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Body structure and homeostasis review

Key terms

TermMeaning
HomeostasisThe tendency to resist change in order to maintain a stable, relatively constant internal environment
Negative feedback loopFeedback loop that acts to oppose the triggering stimulus
Positive feedback loopFeedback loop that amplifies the starting signal
CellSmallest unit of life
TissueMade of a group of similar cells that work together on a specific task
OrganStructure made up of two or more tissues, organized to carry out a specific function
Organ systemGroups of organs with related functions

Maintaining homeostasis

The body maintains homeostasis for many factors. Some of these include body temperature, blood glucose, and various pH levels.
Homeostasis is maintained at many levels, not just the level of the whole body as it is for temperature. For instance, the stomach maintains a pH that's different from that of surrounding organs, and each individual cell maintains ion concentrations different from those of the surrounding fluid. Maintaining homeostasis at each level is key to maintaining the body's overall function.

Feedback loops

Homeostasis typically involves negative feedback loops that counteract changes of various properties from their target values. An example of a negative feedback loop is body temperature regulation.
Example of negative feedback loop
The maintaining of body temperature is an example of a negative feedback loop. When body temperature increases, there are mechanisms that work to decrease temperature, and vice versa.
In contrast to negative feedback loops, positive feedback loops amplify their initiating stimuli, in other words, they move the system away from its starting state.
Example of positive feedback loop
The ripening of fruit is an example of a positive feedback loop, as ethylene continues to trigger ripening in neighboring fruit.

Body structure

The body has levels of organization that build on each other. Cells make up tissues, tissues make up organs, and organs make up organ systems.
From left to right: single muscle cell, multiple muscle cells together forming muscle tissue, organ made up of muscle tissue (bladder), and organ system made up of kidneys, ureter, bladder and urethra.
Image credit: modified from Levels of structural organization of the human body by OpenStax College, Anatomy & Physiology, CC BY 4.0
At each level of organization (cells, tissues, organs, and organ systems), structure is closely related to function.

Common mistakes and misconceptions

  • Negative feedback is not bad for the body. Although the term "negative" is included, these feedback loops are essential and helpful to the body. In this instance, "negative" simply means that the feedback loop works to counter the stimulus, or cue, not that the feedback loop is detrimental.
  • Homeostasis is more than just "keeping things normal, and the body doesn't always know what is best for itself. " The body is constantly regulating itself and the mechanisms to maintain homeostasis are always in play. Sometimes, however, these homeostatic mechanisms can fail. If the conditions are not corrected, a disease or disorder can result. For example, if the amount of calcium in your blood is not properly regulated and becomes too low, you could develop hypocalcemia.

Want to join the conversation?

  • blobby green style avatar for user renae.blomberg
    At what levels of organization does the body need to maintain homeostasis?
    (3 votes)
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    • piceratops ultimate style avatar for user Joshua
      All. Homeostasis is maintained at all levels of organizations, from organisms to cells. Cells undergo homeostasis by diffusing different ions and molecules to maintain their balance and organisms have multiple systems working together to maintain homeostasis (e.g. vasodilation (cardiovascular system) and sweating (integumentary system) to give off heat, which affects the body as a whole).
      (2 votes)
  • blobby green style avatar for user Owen swift
    What are common cause for you body to leave homeostasis and what are way to come back to that state.
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    • piceratops ultimate style avatar for user Joshua
      Your body's homeostasis balance can be thrown off as easily as getting too hot from an exercise or drinking too much water.

      Example 1: If you're in hyperthermia (>38C or >100.4), the body will act accordingly to cool itself down and maintain homeostasis. This includes vasodilation and sweating.

      Example 2: If you're not dehydrated and you drink multiple glasses of water, your body will filter the excess water out of the body via the kidneys and the urinary system. If the over-intake of water is rapid (i.e. water intoxication), the excess water will enter your cells. Sometimes, the body's reflexes will trigger you into vomiting.
      (2 votes)
  • blobby green style avatar for user ANAHY896
    When does your body leave a homeostatic state?
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  • blobby green style avatar for user 81843
    It does change temperature when your cold or hot. It usually doesn't change drastically though, unless you are going through something severe like heat stroke or hypothermia.
    (2 votes)
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  • blobby green style avatar for user mikeyona.witherspoon
    what does hypocalmcemia mean
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  • blobby green style avatar for user jsoto0186
    what happens if your cells start dying
    (1 vote)
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  • boggle blue style avatar for user x.asper
    What are the effects of hypoglycemia?
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    • male robot donald style avatar for user Tybalt
      Hypoglycemia--Low (hypo-) blood (-emia) sugar (-glyc-, refers to glucose)

      Glucose is the main source of energy in the body. If a patient does not get enough, either from diet or an underlying condition like diabetes, they will suffer from a myriad of symptoms. There are physical effects like hunger, tiredness and shakiness, and there are also mental effects like anxiety, confusion, and nervousness. If severe, a patient can become unaware or even die.

      Does this help?
      (1 vote)
  • blobby green style avatar for user Reshma Fahad
    different tissues in arms in human body
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  • blobby green style avatar for user Gulshoda
    How does the heart , brain and nerves maintain homeostasis?
    (1 vote)
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  • leaf green style avatar for user bintoudiallo22
    What is the difference between positive feed back and negative feed back
    (1 vote)
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    • piceratops ultimate style avatar for user Joshua
      A positive feedback loop allows a process to continue whilst a negative feedback loop stops the process.

      An example of a positive feedback loop is the amplification of labour contractions. The contractions are initiated as the baby moves into position, stretching the cervix beyond its normal position. The feedback increases the strength and frequency of the contractions until the baby is born (positive feedback loop stops once the baby is delivered).

      An example of a negative feedback loop is the regulation of insulin by the pancreas. An influx of glucose, say from a carbohydrate-heavy dinner, triggers your pancreas to produce a hormone called insulin. Once the insulin reaches a certain level and is detected by the pancreas, the pancreas will stop producing the hormone.
      (1 vote)