Systemic Alterations in Body Temperature
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Questions and Answers

What is a potential consequence of hyperthermia if body temperature exceeds 42.5°C (108°F)?

  • Death by respiratory failure (correct)
  • Enhanced tissue hydration
  • Improved muscular performance
  • Increased appetite

    • Which of the following is NOT a physical cause of hyperthermia?

  • Poor ventilation
  • Prolonged muscular exertion
  • High environmental temperature
  • Dehydration (correct)

    • What role does a short period of hyperthermia play in infectious diseases?

  • Increases tissue hydration
  • Impairs immune response
  • Decreases metabolic rate
  • Facilitates phagocytosis (correct)

    • How can dehydration affect an animal experiencing hyperthermia?

    <p>It can lead to anorexia</p> Signup and view all the answers

    What is a clinical sign indicating hyperthermia?

    <p>Temperature exceeding 39.5°C</p> Signup and view all the answers

    What is one of the effects of elevated body temperature on heart function?

    <p>Increased heart rate due to myocardial depression</p> Signup and view all the answers

    What occurs when peripheral vasodilatation happens during hyperthermia?

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

    Which of the following indicates a critical elevation in body temperature that could result in death?

    <p>42.5°C</p> Signup and view all the answers

    What primarily determines the body temperature in animals?

    <p>Balance between heat gain and heat loss</p> Signup and view all the answers

    Which of the following is a method of heat gain in the body?

    <p>Muscular and metabolic activities</p> Signup and view all the answers

    What is hypothermia characterized by?

    <p>Subnormal body temperature</p> Signup and view all the answers

    Which of the following factors can lead to excessive heat loss?

    <p>Exposure to severe cold air</p> Signup and view all the answers

    What condition can lead to insufficient heat production?

    <p>Anemia and severe hemorrhage</p> Signup and view all the answers

    How does the body normally respond to decreased body temperature due to cold exposure?

    <p>By increasing metabolic rate</p> Signup and view all the answers

    What role do thermo-receptors in the skin play?

    <p>They maintain temperature balance.</p> Signup and view all the answers

    What is a notable cause of decreased muscle tone related to hypothermia?

    <p>Acute ruminal impaction</p> Signup and view all the answers

    What is a primary effect of increased body temperature on leukocytes?

    <p>Increased motility</p> Signup and view all the answers

    Which of the following is NOT a noted adverse effect of fever?

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

    What treatment is recommended for high or prolonged fever that causes discomfort?

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

    What might occur if the temperature elevation exceeds 42°C (107°F)?

    <p>Reduced tissue response to heat</p> Signup and view all the answers

    Which substance is used to facilitate repair and alleviate inflammation during infections?

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

    What is one of the initial behaviors of an animal experiencing hyperthermia?

    <p>Seeking cool places</p> Signup and view all the answers

    At what body temperature range does respiratory distress begin to occur in hyperthermic animals?

    <p>$41.5-42.5^ ext{°C}$</p> Signup and view all the answers

    Which of the following clinical signs indicates advanced hyperthermia in horses?

    <p>Hyponatremic dehydration and azotemia</p> Signup and view all the answers

    What is an inappropriate treatment for hyperthermia, as it may worsen the condition?

    <p>Immersion in ice baths</p> Signup and view all the answers

    What effect does prolonged hyperthermia have on pregnant animals?

    <p>Potential for abortion</p> Signup and view all the answers

    Which of the following is recommended to manage heat stress in animals?

    <p>Provide cool clean water</p> Signup and view all the answers

    How does hyperthermia initially affect sweating in dogs?

    <p>Sweating increases then decreases</p> Signup and view all the answers

    What should be avoided in the treatment of hyperthermia due to its harmful effects?

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

    What combination primarily characterizes septic fever?

    <p>Hyperthermia and infection or inflammation</p> Signup and view all the answers

    What role does Interleukin-1 play in the pathogenesis of fever?

    <p>It acts as an endogenous pyrogen that stimulates the hypothalamus</p> Signup and view all the answers

    Which condition is classified under aseptic fever?

    <p>Chemical fever due to injection of foreign protein</p> Signup and view all the answers

    During which stage of fever do cutaneous vasoconstriction and muscle shivering occur?

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

    What physiological response occurs during the fastigium stage of fever?

    <p>Flushing of the skin and severe sweating</p> Signup and view all the answers

    Which is NOT a potential cause of fever from the provided content?

    <p>Excess hydration</p> Signup and view all the answers

    Which mechanism contributes to the production of heat during fever?

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

    What is indicated by muscle flaccidity and vasodilatation during fever?

    <p>Fever defervescence</p> Signup and view all the answers

    Study Notes

    Systemic Alterations in Body Temperature

    • Body temperature: A balance between heat gain (muscular activity, metabolism, absorption from the environment) and heat loss (sweating, salivation, respiration, defecation, urination).
    • Heat Regulation: Controlled by the hypothalamus, peripheral thermo-receptors in the skin, maintaining a constant body temperature.
    • Homeothermy: The ability of animals to maintain a relatively stable body temperature.

