Explain the effect of the following on metabolic rate: thyroxine levels, eating, body surface area, muscular exercise, emotional stress, starvation.
Ch. 24 Nutrition, Metabolism, and Energy Balance

Marieb, Hoehn7th EditionHuman Anatomy & PhysiologyISBN: 9780805359091Not the one you use?Change textbook
Chapter 23, Problem 25
While attempting to sail solo from Los Angeles to Tahiti, Seth encountered a storm that marooned him on an uninhabited island. He was able, using his ingenuity and a pocket knife, to obtain plenty of fish to eat, and roots were plentiful. However, the island was barren of fruits and soon his gums began to bleed and he started to develop several infections. Analyze his problem.
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Identify the symptoms Seth is experiencing: bleeding gums and multiple infections. These are classic signs of a deficiency in a specific nutrient.
Recall that bleeding gums and poor wound healing are commonly associated with a deficiency in vitamin C (ascorbic acid), which is essential for collagen synthesis and immune function.
Understand that vitamin C is primarily obtained from fruits and vegetables, which Seth lacks on the island since it is barren of fruits.
Recognize that without adequate vitamin C, collagen production is impaired, leading to weakened blood vessel walls (causing bleeding gums) and compromised immune defense (leading to infections).
Conclude that Seth's problem is scurvy, a disease caused by vitamin C deficiency, and that his diet of fish and roots alone does not provide sufficient vitamin C to prevent this condition.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Vitamin C Deficiency and Scurvy
Vitamin C is essential for collagen synthesis and immune function. A lack of vitamin C, often due to absence of fruits and fresh vegetables, leads to scurvy, characterized by bleeding gums, weakness, and infections. Seth’s symptoms suggest scurvy caused by insufficient vitamin C intake on the barren island.
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Nutritional Requirements for Human Survival
Humans require a balanced intake of macronutrients and micronutrients, including vitamins and minerals, to maintain health. While fish and roots provide protein and carbohydrates, the absence of fruits means missing vital vitamins like vitamin C, leading to deficiency diseases despite adequate caloric intake.
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Role of Collagen and Immune System in Healing
Collagen is a structural protein crucial for tissue repair and gum health, dependent on vitamin C for synthesis. Without enough vitamin C, collagen production falters, weakening gums and skin, and impairing immune response, which increases susceptibility to infections, explaining Seth’s deteriorating condition.
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Related Practice
Textbook Question
Textbook Question
Make a flowchart that indicates the pivotal intermediates through which glucose can be converted to fat.
Textbook Question
Gregor, a large, beefy man, came home from the doctor's office and complained to his wife that his blood tests 'were bad.' He told her that the doctor said he would have to give up some of his steaks and butter. He went on to mourn the fact that he would have to start eating more cottage cheese and olive oil instead. What kind of problem was revealed by his 'bad' blood tests? What do you think of his choice of food substitutes and why? What would you suggest?
Textbook Question
Compare and contrast mechanisms of heat loss with mechanisms of heat promotion, and explain how these mechanisms determine body temperature.
