Podcast
Questions and Answers
What is the primary precursor for steroid hormone synthesis?
What is the primary precursor for steroid hormone synthesis?
- Progesterone
- Corticosterone
- Testosterone
- Cholesterol (correct)
Which of the following hormones is classified as a glucocorticoid?
Which of the following hormones is classified as a glucocorticoid?
- Cortisol (correct)
- Progesterone
- Aldosterone
- Testosterone
What type of hormone does the zona glomerulosa primarily secrete?
What type of hormone does the zona glomerulosa primarily secrete?
- Gonadal steroids
- Mineralocorticoids (correct)
- Glucocorticoids
- Androgens
Which enzyme is essential for glucocorticoid activity?
Which enzyme is essential for glucocorticoid activity?
What stimulates the production of cortisol in the adrenal cortex?
What stimulates the production of cortisol in the adrenal cortex?
Which of the following describes the function of aldosterone?
Which of the following describes the function of aldosterone?
Where are the receptors for ACTH located in cortisol regulation?
Where are the receptors for ACTH located in cortisol regulation?
Which hormone is primarily secreted by the adrenal medulla?
Which hormone is primarily secreted by the adrenal medulla?
Which hormone primarily increases during fasting and contributes to metabolic effects?
Which hormone primarily increases during fasting and contributes to metabolic effects?
What is the role of Growth Hormone (GH) during moderate exercise?
What is the role of Growth Hormone (GH) during moderate exercise?
During which conditions does GH play a critical role?
During which conditions does GH play a critical role?
What happens to insulin and IGF-I levels during fasting?
What happens to insulin and IGF-I levels during fasting?
What are immediate energy sources for muscle activity?
What are immediate energy sources for muscle activity?
Which pathway provides glucose in the fastest manner during anaerobic activity?
Which pathway provides glucose in the fastest manner during anaerobic activity?
What effect does Growth Hormone have on muscle mass?
What effect does Growth Hormone have on muscle mass?
What triggers the secretion of Growth Hormone Releasing Hormone (GHRH)?
What triggers the secretion of Growth Hormone Releasing Hormone (GHRH)?
What is the primary role of gluconeogenesis during fasting?
What is the primary role of gluconeogenesis during fasting?
Which hormone levels decrease significantly during fasting?
Which hormone levels decrease significantly during fasting?
What substance primarily provides energy for the central nervous system during prolonged fasting?
What substance primarily provides energy for the central nervous system during prolonged fasting?
During the transition from fasting to starvation, what metabolic shift occurs?
During the transition from fasting to starvation, what metabolic shift occurs?
Which of the following is a precursor for gluconeogenesis?
Which of the following is a precursor for gluconeogenesis?
What triggers increased glucagon secretion during fasting?
What triggers increased glucagon secretion during fasting?
Which metabolic process occurs in the liver during starvation to provide energy?
Which metabolic process occurs in the liver during starvation to provide energy?
What happens to protein reserves during prolonged fasting?
What happens to protein reserves during prolonged fasting?
What is the primary role of glucagon during prolonged exercise?
What is the primary role of glucagon during prolonged exercise?
Which hormone decreases in concentration during prolonged exercise?
Which hormone decreases in concentration during prolonged exercise?
What is the 'Cori cycle' primarily involved in?
What is the 'Cori cycle' primarily involved in?
Which energy source is primarily utilized during prolonged exercise?
Which energy source is primarily utilized during prolonged exercise?
What process does insulin inhibit to regulate energy production?
What process does insulin inhibit to regulate energy production?
What is the fate of lactate produced by type IIb muscle fibers?
What is the fate of lactate produced by type IIb muscle fibers?
During fasting, which process occurs to provide energy?
During fasting, which process occurs to provide energy?
What role does cortisol play in the metabolism during exercise?
What role does cortisol play in the metabolism during exercise?
What type of energy production becomes critical when muscle glycogen is depleted during exercise?
What type of energy production becomes critical when muscle glycogen is depleted during exercise?