    Hypothermia

    • Subnormal body temperature caused by excessive heat loss or insufficient heat production.

    Excessive Heat Loss

    • Exposure to cold: Cold air can cause heat loss surpassing the ability of metabolic activity, muscle tone, and vasoconstriction to compensate.

    Insufficient Heat Production

    • Decreased Muscle Tone: Experienced in conditions like parturient paresis (milk fever) and acute ruminal impaction.
    • Anesthesia and Sedation: These states often lower body temperature.
    • Decreased Tissue Perfusion: Peripheral vasodilatation during shock can lead to hypothermia.
    • Anemia and Hemorrhage: Both conditions reduce the blood's oxygen-carrying capacity, impacting heat production.
    • Terminal Stages of Disease: Metabolic activity reduction in terminal disease stages can contribute to hypothermia.
    • Old Age and Malnutrition: These conditions often have a diminished ability to maintain body temperature.
    • Good Housing: Foals and calves housed in cold environments may struggle to maintain their body temperature.

    Hyperthermia (Heat Stroke or Heat Exhaustion)

    • Elevated body temperature caused by either excessive heat production or deficient heat loss.

    Etiology of Hyperthermia

    • High Environmental Temperature: Prolonged exposure to high temperatures, especially with high humidity, inadequate ventilation, and a heavy coat, can trigger hyperthermia.
    • Physical Exertion: Prolonged and strenuous activity, particularly in hot environments, can lead to heat stress.
    • Neurogenic Hyperthermia: Damage to the hypothalamus can disrupt temperature regulation.
    • Dehydration: Insufficient fluid levels make it difficult to dissipate heat through evaporation.
    • Excessive Muscular Activity: Certain conditions, such as strychnine poisoning, stimulate constant muscular activity, increasing heat production.
    • Drug Administration: Excessive doses of some drugs, like levamisole (parasympathomimetic) and calcium, can cause hyperthermia.

    Pathogenesis of Hyperthermia

    • Short-Term Hyperthermia: Can be beneficial in infectious diseases, as it enhances phagocytosis, immune body production, and reduces the viability of microorganisms.
    • Increased Metabolic Rate: Leads to hypoglycemia, depletion of liver glycogen, and increased protein catabolism.
    • Anorexia: Due to dehydration.
    • Increased Thirst: Caused by dryness of the mouth.
    • Increased Heart Rate: Due to heightened blood temperature, often combined with peripheral vasodilatation, leading to reduced blood pressure.
    • Increased Respiration: To compensate for the increased temperature, respiration rate and depth increase due to the effect on the respiratory center.
    • Reduced Urine Secretion: Peripheral vasodilatation decreases renal blood flow, leading to oliguria.
    • Body Temperature Beyond Critical Point: Circulatory failure (rapid and irregular heartbeat due to myocardial weakness), depression of the nervous and respiratory centers, and ultimately, death by respiratory failure.

    Clinical Findings of Hyperthermia

    • Elevated Body Temperature: Above 39.5°C (103°F) with death often occurring above 42.5°C (108°F).
    • Early Signs: Increased thirst, seeking cool places, lying in water (dogs), sweating and salivation (dogs and cows), followed by a lack of sweating.
    • Restlessness and Dullness: The animal may show signs of restlessness, dullness, stumbling, and a preference for lying down.
    • Abortion: Prolonged periods of hyperthermia can lead to abortion.
    • Advanced Signs: Labored breathing, shallow and irregular respiration, increased heart rate, rapid and weak pulse, collapse, convulsions, coma, and eventually, death.

    Clinical Pathology of Hyperthermia

    • Simple Hyperthermia: No significant clinic-pathological changes.
    • Advanced Hyperthermia (Horses): Hyponatremic dehydration and azotemia.

    Necropsy Findings of Hyperthermia

    • Peripheral Vasodilatation: Blood vessels are dilated.
    • Rapid Rigor Mortis: The body stiffens quickly after death.
    • Poor Blood Clotting: Slow, poor, and incomplete blood clotting.

    Treatment of Hyperthermia

    • Complete Rest: In a cold, well-ventilated area.
    • Fluid Therapy: Intravenous administration of saline (0.9%) and dextrose (5%) solutions, along with analgesic and antihistaminic drugs. Horses often need 20-40 liters of fluids in the first few hours of treatment. Fluids can also be administered orally but must be monitored to ensure proper gastrointestinal function.
    • Cold Fomentation: Applying cold water or ice bags to the extremities.
    • Cold Enema: Using a cold enema with analgesics.
    • Tranquillizers: Minimizing excessive activity.
    • Avoid Calcium Preparations: Calcium supplements are contraindicated in hyperthermia.
    • Avoid Ice Baths: Immersion in cold water causes peripheral vasoconstriction, which can further elevate core body temperature.

