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Final

study notes for lecture two: endocrine physiology


Department
Physiology
Course Code
PSL201Y1
Professor
Doug Mac Kay
Study Guide
Final

Page:
of 4
LECTURE TWO: ENDOCRINE PHYSIOLOGY
*endocrine physiology = hormone action
((endocrine system controls body functions))
Æhormones bind to receptors
Æbinding triggers signalling pathways within individual or groups of
cells
Æthe signalling pathways cause changes in cell activity
Æcell activity changes result in body function because cells
communicated with each other and regulate body function
example: growth hormone
Æexercise results in growth hormone secretion
Ægrowth hormone enters blood and binds to growth hormone
receptors on fat cell/adipocytes
Æbinding triggers multiple downstream signalling pathways
Æresults in fat breakdown for muscle energy
Æthis energy supplies the energy demands of exercise
Æbody systems do not exist within themselves
\Æbody systems need to communicate with each other to regulate body function
example: endocrine system and nervous system controls energy balance
*insulin action in the brain lowers liver glucose production in rodents
obesity & diabetes
Æhypo = too little insulin => increased glucose levels, increased appetite
Æresistance = too little effect
INSULIN
Binding Site
Mechanism
Effects
Other considerations
- brain
binds to a receptor in the brain
sends a signal via the efferent vagus that runs
between the brain and liver
o controls glucose production
¾ in diabetes and obesity,
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level of brain function
- liver
binds to a receptor on the liver
o controls glucose levels by controlling
production in the liver
¾ lowers glucose levels
¾ controls how much you eat
classical endocrine glands
Æpineal
Æhypothalamus
Æpituitary
Æthyroid
Æparathyroid
Æthymus
Æadrenal
Æpancreas
Æovary
Ætestis
Æ*fat/adipocytes (leptin/adiponectin)
www.notesolution.com
*newly accepted endocrine glands = fat cells} found 2 major hormones in adipocytes
leptin hormone = once made from fat, enters blood, binds to receptor in brain to lower appetite and glucose levels
adiponectin hormone = binds to receptors in the liver/muscle and brain, insulin sensitizer, improves insulin function, lowers glucose in liver
Æendocrine gland functions are tightly linked to hormonal action because it is where hormones are made from glands
Q: how would you determine the function of glands?
A: gain and loss of function experiments?
\Æremove gland and see effects on body function (in rodents)
\Æremove, see effects on body, re-insert, see if effects have reversed
\Æreplace gland or extract
\Æimplant gland or extract to produce excess
\Æpurify extract and test for effect in biological assay
((endocrine glands secrete hormones into the bloodstream))
Æcells at the level of connective tissue
\Æcells can form the endocrine gland where the hormones will be released into the bloodstream
\Æcells can form the exocrine gland where the hormones will be released the duct (external environment)
Æthis distinguishes the endocrine gland from the exocrine gland
HORMONE COMMUNICATION
TYPE
Mechanism
Effect
classic hormones
- secreted into the blood
- travels through the bloodstream
- sustains long communication in the body
maintains and regulates body function
neurohormones
- secreted to the bloodstream
- communicate with other target cells
long communication
neurotransmitters
- binds to adjacent cells
long communication
autocrine
paracrine
- can bind to its own receptor at the same
cell where it was made
- can bind to another cell within the same
organ
- undergo endocytosis
- can be cleared from circulation/system
short communication ability
usually negative effect system (high
level of hormone = high level of
binding to receptors)
hormone function is kept within the cell
it was made
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\Æsmall changes in hormone levels can have large effects in body function
www.notesolution.com
MANY TISSUES CONTAIN INDIVIDUAL ENDROCRINE CELLS THAT SECRETE HORMONES
Tissue
Hormone
Mechanism & Effect
adipose
- leptin
- adiponectin
targets brain and liver
regulates glucose levels and body weight
anterior pituitary
- prolactin
targets breasts
results in milk production
heart
- atrial natiuretic peptide (ANP)
targets kidney
favours sodium excretion
kidney
- erythropoietin
- calciferol
erythropoietin
targets bone marrow
enhances red blood cell production
calciferol
targets intestines
favours calcium absorption
stomach and intestine
- gastrin
- CCK
- secretin
targets GI tract, gut system, brain
digestive functions
maintains digestive system, ensures proper rate and manner of digestion of
meals to allow for efficient and regulated nutrient absorption
((hormones))
Æpotent chemical molecules
Æarouse or excite cells where their receptors are found
Æmade by cells in endocrine gland and other tissues {neurons, fat cells}
Æthey are secreted to communicate among cells via long/short communication methods
Æbind to specific receptors (**receptors define the function of a hormone)
Æalter activity and direct function of target cells
Æmaintain homeostasis or precipitate change in many physiological processes
recall: endocrine system can communicate and coordinate with the neuronal system
recall: classically, insulin binds to its receptor on the liver to alter hepatic function
**Æbut because of the recent link between the nervous system and the endocrine system, the insulin receptors found in the brain, binds insulin via
the nervous system can regulate glucose production in the liver
www.notesolution.com