Introduction to the Endocrine System

 Journal: What
is the function of the
endocrine system?
 After
you complete this journal, hand in
your journals. You should have at least 15
 Series
of organs and glands that secrete
hormones into your bloodstream
What does the Endocrine System control?
1. Growth & development
2. Reproduction
3. Reducing body stress
4. Maintaining water, electrolyte and
nutrient balance
5. Regulating cellular metabolism and
energy balance
6.Maintain homeostasis
Major Endocrine
Hypothalamus &
Pituitary Glands
Thyroid & Parathyroid Gland
Adrenal Glands
 Chemical
messengers released by
endocrine glands that are released into
the blood stream and travel all over your
 Cause a widespread response
Chemical Messenger Comparison
Chemical Messenger
Chemical Messenger
Released at chemical
Intended for close target
Released into bloodstream
Effect happens quickly
Effect takes time
Effect wears off quickly
Effect lasts longer
Affects single cell
Affects many cells
Travels to distant targets
 Hormones
bind to receptors on the
outside or inside of target cells
• If the receptor is on the outside…
 It changes cell membrane permeability
 It changes enzyme activity inside the cell
• If it binds to receptors inside the cell…
 Its called a steroid
 Interact directly with the cell’s DNA to change cell
 Most
endocrine organs are active all the
time, but the amount of hormone
produced changes
 Homeostasis including the amount of
hormones produced is regulated through
positive and negative feedback loops
 Neural Control
• Hormone levels controlled by the nervous system
 Ex: Adrenal gland secretes hormones to prolong
sympathetic response
 Hormonal Control
• Glands are arranged in a hierarchy and each regulate
the gland below them in the chain
 Ex: Hypothalamus controls the pituitary gland which
controls the adrenal gland which produces a hormone
called cortisol, which allows humans to deal with stress
 Humoral Control
• Hormone levels controlled by body fluids
 Ex: Pancreas secretes insulin in response to rising blood