Transcript Notes - Systems and STEM

Systems
Positive and Negative Feedback
Systems


A system is a group of parts that work
together to perform a function or produce a
result
Components




Input
Process
Output
Feedback
Example System
Is this a system?
- Group of parts?
- Working together
to perform a
function?
- YES!
What is the input?
What is the output?
Negative Feedback

To get back to a specific target point
A Nonliving
Example of
Negative
Feedback:
Control of
Room
Temperatur
e
Response
No Heat
Produced
Heater
turned
off
Room
Temperature
Decreases
Too
hot
Set
point
Too
cold
Set
point
Set point
Control center:
thermostat
Room
Temperature
Increases
Heater
turned
on
Response
Heat
Produced
Negative Feedback: Maintenance of Glucose
Homeostasis by Insulin and Glucagon
Body cells
take up more
glucose.
Insulin
Beta cells of
pancreas are stimulated
to release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Rising blood glucose
level (for instance, after
eating a carbohydraterich meal)
Blood glucose level
declines to set point;
stimulus for insulin
release diminishes.
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
Blood glucose level
rises to set point;
stimulus for glucagon
release diminishes.
STIMULUS:
Dropping blood glucose
level (for instance, after
skipping a meal)
Alpha cells of pancreas
are stimulated to release
glucagon into the blood.
Liver breaks
down glycogen
and releases
glucose into
blood.
Glucagon
Positive Feedback

Over amplification and moves away from
the target point
Positive Feedback (Fruit)
Ethylene Gas
An Example of Positive Feedback:
the Induction of Labor
from
ovaries
Oxytocin
from fetus
and mother's
posterior pituitary
Induces oxytocin
receptors on uterus
Stimulates uterus
to contract
Stimulates
placenta to make
Prostaglandins
Stimulate more
contractions
of uterus
Positive feedback
Estrogen
Feedback Flow Chart
Homeostasis
Feedback
Negative
Alteration
Positive
Stabilization
Amplification
Temperature
Regulation
Fruit Ripening
Diabetes
mellitus
Engineering Practices

Two main ideas when designing in
engineering



Criteria – the rules or directions that must be
followed; the requirements that must be met
Constraints – restrictions that keep something
from being the best it can be; problems that arise
or issues that come up.
What were the criteria and constraints in
our design challenge?