Human Body Temperature Regulation
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Questions and Answers

What is the typical internal body temperature humans maintain?

  • 36°C
  • 39°C
  • 38°C
  • 37°C (correct)

    • A body temperature elevation of 10 °C is not life-threatening.

    False

    What do humans typically adjust in response to a systemic bacterial infection?

    body temperature set point

    Lizards are classified as ______ but can regulate their body temperature through behavioral means.

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

    Match the following concepts with their descriptions:

    <p>Homeostasis = The maintenance of stable internal conditions Set point = A target range for physiological parameters Poikilothermic = Organisms that regulate body temperature through behavior Fluid balance = Regulation of water and sodium intake/excretion</p> Signup and view all the answers

    What happens when water intake exceeds water use?

    <p>The body conserves water</p> Signup and view all the answers

    Consuming salty foods can lead to cellular dehydration.

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

    What is the primary effect of vasopressin on the kidneys?

    <p>It conserves water.</p> Signup and view all the answers

    Hypovolemic thirst is stimulated by a reduction in blood ______.

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

    Match the terms with their correct descriptions:

    <p>Osmotic thirst = Caused by cellular dehydration Hypovolemic thirst = Triggered by loss of blood volume Diuresis = Increased urine production due to reduced vasopressin Vasopressin = Hormone that conserves water in the kidneys</p> Signup and view all the answers

    What occurs during the postprandial phase?

    <p>Metabolic fuels enter the bloodstream</p> Signup and view all the answers

    The cephalic phase of insulin release is triggered neurally by sensory stimuli related to food intake.

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

    What hormone is released by the pancreas during fasting to induce lipolysis and glycogenolysis?

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

    During the postabsorptive phase, insulin levels _ and glucagon secretion _ .

    <p>rise, falls</p> Signup and view all the answers

    Match the type of diabetes with its characteristics:

    <p>Type I = Insulin-dependent, autoimmune disorder Type II = Insulin insensitivity, excess insulin production Both = Common symptoms include elevated appetite and high blood sugar</p> Signup and view all the answers

    Which method is used by the liver to produce glucose during fasting?

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

    Symptoms of diabetes mellitus include elevated appetite, hyperglycemia, increased thirst, and increased _ .

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

    Animals with diabetes mellitus are often used to study the relationship between food intake and fuel circulation.

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

    What role does vasopressin play in kidney function?

    <p>Retains water</p> Signup and view all the answers

    Genetic mutations can lead to the inability to produce vasopressin, resulting in diabetes mellitus.

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

    What stimulates the release of vasopressin during prolonged cellular dehydration?

    <p>Thirst centers in the hypothalamus</p> Signup and view all the answers

    Hypovolemia stimulates the production of __________, which is a vasoconstrictor.

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

    Match the hormone to its primary function:

    <p>Vasopressin = Retains water in kidneys Aldosterone = Promotes sodium retention Angiotensin = Vasoconstriction Gut hormones = Increase fuel absorption and satiety</p> Signup and view all the answers

    What motivates individuals to seek and ingest sodium?

    <p>Sodium reservoir depletion</p> Signup and view all the answers

    Short-term mechanisms exclusively control how much energy is consumed.

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

    What influences food intake apart from endogenous signaling factors in humans?

    <p>Experience, habits, mood, and availability</p> Signup and view all the answers

    In many species, there are fewer mechanisms to stop eating than to promote __________.

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

    Which of the following factors can affect hormones associated with food intake?

    <p>All of the above</p> Signup and view all the answers

    What effect does a high-carbohydrate diet have on diabetic animals?

    <p>They overeat.</p> Signup and view all the answers

    Leptin serves only as a satiety hormone.

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

    What condition results from producing too much insulin?

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

    Hunger is a strong motivation to seek out and ingest __________.

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

    Match the following hormones to their main actions:

    <p>Leptin = Signals fat stores and inhibits eating Ghrelin = Induces an increase in food intake Insulin = Signals the central nervous system about metabolic fuels PYY = Reduces food intake</p> Signup and view all the answers

    Which hormone is produced by adipose cells and circulates in proportion to body fat?

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

    Insulin receptors are located exclusively in the pancreas.

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

    What is the role of peripheral signals in food intake regulation?

    <p>They monitor metabolic fuel oxidation and adjust food intake and energy expenditure.</p> Signup and view all the answers

    The __________ nuclei of the hypothalamus have the highest density of leptin receptors.