    Fever (Pyrexia)

    • Elevated body temperature above the normal range.
    • Combination of hyperthermia and infection or inflammation.
    • Hyperthermia and toxemia from substances circulating in the bloodstream.

    Etiology of Fever

    • Septic Fever: Infection with bacteria, viruses, protozoa, or fungi.
      • Localized Infection: Abscesses, cellulitis, empyema.
      • Generalized Infection: Bacteremia (bacteria in the blood), endocarditis (inflammation of the heart lining), septicemic diseases, viremia (virus in the blood), and toxemia.
    • Aseptic Fever:
      • Chemical Fever: Caused by injections of foreign proteins.
      • Surgical Fever: Tissue breakdown and blood vessel damage after surgery.
      • Fever from Tissue Necrosis: Injection of necrotizing material, such as intramuscular injections.
      • Severe Intravascular Hemolysis: Extensive breakdown of red blood cells.
      • Extensive Infarction: Tissue death due to lack of blood supply.
      • Immune Reactions: Anaphylaxis (severe allergic reaction), angioneurotic edema (swelling).
      • Neoplasm Necrosis: Tissue death in rapidly growing tumors.

    Pathogenesis of Fever

    • Exogenous Pyrogens: Substances from outside the body, such as bacteria, viruses, bacterial endotoxins, antigen-antibody complexes, and hemoglobin, trigger an inflammatory response.
    • Phagocytes: Immune cells like macrophages and monocytes engulf the exogenous pyrogens.
    • Interleukin-1: Phagocytes release interleukin-1 (endogenous pyrogen) into the bloodstream.
    • Hypothalamus: Interleukin-1 stimulates the hypothalamus, specifically the anterior hypothalamus, to increase the production of prostaglandin E2 (PGE2).
    • Thermostatic Set Point: PGE2 raises the hypothalamic thermoregulatory set point.
    • Heat Conservation and Production: The body initiates mechanisms to conserve heat (e.g., vasoconstriction) and generate heat (e.g., shivering) to raise the body temperature until it matches the new set point.

    Stages and Clinical Signs of Fever

    • Increment (Chill): Cutaneous vasoconstriction leading to cold and dry skin, absence of sweating, muscle shivering, reduced respiratory rate, increased pulse rate, elevated rectal temperature, and reduced urine formation.
    • Fastigium (Constant Temperature): Cutaneous vasodilatation causes flushing of the skin and mucous membranes, severe sweating, increased urination (diuresis), decreased ruminal motility, and constipation.
    • Decrement (Fever Defervescence): Stored heat is dissipated, leading to vasodilatation, sweating, muscle flaccidity, and a decline in body temperature.

    Benefits of Fever

    • Enhanced Immune Response: Higher body temperature increases leukocyte (white blood cell) motility, bactericidal activity, phagocytosis, lymphocyte transformation, and the effects of interferon and interleukin-1.

    Adverse Effects of Fever

    • Anorexia and Wasting: Loss of appetite and weight loss due to excessive catabolism if the fever is prolonged.
    • Central Nervous System Effects: Can lead to convulsions.
    • Increased Respiration: More rapid breathing.
    • Increased Heart Rate: Higher heartbeat.
    • Increased Thirst: More frequent need for water.
    • Scant Feces: Reduced stool production.
    • Oliguria and Albuminuria: Reduced urine output and presence of protein in the urine.
    • Depression and Muscular Weakness: Lowered energy levels and reduced muscle strength.
    • Important Note:* The temperature elevation associated with fever is rarely above 42°C (107°F). Severe toxemia accompanying hyperthermia can lead to a loss of tissue response to heat production and conservation, resulting in a fall in body temperature (heat collapse) as death approaches.

    Treatment of Fever

    • Control Infection: The primary goal is to control infection by identifying and treating the underlying cause with antibacterial drugs. Broad-spectrum antibiotics are used for fevers of unknown origin.
    • Reduce Discomfort: If the fever causes discomfort, anorexia, or a risk of death, use antipyretics (Analgin, Novlgin, etc.) to reduce the fever.
    • Antidotes: Use specific antidotes for toxins if known.
    • Cold Fomentation: Apply cold water or ice bags, alcohol, or vinegar to the skin.
    • Fluid Therapy: Administer intravenous fluids, containing 5% dextrose or saline solutions.
    • Glucocorticoids: To facilitate tissue repair and alleviate inflammation associated with infection.
    • Antihistaminic Medications: To reduce allergic reactions.

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    Description

    This quiz explores the physiological concepts of body temperature regulation, the role of the hypothalamus, and conditions like hypothermia. Learn how heat gain and loss are balanced in maintaining homeothermy and the impacts of various factors on body temperature.

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