Download Intro to Endocrinology

Intro to Endocrinology
The Endocrine System
• With the nervous system,
coordinates and directs the
activity of the body’s cells
• Widespread effects, but
controls major processes:
– Reproduction
– Growth & development
– Mobilizing body defenses
against stressors
– Maintaining blood
electrolyte, nutrients, and
water levels
– Regulates cellular
metabolism and energy
balance
A comparison:
Endocrine System
• Regulates the body
• Uses chemical signals called
hormones
• Slow to kick in and effects
are long-lasting
Nervous System
• Regulates the body
• Uses nerve
impulses/neurotransmitters
• Very fast- muscles and
glands into immediate
action
Quick brainstorm!
You are walking barefoot
and step on a piece of
broken glass (ouch!). You
immediately pull your foot
back.
Why is it a good thing that the
nervous system was in charge of
responding to this stimulus rather
than the endocrine?
Hormones
• Chemical substances secreted by endocrine cells
into the extracellular fluids
• Regulate metabolic activity of other cells
Turn & briefly discuss with your neighbor:
All hormones circulate in the bloodstream at the
same time, so how do tissues “know” which
hormones to “listen” to?
Hormones
• Each hormone ONLY acts on one type of cell
(a target cell) or tissue (target tissue)
• Each target cell has a receptor for that
hormone ONLY.
Lock and key!
• Locations of receptors:
– Plasma membrane
– Interior of cell
When a hormone binds to its
receptor…
• Causes one or more of the
following changes:
1. Changes permeability of the
plasma membrane
2. Synthesis of proteins or certain
regulatory molecules (like
enzymes)
3. Activation or inactivation of
enzymes
4. Stimulation of mitosis
5. Promotion of secretory activity
Talk at your table and
be ready to share:
1. What does this mean?
2. What does “synthesis”
refer to?
3. What are enzymes
for?
4. What’s the result of
this?
5. What does this mean?
Hormone chemistry
• Peptide (protein)-derived
• Amino acid-derived
• Lipid-derived
Oxytocin 
Polypeptide-Derived Hormones
• Made by the process of translation
–
–
–
–
Gene on DNA is copied by mRNA
mRNA is “read” by a ribosome
The ribosome + tRNA make a protein
The protein folds and does its job
• Not lipid soluble; bind to receptors
on cell surface
• Ex: insulin
Growth hormone
Amino Acid-Derived Hormones
• Amino acids are the building blocks of
proteins
• These hormones are modified amino acids
– Mainly tyrosine and tryptophan
• Not lipid soluble; bind to surface receptors
• End in “-ine” (ex: epinephrine, thyroxine)
Tryosine
Thyroxine
Lipid-Derived Hormones
• Most are steroid
hormones (cholesterol
derived)
• Unlike protein hormonesthese are not stored in
large amounts
• Lipid soluble; act on
intracelluar receptors (in
cytoplasm or nucleus)
• End in –ol or –one (ex:
testosterone, cortisol)
Cholesterol
Testosterone
Be ready to answer!
• Describe the relative speed of the nervous
system compared to the endocrine system.
• How does the endocrine system relate to the
digestive system?
• At some given time, there are 5 hormones in
the blood. How does the target cell know
which one to “listen” to?
• Which class of hormone acts on intracellular
receptors of a cell?
Feedback loops
• Most work by negative
feedback to maintain
homeostasis
• Rate of the process decreases
as the concentration of the
product increases
• Avoids accumulation of a
product
• Thyroid hormone
Hypothalamus
TRH
Anterior pituitary
TSH
Thyroid gland
Thyroid hormones
Target cells
Feedback loops
• A few work by positive
feedback
• Original stimulus is
promoted
• Rate of the process
increases as the
concentration of the
product increases
• Continues until stimulus
ends or product
consumed
• Childbirth
Oxytocin causes
uterus to
contract/push
baby towards
cervix
Baby pushes
against cervix
Brain stimulates
pituitary to
release oxytocin
Stretching sends
nerve impulses
to brain
Stimulating Endocrine Glands
• Hormonal stimuli
– Most common stimulus
– Endocrine organs prodded into action by other
hormones
– Ex) Hypothalamus  pituitary  another endo organ
Stimulating Endocrine Glands
• Humoral Stimuli
– Changing levels of something in the blood (ions,
nutrients) stimulates hormone release
– Example: PTH released when blood calcium drops
Stimulating Endocrine Glands
• Neural Stimuli
– Rarest
– Nerve fibers stimulate hormone release
– EX: Sympathetic stimulates release of adrenaline and
noradrenaline from adrenal glands
Crash Crouse:
Great Glands- Your Endocrine System
• During the video, take notes on the general
job of each gland. It’s a good preview for
what’s coming up!
• https://www.youtube.com/watch?v=WVrlHH14q3o