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

    What happens to energy intake when insulin levels drop?

    <p>Food intake increases.</p> Signup and view all the answers

    Which hormone is primarily thought to provoke feelings of satiety?

    <p>Cholecystokinin (CCK)</p> Signup and view all the answers

    Amylin delays gut emptying and decreases food intake.

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

    What is the effect of bombesin on feeding behavior in rats?

    <p>It reduces feeding behavior.</p> Signup and view all the answers

    The hormone __________ is released from both the gut and the brain and is involved in reducing food intake.

    <p>Glucagon-like peptide-1 (GLP-1)</p> Signup and view all the answers

    Match the following substances with their effects on feeding behavior:

    <p>Cholecystokinin (CCK) = Promotes satiety Amylin = Delays gastric emptying Corticotropin-releasing hormone (CRH) = Rapidly reduces food intake Bombesin = Inhibits feeding behavior</p> Signup and view all the answers

    What effect does stress have on food intake in chronically stressed rats?

    <p>Craves high-fat foods</p> Signup and view all the answers

    Endorphins are thought to make food less rewarding when antagonized.

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

    Explain the effect of estrogen on food intake in ovariectomized female rats.

    <p>It increases food intake and energy storage.</p> Signup and view all the answers

    In rats, high levels of __________ are associated with reduced food intake and body mass.

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

    Which of the following hormones is involved in the feedback mechanism relating fat depots to the brain?

    <p>Corticotropin-releasing hormone (CRH)</p> Signup and view all the answers

    High-fat meals empty from the stomach faster than high-carbohydrate meals.

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

    What roles do androgens play in food intake and body mass?

    <p>Androgens contribute to maintaining male size dimorphism and influence food intake.</p> Signup and view all the answers

    Match the following hormones with their sources:

    <p>Amylin = Islet cells of the pancreas Adiponectin = Adipose tissue GLP-1 = Gut Cholecystokinin (CCK) = GI tract and brain stem</p> Signup and view all the answers

    What is the effect of glucagon on food intake?

    <p>Reduces food intake</p> Signup and view all the answers

    Study Notes

    Homeostasis

    • Homeostasis is the body's ability to maintain relatively constant internal conditions within defined limits.
    • Claude Bernard first described this concept in relation to internal bodily systems.
    • Walter Cannon later coined the term "homeostasis" in 1929.
    • Homeostasis involves optimal body temperature (for humans, 36°C to 38°C), optimal blood concentrations of various substances (sugars, proteins, sodium, potassium, etc.), and optimal blood pH.

    Homeostasis and Behavior

    • Many homeostatic systems are entirely physiological, but some also involve behavioral components.
    • A key example is the maintenance of water and salt balance (drinking behavior).
    • Physiological systems (like aldosterone production by the adrenal glands) are not always sufficient for balance.
    • Behavioral compensatory mechanisms can be crucial in such cases, as seen in adrenalectomized rats.

    Pica in Humans

    • Pica is a disorder where individuals consume inedible/non-food items.
    • It's named after the European magpie (Pica pica).
    • Pica is commonly observed in young children, pregnant people, and those with certain mental health conditions.
    • A link often exists between pica and nutritional deficiencies (e.g., calcium, iron, zinc).

    Hormones and Homeostasis

    • Many hormones involved in physiological homeostasis also mediate behaviors vital for homeostasis.

    Archetypal Homeostat

    • The archetypal homeostatic device is a thermostatically controlled heating and cooling system.
    • Humans maintain a core body temperature of approximately 37°C
    • Variations in temperature up to 35°C to 38°C are not life-threatening.

    Poikilothermic Organisms (Lizards)

    • Lizards, as poikilothermic animals, can regulate their body temperature through behavioral means.
    • Experiments show that lizards adjust their set points in response to infections.

    Set Point Concept

    • The concept of a set point is valuable for systems requiring precise regulation.
    • It's less useful for systems that can tolerate wider variations.

    Fluid Balance

    • Homeostatic mechanisms regulate water and sodium balance (intake and excretion).
    • Water is essential for virtually all metabolic processes.
    • Water loss through perspiration, respiration, urination, and defecation must be constantly replenished.
    • If water use exceeds intake, the body conserves water.
    • Behavioral compensation is necessary if physiological conservation is insufficient.

