Levels of Organisation and Homeostasis

Levels of Organisation and Homeostasis

Levels of Organisation and Homeostasis

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Chemical and Cellular Level

  • Chemical level
    • Includes atoms (the smallest units of matter that participate in chemical reactions) and molecules (two or more atoms joined together)
    • Molecules combine to form structures at the cellular level
  • Cellular level
    • The basic structural and functional units of an organism
    • Smallest living units in the human body
    • There are many different types of cells in your body including nerve cells and blood cells
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Tissue Level

  • Tissues are groups of cells and the materials surrounding them that work together to perform a particular function
  • There are four primary types of tissue in your body:
    • Muscle
    • Nervous
    • Epithelial
    • Connective
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Organ Level

  • Organs are structures that:
    • Are composed of 2 or more different types of tissues
    • Have specific functions
    • Usually have recognisable shapes
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System Level

  • A system consists of related organs that have a common function
  • There are 11 systems of the human body:
    • Integumentary
    • Skeletal
    • Muscular
    • Nervous
    • Endocrine
    • Cardiovascular 
    • Lymphatic and immune
    • Respiratory
    • Digestive
    • Urinary
    • Reproductive
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Organism Level

  • An organism is any living individual
  • All parts of the human body functioning with one another constitute the total organism - one living person
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  • Homeostasis: The ability of a system or living organism to adjust its internal environment to adjust its internal environment to maintain a stable equilibrium
  • Homeostasis in the human body is continually being disturbed
  • Environment
    • External (outside body), e.g. physical insult such as lack of oxygen or intense heat
    • Internal (within body), e.g. blood glucose is too low
  • Psychological stress in social environment, e.g. demands of school/work
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Regulating Systems

  • The body has many regulating systems that bring the internal environment back into balance
  • Most often, the nervous sytem and the endocrine system, working together or independently, provide the corrective measures needed when homeostasis is disrupted
  • Nervous system - detects deviations from balanced state, sends messages in form of nerve impulses back to organs that counteracts the deviations
  • Endocrine system - secretes hormones into the blood to regulate homeostasis, work more slowly than nervous responses
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Feedback Systems

  • The body can regulate its internal environment through a multitude of feedback systems
  • A feedback system is a cycle of events in which the status of a body condition is continually monitored, evaluated and changed
  • Each monitored variable, e.g. body temperature, blood pressure, blood glucose level, is termed a controlled condition
  • Any disruption that changes a controlled condition is called a stimulus
  • Three basic components make up a feedback system:
    • Sensor
    • Control centre
    • Responder
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  • Sensor
    • a body structure that monitors changes in a controlled condition
  • Control centre
    • sets the range of values within which a controlled condition should be maintained
  • Responder
    • nearly every organ or tissue in the body can behave as a responder
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Feedback Systems

  • Feedback systems can produce either negative feedback or positive feedback
  • If the response reserves the original stimulus, the system is operating by negative feedback
  • If the response enhances or intensifies the original stimulus, the system is operating by positive feedback
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