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Chapter 5 Hormonal Responses to Exercise. EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 6 th edition Scott K. Powers & Edward T. Howley. Objectives. Describe the hormone-receptor interaction - PowerPoint PPT Presentation
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© 2007 McGraw-Hill Higher Education. All rights reserved.
Chapter 5Hormonal Responses
to Exercise
EXERCISE PHYSIOLOGY
Theory and Application to Fitness and Performance, 6th edition
Scott K. Powers & Edward T. Howley
© 2007 McGraw-Hill Higher Education. All rights reserved.
Objectives
• Describe the hormone-receptor interaction• Identify four factors that influence the
contraction of a hormone in the blood• Describe how steroid hormones act on cells• Describe “second messenger” hormone action• Describe the role of hypothalamus-releasing
factors in the control of hormone secretion from the anterior and posterior pituitary
© 2007 McGraw-Hill Higher Education. All rights reserved.
Objectives
• Identify the site of release, stimulus for release, and the predominate action of the following hormones: epinephrine, norepinephrine, glucagon, insulin, cortisol, aldosterone, thyroxine, growth hormone, estrogen, and testosterone
• Discuss the use of anabolic steroid and growth hormone on muscle growth and their potential side effects
© 2007 McGraw-Hill Higher Education. All rights reserved.
Objectives
• Contrast the role of plasma catecholamines with intracellular factors in the mobilization of muscle glycogen during exercise
• Graphically describe the changes in the following hormones during graded and prolonged exercise and discuss how those changes influence the four mechanisms used to maintain the blood glucose concentration: insulin, glucagon, cortisol, growth hormone, epinephrine, and norepinephrine
© 2007 McGraw-Hill Higher Education. All rights reserved.
Objectives
• Describe the effect of changing hormone and substrate levels in the blood on the mobilization of free fatty acids from adipose tissue
© 2007 McGraw-Hill Higher Education. All rights reserved.
Neuroendocrinology• Endocrine glands release hormones directly into
the blood • Hormones alter the activity of tissues that
possess receptors to which the hormone can bind
• The plasma hormone concentration determines the magnitude of the effect at the tissue level
© 2007 McGraw-Hill Higher Education. All rights reserved.
Blood Hormone Concentration
Determined by:• Rate of secretion of hormone from endocrine
gland• Rate of metabolism or excretion of hormone• Quantity of transport protein• Changes in plasma volume
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Control of Hormone Secretion
• Rate of insulin secretion from the pancreas is dependent on:– Magnitude of input– Stimulatory vs. inhibitory
© 2007 McGraw-Hill Higher Education. All rights reserved.
Factors That Influence the Secretion of Hormones
Fig 5.1
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Hormone-Receptor Interactions
• Trigger events at the cell• Magnitude of effect dependent on:
– Concentration of the hormone– Number of receptors on the cell– Affinity of the receptor for the hormone
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Hormone-Receptor Interactions
• Hormones bring about effects by:– Altering membrane transport– Stimulating DNA to increase protein synthesis– Activating second messengers
• Cyclic AMP• Ca++
• Inositol triphosphate• Diacylglycerol
© 2007 McGraw-Hill Higher Education. All rights reserved.
Fig 5.2
Mechanism of Steroid
Hormones
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Fig 5.3
Cyclic AMP“Second
Messenger” Mechanism
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Fig 5.4
Other “Second
Messenger” Systems
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Hormones: Regulation and Action
• Hormones are secreted from endocrine glands– Hypothalamus and pituitary glands– Thyroid and parathyroid glands– Adrenal glands– Pancreas– Testes and ovaries
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Hypothalamus
• Controls activity of the anterior and posterior pituitary glands
• Influenced by positive and negative input
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Fig 5.6
Positive and Negative Input
to the Hypothalamus
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Anterior Pituitary Gland
Fig 5.5
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Growth Hormone
• Secreted from the anterior pituitary gland• Essential for normal growth
– Stimulates protein synthesis and long bone growth
• Increases during exercise– Mobilizes fatty acids from adipose tissue– Aids in the maintenance of blood glucose
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Growth Hormone
Fig 5.6
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Posterior Pituitary Gland
• Secretes antidiuretic hormone (ADH) or vasopressin
• Reduces water loss from the body to maintain plasma volume
• Stimulated by:– High plasma osmolality and low plasma
volume due to sweating– Exercise
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Change in the Plasma ADH Concentration During Exercise
Fig 5.7
© 2007 McGraw-Hill Higher Education. All rights reserved.
Thyroid Gland• Triiodothyronine (T3) and thyroxine (T4)
– Important in maintaining metabolic rate and allowing full effect of other hormones
• Calcitonin
– Regulation of plasma Ca++
• Parathyroid Hormone
– Also involved in plasma Ca++ regulation
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Adrenal Medulla
• Secretes Epinephrine and Norepinephrine
• Increases
–HR, glycogenolysis, lypolysis,
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Adrenal Cortex
• Mineralcorticoids (aldosterone)
– Maintain plasma Na+ and K+
– Regulation of blood pressure
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Change in Mineralcorticoids During Exercise
Fig 5.8
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Adrenal Cortex
• Glucocorticoids (Cortisol)– Stimulated by exercise and long-term
fasting– Promotes the use of free fatty acids as
fuel– Stimulates glucose synthesis – Promotes protein breakdown for
gluconeogenesis and tissue repair
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Control of Cortisol
Secretion
Fig 5.9
© 2007 McGraw-Hill Higher Education. All rights reserved.
