Chapter 11: Endocrine System and Hormonal Responses to Exercise

LEARNING OUTCOMES

1. List the main structures of the endocrine system and the hormones that they produce.

2. Explain the basic actions of the hormones released by the major endocrine glands.

3. Compare and contrast the two major classes of hormones (steroid vs. nonsteroid hormones).

4. Explain the negative feedback system as it relates to endocrine system control of physiological functions.

5. Describe the hormonal regulation of metabolism during exercise, including the hormones involved and how they influence the availability of carbohydrates and fats for energy during prolonged exercise.

6. Describe the hormonal regulation of fluid balance during exercise.

7. Explain the major endocrine system adaptations experienced as a result of chronic exercise training.

ANCILLARY LINK

Visit DavisPlus at http://davisplus.fadavis.com for study and practice resources, including online quizzes, animations that help explain physiological processes, podcasts concerning news and career trends in exercise physiology, and practice references.

VIGNETTE

• As long as Perla can remember, she has dreamed of becoming a competitive gymnast. At the age of 6, Perla's parents enrolled her in her first tumbling class at a local gymnastics center, and she has been continuously involved with the sport since that time. At the age of 13, Perla began competing on a national level and showed promise as an Olympic hopeful. During the transition from regional to national competition, Perla experienced her first menstrual period (menarche) and grew increasingly concerned about her appearance and body weight. To deal with her body-image concerns, Perla focused intently on increasing her practice hours in the gym and decreasing her caloric intake. These alterations in lifestyle directly affected Perla's endocrine system to the point that she stopped menstruating. At first, Perla was pleased with not having to deal with monthly cycles, but she soon learned from her physical education teacher that not menstruating could lead to serious health problems.

  How might Perla's lack of menstrual periods affect her long-term health and performance?

• When Perla was 16, she suffered a severe tibial fracture from landing incorrectly during one of her gymnastics floor routines. Upon further evaluation and testing, Perla's physician noticed that her bone mineral density was below average for a female of Perla's age. This provoked the physician to ask Perla about her dietary habits and the regularity of her menstrual cycles. Perla replied that she was in constant fear of gaining weight, which led her to eat two small, low-calorie meals each day. She also informed her doctor that she had not had a menstrual period since shortly after she experienced menarche, about 3 years ago. The physician referred Perla to a certified eating disorders specialist and directed her to refrain from any type of high-impact physical activity until after her fracture had fully healed and she had completed thorough rehabilitation of her lower leg.