Name: homeostasis and negative feedback
Uploaded: 2023-06-23T15:38:43.000Z
Duration: 1 min 16 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.3.1

What is Homeostasis?

L'homéostasie est la capacité du corps à maintenir des conditions internes stables en réponse à l'environnement extérieur changeant.
Par exemple, lorsqu'il fait chaud dehors, la température corporelle d'une personne peut commencer à augmenter et le corps doit réagir pour contrer l'augmentation.
Les récepteurs, les centres de contrôle et les effecteurs coordonnent les changements physiologiques nécessaires pour répondre à une variable.
Dans le cas d’une augmentation de la température corporelle, les thermorécepteurs sur les cellules de la peau détectent la température élevée et relaient le message par l’influx nerveux au cerveau, le centre de contrôle.
Le cerveau compare le stimulus à un point de consigne – la plage physiologique de la variable. Le point de consigne pour une température normale du corps humain est d’environ 37 °C.
Lorsque la température corporelle dépasse le point de consigne, le cerveau signale aux effecteurs, les glandes sudoripares, de produire de la sueur. L’évaporation de la sueur refroidit le corps.
Une fois que la température corporelle revient au point de consigne, les récepteurs envoient une rétroaction au cerveau pour réduire la production de sueur, assurant ainsi le maintien de l’homéostasie.

qu'est-ce que l'homéostasie ?

Maintenir l'homéostasie nécessite que le corps maintienne continuellement ses conditions internes. Chaque condition physiologique a un point de référence particulier, allant de la température corporelle à la pression artérielle en passant par les niveaux de certains nutriments. Un point de référence est la valeur physiologique autour de laquelle la plage normale fluctue. Une plage normale est un ensemble restreint de valeurs qui est optimal pour la santé et stable. Par exemple, le point de référence de la température corporelle normale humaine est d'environ 37 °C (98,6 °F). Les paramètres physiologiques, tels que la température corporelle et la pression artérielle, ont tendance à fluctuer dans une plage normale quelques degrés au-dessus et en dessous de ce point. Les centres de contrôle dans le cerveau et d'autres parties du corps surveillent et réagissent aux écarts par rapport à l'homéostasie en utilisant une rétroaction négative. La rétroaction négative est un mécanisme qui inverse un écart par rapport au point de référence. Par conséquent, la rétroaction négative maintient les paramètres corporels dans leur plage normale. Maintenir l'homéostasie par la rétroaction négative se poursuit dans tout le corps à tout moment, et comprendre la rétroaction négative est donc fondamental pour comprendre la physiologie humaine. 

 Un capteur, également appelé récepteur, est un composant d'un système de rétroaction qui surveille une valeur physiologique. Cette valeur est signalée au centre de contrôle. Le centre de contrôle est le composant d'un système de rétroaction qui compare la valeur à la plage normale. Le centre de contrôle active un effecteur si la valeur s'écarte trop du point de référence. Un effecteur est un composant d'un système de rétroaction qui provoque un changement pour inverser la situation et ramener la valeur dans la plage normale. 

 Par exemple, pour mettre le système en mouvement, un stimulus doit dépasser la plage normale d'un paramètre physiologique (au-delà de l'homéostasie). Ce stimulus est « perçu » par un capteur spécifique. Dans le contrôle de la glycémie, des cellules endocrines spécifiques du pancréas détectent l'excès de glucose (le stimulus) dans le flux sanguin. Ces cellules bêta pancréatiques réagissent à l'augmentation du taux de glucose sanguin en libérant l'hormone insuline dans le flux sanguin. L'insuline signale aux fibres musculaires squelettiques, aux cellules adipeuses (adipocytes) et aux cellules hépatiques de prendre le glucose en excès, en le retirant du flux sanguin. Lorsque la concentration de glucose dans le flux sanguin diminue, la diminution de la concentration - la rétroaction négative réelle - est détectée par les cellules alpha pancréatiques, et la libération d'insuline s'arrête. Cela empêche le niveau de sucre dans le sang de continuer à baisser en dessous de la plage normale. 

 Ce texte est adapté de <a href="https://openstax.org/books/anatomy-and-physiology-2e/pages/">Openstax, Anatomy and Physiology 2e, Section 1.5: </a>Homeostasis

Qu'est-ce que l'homéostasie ?

Le maintien de l’homéostasie exige que le corps maintienne continuellement ses conditions internes. Chaque condition physiologique a un point de consigne particulier, ...

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homeostasis and negative feedback

Homeostasis keeps the body’s internal conditions stable. The body does this by holding each physiological condition near a set point. A set point is the value around which the normal range changes, and the normal range is the small group of values that is healthiest and most stable. Human body temperature is a common example. Its set point is about 37°C, or 98.6°F, and it can shift a little above or below that point while still staying in range.

Negative feedback helps maintain homeostasis. This process reverses a change that moves a body value away from its set point. Control centers in the brain and other body parts monitor these changes and respond when conditions drift too far. Because this happens throughout the body all the time, negative feedback is a key idea in human physiology.

A feedback system has three main parts: a sensor, a control center, and an effector. A sensor, also called a receptor, watches a physiological value and sends that information to the control center. The control center compares the value with the normal range. If the value moves too far from the set point, the control center activates an effector. The effector causes a change that brings the value back toward normal.

Blood glucose control shows how this works. When blood sugar rises too high, pancreatic beta cells detect the excess glucose in the bloodstream. These endocrine cells release insulin into the blood. Insulin tells skeletal muscle fibers, fat cells, and liver cells to take up the extra glucose, which removes it from the bloodstream. As glucose levels fall, pancreatic alpha cells detect the drop, and insulin release stops. This keeps blood sugar from falling below the normal range.

Homeostasis and Negative Feedback

overview of anatomy and physiology

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what is homeostasis?

Homeostasis keeps the body’s internal conditions stable. The body does this by holding each physiological condition near a set point. A set point is the value around which the normal range changes, and the normal range is the small group of values that is healthiest and most stable. Human body temperature is a common example. Its set point is about 37°C, or 98.6°F, and it can shift a little above or below that point while still staying in range. Negative feedback helps maintain homeostasis.

negative and positive feedback

Feedback Loops in Body Balance

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homeostatic imbalance

How Feedback Failure Disrupts Homeostasis

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key terms and concepts

Learn how homeostasis stays stable through negative feedback, set points, sensors, control centers, and the insulin response to blood glucose.

Homeostasis and Negative Feedback | JoVE K12

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JoVE Core Anatomy and Physiology showcases the anatomical and physiological details of the human body in comprehensive, clear, and engaging video animations. This collection of lessons focuses on the structures, components, functions, and requirements of the human body. It is complemented by scientist-in-action videos that demonstrate the application of this knowledge in real-world medical and research settings.

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Homeostasis and Negative Feedback

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