Homeostasis & Feedback — Drills · Grade 10 Science

Chapter: Body Systems, Signals & Homeostasis

What these drills covers

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

6 questions, multiple choice, numeric 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. a condition in which nothing inside the body changes
  2. the maintenance of internal conditions within a range around a set point
  3. the absence of any feedback
  4. a process that stops during exercise
Answer and explanation

the maintenance of internal conditions within a range around a set point

Internal conditions fluctuate continuously; homeostasis keeps them within a workable range rather than holding them perfectly constant.

Problem 2

In a negative feedback loop, the effector's action
  1. amplifies the original change
  2. opposes the original change
  3. has no effect on the variable
  4. replaces the receptor
Answer and explanation

opposes the original change

Negative feedback produces a response that counteracts the detected deviation, returning the variable toward its set point.

Problem 3

Fasting blood glucose is about 90 mg/dL and rises to 140 mg/dL after a meal. What is the increase in mg/dL?
Answer and explanation

50 mg/dL

140 − 90 = 50 mg/dL. Insulin release then lowers it back toward the fasting value.

Problem 4

Which is an example of positive rather than negative feedback?
  1. Sweating when body temperature rises
  2. Insulin release after a meal
  3. Contractions intensifying during childbirth until delivery
  4. Shivering when body temperature falls
Answer and explanation

Contractions intensifying during childbirth until delivery

Positive feedback amplifies a change until an endpoint ends the loop; the other three oppose a change.

Problem 5

Core temperature rises from 37.0 °C to 38.5 °C during exercise. State the deviation from the set point in degrees Celsius.
Answer and explanation

1.5 °C

38.5 − 37.0 = 1.5 °C. Sweating and increased skin blood flow act to reduce this deviation.

Problem 6

Name the three components of a feedback loop and identify each for body-temperature regulation on a hot day.
Answer and explanation

A receptor detects the change, a control centre compares it with the set point and issues instructions, and an effector carries out the response. On a hot day, temperature receptors in the skin and hypothalamus detect the rise, the hypothalamus acts as the control centre, and the effectors are the sweat glands and the blood vessels in the skin, which widen to release heat. The response opposes the rise, which makes it negative feedback.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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