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Biology · 5. Coordination and homeostasis

Negative feedback, nervous and endocrine control

Model homeostasis and explain nerve signals using ion gradients rather than wire-like electricity.

40 minutesContent version: 2.1
Start the interactive pathwayOpen the virtual experiment

Driving question

How does the body keep variables near a set point and transmit rapid information?

Curriculum coverage

Vietnam Biology 11; Cambridge IGCSE/AS coordination and homeostasis.

Model scope and limitations

The simplified Hodgkin–Huxley model illustrates ion channels; real neurons have diverse channels, shapes and modulation.

Learning objectives

  • Describe a negative-feedback loop.
  • Explain major action-potential phases.
  • Compare nervous and hormonal communication.

Prerequisite knowledge

  • Cell membranes, ions and active transport.

Core knowledge

Negative feedback

A receptor detects deviation, a coordinator processes it and an effector opposes the deviation.

Action potential

Depolarisation mainly involves Na⁺ entry and repolarisation K⁺ exit; the Na⁺/K⁺ pump maintains long-term gradients.

Signal coding

Action-potential amplitude is nearly fixed; stimulus strength is often encoded by firing frequency.

Worked example

When blood glucose rises, β cells release insulin; tissues increase uptake/storage so glucose falls. Near the set point, insulin stimulation decreases: negative feedback.

Misconceptions to avoid

  • The Na⁺/K⁺ pump does not directly create the whole upstroke; voltage-gated channel currents make the rapid change.
  • Negative feedback does not mean every signal decreases; it means the response opposes deviation.

Virtual experiment procedure: Neuronal action potential

  1. Begin below threshold and increase to identify threshold.
  2. Record membrane potential over time and mark depolarisation, repolarisation and hyperpolarisation.
  3. Compare stronger stimulation in terms of spike amplitude and frequency.

Safety and cautions

  • This is a simulation; never apply experimental electrical stimulation to people or animals.

Evidence to collect

  • A graph with mV, ms and ion-channel annotations at three phases.
Open the virtual experiment

Diagnostic check

1. Which response is negative feedback?

  1. Sweating as body temperature rises
  2. Muscle activity raising temperature without limit
  3. Clotting amplification until sealed
Show answer and explanation

Correct answer: Sweating as body temperature rises

Sweating increases heat loss and opposes the temperature rise.

2. Which ion mainly enters during typical neuronal depolarisation?

  1. Na⁺
  2. K⁺
  3. Protein⁻
Show answer and explanation

Correct answer: Na⁺

Voltage-gated Na⁺ channels open rapidly, allowing Na⁺ entry.

Application practice

1. A sub-threshold stimulus usually creates?

  1. No full action potential
  2. A half-amplitude travelling spike
  3. An always larger spike
Show answer and explanation

Correct answer: No full action potential

Action potentials follow an all-or-none principle.

2. Repolarisation mainly involves?

  1. K⁺ leaving
  2. Faster Na⁺ entry
  3. Glucose entry
Show answer and explanation

Correct answer: K⁺ leaving

K⁺ channels open and outward K⁺ current restores negativity.

3. How do hormones commonly differ from nerve impulses?

  1. Slower but longer-lasting
  2. Always faster
  3. Need no receptors
Show answer and explanation

Correct answer: Slower but longer-lasting

Hormones travel in blood and affect cells with matching receptors.

Academic references

  1. OpenStax Biology 2e — peer-reviewed foundational biology

This lesson is maintained against the cited sources below. Simulations are learning models and do not replace supervised physical-laboratory safety procedures.

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WebLab STEM
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Đức Tiến — Control & Automation Engineer