Hormones Learning Objectives (L19) Flashcards
Learning Objectives - Identify hormones involved in anabolic and catabolic processes, and describe the functions they mediate - Describe the response (and adaptive response) profile for each hormone during exercise and discuss their actions on energy provision and tissue function
What is the exercise-mediated adaptive (acute) response of adrenaline (i.e.: what does it do to the body/systems)? At what intensity is it released?
Acute stress response (SNS activation):
- Increase CO
- Increase HR (slightly)
- Alter blood flow: Decrease TPR to skeletal muscle
- Energy provision via glycogenolysis & lipolysis
- Mental alertness and focus
Released @ 75% of VO2max (VIGOROUS EXERCISE)
What is the exercise-mediated adaptive (acute) response of NA (i.e.: what does it do to the body/systems)? At what intensity is it released?
Acute stress response (SNS activation):
- Increase CO
- Increase HR (slightly)
- Alter blood flow: Decrease TPR to skeletal muscle
- Energy provision via glycogenolysis & lipolysis
- Mental alertness and focus
Released @ 50% of VO2max (MODERATE EXERCISE)
NA and Adr. are closely linked with intensity and metabolic pathways. What is the goal of energy provision for adrenaline during exercise?
Adrenaline is released @ 75% of VO2max (VIGOROUS EXERCISE), levels also rise more sharply with high intensity exercise:
- Rapid mobilization of glycogen stores to support anaerobic activity.
- Inhibits insulin release. Adrenaline prevents insulin from performing glycogenesis.
NA and Adr. are closely linked with intensity and metabolic pathways. What is the goal of energy provision for NA during exercise?
- NA is released @ 50% of VO2max (MODERATE EXERCISE):
- Helps mobilise energy stores (lipids and glycogen) and redistributes blood flow to active muscles.
Cortisol increase with _____ intensity exercise and _____ duration exercise.
higher, longer
What are the system wide effects of elevated cortisol?
Anti-inflammatory, immune suppression
Why might stressed people who often overtrain be predisposed to illness
Higher cortisol levels supress the immune system
Describe the feedback loop for cortisol and how it is regulated
ACTH (from ant. pit.) stimulates release of cortisol (from adrenal cortex). Cortisol can then inhibit the secretion of ACTH
What is the exercise-mediated adaptive (acute) response of cortisol (i.e.: what does it do to the body/systems)?
- Metabolism regulation and energy provision (mobilising glucose via gluconeogenesis)
- **Suppresses immune system (reduces resources and prevents excessive inflammation)
- **Increase BP via the synergistic effect on adrenaline
Why is cortisol helpful during prolonged exercise where glycogen stores might become depleted?
Gluconeogenesis: Cortisol helps mobilise glucose by promoting gluconeogenesis in the liver. This ensures a steady supply of glucose for energy during exercise, especially during prolonged or intense activity when glycogen stores become depleted.
How long does it take for cortisol to spike during periods of a) psychological stress and b) exercise?
a) 10min, b) 20min (sustained release, levels stay reasonably high)
Glucagon is secreted from which cells?
alpha cells of the pancreas
Insulin is secreted from which cells?
beta cells of the pancreas
What stimulates glucagon secretion?
Low blood glucose levels
What stimulates insulin secretion?
High blood glucose levels
What is glucagon’s main function in energy provision?
Breakdown of substrates to glucose (via lipolysis, glycogenolysis, gluconeogenesis)
What is insulin’s main function in energy provision? (hint: it works on all 3 macromolecules)
Glucose provision:
- Promotes glucose uptake via GLUT-4 transporters (muscle, liver)
- Stimulates glycogenesis (conversion of glucose to glycogen)
Protein provision:
- Increases uptake of amino acids into tissue and protein synthesis
TAG provision
- Increases uptake of FFAs and glycerol into adipose tissue (form TGs)
With regards to exercise, what periods are high insulin levels a) desirable, and b) non-desirable?
a) recovery from exercise (after), b) during exercise
When blood glucose levels are high and you aren’t exercising, how do liver and muscle cells obtain glucose?
Insulin: Insulin binds to membrane receptors which increases the expression of GLUT-4 membrane proteins
When blood glucose levels are high and you are exercising, how do liver and muscle cells obtain glucose?
Alternate pathway: Expression of GLUT-4 membrane proteins which increase the uptake of glucose, independent of insulin
During which intensity is prolactin secreted? What is one (non-exercise) reason why it might also increase in females?
Release increases during high intensity exercise. Increases more in females exercising without bra support
Compare T3 to T4, which is more abundant and which is more active?
T4 more abundant (than T3)
T3 more active (than T4)
What does it mean when T3 and T4 are ‘permissive’?
They amplify the actions of other hormones (like growth hormone and catecholamines)
Why might someone with thyroid damage put on weight?
Damage to the thyroid can result in a decrease in thyroid hormones. Both T3 and T4 increase the basal metabolic rate (BMR). They increase the aerobic ATP production, which increases oxygen consumption and heat production in tissues, reflecting an increase in total energy expenditure.
How much does exercise increase T4 by (in %)
~35%
What gland (and region of the gland) is growth hormone released?
Anterior pituitary
When is growth hormone mostly released?
Mostly released during sleep
Which is growth hormone: catabolic, anabolic, and/or permissive?
All 3
How does exercise intensity affect the secretion of growth hormone?
Exercise intensity causes a proportional increase in GH secretion
If we compare the NA and Adrenaline levels of a) pre-trained athlete working at 70% HRmax, and b) the same athlete 10-weeks after commencing a training plan, working at 70% HRmax, what would we except to see? Why?
(b > a). We would see higher levels of NA and adrenaline in 10-weeks (b) than untrained (a). This is because the athletes fitness level improves, also improving efficiency of various body systems. This allows them to work harder at the same percentage of HRmax. So effectively, (b) athlete is working harder at the same relative intensity compared with athlete (a)
Exercise training increases NA and Adrenaline responses to the same relative intensity of exercise (in this case its 70% HRmax)
If we compare the NA and Adrenaline levels of a) an untrained athlete playing 30mins of soccer, and b) the same athlete 10-weeks after commencing a training plan, playing 30mins of soccer, what would we except to see? Why?
(a > b). We would see higher levels of NA and adrenaline in untrained (a) than 10-weeks (b). This is because the athletes fitness level improves, also improving efficiency of various body systems. Playing 30mins of soccer is easier and less demanding for the trained athlete than the untrained. So effectively, (a) athlete is working harder at the same absolute workload compared with athlete (b)
Exercise training reduces NA and Adrenaline responses to the same absolute workload of exercise
If we compare the glucagon and insulin levels of a) an untrained athlete doing a 20min (submax) aerobic class, and b) the same athlete 20-weeks after commencing a training plan, doing the same 20mins (submax) aerobic class, what would we except to see? Why?
(a > b). We would see higher levels of glucagon and insulin in untrained (a) than 10-weeks (b). This is because as the athletes fitness level improves, regulation of glucose also improves. Blood glucose is better managed, meaning glucagon and insulin more accurately metabolise substrates to provide the correct amount of blood glucose. So effectively, (a) athlete is less efficient in regulating blood sugar levels at the same absolute workload compared with athlete (b)
Glucagon and insulin responses to the same absolute workload are reduced after 20 weeks training at 60-80% of VO2max
