Feedback and Homeostasis
Aligned to HS-LS1-3 — Next Generation Science Standards.
What this lesson teaches
Bodies hold internal conditions steady by sensing change and responding. Negative feedback loops reverse a shift, like a rise in temperature or blood sugar, back toward a set point.
Worked examples
Example 1
After a meal, rising blood glucose triggers insulin release; cells take in glucose, levels fall, and insulin release slows, a negative feedback loop keeping glucose near a set point.
Example 2
Positive feedback does the opposite: in childbirth, contractions release oxytocin, which strengthens contractions, until the process ends itself.
Example 3
Negative feedback needs a sensor, a set point and an effector. Remove any one and the loop cannot correct anything.
Practice questions
- Plan the measurements you would record to show body temperature returns to normal after exercise.
- Draw the sensor, control, and response loop for blood glucose regulation.
- Design an investigation to test whether shivering is triggered by cold, and identify the variable you would control.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Retroalimentación y homeostasis
El cuerpo mantiene estables sus condiciones internas al detectar los cambios y responder a ellos. Los mecanismos de retroalimentación negativa revierten una variación, como un aumento de temperatura o de azúcar en la sangre, de regreso a un punto de referencia.
Ejemplo 1: Después de comer, el aumento de glucosa en la sangre provoca la liberación de insulina; las células captan la glucosa, los niveles bajan y la liberación de insulina disminuye: un mecanismo de retroalimentación negativa que mantiene la glucosa cerca de un punto de referencia.
Ejemplo 2: La retroalimentación positiva hace lo contrario: en el parto, las contracciones liberan oxitocina, que fortalece las contracciones, hasta que el proceso se termina solo.
Ejemplo 3: La retroalimentación negativa necesita un sensor, un punto de ajuste y un efector. Quita cualquiera y el circuito no puede corregir nada.
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