Colorado Life Science 2.6: Cells, tissues, organs, and
organ systems maintain relatively stable internal
environments, even in the face of changing external
environments
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Process that occurs in
all living things
All organ systems work
together to achieve
___________.
◦ Ability of an organism to
maintain its internal
environment, despite
changes to its internal or
________ environment!
http://en.wikipedia.org/wiki/File:Tightrope_artist_Cologne_1.jpg

pathways
◦ A cellular relay race!
◦ Specific organs and
structures must
communicate with each
other in response to
changes in the body
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http://en.wikipedia.org/wiki/File:Southern_12_stage-02_1988.jpg
Keeps levels of certain
processes within a
normal
.
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Body Temperature
Blood pressure
Blood pH
O2 and CO2 concentration
Osmoregulation-Water balance
Blood glucose

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Stimulus
Receptor
Integrating
center
Effector
Response
◦ Reverses the
stimulus

Consider temperature in your home….


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Stimulus- low thermal
energy in the room (it’s
cold)
Receptor- sensor in
thermostat
Integrating centerthermostat
Effector- Heater
Response- increased
thermal energy (it’s
warmer)
Also called feedback
. Way in
which MOST homeostatic mechanisms work
 Stimulus produces a response that opposes
or
the original stimulus

◦ In other words, the
product of a negative
feedback pathway inhibits
or shuts down the original
signal.
Stimulus

Living Example
_______________________
Sweating (cooling) vs. shivering (warming)
Blood Pressure
Vasconstriction vs. vasodilation
Osmoregulation
Hypotonic vs. hypertonic


Takes body out of
homeostasis (which
can be necessary in
certain
circumstances)
Stimulus causes a
_________ that causes
more of the stimulus
A
B

Examples
Increase in births
increases population
which increases births –
and so on.
Examples in Our Body
 Blood clotting


Injured tissue signals platelets to be activated, activated
platelets produce chemical signal that activates more
platelets
______________

The hormone oxytocin signals a contraction, which
signals they brain to produce more oxytocin

Identify the following as examples of positive
or negative feedback loops within the body?

Functions of Integumentary System:
◦
◦
◦
◦
◦
Protection
Body Temperature Regulation
Excretion
Information Gathering
Vitamin D Production


If cold, ___________
generates heat and goose
bumps and constricted
blood vessels help
decrease the heat loss
from skin
If hot, __________ blood
vessels allows excess heat
released from skin and
sweating allows energy to
leave the body

Function of Circulatory System
◦ Transport Oxygen,
CO2, nutrients and waste
to and from cells, as needed


_________ are exchanged in the lungs (Oxygen
in and Carbon Dioxide out)
Heart pumps blood from the body to the
lungs and then to the rest of the body

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Blood has pH of 7.4 (7.35-7.45)
Below 6.8 or above ______ cells stop
functioning

Blood Sugar Regulation!
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_________ – food into mouth
Digestion – mechanical and
chemical break down –
starts in mouth, continues
to break down in stomach
and small intestine
___________ – bloodstream
absorbs nutrients in small
intestine and absorbs water
in large intestine
Elimination – Waste
eliminated through anus


Glycogen- Stored glucose (polysaccharide of glucose)
Glucagon- Hormone secreted by pancreas that
_________ blood sugar (break down glycogen into
glucose)
◦ Produced by alpha-cells of the pancreas
◦ Released into the circulatory system when blood glucose is low
◦ Signals the liver to break down glycogen into simple glucose

Insulin- Hormone secreted by the pancreas that _________
blood sugar (glucose to glycogen)
◦ Produced by beta-cells of the pancreas
◦ Released into circulatory system when blood glucose is high
◦ Facilitates the transport of glucose into target cells
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Blood sugar regulation:
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On average, how many organ systems
are involved in each of the processes
we’ve explored?
Are there any organ systems that you see
in all of these processes?
What might happen to these pathways if
just one system was not functioning
properly?