1. (2

2. * The endocrine system helps to regulate body
function like the metabolism by releasing
certain hormones.
* The nervous system is what sends impulses to
the brain to assist the endocrine system.
* “Both function to achieve and maintain
stability of the internal environment” (2).
(23 ©)

3. * The endocrine system is much slower than the
nervous system.
* Instead of shooting impulses straight to the
brain through nerves, the hormones are
released and move through the bloodstream to
their target cells (2).
* The endocrine system controls more of the
internal body than the nervous system.

4. * Hormones are chemical messengers and are
produced by the ENDOCRINE SYSTEM. They are
distributed throughout the body by diffusion into
the bloodstream. They travel through the blood to
whichever organ or muscle they are meant to effect
which are called target organs or target cells. Only
the specific target will be affected by the
particular hormone that goes with it. Endocrine
glands are ductless glands. The glands make the
hormones but the hormones are not excreted
through ducts but by diffusion.

5. * These are the major endocrine glands: The Hypothalamus,
the Pituitary and the Pineal gland are located in the brain.
The Thyroid and Parathyroid glands are each paired and are
located in the neck. The Thymus gland is located right in the
center of the chest (also called the mediastinum.) The
Adrenal glands are a pair and they are located in the
abdominal cavity. Also in the abdominal cavity are the
Pancreatic Islets, near the pancreas. In a female, there are
two ovaries located in the pelvic cavity. In a male, there are
two Testes, located in the scrotum. Another Endocrine gland
is the placenta in a pregnant female.
* There are many useful ways to classify the various hormones
that these glands produce. One way is by function. Tropic
hormones target other endocrine glands and stimulate their
growth and secretions. Sex hormones, the kind we are most
familiar with, relate to reproductive organs and their
functions. Anabolic hormones stimulate anabolism in their
target cells.

6. * Steroid hormone molecules are manufactured
by endocrine cells from cholesterol, an
important type of lipid in the human body.
* Nonsteriod hormones are synthesized primarily
from amino acids rather than from cholesterol.
Some nonsteroid hormones are protein
hormones.

7. * Hormones signal a cell by binding to specific
receptors on or in the cell.
* In a “lock-and-key” mechanism , hormones will bind
only to receptor molecules that “fit” them exactly.
Any cell with one or more receptors for a particular
hormone is said to be a target of that hormone.
* A common type of combined action of hormones is
seen in the phenomenon of antagonism. In
antagonism, one hormone produces the opposite
effect of another hormone.

9. Hormone Source Targets Principal Action
Growth hormone-releasing hormone Hypothalamus Adenohypophysis Stimulates secretion of growth hormone
GRH (somatotrophs)
Growth hormone- inhibiting hormone Hypothalamus Adenohypophysis Inhibits secretion of growth hormone
GIH, or somatostatin (somatotrophs)
Corticoptropin- releasing hormone CRH Hypothalamus Adenohypophysis Stimulates release of adrenocorticotrophic hormone ACTH
(corticotrophs)
Thyrotropin-releasing hormone TRH Hypothalamus Adenohypophysis Stimulates release of thyroid-stimulating TSH
(thyrotrophs)
Gonadotropin- releasing hormone Hypothalamus Adenohypophysis Stimulates release of gonadotropins (FSH and LH)
GNRH (gonadotrophs)
Prolactin-releasing hormone PRH Hypothalamus Adenohypophysis Stimulates secretion of prolactin
(corticotrophs)
Prolactin- inhibiting hormone PIH Hypothalamus Adenohypophysis Inhibits secretion of prolactin
(corticotrophs)
Growth hormone GH (somatotrophs Adenohypophysis General Promotes growth by stimulating protein anabolism
[STH]) (somatotrophs)
Prolactin PRL (lactogenic hormone) Adenohypophysis Mammary glands Promotes milk secretion
(lactotrophs) (alveolar secretory
cells)
Thyroid-stimulating hormone TSH Adenohypophysis Thyroid gland Stimulates development and secretion in the thyroid gland
(thyrotrophs)
Adenocorticotrophic hormone ACTH Adenohypophysis Adrenal cortex Promotes development and secretion in the adrenal cortex
(corticotrophs)
Follicle-stimulating hormone FSH Adenohypophysis Gonads (primary Female: promotes development of ovarian follicle; stimulates
(gonadotrophs) sex organs) estrogen secretion
Male: promotes development of testis; stimulates sperm production
Luteinizing hormone LH Adenohypophysis Gonads Female: triggers ovulation; promotes development of corpus luteum
(gonadotrophs) Male: simulates production of testosterone
Antidiuretic hormone ADH Neurohypophysis Kidney Promotes water retention by kidney tubules
Oxytocin OT Neurohypophysis Uterus and Stimulates uterine contractions; stimulates ejection of milk into
mammary gland mammary glands

