Human Anatomy & Physiology (Human Body Systems)

Unit 2: Unit 2: Communication (Nervous & Endocrine)HBS 2.2Human Body Systems: endocrine system

Diagram a negative feedback loop

Label the setpoint, sensor, control center, and effector and show how a negative feedback loop opposes a change to hold homeostasis.

Builds on (2 levels back)inferred · high confidence

Homeostasis (steady internal state): A feedback loop only makes sense if you know the body works to keep a stable internal value, called homeostasis.
Reading a cause-and-effect chain: A loop is a chain of steps where each arrow causes the next; you must follow arrows in order before you can see how it returns to the setpoint.

Prerequisites are inferred: pending teacher review.

Re-learn the skill with worked practice and clear examples.

A negative feedback loop has a sensor, a control center, and an effector. It opposes a change: when a value rises, the response lowers it; when a value falls, the response raises it, returning the value to the setpoint.

Step 1: Define the parts

Setpoint = the value the body aims to hold. Sensor = the part that detects the change. Control center = compares the value to the setpoint and decides the response. Effector = the muscle or gland that carries out the response. A hormone is a chemical messenger carried in the blood that often acts as the signal between these parts.

Step 2: See why it is 'negative'

Negative feedback means the response opposes (works against) the change. If the value goes up, the response brings it down. If the value goes down, the response brings it up. Either way it pushes back toward the setpoint.

Step 3: Trace the loop

Change away from setpoint → sensor detects it → control center compares and signals → effector responds → value moves back toward the setpoint → sensor reads it as normal and the response eases off. This is the loop you will be asked to diagram on the WebXam (the state CTE end-of-course exam).

Practice

Body temperature rises above its setpoint on a hot day. Sweat glands release sweat, and as it evaporates the body cools back toward the setpoint. What kind of feedback is this, and why?

Reviewed

A four-box loop arranged in a ring. Box 1: 'Temperature rises above setpoint'. Arrow to Box 2: 'Sensor in skin/brain detects rise'. Arrow to Box 3: 'Control center signals sweat glands (effector)'. Arrow to Box 4: 'Sweat evaporates, body cools'. A return arrow from Box 4 back to Box 1 is labeled 'returns toward setpoint'.

A.Positive feedback, because sweating adds a new response
B.Negative feedback, because the response opposes the change and returns temperature toward the setpoint
C.Negative feedback, because the temperature keeps rising
D.Positive feedback, because the body cools down

Show the worked solution ▾

Answer: B. Negative feedback, because the response opposes the change and returns temperature toward the setpoint

Step 1: Name the change: The value (temperature) rose above the setpoint. The body needs to bring it back down.
Step 2: Check the response direction: Sweating cools the body, so the response moves the value the opposite way from the change: it opposes the rise.
Step 3: Match the definition: A response that opposes the change and returns the value toward the setpoint is negative feedback.

Why it's right: The response (sweating, which cools) opposes the change (rising temperature) and returns the value toward the setpoint, which is the definition of negative feedback.

Why the others miss:

A: Sweating is the loop's response that opposes the change, not an added amplifying step; this loop is negative, not positive.
C: The temperature does not keep rising: the response brings it back down, so this reasoning is wrong.
D: Cooling down is correct, but cooling that opposes a rise is negative feedback, not positive.

Aligned to Human Body Systems: negative feedback · reading level ~grade 9

Where you'd see this

Charting a patient's temperature over time shows the value dipping back toward normal after a fever breaks: the visible result of a negative feedback loop doing its job.

Careers that use this

Nurse: Watches whether a patient's vital signs are returning toward their setpoint, which tells them the body's feedback loops are working or need help.

Video library

Watch: Diagram a negative feedback loop

Homeostasis and Negative/Positive Feedback

Amoeba Sisters · 7 min

Guided notes

Fill these in as you work through the lesson.

Big idea: In a negative feedback loop the body senses a change away from its setpoint and triggers a response that opposes the change, pushing the value back toward the setpoint.

Key terms: write the meaning

Hormone (chemical messenger carried in the blood):
Negative feedback (response opposes the change):
Setpoint (the value the body aims to hold):
Sensor (detects the change):
Effector (carries out the response):

The rule

In negative feedback, when a value rises above the setpoint the response works to it, and when it falls below the setpoint the response works to it, so the value returns toward the .

Check yourself

Name the four parts of a feedback loop in the order a signal passes through them.
Explain why it is called 'negative' feedback even when the response can raise a value.
A room thermostat is set to 70 °F. The room reaches 75 °F and the air conditioning turns on. Which part is the sensor and which is the effector?

Work one example

Body temperature climbs above its setpoint of about 37 °C on a hot day. Draw the loop: name the sensor, the control center, the effector, and the response, and show how the loop brings temperature back down toward the setpoint.