Biology Chapter on Homeostasis
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Questions and Answers

What is the primary mechanism of homeostasis?

  • Negative feedback (correct)
  • Positive feedback
  • Chemical signaling
  • Dynamic equilibrium

    • Homeostasis refers to a steady state that does not change over time.

    False

    What part of the brain serves as the integrator in homeostatic mechanisms for temperature regulation?

    Hypothalamus

    The ___ detects any environmental stimulus to the body.

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

    Match the following components of homeostatic mechanisms to their functions:

    <p>Sensor = Detects environmental changes Integrator = Compares signals to set point Effector = Responds to regulatory signals Stimulus = Triggers a physical or behavioral change</p> Signup and view all the answers

    Which of the following best describes positive feedback?

    <p>It increases the effect of changes within a system</p> Signup and view all the answers

    Hormones are electrical signals used for rapid responses to stimuli.

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

    What is the optimal value for a variable in a homeostatic mechanism called?

    <p>Set point</p> Signup and view all the answers

    What is the primary function of the excretory system?

    <p>Concentrate wastes and expel them from the body</p> Signup and view all the answers

    The renal cortex is the inner layer of the kidney.

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

    What is urine four times more concentrated than?

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

    The kidney's functional unit is called a _______.

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

    Match the kidney structure with its function:

    <p>Renal pelvis = Connects kidney to ureter Renal cortex = Outer layer of the kidney Medulla = Inner layer beneath the cortex Nephron = Functional unit of the kidney</p> Signup and view all the answers

    Which component is NOT part of the metabolic waste in urine?

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

    Kidney stones can form from a buildup of mineral solutes combined with calcium.

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

    How much liquid loss occurs on average daily?

    <p>2L</p> Signup and view all the answers

    The _______ artery brings blood into the kidneys.

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

    Which part of the nephron is responsible for reabsorbing the majority of ions and water?

    <p>Proximal convoluted tubule</p> Signup and view all the answers

    Which term describes the process of reducing metabolic rate and body temperature during periods of inactivity?

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

    Endotherms are animals that rely on behavioral mechanisms to regulate their body temperature.

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

    What does osmoregulation refer to?

    <p>Regulation of osmotic pressure in bodily fluids and cells to maintain balance.</p> Signup and view all the answers

    ___ is the flow of energy through direct contact between molecules.

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

    Match the following nitrogenous waste products with their properties:

    <p>Ammonia = Highly soluble and very toxic Urea = Low toxicity and requires less water for excretion Uric Acid = Non-toxic and excreted as a semisolid paste</p> Signup and view all the answers

    What is the primary role of the hypothalamus in thermoregulation?

    <p>Signaling other organs for heat regulation</p> Signup and view all the answers

    Evaporation cools the body by the conversion of liquids to gases.

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

    What happens to body temperature during hibernation?

    <p>It decreases significantly, often by 20 °C or more.</p> Signup and view all the answers

    The process of removing waste products from the body, excluding feces, is known as ___.

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

    Match the animal with their osmoregulation method:

    <p>Marine Iguana = Removes excess salt through specialized organ Pacific Salmon = Regulates body water content in varying environments</p> Signup and view all the answers

    What is the main nitrogenous waste excreted by fish?

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

    Hyperosmotic solutions have higher water concentrations compared to hypoosmotic solutions.

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

    What is the major waste product excreted by mammals?

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

    ___ occurs when skin blood vessels dilate to release heat.

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

    Study Notes

    Maintaining Internal Balance (Homeostasis)

    • Homeostasis is not a steady state; it's dynamic equilibrium.
    • Body cells maintain an internal temperature of roughly 37°C. Temperatures below 35°C or above 37.8°C cause malfunction.
    • The nervous system coordinates rapid responses via electrical signals (action potentials).
    • The endocrine system coordinates long-term responses using chemical signals (hormones).
    • Hormones are chemical signals carried in the blood, affecting target cells.
    • A stimulus triggers physical or behavioral changes.
    • The set point is the optimal value for a system variable.
    • Homeostatic mechanisms maintain balance and respond to external/internal changes using three components:
      • Sensor: detects environmental stimuli.
      • Integrator: receives and processes sensor signals, comparing them to the set point.
      • Effector: cells that respond to regulatory signals.

    Feedback Mechanisms and Thermoregulation

    • Negative feedback: maintains equilibrium by counteracting changes. It's the primary homeostatic mechanism. It produces an opposite effect. Example: a thermostat.
    • Sensors: detect changes in the environment (e.g., pH, temperature, molecule concentrations) in tissues and organs.
    • Integrators are usually part of the nervous or endocrine systems, and effectors are in many tissues/organs.
    • Mammals and birds: have a homeostatic mechanism with an integrator in the hypothalamus.
    • Humans: have neurons in the anterior hypothalamus, detecting temperature changes via thermoreceptors and comparing them to the 37°C set point. This triggers responses to restore balance.
    • Positive feedback: increases the effect of changes, not restoring homeostasis (an example is blood clotting).
    • Thermoregulation: in animals involves regulating internal body temperatures.

