Body Fluid Distribution and Water Balance
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Questions and Answers

What role does the integrating centre play in the body's response to environmental changes?

  • It serves as the primary sensor for monitoring the external environment.
  • It detects specific variables such as temperature and blood pressure.
  • It determines the appropriate response to correct imbalances. (correct)
  • It directly executes the physiological actions based on received signals.

    • Which of the following accurately describes negative feedback in the context of homeostasis?

  • The process enhances a deviation from the set point until equilibrium is achieved.
  • The effectors work to reverse conditions when they go beyond the set point. (correct)
  • It stops the functioning of effectors entirely once the set point is achieved.
  • It activates physiological mechanisms that could lead to a continuous rise in temperature.

    • What is the primary function of effectors in a feedback control system?

  • To process environmental changes and send signals to the integrating centre.
  • To receive signals from the brain without generating a physiological response.
  • To serve as the initial receptors that detect changes in the environment.
  • To carry out responses that restore balance after receiving instructions. (correct)

    • What kind of receptors are responsible for detecting temperature changes in the body?

    <p>Temperature receptors in the skin or hypothalamus.</p> Signup and view all the answers

    What happens to the secretion of insulin when blood sugar levels normalize?

    <p>Insulin secretion completely stops and does not resume.</p> Signup and view all the answers

    What is the primary factor that prevents net water movement across cell membranes between intracellular fluid (ICF) and extracellular fluid (ECF)?

    <p>Similar osmolarity</p> Signup and view all the answers

    If the body loses 2.5 L of water per day, approximately how long can a person theoretically survive without further water intake?

    <p>17 days</p> Signup and view all the answers

    Which fluid compartment is characterized by high concentrations of Na⁺ and Ca²⁺?

    <p>Extracellular Fluid (ECF)</p> Signup and view all the answers

    What is the total daily water loss in a typical day according to the information provided?

    <p>2.5 L</p> Signup and view all the answers

    What role does exercise play in the body's regulation of water?

    <p>Increases the rate of water loss</p> Signup and view all the answers

    Which of the following is NOT a primary method of water excretion in the human body?

    <p>Digestion through stomach</p> Signup and view all the answers

    What is one significant factor that affects the body's daily water loss?

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

    Which solute is predominantly found in high concentrations in Intracellular Fluid (ICF)?

    <p>K⁺</p> Signup and view all the answers

    What term did Walter Cannon coin to describe the body's ability to maintain internal stability?

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

    Which mechanism is used by the body to increase temperature when it is too cold?

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

    How does the body respond if blood pressure rises too high?

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

    What role does the autonomic nervous system play in homeostasis?

    <p>It regulates heart rate</p> Signup and view all the answers

    Which term is used for the feedback mechanism that amplifies a change during processes like childbirth?

    <p>Positive feedback</p> Signup and view all the answers

    What is the primary function of insulin in the context of homeostasis?

    <p>Lower blood glucose levels</p> Signup and view all the answers

    Which ion's levels are primarily regulated to ensure normal cellular function?

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

    In what situation would the body increase respiration rate?

    <p>When carbon dioxide levels rise</p> Signup and view all the answers

    What is the term for the body's response to low blood glucose levels?

    <p>Secretion of glucagon</p> Signup and view all the answers

    Which mechanism contrasts negative feedback by amplifying changes within the body?

    <p>Positive feedback</p> Signup and view all the answers

    What is the primary location where filtration occurs in the kidneys?

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

    Which process involves selectively reabsorbing substances back into the bloodstream?

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

    What is the role of the basement membrane in kidney filtration?

    <p>To act as a filtration barrier for large molecules</p> Signup and view all the answers

    Which characteristic of the basement membrane contributes to its function in filtration?

    <p>Negatively charged</p> Signup and view all the answers

    What type of cells are podocytes and what is their role?

    <p>Epithelial cells that form filtration slits</p> Signup and view all the answers

    What substances are primarily removed during the filtration process in the kidneys?

    <p>Water and waste products</p> Signup and view all the answers

    How do the kidneys contribute to the balance of electrolytes?

    <p>By regulating which ions are filtered and reabsorbed</p> Signup and view all the answers

    What percentage of a kidney's function is attributed to filtration?

    <p>50%</p> Signup and view all the answers

    What is the structural feature of podocytes that contributes to their function?

    <p>Foot-like projections for filtration</p> Signup and view all the answers

    What process in the kidneys ensures that essential substances are not lost in urine?

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

    What role do aquaporins play in water transport across epithelial cells?

    <p>They facilitate rapid water transport across cell membranes.</p> Signup and view all the answers

    Which of the following mechanisms contributes to water loss through the skin?

    <p>Increased evaporation due to sweating.</p> Signup and view all the answers

    How can diarrhea lead to dehydration?

