Download Hormonal Responses to Exercise Objectives Objectives

Chapter 5
Hormonal Responses to Exercise
Objectives
• Describe the hormone-receptor interaction
• Identify 4 factors that influence the contraction of
a hormone in the blood
• Describe how steroid hormones act on cell
• Describe “second messenger” hormone action
• Describe the role of hypothalamus-releasing
factors in the control of hormone secretion from
the anterior and posterior pituitary
Objectives
• Identify the site of release, stimulus for release, &
the predominate action of the following hormones:
epinephrine, norepinephrine, glucagon, insulin,
cortisol, aldosterone, thyroxine & growth hormone
• Discuss the use of anabolic steroid & growth
hormone on muscle growth and their potential side
effects
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Objectives
• Contrast the role of plasma catecholamines w/
intracellular factors in the mobilization of muscle
glycogen during exercise
• Graphically describe the chagnes in the following
hormones during graded and prolonged exercise &
discuss how those changes influence the 4
mechanisms used to maintain the blood glucose
concentration: insulin, glucagon, cortisol, growth
hormone, epinephrine, and norepinephrine
Objectives
• Describe the effect of changing hormone &
substrate levels in the bld on the mobilization
of free fatty acids from adipose tissue
Neuroendocrinology
• Endocrine glands release hormones
directly into the bld
• 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
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Bld Hormone Concentration
Determined by:
• Rate of secretion of hormone from endocrine
gland
• Rate of metabolism or excretion of hormone
• Quantity of transport pro
• ∆s in plasma volume
Control of Hormone Secretion
• Rate of insulin secretion from the pancreas
is dependent on:
– Magnitude of input
– Stimulatory vs. inhibitory
Factors That Influence the
Secretion of Hormones
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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
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
Steroid Hormones Mechanism
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Non-Steroid Hormone Mechanism
Cyclic AMP
“Second
Messenger”
Mechanism
Hormones: Regulation & Action
• Hormones are secreted from endocrine
glands
– Hypothalamus & pituitary glands
– Thyroid & parathyroid glands
– Adrenal glands
– Pancreas
Hypothalamus
• Controls activity of the anterior & posterior
pituitary glands
• Influenced by (+) & (-) input
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Positive & Negative Input to the
Hypothalamus
Anterior Pituitary Gland
Growth Hormone
• Secreted from the anterior pituitary gland
• Essential for normal growth
– Stimulates protein synthesis & long bone growth
• ↑s during exercise
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Growth
Hormone
Posterior Pituitary Gland
• Secretes antidiuretic hormone (ADH)
• Reduces water loss from the body to
maintain plasma volume
• Stimulated by:
∆ in the Plasma ADH
Concentration During Exercise
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Thyroid Gland
• Triiodothyronine (T3) & thyroxine (T4)
– Important in maintaining metabolic rate &
allowing full effect of other hormones
• Calcitonin
– Regulation of plasma Ca++
• Parathyroid Hormone
– Also involved in plasma Ca++ regulation
Adrenal Gland
• Adrenal medulla
– Secretes catecholamines
• Epinephrine and norepinephrine
– ↑s Î HR, Glycogenolysis, Lypolysis,
• Adrenal cortex
– Secretes steroid hormones
• Mineralcorticoids, glucocorticoids & sex steroids
Adrenal Medulla
• Part of the sympathetic nervous system
– Secrete catecholamines
• Epinephrine (E) & norepinephrine (NE)
– Bind to receptors on effector organs
• Alpha (α) & beta (β) receptors
– Bring about ∆s in cellular activity via second
messengers
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Response to Catecholamines: Role
of Receptor Type
Receptor
Type
Effect of
E/NE
Membrane-bound
enzyme
Intracellular
mediator
β1
E=NE
Adenylate cyclase
↑ cAMP
↑ Heart rate
↑ Glycogenolysis
↑ Lipolysis
Effects on Various
Tissues
β2
E>>>NE
Adenylate cyclase
↑ cAMP
↑ Bronchodilation
↑ Vasodilation
α1
E≥NE
Phospholipase C
↑ Ca++
↑ Phosphodiesterase
↑ Vasoconstriction
α2
E≥NE
Adenylate cyclase
↓cAMP
Opposes action of β1 & β2
receptors
Adrenal Cortex
• Mineralcorticoids (aldosterone)
– Involved in maintaining plasma Na+ & K+
– Part of the renin-angiotensin-aldosterone
system of bld pressure regulation
∆ in Mineralcorticoids During
Exercise
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Adrenal Cortex
• Glucocorticoids (Cortisol)
Control of Cortisol Secretion
Pancreas
• Secretes digestive enzymes & HCO3- into
small intestine
• Releases insulin & glucagon
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Insulin
• Secreted by the β cells of the islets of Langerhans
• Promotes the storage of glu, amino acids & fats
• Diabetes mellitus is characterized as a lack of
insulin (Type 1) or a lack of insulin receptors
(Type 2)
Glucagon
Glucagon
• Released from the α cells of the islets of Langerhans
• Promotes the mobilization of fatty acids & glu
Muscle Glycogen Utilization
• Breakdown of muscle glycogen is under dual
control
– Epinephrine-cyclic AMP
– Ca++-calmodulin
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Control of Glycogenolysis
Muscle Glycogen Utilization
• Glycogen breakdown is related to exercise
intensity
Glycogen Depletion During Exercise
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Plasma EPI Concentration
During Exercise
Maintenance of Plasma Glu During
Exercise
• Mobilization of glu from liver glycogen stores
• Mobilization of FFA from adipose tissue
– Spares bld glu
• Gluconeogenesis from AA, lactic acid &
glycerol
• Blocking the entry of glu into cells
– Forces use of FFA as a fuel
Bld Glu Homeostasis During
Exercise
• Permissive & 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 AA for gluconeogenesis
• Blocks entry of glu into cells
Role of Cortisol in the Maintenance
of Bld Glu
Plasma Cortisol During Exercise
• At lo intensity
• At hi intensity
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∆s in Plasma Cortisol During
Exercise
Growth Hormone
• Important in the maintenance of plasma glu
Role of Growth Hormone in the
Maintenance of Plasma Glu
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Growth Hormone During Exercise:
Effect of Intensity
Growth Hormone During Exercise:
Trained vs. Untrained
Bld Glu Homeostasis During
Exercise
• Fast-acting hormones
• Maintain plasma glu
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Role of Catecholamines in
Substrate Mobilization
Epinephrine & Norepinephrine
During Exercise
• ↑ linearly during exercise
• Favor the mobilization of FFA & maintenance
of plasma glu
∆ in Plasma Catecholamines
During Exercise
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Epinephrine & Norepinephrine
Following Training
• ↓d plasma levels in response to exercise bout
• Parallels reduction in glu mobilization
Plasma Catecholamines During
Exercise Following Training
Effect of Insulin and Glucagon on
FFA Uptake & Oxidation
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Insulin During Exercise
• Plasma insulin decreases during exercise
∆s in Plasma Insulin During
Exercise
Effect of Training on Plasma
Insulin During Exercise
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Effect of Training on Plasma
Glucagon During Exercise
Control of Insulin & Glucagon
Secretion During Exercise
Effect of SNS on Substrate
Mobilization
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Hormonal Responses to Exercise
Free Fatty Acid Mobilization During
Exercise
• FFA mobilization ↓s during heavy exercise
• Could be due to hi levels of lactic acid
Effect of Lactic Acid on FFA
Mobilization
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