Homeostasis & Feedback — Practice · Grade 10 Science

Chapter: Body Systems, Signals & Homeostasis

What this practice covers

By the end of Homeostasis & Feedback you should be able to:

11 questions, multiple choice and written answer, each with a worked explanation.

Vocabulary used: homeostasis, set point, stimulus, receptor, effector, negative feedback, positive feedback.

Problem 1

Homeostasis is best described as
  1. maintaining a stable internal environment despite changes outside
  2. the total lack of any internal change
  3. the process of a cell dividing
  4. the buildup of waste inside a cell
Answer and explanation

maintaining a stable internal environment despite changes outside

Homeostasis is the active maintenance of stable internal conditions (temperature, pH, glucose, water) even as the outside world changes.

Problem 2

In a negative feedback loop, the response
  1. permanently raises the set point
  2. reverses the change and pushes the condition back toward its set point
  3. amplifies the change until a process finishes
  4. has no effect on the condition
Answer and explanation

reverses the change and pushes the condition back toward its set point

Negative feedback counteracts (reverses) the change, restoring the set point — the most common form of homeostatic control.

Problem 3

Which of these is an example of POSITIVE feedback?
  1. Shivering to warm up when cold
  2. Insulin lowering blood sugar after a meal
  3. Contractions during childbirth strengthening until the baby is born
  4. Sweating to cool down when overheated
Answer and explanation

Contractions during childbirth strengthening until the baby is born

Childbirth contractions amplify themselves (positive feedback); sweating, shivering, and insulin all reverse a change (negative feedback).

Problem 4

Describe how the body uses negative feedback to lower blood sugar after a meal.
Answer and explanation

After a meal blood glucose rises. The pancreas detects this and releases insulin, which signals body cells to take glucose out of the blood. This lowers blood glucose back toward its set point, reversing the original rise — a negative feedback loop.

Problem 5

Which puts the parts of a feedback loop in the correct order?
  1. response → effector → stimulus → receptor → control center
  2. effector → stimulus → response → receptor → control center
  3. control center → response → stimulus → receptor → effector
  4. stimulus → receptor → control center → effector → response
Answer and explanation

stimulus → receptor → control center → effector → response

A stimulus is detected by a receptor, reported to a control center, which signals an effector to produce a response that restores the set point.

Problem 6

Explain how the cell membrane and cellular transport help a cell maintain homeostasis.
Answer and explanation

The selectively permeable membrane controls what enters and leaves, and transport processes (diffusion, osmosis, facilitated diffusion, and active transport) let the cell take in needed materials like glucose and oxygen, remove wastes, and balance water and ions. Together they keep the cell's internal conditions steady, which is homeostasis at the cellular level.

Problem 7

Body temperature rises and sweating increases. Identify the loop and its effect. Explain the reasoning in your own words.
Answer and explanation

A negative-feedback response helping restore temperature toward its regulated range.

The deviation is increased temperature.

Evaporation of sweat can increase heat transfer out, opposing the rise.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 8

Body temperature rises and sweating increases heat loss. Classify the loop. Show the reasoning, not just the conclusion.
Hints

Negative means opposing a deviation, not an unhealthy effect.

Answer and explanation

Negative feedback: the response tends to reduce the initial temperature rise.

Problem 9

Why might multiple organs participate in one homeostatic response?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Sensors, signaling pathways, effectors and the regulated variable can be distributed across interacting systems.

Problem 10

Positive feedback amplifies an initiating processPositive feedback amplifies an initiating processInitialresponseFurtheractivationAn amplifying loop needs a stopping condition or other regulation.
Original selected amplification loop, not a complete clotting cascade or treatment guide.
Interpret the supplied visual. Why must an explanation include the return effect and stopping condition?
Answer and explanation

Without the return effect it is merely a chain; without a stopping/limiting mechanism it incorrectly suggests unlimited amplification.

Positive feedback increases the initiating process through a return effect. Selected clotting reactions can amplify local activation until injury conditions and other regulatory mechanisms stop or limit the process. This is not a claim that all clots grow indefinitely or that positive means beneficial. A rising output alone is not enough to classify feedback: identify what feeds back and how it changes the starting process. An endpoint, substrate depletion, spatial restriction or opposing regulation can constrain an amplifying loop.

Without the return effect it is merely a chain; without a stopping/limiting mechanism it incorrectly suggests unlimited amplification.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 11

A regulated variable is below target. An effector raises it toward target but overshoots temporarily after a delay. Classify the intended feedback and explain the overshoot.
Answer and explanation

The intended response is negative feedback because it opposes the deviation. Delayed sensing/response and changing inputs can produce overshoot; a rising value alone does not define positive feedback.

The intended response is negative feedback because it opposes the deviation. Delayed sensing/response and changing inputs can produce overshoot; a rising value alone does not define positive feedback.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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