Biology Homeostasis and Feedback Systems
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What is the role of the modulator in the feedback system?

  • Communicates using nerve impulses only
  • Detects the stimulus in the environment
  • Processes information from the receptor (correct)
  • Carries out a response to the stimulus

    • What does homeostasis primarily refer to?

  • The ability to evolve over generations
  • The ability to thrive in various climates
  • The ability to adapt to environmental changes quickly
  • The ability to maintain a constant internal environment (correct)

    • What happens to enzymes during hyperthermia?

  • They operate at optimal levels
  • They are completely inactivated
  • They become more active
  • They denature and cause metabolic reactions to fail (correct)

    • Which of the following is NOT an internal environmental factor that the body regulates for homeostasis?

    <p>Air pressure outside the body</p> Signup and view all the answers

    Which of the following is NOT one of the methods of heat transfer?

    <p>Absorption</p> Signup and view all the answers

    Which organ is primarily responsible for thermoregulation?

    <p>Skin</p> Signup and view all the answers

    What is the primary function of negative feedback in homeostasis?

    <p>To maintain conditions within a narrow range</p> Signup and view all the answers

    Which situation is an example of positive feedback?

    <p>Contractions during childbirth</p> Signup and view all the answers

    What does the hypothalamus monitor in the body?

    <p>Body core temperature</p> Signup and view all the answers

    What are tolerance limits?

    <p>The acceptable range for internal factors sustaining life</p> Signup and view all the answers

    Which method of heat transfer exclusively removes heat?

    <p>Evaporation</p> Signup and view all the answers

    What is the primary function of peripheral thermoreceptors?

    <p>Detect changes in external temperature</p> Signup and view all the answers

    Why are mammals considered a successful group concerning homeostasis?

    <p>They maintain constant levels of activity despite fluctuations in conditions.</p> Signup and view all the answers

    Which significant effect occurs during cell respiration related to thermoregulation?

    <p>Production of ATP</p> Signup and view all the answers

    In a feedback system, what does a stimulus do?

    <p>It triggers a response that alters the original condition.</p> Signup and view all the answers

    What is a potential harmful effect of positive feedback?

    <p>Exacerbation of conditions like heat stroke</p> Signup and view all the answers

    What is the primary role of the hypothalamus in thermoregulation?

    <p>Serving as the thermoregulatory centre</p> Signup and view all the answers

    Which effectors are involved in responding to decreased temperature?

    <p>Skeletal muscles and skin-based effectors</p> Signup and view all the answers

    How do hair erector muscles respond to cold temperatures?

    <p>They contract to trap an insulating layer of air</p> Signup and view all the answers

    What occurs in the body when temperatures increase?

    <p>Increased sweat production</p> Signup and view all the answers

    Which mechanism helps to increase heat loss at elevated temperatures?

    <p>Relaxation of hair erector muscles</p> Signup and view all the answers

    What effect does hyperglycemia have on cells in the body?

    <p>Inhibits chemical reactions due to osmotic changes</p> Signup and view all the answers

    What is the effect of skeletal muscle activity during cold exposure?

    <p>Muscles undergo involuntary contraction to generate heat</p> Signup and view all the answers

    Which of the following describes the role of endocrine glands during increased body temperature?

    <p>They decrease metabolic activity to reduce heat production.</p> Signup and view all the answers

    What is the primary role of the liver in blood glucose regulation?

    <p>Converts glycogen to glucose for release into the blood</p> Signup and view all the answers

    Which type of cells in the pancreas secrete glucagon?

    <p>Alpha cells</p> Signup and view all the answers

    What condition occurs when blood glucose levels are too low?

    <p>Hypoglycemia</p> Signup and view all the answers

    What is the function of antidiuretic hormone (ADH)?

    <p>Promotes water reabsorption in kidneys</p> Signup and view all the answers

    Which glands secrete glucocorticoids such as cortisol?

    <p>Adrenal cortex</p> Signup and view all the answers

    Which of the following describes gluconeogenesis?

    <p>Conversion of fats and amino acids to glucose</p> Signup and view all the answers

    What role does the pancreas play in the regulation of blood sugar levels?

    <p>Secretes glucagon and insulin</p> Signup and view all the answers

    What happens to cells if there is too much water in the body?

    <p>Cells undergo cytolysis</p> Signup and view all the answers

    Which hormone is primarily responsible for increasing the permeability of kidney tubules to sodium and water?

    <p>Aldosterone</p> Signup and view all the answers

    What is the main consequence of increased CO2 levels in the body?

    <p>Potential damage to cells</p> Signup and view all the answers

    Where are central chemoreceptors located, and what do they primarily detect?

    <p>In the medulla oblongata, detecting carbon dioxide levels</p> Signup and view all the answers

    Which of the following correctly describes the role of the inspiratory centre?

    <p>It initiates inhalation by triggering respiratory muscles.</p> Signup and view all the answers

    How does voluntary control of breathing primarily occur?