What effect does Growth Hormone have on muscle tissue?
What effect does Growth Hormone have on muscle tissue?
Which component is primarily involved in the mobilization of fatty acids during prolonged exercise?
Which component is primarily involved in the mobilization of fatty acids during prolonged exercise?
How does Growth Hormone affect glucose metabolism?
How does Growth Hormone affect glucose metabolism?
What is one of the primary roles of glucocorticoids?
What is one of the primary roles of glucocorticoids?
Which mechanism is NOT a function of Growth Hormone?
Which mechanism is NOT a function of Growth Hormone?
In terms of metabolic actions, how does Growth Hormone act?
In terms of metabolic actions, how does Growth Hormone act?
What happens to blood glucose levels in a growing individual under the influence of Growth Hormone?
What happens to blood glucose levels in a growing individual under the influence of Growth Hormone?
What is a major effect of decreased glucose uptake in adipose tissue due to Growth Hormone?
What is a major effect of decreased glucose uptake in adipose tissue due to Growth Hormone?
What role does lipolysis play in the effects of Growth Hormone?
What role does lipolysis play in the effects of Growth Hormone?
Which effect is associated with glucocorticoids regarding inflammatory responses?
Which effect is associated with glucocorticoids regarding inflammatory responses?
How does starvation induce hypoglycemia?
How does starvation induce hypoglycemia?
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Study Notes
Secretion of Steroid Hormones
- Steroid hormones are synthesized from cholesterol.
- The adrenal cortex is divided into three zones, each producing specific hormones.
- The zona glomerulosa produces aldosterone - a mineralocorticoid.
- The zona fasciculata and zona reticularis produce cortisol and corticosterone - glucocorticoids.
- The adrenal medulla secretes adrenaline and noradrenaline.
Regulation of Glucocorticoids
- Glucocorticoids are regulated by the hypothalamic-pituitary-adrenal (HPA) axis.
- Corticotrophin-releasing hormone (CRH) from the hypothalamus stimulates the release of adrenocorticotrophic hormone (ACTH) from the anterior pituitary gland.
- ACTH binds to melanocortin type 2 receptors (MC2-R) on adrenal cortical cells.
- ACTH stimulates the production of cortisol by increasing cholesterol uptake, trafficking, and the expression of key enzymes like P-450ssc and P-450c11.
Effects of Cortisol
- Cortisol plays a crucial role in stress response and energy metabolism.
- Its actions include increasing glucose output from the liver and promoting catabolism in peripheral tissues like muscle and adipose tissue.
- Cortisol is also required for normal vascular reactivity and water excretion.
Growth Hormone and Metabolism
- Growth hormone (GH) is a major determinant of growth, promoting cell growth and bone elongation.
- GH has metabolic effects that are distinct from its growth-promoting actions, impacting muscle, adipose tissue, and liver.
- GH stimulates protein synthesis, decreases protein breakdown, and increases lipolysis.
- GH is critical for maintaining muscle mass and helps maintain blood glucose levels during starvation and exercise.
Exercise and Energy
- Muscle energy utilization is dependent on the intensity and duration of the exercise.
- During moderate exercise, GH stimulates lipolysis to provide alternative energy sources.
- During intense exercise, the body relies on stored glycogen, glucose, and fat for energy.
- Lactate produced during anaerobic exercise is used by other muscle fibers as an energy source and is also converted back to glucose by the liver.
Eating, Fasting, and Starvation
- Ingestion of a meal stimulates the release of insulin, which promotes energy storage in the form of glycogen, protein, and fat.
- Insulin inhibits lipolysis by suppressing hormone-sensitive lipase (HSL).
- Fasting leads to a decrease in insulin and an increase in glucagon, triggering glycogenolysis, gluconeogenesis, and lipolysis to maintain energy levels.
- During prolonged starvation, the body shifts from gluconeogenesis to ketogenesis, utilizing fatty acids as the main energy source.
- Ketone bodies are produced in the liver from fatty acids and become an alternative fuel source for the brain and other tissues during prolonged starvation.
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