Podcast
Questions and Answers
Which of the following hormones promotes protein synthesis?
Which of the following hormones promotes protein synthesis?
Which of the following factors stimulates growth hormone secretion?
Which of the following factors stimulates growth hormone secretion?
Which of the following hormones has an anti-lipolytic effect?
Which of the following hormones has an anti-lipolytic effect?
Which of the following is a direct action of growth hormone?
Which of the following is a direct action of growth hormone?
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Which of the following hormones is most responsible for increasing free fatty acid levels in the blood?
Which of the following hormones is most responsible for increasing free fatty acid levels in the blood?
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Which hormone levels are increased in a fasting state compared to the fed state?
Which hormone levels are increased in a fasting state compared to the fed state?
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Which of these hormones is primarily responsible for promoting the storage of glucose in the fed state?
Which of these hormones is primarily responsible for promoting the storage of glucose in the fed state?
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Which hormone is suppressed during starvation?
Which hormone is suppressed during starvation?
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Which hormone is known to have a synergistic effect with both epinephrine and glucagon during extended fasting?
Which hormone is known to have a synergistic effect with both epinephrine and glucagon during extended fasting?
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What is the primary effect of increased glucagon secretion in the fasting state?
What is the primary effect of increased glucagon secretion in the fasting state?
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Which of these factors does NOT stimulate glucagon secretion?
Which of these factors does NOT stimulate glucagon secretion?
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Which of these hormones acts on both the liver and muscle to stimulate glycogenolysis?
Which of these hormones acts on both the liver and muscle to stimulate glycogenolysis?
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Which of these effects is NOT associated with cortisol's actions?
Which of these effects is NOT associated with cortisol's actions?
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Which of these is a direct effect of glucagon in the liver?
Which of these is a direct effect of glucagon in the liver?
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Which of these is a direct effect of epinephrine in the heart?
Which of these is a direct effect of epinephrine in the heart?
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Which of these is a direct effect of cortisol in the adipose tissue?
Which of these is a direct effect of cortisol in the adipose tissue?
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Which of the following hormones directly inhibits insulin secretion?
Which of the following hormones directly inhibits insulin secretion?
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Which of these is a hallmark symptom of Addison's disease?
Which of these is a hallmark symptom of Addison's disease?
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Which of these is a hallmark symptom of Cushing's syndrome?
Which of these is a hallmark symptom of Cushing's syndrome?
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Which of these hormones enhances the effects of glucagon and epinephrine in the liver?
Which of these hormones enhances the effects of glucagon and epinephrine in the liver?
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Study Notes
Growth Hormone (GH)
- GH has various effects: sodium retention, decreased insulin sensitivity, lipolysis, protein synthesis (anabolic), bone growth stimulation, and IGF-1 secretion stimulation.
- GH and insulin are both anabolic hormones promoting protein synthesis, but insulin also promotes triglyceride and glycogen synthesis, unlike GH.
IGF-1 Functions
- IGF-1 mimics insulin's actions, has anti-lipolytic activity, and promotes protein synthesis.
GH Actions Summary
- Direct: Stimulates protein synthesis.
- Indirect: Promotes protein synthesis via IGF-1, stimulates bone growth, increases muscle protein synthesis, increases glucose production and gluconeogenesis in the liver, decreases insulin's effect on glucose uptake, increases lipolytic agent (e.g., epinephrine, glucagon) action, and raises free fatty acid and ketone levels.
GH Secretion Stimulators
- Hypoglycemia
- Stress
- Exercise
- Protein meals (amino acids like arginine)
- Sleep (onset)
- Androgens and estrogens
GH Levels Across Lifespan
- Highest during adolescence, second-highest in childhood, lower in adults, and lowest in the elderly.
Low GH Effects
- Reduced lean body mass, smaller protein mass, reduced bone mass.
GH Inhibitors
- Free fatty acids
- Cortisol
- Glucose
- REM sleep
- IGF-1
GH Effects on 16-Year-Old Boy
- GH increases both protein and glucose production.
Catabolic Hormones Overview
- These hormones (glucagon, epinephrine, cortisol) have a clear catabolic effect.
Glucagon
- Secretion: Pancreatic alpha cells, triggered by low glucose (fasting).
- Actions (Liver): Stimulates gluconeogenesis and glycogenolysis.
- Actions (Fat Tissue): Stimulates lipolysis.
- Synthesis: Processed from a large precursor molecule.
- Different cells produce different products due to varying enzymes.