    <p>Through connections between cerebral cortex and spinal cord.</p> Signup and view all the answers

    Which of the following components are involved in the regulation of gas concentrations in the body?

    <p>Respiratory and circulatory systems</p> Signup and view all the answers

    What primary function do peripheral chemoreceptors serve?

    <p>Detect changes in H+ (pH) concentration</p> Signup and view all the answers

    In osmoregulation, what role does aldosterone play?

    <p>Increases sodium and water reabsorption</p> Signup and view all the answers

    Study Notes

    Homeostasis

    • The ability of an organism to maintain a constant internal environment within small tolerance limits necessary for life.
    • Important internal environmental factors that the body regulates include:
      • Body temperature
      • Blood pH
      • Blood pressure
      • Concentrations of dissolved substances in body fluids
      • Concentration of blood glucose
      • Concentration of O2 & CO2
      • Concentration of metabolic wastes
    • Tolerance limits are the upper and lower limits of a normal range of a factor.
    • Homeostasis provides the body with a degree of independence from the environment.
    • Mammals are successful because they can maintain constant levels of activity despite fluctuations in external and internal environmental conditions.
    • This steady state is maintained by feedback systems, usually operated through negative feedback.

    Feedback systems

    • A feedback system is a circular situation in which the body responds to a stimulus, with the response altering the original stimulus.
    • Negative feedback:
      • Involved in maintaining conditions within a narrow range.
      • Responses counteract the original stimulus and restore the system to its original state.
      • The response reverses the direction of the stimulus.
      • Example: Controlling blood glucose levels.
    • Positive feedback:
      • A stimulus causes responses that increase the stimulus in the same direction.
      • Acts as an amplifier of response.
      • Does not contribute to homeostasis and can be damaging to the body.
      • Example: High fever/heat stroke, uterine contractions during childbirth.

    Components of a feedback system

    • Receptor (detector): Specialized cells in the brain or organs detect the stimulus.
      • A stimulus never stays exactly constant but fluctuates around the set value (set point).
    • Modulator (processing centre): Processes information from the receptor and sends information to the effector.
    • Effector: Organs, muscles, or glands carry out a response that reverses the stimulus.
    • Communication in the feedback system can be by hormones or nerve impulses.

    Thermoregulation

    • The process of regulating body temperature.
    • Important because:
      • High body temperature (hyperthermia) denatures enzymes, causing metabolic reactions to fail.
      • Low body temperature (hypothermia) inactivates enzymes, slowing down metabolic activities.
    • Involves controlling the amount of heat lost and heat gained across the body surface.
    • Heat can be transferred in and out of the body through conduction, convection, and radiation.
    • Evaporation can only remove heat.
    • Heat can also be gained through metabolism.
    • During cell respiration, food is oxidized to release energy.
      • Some energy is used for cellular work, like active transport and cell division.
      • Most of the energy is released as heat energy.
    • Thermoregulation is controlled by the hypothalamus in the brain.
      • Monitors the body's core temperature.
    • The skin is the major homeostatic organ involved in thermoregulation, due to its large surface area.

    Components of the thermoregulatory system

    • Receptors:
      • Peripheral thermoreceptors in the skin (warm and cold receptors) detect changes in external temperature.
      • Central thermoreceptors in the hypothalamus detect changes in blood temperature.
    • Modulator: Thermoregulatory centre in the hypothalamus.
    • Effectors:
      • Skin-based effectors:
        • Sweat glands
        • Hair erector muscles
        • Skin arterioles/capillaries
      • Skeletal Muscles
      • Endocrine glands:
        • Adrenal gland
        • Thyroid gland

    Responding to decreased temperature (increase heat gain & reduce heat loss)

    • Effectors:
      • Skin-based effectors:
        • Sweat glands: Not stimulated. No sweat production. No evaporation of sweat.
        • Hair erector muscles: Contract, raising the hairs and trapping a layer of air, which acts as an insulating layer to reduce heat loss.
        • Skin arterioles/capillaries: Vasoconstriction. Less blood flows to the surface of the skin, reducing heat loss by radiation.
      • Skeletal muscles: Shiver (involuntary contraction) to produce heat.
      • Endocrine glands:
        • Adrenal gland: Stimulated to release adrenaline, which increases the body's metabolic rate in the liver to generate heat.
        • Thyroid gland: Stimulated to release thyroxine, which also increases metabolic rate.

    Responding to increased temperature (reduce heat gain & increase heat loss)

    • Effectors:
      • Skin-based effectors:
        • Sweat glands: Stimulated to produce and release sweat. Evaporation of sweat removes heat from the skin surface.
        • Hair erector muscles: Relax, lowering the hairs and minimizing trapped air layer, allowing heat loss.
        • Skin arterioles/capillaries: Vasodilation. More blood flows closer to the surface of the skin, increasing heat loss by radiation.
      • Skeletal muscles: Not stimulated, no shivering. No heat production.
      • Endocrine glands:
        • Adrenal gland: Not stimulated, no adrenaline secretion. No heat production.
        • Thyroid gland: Not stimulated, no thyroxine secretion. No heat production.

