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Homeostasis Study Guide – Honors Biology
Quiz – Minor Assessment
Items to study:
28.2-28.3 Notes Sheet, 28.2-28.3 Reinforcements, Feedback Loop Scenario WS,
Webquest, Liver Lab
Homeostasis
1. What is homeostasis?
It is the ability to maintain an internal stable condition. (maintaining proper pH,
temperature, water content, salt concentration).
2. Match each part with the role that they play in thermoregulation:
__B___Brain
A. Sensor
__A___Receptors in skin
B. Control Center
__D___Sweat glands
C. Communication system
___C__Nervous system
D. Target
3. What are the four parts of a control system? What are their jobs?
1. Sensors, aka receptors, gather information about conditions in & out of the body.
2. Control center, often the brain, receives info from the sensors and compares these
values to the ideal values.
3. Communication system: Communication is controlled by the nervous system and
endocrine system which carry messages to all parts of the body and tells them how to
respond to changes.
4. Target: Any organ, tissue, or cell that changes its level of activity in response to a
message.
4. What happens in a negative feedback loop? Describe an example.
• Negative feedback loops: control system counteracts any change in the body that
moves conditions above or below a set point (reversing change to return conditions
to their set points)-most functions in the body are regulated this way.
• Ex.: Thermostats, holding your breath
5. What happens in a positive feedback loop? Describe an example.
• Positive feedback loops: Control center uses information to increase rate of change
away from set points.
• Ex.: Cut finger increases clotting factors in blood.
6. What is thermoregulation? What are some ways that your body regulates this?
The process of maintaining a steady body temperature.
Your body will sweat when you heat up to cool you down. Your blood vessels dilate to help
reduce heat. When you are cold you shiver because your muscles are trying to create heat.
In addition, your vessels constrict to reduce blood flow and heat loss from your skin.
7. What is osmoregulation? What are some ways that your body regulates this?
Maintaining the proper water levels. Keeps fluid levels from becoming too concentrated
and too diluted.
Your body controls water levels by: urination, sweating, and water vapor in your breath
8. What are four ways that homeostasis can be disrupted?
•
•
•
•
Sensors fail to detect changes in internal or external environment
Wrong messages sent or correct ones fail to reach targets.
Serious injuries overwhelm homeostatic mechanisms.
Viruses or bacteria change body’s internal chemistry.
9. When you exercise, heart rate increases. How does this show that your body is
maintaining homeostasis?
Your heart pumps blood through your whole body. This blood carries oxygen to all of your
muscles. When you use your muscles faster the blood needs to get to your muscles faster.
Your heart needs to send the blood there faster and it increases its beats. This is how your
heart helps you to maintain homeostasis.
10. When you exercise, your breathing rate increases. How does this show that your body
is maintaining homeostasis?
When you breathe you take in oxygen and get rid of carbon dioxide. When you are working
out you need the oxygen faster, this is why you need to breathe faster to maintain
homeostasis.
11. When you exercise, sweating increases. How does this show that your body is
maintaining homeostasis?
Thermoregulation is maintaining the proper temperature. Sweating helps you cool down
when you have been working out. By producing sweat the body is cooling itself to maintain
homeostasis.
12.
Explain what each line on the graph
represents and how you know. Why are these
results important for living things?
Line A represents a base added to water. I know this because water does not
contain buffers to regulate their pH and this line showed an extreme change from neutral
to a very high pH. Bases have high pH numbers. Line D represents an acid added to water. I
know this because water does not contain buffers to regulate their pH and this lined
showed an extreme change from neutral to a very low pH. Acids have low pH numbers. Line
B represents liver with base added to it. Liver contains cells and cells contain buffers, which
help to maintain homeostasis in regards to pH. This is why there is not a dramatic change
in the overall pH of the liver. I know this was a base because the line goes slightly up. Same
situation with line C. This is liver with acid (liver has buffers to help maintain a neutral pH).
I know it is an acid because the line points slightly down showing an acid was added to
liver.
These results are important to living things because we need to maintain balance aka
homeostasis. Without buffers to regulate our pH we could die. Living things can only
maintain a small physiological range in regards to their pH. Buffers help to maintain our
proper pH so that we do not exceed that acceptable range.