- Pancreatic alpha cells produce: glucagon, MPGF, GPRP, GRPP
- Intestinal L cells produce: GLP-1 and other molecules
Glucagon Action Summary
- Stimulates glycogenolysis in the liver
- Stimulates gluconeogenesis
- Stimulates lipolysis
- Generates ketones
- Mobilizes energy stores
Increasing Glucose Output from the Liver
- Activates protein kinase A
- Stimulates glycogen breakdown
- Inhibits glucose metabolism
- Maintains glucose levels by releasing from glycogen, preventing further decrease
Increasing Lipolysis in Fat Tissue
- Activates hormone-sensitive lipase
- Accelerates triglyceride breakdown into glycerol and free fatty acids
Glucagon Secretion Stimulators
- Amino acids
- GI hormones (CCK, gastrin)
- Cortisol
- Exercise
- Infection
- Fasting
Glucagon Secretion Inhibitors
- Glucose
- Free fatty acids
- Ketones
- Secretin
- Insulin
- Somatostatin (inhibits glucagon and insulin)
- Alpha-adrenergic stimulation
- Beta-adrenergic stimulation (stimulates glucagon)
Epinephrine
- Production: Adrenal medulla
- Actions: Glycogenolysis (liver and muscle), stimulates gluconeogenesis, decreases glucose uptake, stimulates lipolysis, stimulates ketogenesis, mobilizes energy stores.
Epinephrine Release Stimulators
- Anxiety, fear, pain, hypoglycemia, hypotension, hypovolemia, hypothermia, hypoxia, exercise
Epinephrine Receptor Effects
- Beta-1 (Heart): Increases heart rate, stroke volume, cardiac output, blood pressure
- Alpha-1 (Vascular smooth muscle): Vasoconstriction
- Beta-2 (Skeletal muscle): Vasodilation
- Beta-2 (Liver): Glycogenolysis
- Alpha (Liver): Gluconeogenesis
- Beta-2 (Adipose Tissue): Lipolysis
- Beta-2 (Skeletal Muscle): Glycogenolysis
- Alpha (Pancreas): Inhibits insulin
- Beta-2 (Pancreas): Stimulates glucagon
Cortisol
- Stimulation Factors: Pain, low glucose, low blood pressure, low volume, low temperature, low oxygen, exercise
- Actions (Liver): Enhances norepinephrine and glucagon on gluconeogenesis
- Actions (Adipose Tissue): Promotes lipolysis
- Actions (Skeletal Muscle): Facilitates protein breakdown and glycogenolysis
- Glucocorticoid effects: Inhibit calcium uptake in the gut, bone formation, collagen synthesis, and IGF-1 actions on bone and muscle.
Glucocorticoids Net Effects
- Inhibits growth
- Decreases stature in children
- Causes osteoporosis and muscle atrophy in adults
Combined Catabolic Effects (Glucagon, Epinephrine, Cortisol) During Fasting
- Hypoglycemia triggers glucagon and epinephrine release.
- Glucagon and epinephrine stimulate gluconeogenesis and glycogenolysis to increase glucose production.
- Cortisol enhances glucagon and epinephrine effects by synthesizing enzymes and has a slower effect.
- Increases glycogen storage, breaks down skeletal muscle protein.
Cortisol Excess (Cushing's Syndrome)
- Hyperglycemia, insulin resistance, protein wasting, poor wound healing, truncal obesity, hypertension, hypervolemia, hypernatremia, hypokalemia, increased infection susceptibility, reduced inflammatory response, euphoria.
Cortisol Deficiency (Addison's Disease)
- Hypoglycemia, low blood pressure, poor response to angiotensin II, low volume and sodium, high potassium, depression, skin hyperpigmentation (due to elevated ACTH and MSH).
Hormonal Changes in Different Metabolic States
- Fed State: Increased glucose, insulin, glucagon (due to amino acids), and baseline epinephrine, GH, and cortisol; net effect: absorption and storage.
- Fasting: Decreased glucose, insulin, increased glucagon, epinephrine, GH, and cortisol; net effect: mobilization of stored fuel.
- Extended Fasting: Decreased glucose, insulin, increased glucagon, epinephrine, GH, and cortisol; ketones become a fuel source.
- Starvation: Very low glucose, insulin, suppressed glucagon, increased epinephrine, GH, and cortisol.
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Description
Test your knowledge on various hormones of the endocrine system, including growth hormone, glucagon, and cortisol. This quiz explores their functions, interactions, and secretion factors. Perfect for biology students seeking to deepen their understanding of hormone roles in metabolism and physiological processes.