    Regulation of blood sugar levels

    • Important because:
      • High blood glucose level (hyperglycemia) increases blood osmotic pressure, causing water to move out of cells. This can stop chemical reactions.
      • Low blood glucose level (hypoglycemia) means cells do not have enough glucose for respiration. This can also disrupt metabolism.
    • Organs involved:
      • Liver
      • Pancreas
      • Adrenal glands

    Role of the liver

    • Converts glucose into glycogen for storage or glycogen to glucose for release into the blood.

    Role of the pancreas

    • Contains clusters of hormone-secreting cells called the islets of Langerhans.
    • These clusters contain α cells and β cells:
      • α cells secrete glucagon.
      • β cells secrete insulin.
    • Effects of insulin:
      • Increases glucose uptake by cells.
      • Promotes glycogen formation from glucose in the liver.
      • Promotes protein synthesis.
      • Suppresses gluconeogenesis.
      • Inhibits lipolysis.
    • Effects of glucagon:
      • Increases glycogen breakdown to glucose in the liver.
      • Promotes gluconeogenesis.
      • Increases lipolysis.

    Role of the adrenal glands

    • Adrenal glands consist of two parts:
      • Adrenal medulla (inner): Secretes adrenaline and noradrenaline.
      • Adrenal cortex (outer): Secretes glucocorticoids (cortisol).

    Treatment of diabetes mellitus using gene therapy

    • Involves taking a copy of the insulin gene and finding a way to get it into target cells so they can produce insulin.
    • A vector (like a virus) is used to carry the insulin gene and deliver it into the cell.
    • Once inside the cell, the gene is expressed to produce therapeutic insulin.

    Regulation of body fluid concentrations

    • Osmoregulation is very important because:
      • Too much water: Cells undergo cytolysis (bursting) as water enters the cells by osmosis.
      • Too little water: Chemical reactions stop, blood pressure drops, and toxic wastes accumulate.
    • Like thermoregulation, osmoregulation is based on a balance between fluid gain and fluid loss.
    • A constant composition of body fluids is achieved when fluid gain equals fluid loss.

    The kidneys

    • Important excretory and osmoregulatory homeostatic organs.
    • The functional units of the kidneys are called nephrons.

    Antidiuretic hormone (ADH)

    • Also known as vasopressin.
    • Released from the posterior pituitary gland.
    • Causes the distal convoluted tubule and collecting duct of the nephron to become more permeable to water.

    Aldosterone

    • Plays an important role in osmoregulation.
    • Released from the adrenal cortex.
    • Increases the permeability of kidney tubules, leading to greater sodium reabsorption into the bloodstream.
    • As a result, more water is reabsorbed.

    Regulating water intake by the thirst mechanism

    • The thirst mechanism is triggered by a decrease in blood volume and an increase in blood osmolarity (concentration of solutes in the blood)
    • Specialized receptors in the hypothalamus sense these changes and trigger the feeling of thirst.

    Regulation of gas concentrations

    • The levels of respiratory gases (oxygen and carbon dioxide) must be regulated properly to ensure a continuous supply of oxygen for cell respiration and to remove carbon dioxide, a toxic waste product.
    • Too much carbon dioxide will cause a drop in blood pH, which can damage cells and disrupt metabolism.
    • Carbon dioxide is carried to the lungs by blood and later excreted in expired air, while oxygen from inspired air is delivered to the cells by blood.
    • Both the respiratory and circulatory systems are involved in the regulation of gas concentrations.

    Control of breathing

    • Breathing rate is regulated by the respiratory centre located in the medulla oblongata.
    • The respiratory centre contains two regions:
      • Inspiratory centre: Controls inhalation.
      • Expiratory centre: Controls exhalation.
    • Carbon dioxide and hydrogen ions (pH) are the main chemical factors that affect breathing rate.
      • Increases in their concentrations are detected by chemoreceptors:
        • Central chemoreceptors (located in the medulla oblongata) detect changes in carbon dioxide concentration in the blood.
        • Peripheral chemoreceptors (located in the aorta and carotid arteries) detect changes in hydrogen ion concentration in the blood.

    Voluntary control of breathing

    • Voluntary control comes from connections between the cerebral cortex and spinal cord.
    • It bypasses the respiratory centre in the medulla oblongata.
    • It provides protection by preventing harmful/irritating gases and water from entering the lungs.

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    Description

    Explore the essential concepts of homeostasis and feedback systems in biology. This quiz covers the mechanisms through which organisms maintain a stable internal environment and respond to stimuli. Test your knowledge on key regulatory processes and their significance for survival.

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