4. THE ENDOCRINE
SYSTEM
The word endocrine derives from the Greek words "endo,"
meaning within, and "crinis," meaning to secrete. In
general, a gland selects and removes materials from the
blood, processes them and secretes the finished chemical
product for use somewhere in the body. The endocrine
system affects almost every organ and cell in the body.
The endocrine system is the collection of glands that
produce hormones that regulate metabolism, growth and
development, tissue function, sexual function,
reproduction, sleep, and mood, among other things.
ORGANS
The endocrine system is made up of the pituitary gland,
thyroid gland, parathyroid glands, adrenal glands,
pancreas, ovaries (in females) and testicles (in males).
6. • ADRENAL GANDS
• IT SECRETES ADRENALINE HORMONE WHEN THE
BODY IS UNDER STRESS.
• HYPOTHALAMUS
• IT CONTROLS HORMONE PRODUCTION BY
RELEASING DIFFERENT CHEMICALS TO PITUITARY
GLANDS.
• OVARIES
• PRODUCE ESTROGENS AND PROGESTERONE,
ALSO INVOLVE IN EGG-CELL PRODUCTION.
• PANCREAS
• IT SECRETES INSULIN.
9. • Steroid hormones are derived
from cholesterol.
• The endocrine glands are
responsible for the production of
steroid hormones, the adrenal
gland, the ovary, and the testis,
commonly known as the gonads.
• Steroid hormones have a few
important functions in the body
including water balance, sexual
development and stress response.
• Many but not all steroids are
hormones, however, not all
steroids are hormones.
10. • Five classes of steroid hormones:
• 1. ANDROGENS
• 2. ESTROGENS
• 3. PROGESTINS
• 4. MINERALOCORTICOIDS
• 5. GLUCOCORTICOIDS
• Androgens- Promote male sex development and
maintain male sex characteristics.
• Estrogens-Promote female sex development.
• In plants, auxin is an example of a steroid hormone that
regulates longitudinal cell structure so as to allow
bending of the stalk or stem in phototrophic response.
11. • Glucocorticoids
• Glucocorticoids originate in the adrenal cortex and affect
mainly metabolism; decrease inflammation and increase
resistance to stress.
• Mineralocorticoids
• Mineralocorticoids originate in adrenal cortex and
maintain salt and water balance.
• Progestin
• Progestin originate from both ovaries and placenta, and
mediate menstrual cycle and maintain pregnancy.
13. • Polypeptide hormones, or simply
peptide hormones, are hormones
made up of amino acids that are
secreted by the endocrine system.
• Endocrine organs that secrete
peptide hormones include the
hypothalamus, pituitary gland,
thyroid gland, adrenals, ovaries,
endocrine pancreas, and adipose
tissues.
• Peptide hormones secreted by the
hypothalamus are generally named
releasing factors, and include
corticotropin-, gonadotropin-,
somatotropin-, and thyrotropin-
releasing factor.
14. • Those secreted by the anterior
pituitary include melanocyte-
stimulating hormone, follicle-
stimulating hormone, luteinizing
hormone, adrenocorticotropic
hormone (ACTH), thyrotropic
hormone, and growth hormone or
somatotropin.
• The posterior pituitary secretes
vasopressin and oxytocin.
• Other peptide hormones include
thyroxine from the thyroid gland,
cortisol from the adrenals, and
insulin from the pancreas.
• Peptide hormones are secreted by
the hypothalamus, located in the
limbic system.
16. • Derived from Tyrosine.
• The thyroid hormones are synthesized and stored in
the thyroid gland and incorporated into
macromolecules of the protein thyroglobulin, which is
stored in large follicles within the thyroid gland.
• Hormone secretion occurs when the amines are split
from thyroglobulin, and the free hormones are then
released into the blood stream.
• After entering the blood, most of the thyroid
hormones combine with plasma proteins, especially
thyroxine-binding globulin, which slowly releases the
hormones to the target tissues.
• Epinephrine and norepinephrine are formed in the
adrenal medulla.
• Catecholaminesare taken up into preformed vesicles
and stored until secreted.
• Similar to the protein hormones stored in secretory
granules, catecholamines are also released from
adrenal medullary cells by exocytosis.
• Once the catecholamines enter the circulation, they
can exist in the plasma in free form or in conjugation
with other substances.
17. • Endocrine disorders involve either too much or too little hormone
secretion.
• Disorders may result from a problem in the gland itself, or because
the hypothalamic-pituitary axis provides too much or too little
stimulation.
• Depending on the type of cell they originate in, tumors can produce
excess hormones or destroy normal glandular tissue, decreasing
hormone production.
• Sometimes the body's immune system attacks an endocrine gland,
decreasing hormone production.
• Doctors usually measure levels of hormones in the blood to tell how
an endocrine gland is functioning.
• Sometimes blood levels alone do not give enough information about
endocrine gland function, so doctors measure hormone levels after
giving a stimulus (such as a sugar-containing drink, a drug, or a
hormone that can trigger hormone release) or after having the patient
take an action (such as fasting).