    Thermoregulation Mechanisms

    • Conduction: energy transfer through direct contact.
    • Convection: heat loss through moving air or water.
    • Radiation: energy transfer via electromagnetic waves.
    • Evaporation: heat loss via water vaporization.
    • Endotherms: regulate body temperature internally.
    • Ectotherms: utilize environmental mechanisms for temperature regulation.
    • Torpor: short-term reduction in metabolic rate and temperature for energy conservation during inactivity.
      • Example: hummingbirds lowering their bodies temperature at night.
    • Hibernation: long-term reduction in metabolism and activity for winter survival.
      • Examples: hedgehogs, groundhogs, and squirrels dropping their body temperatures by 20°C or more.
    • Estivation: summer torpor for energy conservation during heat.
      • Example: ground squirrels staying inactive in cool burrows in summer.
    • Thermoregulation in Humans:
      • Hyperthermia (above 37°C): potential for infection.
      • Hypothermia (below 37°C): potential for cell death.
      • Heat stress in humans triggers mechanisms controlled by the hypothalamus to cool the body:
        • Thermoreceptors detect rising body temperature.
        • The hypothalamus signals sweat glands via motor nerves.
        • Sweat glands produce sweat to cool the body via evaporation.
        • Skin blood vessels dilate to increase blood flow to release heat.
      • Cold stress in humans involves the hypothalamus coordinating mechanisms to warm the body:
        • Thermoreceptors detect lowered body temperature.
        • Skin arterioles constrict to reduce blood flow and heat loss.
        • Hair muscles contract causing hair to stand up to trap warm air.
        • Skeletal muscles contract causing shivering to increase metabolism and generate heat.
    • Hypothalamus: brain area producing hormones.

    Water Balance and Osmoregulation

    • Osmosis: water movement across a selectively permeable membrane from high to low water concentration.
    • Osmotic pressure: results from the water concentration gradient. Larger gradients produce higher pressure differences.
    • Hyperosmotic: solution with lower water concentration.
    • Hypoosmotic: solution with higher water concentration.
    • Isosmotic: solutions with equal water concentrations.
    • Osmoregulation: the regulation of osmotic pressure in bodily fluids and cells to maintain balance.
    • Osmoregulation Functions: managing water content and blood pressure, regulating solute composition and metabolite levels, controlling solute movement by excreting metabolic waste.

    Examples of Osmoregulators

    • Marine iguana: removes excess salt through a specialized organ on its head.
    • Pacific salmon: adapts from freshwater to saltwater environments by regulating body water content.

    Osmoregulation and Excretion

    • Excretion: removing waste products and foreign matter from the body.
    • Functions: Maintaining metabolic concentration, regulating blood pH, volume, and pressure.
    • Excretion removes metabolic waste, by-products of cellular processes, from the breakdown of proteins and nucleic acids.
    • Excretory system: main organs are kidneys and bladder.
    • Major waste products: ammonia, urea, and uric acid.

    Ammonia

    • Production: released when the liver breaks down proteins (amino acids).
    • Properties: highly soluble and toxic, requiring large water volumes for dilution and excretion.
    • Common in aquatic species: where water availability facilitates dilution.

    Urea

    • Formation: produced in the liver by combining ammonia and carbon dioxide.
    • Properties: low toxicity, highly soluble, requires less water for excretion than ammonia.
    • Role: major component of urine in mammals, some reptiles, and most amphibians.

    Uric Acid

    • Formation: produced in the liver during the breakdown of purine bases.
    • Properties: non-toxic, low water solubility, excreted as a semisolid paste reducing water loss.
    • Role: common in birds, minimizing water loss.

    Excretory System (Multicellular Organisms)

    • Individual cells cannot effectively secrete waste to the external environment.
    • Main functions of the excretory system include concentrating wastes and expelling them from the body and regulating the body's fluid and water content.

    Kidneys

    • Bean-shaped excretory organs in vertebrates.
    • Parts include the renal cortex, medulla, and renal pelvis.
    • Functions: waste removal, blood pH balance, and water regulation.
    • Filter blood, excreting wastes and water as urine.

    Urine Composition

    • Urine is much more concentrated than blood.
    • Consists of water, salts, organic compounds, urea, and other wastes/toxins.

    Urine Formation Pathway

    • Urine formation follows a specific pathway: filtration, reabsorption, secretion, excretion.
    • Filtration, reabsorption (proximal tubule, loop of Henle, distal tubule), secretion, and excretion processes are all taking place.

    Kidney Stones

    • Buildup of mineral solutes (oxalates, phosphates, carbonates) combined with calcium may form stones.
    • Sharp stones can get lodged in the renal pelvis or ureters.

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    Description

    Explore the concept of homeostasis, its mechanisms, and feedback systems in maintaining internal balance. Learn how the nervous and endocrine systems work together to regulate body functions and respond to stimuli. This quiz covers essential components such as sensors, integrators, and effectors.

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