Systems 2 Ch10
Endocrine System
Nicole Sullivan
Michaela Childress
Definition - The Endocrine System
The endocrine system refers to the collection of glands of an
organism that secrete hormones directly into the circulatory
system to be carried towards distant target organs.
Vocab to Know  to Understand Content
• Hormones - a regulatory substance produced in an organism and
transported in tissue fluids such as blood or sap to stimulate
specific cells or tissues into action.
• Secretion- a process by which substances are produced and
discharged from a cell, gland, or organ for a particular function in
the organism or for excretion.
Hormones
• Products of endocrine glands
• Endocrine glands secrete hormones
for a function
• Proteins or steroids
• Proteins- amino acids,
inactivated by acid & pepsin in
stomach
 injection (ex: insulin)
• Steroids- lipid soluble, taken
orally (sex hormones and those
taken from adrenal cortex)
Endocrine Gland Hormone Secretion
The major endocrine glands are a system interrelationships
& similar mechanisms of action, even though they’re all
scattered around the body
Mechanism of Hormone Action
• Hormones are carried through blood, only affect certain
cells
• Cells that respond to a hormone  have receptor sites
• Receptor sites-lock & key mechanism
• “If the key fits the lock, then the door will open”
• if the hormone fits the receptor site there will be an effect
• Located on the surface of the cell membrane or in the interior
of the cell
Target Tissue
• All cells that have receptor sites for a hormone make
up the target tissue for that hormone.
• Target Tissue- Cells that have receptors for a given
hormone
• It’s either localized in a single gland or organ, or
scattered throughout the body where more areas are
affected
• Cells in a target tissue have receptor sites for specific
hormones.
Insulin
• Beta cells in pancreatic islets produce insulin
• Works in response to high glucose levels in blood
• Lowers blood glucose levels
• Antagonistic to glucagon
• Stimulates liver to remove glucose from blood and
store it as glycogen
Growth Hormone
• Produced by the adenohypophysis
• Protein that stimulates the growth of bones,
muscles, & organs via protein synthesis
• Influences height- too little or too much affects
appearance
• Acromegaly (acrom-egaly)
• Ossification has taken place: Bone formation
is complete, increase in bone length stops &
bones increase in diameter (hands and face
bones become abnormally large)
Calcitonin
• Secreted by the parafollicular cells of the thyroid gland
• Hormone opposes the action of parathyroid glands by reducing
calcium level in blood
• Reduce rate at which calcium is released from bone
Aldosterone
• Mineralocorticoid are hormones secreted by the
outermost region of the adrenal cortex
• It is the Principal Mineralocorticoid
• Effect is to conserve sodium and water
• Primarily affects the kidneys
• Also acts on intestines, salivary glands, and sweat
glands
Epinephrine
• One of the two hormones secreted by the adrenal
medulla
• Epinephrine is also known as adrenaline
• Makes up 80 percent of the medullary secretion
• Made in response to stimulation of the sympathetic
nerves (particularly in stressful situations)
• Epinephrine and norepinephrine together cause
increased heart rates
Prostaglandins (prahs-tih-GLAN-dins)
• Potent chemical regulators that are produced in minute amounts
• Found widely distributed in cells throughout the body
• Similar to hormones but there is enough difference to not be
categorized as hormones
• Has short-term, localized, immediate effect
Pineal Gland
• Also called pineal body or epiphysis cerebri
• Small cone-shaped structure that extends posteriorly from the
third ventricle of the brain
• Source of melatonin
• Active throughout the life of an individual
• The presence of calcium in the gland suggests high
metabolic activity
 Chapter Quiz
Recall
1.
2.
3.
4.
5.
6.
Product of an endocrine gland  E) Hormone
Cells that have receptors for a given hormone  J) Target tissue
Lipid-soluble hormones  I) Steroid
Produced by the adenohypophysis  D) Growth hormone
Produced by the thyroid gland  B) Calcitonin
Effect is to conserve sodium and water  A) Aldosterone
7. Secreted by the adrenal medulla  C) Epinephrine
8. Lowers blood glucose levels  F) Insulin
9. Has short-term, localized, immediate effect  H) Prostaglandin
10. Source of melatonin  E) Pineal gland
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
Aldosterone
Calcitonin
Epinephrine
Growth hormone
Hormone
Insulin
Pineal gland
Prostaglandin
Steroid
Target tissue