Pancreas• Secretes digestive enzymes and bicarbonate
into small intestine• Releases
– Insulin - Promotes the storage of glucose, amino acids, and fats
– Glucagon - Promotes the mobilization of fatty acids and glucose
– Somatostatin - Controls rate of entry of nutrients into the circulation
© 2007 McGraw-Hill Higher Education. All rights reserved.
Testes
• Release testosterone
– Anabolic steroid
• Promotes tissue (muscle) building
• Performance enhancement
– Androgenic steroid
• Promotes masculine characteristics
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Control of Testosterone
Secretion
Fig 5.10
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Estrogen
• Establish and maintain reproductive function
• Levels vary throughout the menstrual cycle
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Control of Estrogen Secretion
Fig 5.11
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Muscle Glycogen Utilization
• Breakdown of muscle glycogen is under dual control– Epinephrine-cyclic AMP– Ca2+-calmodulin
• Delivery of glucose parallels activation of muscle contraction
• Glycogenolysis – breakdown of glycogen
Fig 5.16
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Control of Glycogenolysis
Fig 5.16
Glycogenolysis
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Muscle Glycogen Utilization
• Glycogenolysis is related to exercise intensity– High-intensity of exercise results in greater
and more rapid glycogen depletion
• Plasma epinephrine is a powerful simulator of glycogenolysis– High-intensity of exercise results in greater
increases in plasma epinephrine Fig 5.14
Fig 5.13
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Glycogen Depletion During Exercise
Fig 5.13
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Plasma Epinephrine Concentration During Exercise
Fig 5.14
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Maintenance of Plasma Glucose During Exercise
• Mobilization of glucose from liver glycogen stores
• Mobilization of FFA from adipose tissue – Spares blood glucose
• Gluconeogenesis from amino acids, lactic acid, and glycerol
• Blocking the entry of glucose into cells– Forces use of FFA as a fuel
© 2007 McGraw-Hill Higher Education. All rights reserved.
Blood Glucose Homeostasis During Exercise
• Permissive and slow-acting hormones
– Thyroxine
– Cortisol
– Growth hormone
• Act in a permissive manner to support actions of other hormones
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Cortisol
• Stimulates FFA mobilization from adipose tissue
• Mobilizes amino acids for gluconeogenesis
• Blocks entry of glucose into cells
Fig 5.17
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Role of Cortisol in the Maintenance of Blood
Glucose
Fig 5.17
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Plasma Cortisol During Exercise
• At low intensity – plasma cortisol decreases
• At high intensity – plasma cortisol increases
Fig 5.18
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Changes in Plasma Cortisol During Exercise
Fig 5.18
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Growth Hormone
• Important in the maintenance of plasma glucose– Decreases glucose uptake– Increases FFA mobilization– Enhances gluconeogenesis
Fig 5.19
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Growth Hormone in the Maintenance of Plasma Glucose
Fig 5.19
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Growth Hormone During Exercise:Effect of Intensity
Fig 5.20
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Growth Hormone During Exercise:Trained vs. Untrained
Fig 5.20
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Blood Glucose Homeostasis During Exercise
• Fast-acting hormones– Norepinephrine and epinephrine– Insulin and glucagon
• Maintain plasma glucose– Increasing liver glucose mobilization– Increased levels of plasma FFA– Decreasing glucose uptake – Increasing gluconeogenesis
Fig 5.21
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Role of Catecholamines in Substrate Mobilization
Fig 5.21
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Epinephrine & Norepinephrine During Exercise
• Increase linearly during exercise• Favor the mobilization of FFA and
maintenance of plasma glucose
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Change in Plasma Catecholamines During Exercise
Fig 5.22
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Epinephrine & Norepinephrine Following Training
• Decreased plasma levels in response to exercise bout
• Parallels reduction in glucose mobilization
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Plasma Catecholamines During Exercise Following
Training
Fig 5.23
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Effects of Insulin & Glucagon
Fig 5.24
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Insulin During Exercise
• Plasma insulin decreases during exercise– Prevents rapid uptake of plasma glucose– Favors mobilization of liver glucose and
lipid FFA
• Trained subjects during exercise– More rapid decrease in plasma insulin– Increase in plasma glucagon
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Changes in Plasma Insulin During Exercise
Fig 5.25
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Effect of Training on Plasma Insulin During Exercise
Fig 5.25
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Effect of Training on Plasma Glucagon During Exercise
Fig 5.26
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Effect of SNS on Substrate Mobilization
Fig 5.28
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Hormonal Responses to Exercise
Fig 5.29a
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Hormonal Responses to Exercise
Fig 5.29b
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Free Fatty Acid Mobilization During Heavy Exercise
• FFA mobilization decreases during heavy exercise– This occurs in spite of persisting hormonal
stimulation for FFA mobilization• May be due to high levels of lactic acid
– Promotes resynthesis of triglycerides– Inadequate blood flow to adipose tissue– Insufficient transporter for FFA in plasma
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Effect of Lactic Acid on FFA Mobilization
Fig 5.30
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Chapter 5Hormonal Responses
to Exercise