10. Hormone Source Targets Principal Action
Triiodothyronine (T3) Thyroid gland (follicular cells) General Increase rate of metabolism
Tetaiodothyronine (T4) Thyroid gland (follicular cells) General Increases rate of metabolism (usually converted to T3 first)
or thyroxine
Calcitonin CT Thyroid gland (parafollicular cells) Bone tissue Increases calcium storage in bone; lowering blood Ca++ levels
Parathyroid hormone Parathyroid glands Bone tissue and kidney Increases removal from storage in bone and produces the
PTH or parathromone active form of vitamin D in the kidneys, increasing absorption
of calcium by intestines and increasing blood Ca++ levels
Aldosterone Adrenal cortex (zona glomerlulosa) Kidney Stimulates kidney tubules to conserve sodium, which, in turn,
triggers, the release of ADH and the resulting conservation of
water by the kidney
Cortisol (hydrocortisone) Adrenal cortex (zona fasciculata) General Influences metabolism of food molecules; in large amounts, it
has an anti-inflammatory effect
Adrenal androgens Adrenal cortex (zona reticularis) Sex organs, other Exact role uncertain, but may support sexual function
effectors
Adrenal estrogens Adrenal cortex (zona reticularis) Sex organs Thought to be physiologically insignificant
Epinephrine (adrenaline) Adrenal medulla Sympathetic effectors Enhances and prolongs the effects of the sympathetic division
of the autonomic nervous system
Norepinephrine Adrenal medulla Sympathetic effectors Enhances and prolongs the effects of the sympathetic division
of the autonomic nervous system
Glucagon Pancreatic islets (alpha [a] cells or A General Promotes movement of glucose from storage and into the
cells) blood
Insulin Pancreatic islets (beta [b] cells or B General Promotes movement of glucose out of the blood and into cells
cells)
Somatostatin Pancreatic islets (delta [d] cells or D Pancreatic cells and Can have general effects in the body, but primary role seems
cells) other effectors to be regulation of secretion of other pancreatic hormones
Pancreatic polypeptide Pancreatic islets (pancreatic Intestinal cells and Exact function uncertain, but seems to influence absorption
polypeptide [PP] of F cells) other effectors in the digestive tract

12. Growth hormone- Hypothalamus Adenohypophysis Stimulates secretion of
releasing hormone growth hormone
Growth hormone- Hypothalamus Adenohypophysis Inhibits secretion of
inhibiting hormone growth hormone
Corticotropin- Hypothalamus Adenohypophysis Stimulates release of
releasing hormone adrenocorticotropic
hormone
Thyrotropin- releasing Hypothalamus Adenohypophysis Stimulates release of
hormone thyroid-stimulating
hormone
Gonadotropin- Hypothalamus Adenohypophysis Stimulates release of
releasing hormone gonadotropins
Prolactin- releasing Hypothalamus Adenohypophysis Stimulates secretion of
hormone prolactin

13. Prolactin- inhibiting Hypothalamus Adenohypophysis Inhibits secretion of
hormone prolactin
Growth Hormone Adenohypophysis General Promotes growth by
stimulating protein
anabolism and fat
Prolactin Adenohypophysis Mammary glands Promotes milk
secretion
Thyroid-stimulating Adenohypophysis Thyroid Glad Stimulates
hormone development and
secretion in the
thyroid gland
Adrenocorticotropic Adenohypophysis Adrenal Cortex Promotes
development and
secretion in the
adrenal cortex

14. Follicle-stimulating Adenohypophysis Gonads Female: Promotes
hormone development of ovarian
follicle; simulates estrogen
secretion
Male: development of
testies; sperm productions
Luteinizing hormone Adenohypophysis Gonads Female: triggers ovulation;
promotes corpus luteum
Male: stimulates
production of testosterone
Antidiurectic hormone Adenohypophysis Kidney Promotes water retention
by kidney tubules
Oxytocin Uterus and Stimulates uterine
mammary contractions; stimulates
ejection in mammary
Triiodothyronine Thyroid gland General Increases rate of
metabolism
Tetraiodothyronine Thyroid Gland General Increases, rate of
metabolism

15. lowering blood Ca level
Parathyroid Parathyroid Gland Bone Tissue and Increases calcium removal from
hormone Kidney storage in bone and produces the
active form of vitamin D in the kidneys,
increasing absorption of calcium by
intestines and increasing blood
Aldosterone Adrenal Cortex Kidney Stimulates kidney tubules to conserve
sodium, which in turn, triggers the
release of ADH and the resulting
conservation of water by the kidney
Cortisol Adrenal Cortex General Influences metabolism of food
molecules
Adrenal Adrenal Cortex Sex organs other Exact role uncertain, but may support
Androgens effectors sexual function
Adrenal Adrenal Cortex Sex organs Though to be physiologically
Estrogens insignificant
Epinephrine Adrenal Medulla Sympathetic Enhances and prolongs effects of
effectors sympathetic division of nervous system
Norenpine- Adrenal Medulla Sympathetic Enhances and prolongs effects of
phrine effectors sympathetic division of nervous system

16. Glucagon Pancreatic Islets General Movement of glucose
to blood
Insulin Pancreatic Islets General Movement of glucose
out of blood into cells
Somatostatin Pancreatic Islets Pancreatic cells and Secretion of pancreatic
other effectors hormones
Pancreatic Polypeptide Pancreatic Islets Intestinal Cells and Influence absorption in
other effectors digestive tract