones or proteins ? stored in vesicles ?
  release upon appropriate stimulus into the blood
• synthesis of steroid hormones
• Types of steroid hormones
• Glucocorticoids
• Mineralocorticoids
• Androgens
• estrogens
• progestins

5
(No Transcript)
6
A
B
C
7

• They all come from a common precursor
  cholesterol
• Once they are synthesized, they diffuse across
  the cell membrane into the interstitial fluid
  then into the blood so that their rate of release
  is determined by their rate of synthesis.
• synthesis and secretion of hormones from tyrosine
  derivatives
• Hormone transport and inactivation
• Once released into the blood stream,
  lipid-soluble hormones, e.g. thyroid and steroid
  hormones, are carried bound to various plasma
  proteins.
• Free form ?? bound form a dynamic equilibrium

8
(No Transcript)
9
(No Transcript)
10

• half-life of hormones minutes to days
• Inactivation may occur in the blood, in the
  liver, or kidney, or in the target tissues.
• Hormone actions
• membrane permeability
• activity of rate-limiting enzymes in reaction
  pathways
• protein synthesis
• gene activation leading to the transcription of
  new mRNA species
• Control of hormone secretion
• negative feedback mechanism
• positive feedback mechanism

11

• Mechanisms of Hormone Action
• second messenger model
• cyclic AMP
• inositol triphosphate (IP3 ) and diacyglycerol
  (DG)
• ions
• gene expression model
• The time of action for hormone using the two
  models

12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16

• The two second messengers diacylglycerol (DAG)
  and inositol triphosphate (IP3)

17
(No Transcript)
18

• 2. The Important Endocrine Glands and Their
  Hormones
• A. The pituitary hormones
• anatomy of the pituitary gland and its relation
  to the hypothalamus
• anterior lobe
• intermediate lobe
• posterior lobe
• pituitary stalk
• supraoptic neucleus
• paraventricular nucleus
• hypothalamus-pituitary portal system
• short portal system

19
(No Transcript)
20

• Regulation of pituitary hormone secretion by the
  hypothalamus
• secretion of posterior pituitary hormones a
  typical neuroendocrine regulatory mechanism
• secretion of anterior pituitary hormones a
  typical endocrine regulatory mechanism
• important releasing/inhibiting hormones produced
  in hypothalamus
• Corticotropin-releasing hormone (CRH)
• Thyrotropin-releasing hormone (TRH)
• Gonadotropin-releasing hormone (GnRH)
• Growth-hormone-releasing hormone (GHRH)
• Prolactin-releasing hormone (PRH)
• Prolactin-inhibitory hormone (PIH)

21

• Posterior pituitary hormones
• Antidiuretic hormone (ADH, vasppressin)
• chemistry 9 amino acid peptide, produced
  primarily by supraoptic nucleus and small amount
  by paraventricular nucleus
• actions
• 1) water retention by the kidney ?
  ?urine volume and ? ECF
• 2) vasoconstriction (in large amounts)
• regulation/stimuli
• 1) blood (or ECF) osmolality/osmoreceptors 2)
  blood volume

22

• 3) others alcohol, nicotine, barbiturates, etc.
• abnormality diabetes insipidus
• Oxytocin
• chemistry 9 amino acid peptide, produced
  primarily by paraventricular nucleus and small
  amount by supraoptic nucleus
• actions 1) regulating breast milk release
• 2) contraction of pregnant uterus
• regulation/stimuli
• suckling by a nursing infant
• crying sounds from a baby
• fear and stress inhibit release

23

• anterior pituitary hormones
• Growth hormone
• Prolactin
• Thyroid-stimulating hormone
• Adrenocorticotrophic hormone
• Folicle-stimulating hormone
• Luteinizing hormone
• Growth hormone (GH)
• chemistry191 peptide
• actions see Fig.13-7
• regulation/stimuli
• Growth hormone releasing hormone (GHRH)

24
(No Transcript)
25
(No Transcript)
26

• Growth hormone inhibitory hormone (somatostadin)
• other stimuli
• deep sleep
• low blood glucose
• stress
• amino acids (arginine)
• abnormality
• dwarfism
• gigantism (acromegaly)

27
(No Transcript)