Hormones &
The Endocrine Glands
10.1 & 10.2
Hormones
• chemicals produced by cells in one part
of the body that regulate processes in
another part of the body
• endocrine glands secrete hormones
directly into the blood (exocrine glands
into ducts)
Endocrine vs. Nervous
• both systems integrate and control
organs and tissues
• nervous system helps body to adjust
quickly to changes
• endocrine system maintains control
over longer periods of time
Types of hormones
• protein hormones are amino acid
chains and are water-soluble; diffuse
well through blood and fluids
• steroid hormones are derived from
cholesterol and are soluble in blood
when combined with hydrophilic carrier
proteins
Water-Soluble Hormones
Animation…
• Narrated animation of water-soluble
(protein) hormones. Specific example of
using cAMP to activate proteins in the
target cell:
• http://highered.mcgrawhill.com/sites/0072943696/student_view0/chapter10/
animation__second_messenger__camp.html
Fat-Soluble Hormones
Animation…
• Narrated animation of steroid hormone
action:
• http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/si
tes/dl/free/0072437316/120109/bio46.swf::Mechanis
m%20of%20Steroid%20Hormone%20Action
Hypothalamus
• part of the nervous system
• produces neurohormones which
diffuse into the blood and travel to the
pituitary gland
Pituitary Gland
• “master gland”
• secretes hormones that control other
endocrine glands
• under the nervous control of the
hypothalamus
Pituitary Gland
Anterior Pituitary
• neurohormones from the hypothalamus
stimulate or inhibit release of hormones
• produces, stores & releases:
– prolactin (PSH)
– growth hormone
– tropic hormones (TSH, ACTH, FSH, LH)
– melanocyte-stimulating hormone MSH
“Intermediate Lobe”
• not very developed in humans
• releases endorphins, “natural
painkillers”
• endorphins function in the nervous
system in pathways that control pain)
Posterior Pituitary
• stores and releases hormones
produced by the hypothalamus:
– anti-diuretic hormone (ADH)
– oxytocin
Thyroid Glands
• stimulated by TSH secrete thyroxin (T4)
• in target cell, T4 is converted to T3,
triiodothyronine, which enters nucleus
and combines with receptors
• affects growth, development,
metabolism, etc.
Thyroid Glands
• also has specialized cells that secrete
calcitonin (protein hormone)
• lowers Ca2+ levels in blood by
stimulating deposition in bones, and
reducing Ca2+ uptake by kidneys
Negative Feedback
• hypothalamus release TRH
• TRH causes the anterior pituitary to
release TSH
• TSH causes the thyroid to release T4
• T4 inhibits secretion of TSH by the
anterior pituitary
Parathyroid Glands
• produce parathyroid hormone (PTH)
• when Ca2+ levels are too low, PTH is
released:
– stimulates bones to release Ca2+
– stimulates kidneys to activate vitamin D,
which acts on cells in intestines to increase
Ca2+ absorption
Adrenal Glands
• adrenal medulla secretes epinephrine &
norepinephrine
– “fight or flight” situations
• adrenal cortex secretes hormones such
as aldosterone (osmoregulation),
cortisol (blood glucose regulation)
Pineal Gland
• regulates biological rhythms due to
secretion of melatonin
• light (detected by the eye) inhibits
melatonin secretion