    Sodium and Water Regulation

    • The regulation of sodium and water is closely linked.
    • Sodium is crucial in moving water between compartments (extracellular and intracellular).
    • Cell membranes act as barriers between these compartments.
    • Osmotic balance between compartments is critical for maintaining water balance.

    Vasopressin and Kidneys

    • Vasopressin conserves water in the kidneys.
    • If excessive water is consumed, reduced plasma osmolality inhibits vasopressin release leading to increased urine production (diuresis).

    Blood Plasma Volume

    • A different regulatory system maintains blood plasma volume.
    • Loss of fluid/electrolytes leads to hypovolemic thirst.
    • Kidney function compromise can lead to fluid imbalances.

    Endocrine Regulation of Fluid Balance and Thirst

    • Vasopressin acts on the kidneys to retain water.
    • Genetic mutations related to vasopressin production lead to diabetes insipidus.

    Cerebral Osmoreceptors

    • Cerebral osmoreceptors signaling the hypothalamus regulate vasopressin production based on dehydration levels.

    Insulin and Blood Plasma Volume

    • Stretch receptors in cardiac blood vessels regulate vasopressin and signal via the vagus nerve for thirst in response to blood plasma volume changes.
    • Hypovolemia leads to angiotensin production and aldosterone release.
    • Aldosterone promotes sodium retention and reduces urine production.

    Sodium Balance

    • Interstitial fluid sodium reservoirs buffer brain cells from sodium fluctuations.
    • Insufficient sodium necessitates seeking and consuming it.

    Energy Balance

    • Animals must consume food for raw materials and energy.
    • The balance between energy storage, expenditure, and intake varies across species.
    • Mechanisms for stopping eating (satiety signaling) are often weaker than hunger signals.

    Long-Term Energy Balance

    • Homeostatic mechanisms control long-term body mass within a relatively fixed range over weeks, months, or years.

    Food Consumption – Humans

    • Human food intake relies on endogenous signaling, experiences, habits, mood, and availability.
    • Anticipation of food can affect associated hormones.

    Gut Hormones

    • Several gut hormones function to increase fuel absorption, oxidation, thermogenesis, and body temperature.
    • Gut hormone secretion is generally proportional to calorie consumption.

    Metabolism During Well-Fed State

    • Two phases of energy utilization/storage follow food consumption.
    • Postprandial phase: metabolic fuels enter the bloodstream.
    • Postabsorptive phase: excess energy is stored. -Two distinct phases of insulin release: Cephalic and Gastrointestinal.

    Metabolism During Fasting State

    • When energy intake is insufficient, energy must be obtained from storage.
    • The brain needs a consistent energy supply.
    • Pancreatic glucagon release prompts lipolysis and glycogenolysis.
    • Gluconeogenesis occurs in the liver.
    • SNS also stimulates fat breakdown.

    Dysregulated Energy Metabolism

    • Problems taking up energy into cells can arise from insulin issues.
    • Diabetes mellitus type I (autoimmune destruction of pancreatic insulin-producing cells).
    • Diabetes mellitus type II (tissue insensitivity to insulin).

    Diabetes Symptoms

    • Elevated appetite.
    • High blood sugar (hyperglycemia).
    • Increased thirst.
    • Increased urination.

    Measuring Fuel Oxidation

    • Animals with diabetes mellitus are used to study fuel oxidation's role in food intake.
    • Food intake is related to fuel availability, not just circulating levels.

    Hyperinsulinemia

    • Hyperinsulinemia is the condition where individuals produce too much insulin.
    • It leads to increased glucose uptake, inhibited lipolysis, and low blood sugar.
    • Obesity is a potential result.

    Primary Sensory Signals

    • Preparatory factors (prior to food intake) influence hormone production.
    • A fixed meal schedule demonstrates significant anticipatory ghrelin release in humans and rats.

    Control of Food Intake

    • Humans eat based on internal and external cues.
    • Factors include how much to consume, what kind of food to consume, when to start eating, and when to stop.
    • Consumption of the wrong calorie-dense foods disrupts normal hormonal processes and may drive cravings, hunger, or over-consumption.
    • Eating depends on intrinsic factors (e.g., stored energy, food composition, gut signals) and extrinsic factors (availability, culture, environment).

    Hunger

    • Hunger is the motivated seeking and consuming of food.
    • It's a psychological state that's triggered by decreases in satiety.
    • The body monitors long-term energy stores, intake, and utilization.

