Transcript FEEDBACK MECHANISMS - Kenmore Tonawanda UFSD

BELLWORK – 2/4/2014
1. Read pages 29-31 in your review book on
FEEDBACK and HOMEOSTASIS.
2. Read and discuss QUIETLY the ESSENTIAL
question below with your table partner (be prepared to
explain if called upon):
• During hot weather and vigorous exercise, people
sweat. As the water on their skin evaporates, the
water molecules absorb heat energy.
• Explain why this process is important to the
individual.
Dynamic Equilibrium
• Our bodies are constantly responding and adjusting to
external and internal stimuli, causes small changes in our
body temperature, blood sugar level, etc.
• We refer to these small changes as dynamic equilibrium.
This allows us to maintain homeostasis (internal balance).
• All living things must maintain homeostasis in order to survive.
EX. Human body temp is 37 C; if temp is altered, processes that keep
us going will begin to fail
Dynamic Equilibrium
• Constant small corrections that keep internal
environment w/in stable limit
BODY TEMP
BLOOD SUGAR LEVEL
AFTER MEAL
TIME
TIME
FEEDBACK MECHANISMS
• Help regulate the
endocrine system
• Maintain
homeostasis
• Let’s watch:
• http://www.brainpop.com/he
alth/bodysystems/homeosta
sis/
•
http://www.learnerstv.com/animati
on/animation.php?ani=241&cat=Bi
ology
TYPES OF FEEDBACK MECHANISM
1. Negative Feedback
• considered
negative
because the
original signal is
lowered or shut
off.
Stimulus
Negative
Feedback
Reaction
Response
Examples OF FEEDBACK MECHANISM
EX: Thermostat
FURNACE
KICKS
OFF
ROOM
WARMS
UP
Ex. Body Temperature
Stimulus:
Brain senses
a drop in
blood
temperature.
ROOM
COOLS
DOWN
FURNACE
KICKS
ON
Negative
Feedback:
Warmer blood
triggers brain to
turn-off shivering.
Reaction: Nerve
message sent to
muscles to start
shivering.
Response:
Heat is
generated
that warms
the body and
blood.
Example 3: Glucose
levels in the blood
Blood sugar
regulation by insulin
(secreted by
pancreas)
Video: Insulin, Glucose and you
http://www.youtube.com/watch?v=ae_jC4FDO
Uc
http://bcs.whfreeman.com/thelifewire/conten
t/chp50/5002s.swf
Ex 4. Plants regulating water loss
• Guard cells in plants opening and
closing to prevent water loss
2. Positive Feedback Mechanism –
Change in system  causes greater
change or response
Stimulus: A
contraction pushes
the baby’s head
against the base of
the uterus.
Positive Feedback
Reaction: Pressure
on the base of the
uterus causes
stronger
contractions.
Response: Baby is
born and the
feedback cycle ends.