    <p>By excess secretion of water and electrolytes into the intestinal lumen.</p> Signup and view all the answers

    What is a consequence of impaired water reabsorption in the kidneys?

    <p>Increased urine output and potential dehydration.</p> Signup and view all the answers

    What can lead to increased water loss due to osmotic diuresis?

    <p>High levels of glucose in the urine.</p> Signup and view all the answers

    What happens during the filtration process in the kidneys?

    <p>Excess water and waste products are filtered out of the blood.</p> Signup and view all the answers

    What is considered insensible water loss?

    <p>Water vapor lost during respiration.</p> Signup and view all the answers

    What effect can cholera toxin have on intestinal function?

    <p>It causes excessive secretion of water and electrolytes.</p> Signup and view all the answers

    During normal respiration, what mechanism primarily accounts for water loss in the lungs?

    <p>Evaporation during exhalation of water vapor.</p> Signup and view all the answers

    Which condition can lead to an increase in sensible water loss?

    <p>High ambient temperature leading to sweating.</p> Signup and view all the answers

    Study Notes

    Body Fluid Distribution: ICF & ECF

    • Intracellular Fluid (ICF): Fluid inside cells, approximately 28 liters
    • Extracellular Fluid (ECF): Fluid outside cells, approximately 14 liters
    • ECF includes blood plasma and interstitial fluid
    • Both ICF and ECF have equal osmolarity (~280 mOsm), preventing net water movement across cell membranes.
    • ECF has high concentrations of sodium (Na⁺) and calcium (Ca²⁺)
    • ICF has high concentrations of potassium (K⁺)

    Daily Water Balance

    • Average daily water loss: 2.5 liters
      • Urine: 1.5 liters
      • Lungs (breathing): 0.3 liters
      • Skin/Sweat: 0.6 liters
      • Feces: 0.1 liters
    • Water intake should match water loss for hydration
    • Without water intake, survival is unlikely beyond 3 days due to severe dehydration

    Factors Affecting Water Loss

    • Exercise
    • External temperature
    • Intake of coffee, alcohol, or salt
    • Medical conditions (diseases)

    Maintaining Water Balance

    • Body regulates water levels through:
      • Water intake: Drinking fluids and consuming water-rich foods
      • Water excretion: Primarily through kidneys, but also via lungs, skin, and feces
    • Water moves across epithelia primarily via osmosis, following solutes like sodium and glucose.
    • Aquaporins facilitate rapid water transport across epithelial cells in intestines and kidneys.

    Water Crossing Epithelia

    • Lungs:
      • Water loss as vapor during breathing
      • Increased with exercise or cold, dry environments
    • Skin:
      • Sweating: Water secretion helps cool the body
      • Insensible water loss: Continuous, small water loss through skin, even without sweating
    • Gut:
      • Diarrhea: Increased water excretion due to poor absorption or excessive secretion
    • Kidneys:
      • Filtration: Water filtered out of blood in glomeruli
      • Secretion: Some water secretion into renal tubules
      • Reabsorption: Water reabsorption back into blood in nephrons
      • Reduced reabsorption increases urine output, eliminating excess water

    Filtration in Kidneys: The Protein Mesh

    • Filtration: One of the kidneys' main functions, along with reabsorption
    • Occurs in the glomerulus, where blood is filtered into Bowman's capsule
    • Kidney filtration removes waste products, excess ions, and water, retaining larger molecules like proteins.
    • The protein mesh in the glomerulus is composed of:
      • Basement membrane: Gel-like matrix of collagen and glycoproteins, the primary filtration barrier
      • Podocytes: Specialized epithelial cells with foot-like projections (pedicels) that form filtration slits

    Homeostasis: Maintaining Internal Stability

    • Walter Cannon coined the term "homeostasis"
    • Body's ability to maintain internal stability (temperature, pH, fluid balance) through regulatory mechanisms
    • Examples:
      • Body temperature: Maintained around 37°C (98.6°F)
      • Blood pressure: Regulated for proper blood circulation
      • Heart rate: Adjusted based on activity levels, stress, etc.
      • Respiration rate: Adjusted to maintain oxygen and carbon dioxide balance
    • Other examples:
      • Blood glucose levels: Regulated by insulin and glucagon
      • Electrolyte balance: Regulation of ions like sodium, potassium, and calcium

    Feedback Loops in Homeostasis

    • Sensors (receptors): Detect changes in internal or external environment (temperature, pressure, pH)
    • Integrating centers (control centers): Receive sensor signals, process information, and determine appropriate response
    • Effectors: Organs or systems that carry out the response to restore balance
    • Feedback control: Regulates the response of effectors to maintain homeostasis
      • Negative feedback: Most common type, opposes changes to bring system back to equilibrium
      • Positive feedback: Amplifies changes, often involved in specific processes like childbirth

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