Endocrine System

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Endocrine System
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Systems of Human Body

• When a bunch of organs work together on one big
  project, thats called a system.
• Skeletal
• Digestive
• Muscular
• Lymphatic/Immune
• Endocrine
• Nervous
• Reproductive
• Urinary
• Cardio-vascular

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Glands

• A Gland is a group of cells or tissue that
  produces and secretes or gives off chemicals.

Releases their secretions through ducts
Releases their secretions directly in blood stream
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Endocrine Glands
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Hormone

• Hormone is a chemical substance that is secreted
  into the body fluid by cells that exerts a
  physiological control effect on other cells of
  the body. Hormones transfer information and
  instructions from one set of cells to another.
• The endocrine system is instrumental in
  regulating mood, growth and development, tissue
  function and metabolism as well as sexual
  function Reproductive processes.

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Properties of Hormone

• Hormones are informational molecules.
• Hormones are highly specific in nature.
• Hormones stimulate or inhibit specific biological
  process.
• The effect of hormones is slow and lingering.
• Their deficiency may lead to serious
  consequences.
• Hormones show feed-back mechanism.

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Classification of Hormone
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Hormone Receptors

• These are specialized proteins capable of binding
  the hormone molecule with very high specificity
  and affinity.
• Receptor proteins are present either on surface
  of a cell or in its interior.
• Down Regulation Binding of receptors by hormone
  leads to decrease in the number of receptors,
  which decreases the response of target tissue to
  hormone.

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Hormone Receptors
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Mode of Action
Receptor on the surface of the cell membrane
Receptor inside the cell cytoplasm
All hormones acts by binding to specific receptor
proteins in the target tissue cells.
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Hypothalamus

• The hypothalamus is a collection of specialized
  cells that is located in the lower central part
  of the brain.
• Is the main link between the endocrine and
  nervous systems.
• Nerve cells in the hypothalamus control the
  pituitary
• gland by producing chemicals that either
  stimulate or suppress hormone secretions from the
  pituitary.

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Hormone Secreted by Hypothalamus

• Thyrotropin-releasing hormone (TRH)
• Gonadotrophin-releasing hormone (GnRH)
• Growth hormone-releasing hormone (GHRH)
• Corticotropin-releasing hormone (CRH)
• Somatostatin (Growth factor-inhibiting hormone)
• Dopamine

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Pituitary Gland

• It is unpaired, pea shaped, small gland about 1
  cm, in diameter 0.5 to 1 gram in weight
• Connected to the hypothalamus by the pituitary
  stalk
• Divisible into
• Anterior Lobe (Adenohypophysis)
• Posterior Lobe (Neurohypophysis
• It is also called as hypophysis (from Greek,
  lying under)

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Pituitary Gland
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Hormones
Function
Anterior Lobe (Adenohypophysis)

• Promotes Growth,
• Controls Metabolism
• Stimulates growth and
• activity of thyroid gland
• Synthesis of cortisols
• Stimulation of Lactation

• Growth Hormones
• Thyroid Stimulating Hormone
• Adrenocorticotropic Hormones
• Prolactin

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Anterior Lobe (Adenohypophysis)

• In females, controls the growth of ovarian
  follicle.
• In males, stimulates spermatogenesis.
• In females, promotes maturation of follicle and
  ovulation.
• In males, stimulates interstitial cells.

• Gonadotrophic Hormones
• Follicle Stimulating Hormone
• Luteinizing Hormone

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Hormones
Function
Posterior Lobe (Neurohypophysis)

• Promotes contraction of uterine muscle
• Promotes contraction of myoepithelial cells of
  lactating breast.
• Increases reabsorption of water
• Contraction of smooth muscle.

• Oxytocin
• Anti Diuretic Hormone

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GnRH (Gonadotrophin Releasing Hormone)

• Decapeptide, made up of 10 a.a.
• Secretes two hormones FSH/LH
• Secreted in highly pulsatile manner.
• The amplitude and the frequency at which GnRH is
  produced plays an important role in determining
  which hormone will be produced.
• Higher Frequency LH is secreted
• Lower frequency FSH is secreted.
• The half life is 3-5 mins.

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Hypothalamus
RH
Pituitary Gland
TH
Inhibitory Effect
Stimulatory Effect
Target Gland
Hormone Secreted in Blood
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HPO Axis
Hypothalamus
GnRH
Feedback to Hypothalamus for secretions of FSH
and LH
Pituitary Gland
FSH
LH
Ovary
Estrogen
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