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    Topic 2.1: Organisation & Homeostasis

    Uploaded by

    Jun Hong Tee
    Here are examples of how the body maintains homeostasis in the given situations: a) You have gotten cold while sleeping in the aircond - Your body would activate mechanisms like shivering and vasoconstriction to generate heat and maintain core body temperature. Hormones like thyroxine may also be released to speed up metabolic rate. b) You are exercising by cross-country skilling and need more oxygen for your muscles - Your respiratory rate would increase to take in more oxygen. More blood would be shunted to working muscles. Heart rate would also increase to pump more oxygenated blood throughout the body. c) You ate a lot of ice and it melted and turned into water in your excretory

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    Topic 2.1: Organisation & Homeostasis

    Uploaded by

    Jun Hong Tee
    25 views21 pages
    Here are examples of how the body maintains homeostasis in the given situations: a) You have gotten cold while sleeping in the aircond - Your body would activate mechanisms like shivering and vasoconstriction to generate heat and maintain core body temperature. Hormones like thyroxine may also be released to speed up metabolic rate. b) You are exercising by cross-country skilling and need more oxygen for your muscles - Your respiratory rate would increase to take in more oxygen. More blood would be shunted to working muscles. Heart rate would also increase to pump more oxygenated blood throughout the body. c) You ate a lot of ice and it melted and turned into water in your excretory

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    Original Title

    Homeostasis

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    Here are examples of how the body maintains homeostasis in the given situations: a) You have gotten cold while sleeping in the aircond - Your body would activate mechanisms like shivering and vasoconstriction to generate heat and maintain core body temperature. Hormones like thyroxine may also be released to speed up metabolic rate. b) You are exercising by cross-country skilling and need more oxygen for your muscles - Your respiratory rate would increase to take in more oxygen. More blood would be shunted to working muscles. Heart rate would also increase to pump more oxygenated blood throughout the body. c) You ate a lot of ice and it melted and turned into water in your excretory

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    25 views21 pages

    Topic 2.1: Organisation & Homeostasis

    Uploaded by

    Jun Hong Tee
    Here are examples of how the body maintains homeostasis in the given situations: a) You have gotten cold while sleeping in the aircond - Your body would activate mechanisms like shivering and vasoconstriction to generate heat and maintain core body temperature. Hormones like thyroxine may also be released to speed up metabolic rate. b) You are exercising by cross-country skilling and need more oxygen for your muscles - Your respiratory rate would increase to take in more oxygen. More blood would be shunted to working muscles. Heart rate would also increase to pump more oxygenated blood throughout the body. c) You ate a lot of ice and it melted and turned into water in your excretory

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 21

    Topic 2.

    Organisation
    & Homeostasis
    5 levels of human body organization
    Homeostasis

    Homoios = same, stasis = standing

    Maintenance of a constant internal


    environment within a living
    organism.
    Body response:
    Negative feedback
    • In biological system, homeostasis is usually achieved by
    a process called negative feedback.
    • A change in the level of an internal factor causes
    effectors to restore the internal environment to its
    original level.
    • The internal environment of a multicellular organism is
    the tissue fluid bathing the cells.
    Negative feedback
    Excess Corrective Negative
    mechanism feedback

    Set point Set point

    Negative
    feedback
    Deficiency Corrective
    mechanism
    Positive feedback
    • Sometimes a homeostatic mechanism breaks down and
    negative feedback does not occur.
    • Deviations from the set point are not corrected.
    • Even worse, the deviations may be made larger.
    • This results in a process called positive feedback in
    which a small change in output causes further change
    in the same direction.
    Positive feedback
    Further excess
    Positive feedback
    Excess

    Set point

    Deficiency
    Positive feedback
    Further deficiency
    • Positive feedback is usually harmful because it tends to
    produce unstable conditions.
    • For example, when the negative feedback mechanisms in
    mammalian temperature regulation break down, a rise in
    body temperature can threaten death.
    PANCREAS

    • Insulin hormone (beta


    Langerhans )
    • Glucagon hormone
    (alpha Langerhans )
    Pancreatic hormones regulate blood glucose levels

    Body cells take up more


    glucose
    Beta cells of pancreas
    stimulated to release
    insulin into the blood Liver takes up glucose and Blood glucose
    stores it as glycogen level declines to a
    set point; stimulus
    Stimulus: glucose level
    for insulin release
    diminishes
    Homeostasis: Normal blood glucose level
    (90mg / 100ml)

    Blood glucose Stimulus: glucose level


    level rises to set
    point; stimulus for Alpha cells of pancreas
    glucagon release stimulated to release
    diminishes glucagon into the blood

    Liver breaks down


    glycogen and releases
    glucose to the blood
    The antagonistic actions of insulin & glucagon

    Insulin
    secretion

    Lowers blood
    Raises blood
    glucose level
    glucose level

    Glucagon
    secretion
    Diabetes mellitus
    • Serious hormonal disease in which the body cells are unable to
    absorb glucose from the blood.
    • Diabetes develops when there is not enough insulin in the blood
    or when body cells do not respond normally to blood insulin.
    • The blood glucose concentration becomes so high that the kidney
    is unable to reabsorb all the glucose filtered into its tubules back
    into the blood. Consequently, glucose is excreted in the urine.
    • The high blood glucose is called hyperglycaemia
    • The presence of glucose in the urine is called glycosuria
    • There are treatments for diabetic person – insulin
    supplements or special diets – but no cure.
    • Symptoms: A lack of energy, a craving for sweets,
    frequent urination & persistent thirst.
    • A diagnostic test for diabetes is a glucose tolerance test.
    Insulin & glucagon
    • Care has to be taken with the doses of insulin,
    because an overdose causes too much glucose
    to be withdrawn from the blood, reducing the
    blood glucose concentration below the set point –
    hypoglycaemia.
    • Glucose is the main fuel for brain cells, and a
    lack of glucose can lead to unconsciousness,
    extreme can lead to coma even death!
    Give an example of how your body would maintain
    homeostasis in the following situations:

    a. You have gotten cold while sleeping in the aircond


    b. You are exercising by cross-country skilling and need
    more oxygen for your muscles.
    c. You ate a lot of ice and it melted and turned into water in
    your excretory system.

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