    Peripheral Signals

    • Food intake is regulated based on intracellular changes.
    • A sensory system monitors metabolic fuel levels, oxidation, storage, and breakdown.
    • This regulation controls food intake, energy expenditure, and body fat storage/breakdown.

    Leptin

    • Leptin is produced by fat cells (adipose tissue) and acts as a satiety hormone.
    • Leptin levels are proportional to body fat.
    • Leptin does not consistently prove effective for long-term weight loss.
    • Leptin is too large to pass the blood-brain barrier directly, must be transported.
    • Leptin's effects on the brain include inhibiting eating and influencing reproduction.

    Insulin

    • Insulin is another key adiposity signal.
    • Hunger occurs when insulin levels drop.
    • Insulin signals to the brain through the cerebrospinal fluid.
    • Insulin receptors exist in the brain, especially in the hypothalamus (arcuate nuclei).

    Gastrointestinal Tract Hormones

    • Most GI tract hormones (e.g., pancreatic polypeptide, peptide YY, glucagon-like peptide 1) are involved in decreasing food intake.
    • Ghrelin, produced in the GI tract, stimulates food intake and works oppositely to leptin.

    Central Signals

    • The arcuate nuclei, lateral hypothalamus, and paraventricular nucleus are main control points of food intake.
    • The arcuate nuclei have opposing neural circuits controlled by peripheral hormone signals (related to food, fat stores, etc.).

    Central Signals – Feeding Stimulatory Circuit

    • Neurons in the feeding stimulatory circuit produce NPY and AgRP.
    • NPY directly evokes feeding behavior.
    • AgRP inhibits melanocortin receptors, hence affecting appetite.

    Central Signals – Feeding Inhibitory Circuit

    • CART and POMC are key signaling molecules in the feeding inhibitory circuit.
    • Increased CART secretion decreases food intake.
    • POMC produces a-MSH, inhibiting appetite.
    • High levels of insulin and leptin drive POMC and CART activity, hence reducing food intake.

    Hindbrain and Brainstem

    • The hypothalamus is a major area, but other posterior brain areas can exert control over food intake independently.
    • Studies using rats with isolated hypothalamus showed food intake responses to glucose and fatty acid metabolic blockage.

    Protein Hormones

    • Long delays between nutrients leaving the gut and use/storage could lead to other signaling mechanisms.
    • Neural signals from stomach distension play a role.
    • The rate of digestion is likely involved in signaling satiety.

    Endocrine Signals That Stop Feeding

    • Cholecystokinin (CCK) is a key hormone associated with satiety.
    • CCK works by influencing the gut and the brain stem.

    Other Signals

    • Bombesin.
    • Amylin, similar to insulin's regulating effects.
    • Corticotropin-releasing hormone (CRH): rapidly decreases food intake. -The sympathetic nervous system connects adipose tissues and the brain. -Chronic stress affects the HPA axis leading to changes in food intake. -Other hormones, like GLP-1, adiponectin, and PYY, also likely affect feeding behavior.

    Other Factors Influencing Food Intake

    • Endorphins may influence food intake.
    • Treatment with the opioid antagonist naloxone reduces food intake.
    • Sugars and oils appear associated with endorphin release.
    • Comfort food potentially also involves similar signaling.

    Gonadal Steroid Hormones

    • Gonadal steroids influence feeding behavior and subsequent body mass.
    • Evidence shows appetite regulation links closely to reproductive behavior.
    • Estrogen generally increases energy expenditure, while progesterone has a potentially opposite influence.
    • Hormonal changes through the ovarian cycle influence eating and body mass in rats and primates.

    Adipose Tissue Metabolism

    • Adipose tissue has receptors for estrogens and progestins.
    • Estradiol decreases lipoprotein lipase (LPL) activity.
    • Progesterone increases LPL activity.

    Androgens

    • Sexual dimorphism (differences in size between sexes) appears to be affected by androgens peri-natally.
    • Androgens also influence the degree of dimorphism throughout time.
    • Castration in rats reduces food intake and limits weight gain, including muscle mass.

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    Description

    Test your knowledge on human body temperature regulation and responses to infections. This quiz covers key concepts related to thermoregulation, water balance, and hormonal effects on the kidneys. Challenge yourself with matching terms and descriptions.

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