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L.E. Bio Topic 10 Regulation
Part II. The Endocrine System
Part II. The Endocrine System
• Made up of:
– Endocrine Glands
• Send hormones directly into blood stream
• No tubes ductless
• Exocrine glands have tubes or ducts
– Hyper secretion - too much of a hormone is secreted
– Hypo secretion – too little of a hormone is secreted
Human Endocrine Glands
Picture of the Endocrine System
Hypothalamus
• A small region of the brain
• Releases hormones that link the endocrine system with
the nervous system
• Major link between the body's two Regulatory systems!
Pituitary Gland
• At base of brain
• “Master Gland”
• Regulates other
endocrine glands
• Makes many
hormones –
– Direct, acts on
effectors
– Indirect, acts on other
glands
Pituitary Hormones LDHB 602-605
• GSH – Growth stimulating hormone - Direct
– Stimulates growth of long bones
– Hypo secretion – Dwarfism
– Hyper secretion – Giantism LDHB 611-615
Pituitary Hormones
• TSH – Thyroid Stimulating Hormone - Indirect
– Stimulates the thyroid to stimulate thyroxin
Pituitary Hormones
• FSH – Follicle Stimulating Hormone - Indirect
– Stimulates development of follicles (eggs) in ovaries
(females)
– Influences sperm production (males)
Pituitary Hormones
• ACTH – Adrenocorticotropic Hormone - Indirect
– Stimulates adrenal gland to secrete cortisone
Pituitary Hormones
• LH – Lutenizing Hormone - Indirect
– Stimulates formation of the corpus lutetium (ovary)
– Stimulates secretion of testosterone (testies)
Pituitary Hormones
• Prolactin - Indirect
– Milk secretion in females
• Vasopresin - Indirect
– Controls reabsorption of water in kidneys
• Oxytocin - Indirect
– Stimulates contraction of uterus during labor
Thyroid Gland
• In neck
• Secrets Thyroxin
– regulates rate of
metabolism
– Essential for normal
physical and mental
development
• Iodine needed Goiter
Goiter
Why we use iodized salt
Thyroid Gland (thyroxin)
• Hypo Secretion
(too little)
– Low metabolic rate
– Person is tired and
often over weight
– Creationism
• Hyper Secretion
(too much)
– High metabolic rate
– Person is “Hyper” and
often thin
Parathyroid Gland
• Embedded in the thyroid
gland
• Secretes parathormone
– Controls calcium (Ca)
metabolism
– Necessary for nerve and
muscle function, blood
clotting, growth of bone
and teeth
Adrenal Glands
• Located on top of kidneys
• Secrete adrenaline
– Raises heart rate and
blood pressure
– Helps in times of stress
• Secretes cortisone
– For healthy joints
• Secretes steroids
– Converts fats and proteins
to glucose
Islets of Langerhans (pancreas)
• Small groups of cells on the pancreas
• Secret Insulin
– Lowers blood sugar – promotes absorption into cells
• Secretes Glucagon
– Raises blood sugar – promotes the conversion of
glycogen into glucose
The Gonads (Sex Glands)
• Ovaries– Secrete estrogen
• Egg development
• Development of secondary sex characteristics (list)
– Secrete progesterone
• Promotes the thickening if the uterine lining
• Testis– Secrets testosterone
• Development of secondary sex characteristics (list)
• Sperm Production
Thymus
• Underneath the sternum
– Secretes Thymosin
• Helps to develop the immune system
• Shrinks with age.
Feedback
• A change in one quantity causes a change in a
second quantity, which then in turn causes a
change in the first quantity.
• Types
– Positive Feedback, Levels will continue to escalate
• Keeping up with the Jones’.
– Negative Feedback, a type of feedback that opposes
the initial change. A stabilizing effect
Maintaining homeostasis
Feedback
hormone 1
lowers
body condition
gland
high
specific body condition
low
raises
body condition
gland
hormone 2
Negative Feedback
• Level of one hormone stimulate or inhibit the
production of a second hormone.
• The second hormone level in the blood then in
turn stimulates or inhibits the production of the
first hormone.
• See diagram and example
Negative Feedback
• Response to changed body condition
– if body is high or low from normal level
• signal tells body to make changes that will bring body back to
normal level
– once body is back
to normal level,
signal is
turned off
hormone 1
gland
lowers
body condition
high
specific body condition
Negative Feedback Example
• TSH and Thyroxin
• When Thyroxin level drops below the
homeostatic level, the pituitary is stimulated to
secrete TSH.
• TSH then stimulates the thyroid gland to secrete
thyroxin.
• When Thyroxin level rises to the homeostatic
level, TSH secretion by the pituitary is inhibited.
Negative Feedback pict.
TSH
TSH
Thyroxin
Endocrine System Control
Feedback
Regulation of Blood Sugar
insulin
body
cells take
up sugar
from blood
pancreas
liver stores
sugar
high
blood sugar level
(90mg/100ml)
low
triggers
hunger
liver
releases
sugar
liver
reduces
appetite
liver
pancreas
glucagon
Diabetes: insulin deficiencyresults in an elevated blood sugar
level (glucose)
Cell Membrane Receptors
Many cell
membranes have
receptor molecules
on their
surface. These
receptor sites play
an important role in
allowing cells and
organs to
communicate with
one another.
A Hormonal Feedback
Mechanism
The animation at
the right
illustrates how a
hormone can bind
to receptors on a
cell membrane
and trigger that
cell to produce a
needed
compound.
Responding to hormones
• Lock and key system
– hormone fits receptor on “target” cell
target
cell
secreting
cell
can’t
read
signal
nontarget
cells
can’t
read
signal
Regulation by chemical messengers
• Neurotransmitters released by neurons
• Hormones release by endocrine glands
endocrine gland
neurotransmitter
axon
hormone carried
by blood
receptor proteins
receptor proteins
target cell