Homeostasis
Homeostasis
Negative feedback systems in
Negative feedback systems in
the human body
the human body
By Karyn Coulon
By Karyn Coulon
Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.
What is homeostasis?
What is homeostasis?
Process that occurs in all
Process that occurs in all
living things
living things
All organ systems work
All organ systems work
together to achieve
together to achieve
homeostasis
homeostasis
Ability of an organism to
Ability of an organism to
maintain its internal
maintain its internal
environment, despite
environment, despite
changes to its internal or
changes to its internal or
external environment
external environment
How does homeostasis work?
How does homeostasis work?
Feedback pathways
Feedback pathways
A cellular relay race!
A cellular relay race!
Specific organs and
Specific organs and
structures must
structures must
communicate with each
communicate with each
other in response to
other in response to
changes in the body
changes in the body
Keeps levels of certain
Keeps levels of certain
processes within a
processes within a
normal range
normal range
Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.
What things in your body need to be
What things in your body need to be
kept within a range?
kept within a range?
Body Temperature
Body Temperature
Blood pressure
Blood pressure
Blood pH
Blood pH
O
O
2
2
and CO
and CO
2
2
concentration
concentration
Osmoregulation-Water balance
Osmoregulation-Water balance
Cellular Relay Race
Cellular Relay Race
Stimulus
Stimulus
Receptor
Receptor
Integrating
Integrating
center
center
Effector
Effector
Response
Response
Reverses the
Reverses the
Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.
Negative Feedback Pathways
Negative Feedback Pathways
Way in which most
Way in which most
homeostatic
homeostatic
mechanisms work
mechanisms work
The product of the
The product of the
pathway inhibits, or
pathway inhibits, or
shuts down, the
shuts down, the
original signal
original signal
Why is this an
Why is this an
important feature in
important feature in
living things?
Why is feedback important in
Why is feedback important in
living things?
living things?
Allows baseline to be
Allows baseline to be
regained
regained
Conserves resources
Conserves resources
mouth
Stomach
Sm. Intestine
Pancreas
ß-cells
Target
cells-Muscle
Target cells-
Liver
Target cells-
Brain
Circulatory Runners
Game set-up
http://commons.wikimedia.org/wiki/File:Pictgram_running_man.svg
http://en.wikipedia.org/wiki/File:Archery_Target_80cm.svg
http://en.wikipedia.org/wiki/File:Llave_bronce.jpg
http://commons.wikimedia.org/wiki/File:Day-template.svg http://commons.wikimedia.org/wiki/File:Icon_announcer.svg
mouth
Stomach
Sm. Intestine
Pancreas
Target
cells-Muscle
Target cells-
Liver
Target cells-
Brain
Circulatory Runners
“Glucose!! Release the insulin!”
mouth
Stomach
Sm. Intestine
Pancreas
ß-cells
Target
cells-Muscle
Target cells-
Liver
Target cells-
Brain
Circulatory Runners
“Glucose!! Release the insulin!”
Insulin has been
passed to the
target cells.
Targets can now
receive glucose.
http://commons.wikimedia.org/wiki/File:Pictgram_running_man.svg http://en.wikipedia.org/wiki/File:Archery_Target_80cm.svg http://en.wikipedia.org/wiki/File:Llave_bronce.jpg http://commons.wikimedia.org/wiki/File:Day-template.svg http://commons.wikimedia.org/wiki/File:Icon_announcer.svg
mouth
Stomach
Sm. Intestine
Pancreas
Target
cells-Muscle
Target cells-
Liver
Target cells-
Brain
Circulatory Runners
“Hold insulin production”
Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.
Dueling Hormones
Dueling Hormones
What goes up, must come down!
What goes up, must come down!
Insulin
Insulin
Produced by
Produced by
-cells
-cells
of the Pancreas
of the Pancreas
Released into
Released into
circulatory system
circulatory system
when blood glucose is
when blood glucose is
high
high
Facilitates the
Facilitates the
transport of glucose
transport of glucose
into target cells
into target cells
Glucagon
Glucagon
Produced by
Produced by
-cells
-cells
of the pancreas
of the pancreas
Released into the
Released into the
circulatory system
circulatory system
when blood glucose is
when blood glucose is
low
low
Signals the liver to
Signals the liver to
break down glycogen
break down glycogen
into simple glucose
Dueling Mechanisms
Dueling Mechanisms
What goes up, must come down!
What goes up, must come down!
Thermoregulation
Thermoregulation
Sweating (cooling) vs. shivering (warming)
Sweating (cooling) vs. shivering (warming)
Blood Pressure
Blood Pressure
Vasconstriction vs. vasodilation
Vasconstriction vs. vasodilation
Osmoregulation
Osmoregulation
Hypotonic vs. hypertonic
Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.
Food for thought…
Food for thought…
On average, how many organ systems are
On average, how many organ systems are
involved in each of the processes we’ve
involved in each of the processes we’ve
explored?
explored?
Are there any organ systems that you see in
Are there any organ systems that you see in
all
all
of these processes?
of these processes?
What might happen to these pathways if just
What might happen to these pathways if just
one
