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HUBS2503 > Lecture 19 - Endocrine Function and Exercise > Flashcards

Lecture 19 - Endocrine Function and Exercise Flashcards

1
Q

Which hormones are post-exercise hormones (tissue building)? Anabolic or Catabolic?

A

Anabolic

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2
Q

Which hormones are exercise hormones? Anabolic or Catabolic?

A

Catabolic (stress)

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3
Q

Glucose uptake is regulated by which hormone at rest?

A

Insulin

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4
Q

How is glucose uptake achieved? What receptors are involved, what target protein is involved, what transporter(s) are involved?

A

At rest;
- Insulin binds to tyrosine kinase receptors (insulin receptors)
- Phosphorylates IRS-I
- Increases GLUT2 (liver) and GLUT4 (muscle) expression
- Promotes glucose uptake

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5
Q

What are the stimulatory effects of insulin?

A

Fats:
- Conversion of Acetyl-CoA to TAGs (Lipogenesis)
- Lipid uptake

Carbs:
- Conversion of Glucose to G6Ph, and Conversion of Glucose to Acetyl-CoA (Glycolysis)
- Branch Formation (Glycogenesis)
- GLUT2 (liver) and GLUT4 (muscle) expression (Glucose Uptake)

Protein:
- Uptake of AAs (Liver & Muscle - AA Uptake)
- AAs to Proteins (Protein Synthesis)

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6
Q

What are the inhibitory effects of insulin?

A
  • Inhibits the breakdown of Glycogen to Glucose (Glycogenolysis)
  • Inhibits the breakdown of Proteins to AAs (Protein Degradation)
  • Inhibits the breakdown of TAGs to FFAs (Lipolysis)
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7
Q

What hormone is primarily responsible for AA lipid uptake?

A

Insulin

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8
Q

What hormones are primarily responsible for AA uptake?

A

Insulin, GH, androgens, oestrogens

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9
Q

When is insulin important with respect to exercise?

A

Insulin important during recovery from exercise

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10
Q

Which GLUTs obtain glucose independent of insulin? (Of GLUTs 1, 2, 3 & 4)

A

GLUT 1, 2 and 3

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11
Q

Where are GLUT1 found?

A

Abundant in RBCs and BBB

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12
Q

Where are GLUT2 found?

A

Liver, pancreatic B-cells
- also intestines and kidneys

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13
Q

Where are GLUT3 found?

A

Neurons and placenta

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14
Q

Where are GLUT4 found?

A

Only insulin regulated glucose transporter: Adipose Tissue and Muscles

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15
Q

Is skeletal muscle dependent on insulin for glucose uptake during exercise?

A

No. skeletal muscle is not dependent on insulin for glucose uptake during exercise (alternate pathway can be utilised, exercise responsive GLUT4 vesicles as opposed to insulin responsive GLUT4 vesicles)

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16
Q

Of glucagon and insulin, which is released and which is inhibited during exercise? Why?

A

Glucagon
* Release increases during exercise
* Glucagon effects are CATABOLIC

Insulin
* Release is INHIBITED during exercise
* Insulin effects are ANABOLIC

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17
Q

What inhibits the exercise mediated effects of insulin?

A

Inhibited by adrenaline.
During physical activity, adrenaline is released from the adrenal glands as part of the body’s stress response to support increased energy demands. One of the primary functions of adrenaline during exercise is to mobilize glucose and fatty acids to provide energy to working muscles.

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18
Q

What are the most acute metabolic responses mediated by exercise (don’t list the hormones)

A
  • Increase glycogenolysis
  • Increase glycolysis
  • Increase lipolysis
  • Increase gluconeogenesis
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19
Q

What is the main purpose of stress hormones during exercise?

A

Main effects are to provide energy during exercise

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20
Q

What stimulates the release of adrenaline and noradrenaline

A

Activation of the SNS

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21
Q

Where is adrenaline and noradrenaline released from? (gland of origin)

A

Released from adrenal medulla (adrenals)
- Noradrenaline also released from sympathetic nerve endings

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22
Q

What is the relationship between quantity of Adr and NA released and intensity of exercise (in VO2max)?

A

Release increases at higher exercise intensities
* NA > 50% of VO2max (moderate)
* Adr > 75% of VO2max (vigorous)

23
Q

Is Adr and NA catabolic or anabolic?

A

Catabolic

24
Q

What are the effects (+ and -) of Adr. and N.A.?

A

Increases glycogenolysis in skeletal muscle & liver
Increases lipolysis in adipose tissue
Inhibits insulin release (Adrenaline only)

25
Q

What is the most important effect Adr. has on insulin? What are the consequences? When does it occur?

A

Inhibition of its action
- Adrenaline antagonizes the effects of insulin by reducing insulin sensitivity in peripheral tissues such as muscle and adipose tissue

Consequences
- Increased Blood Glucose Levels
- Decreased Glycogen Synthesis
- Antagonism of Insulin’s Anabolic Effects

26
Q

What hormones regulate glycolysis? Where does it occur?

A

Regulated by adrenaline & glucagon. Occurs in skeletal muscle.

27
Q

What hormones regulate glycogenolysis? Where does it occur?

A

Regulated by adrenaline & glucagon. T3 & T4 (permissive). Occurs in skeletal muscle & liver.

28
Q

What hormones regulate lipolysis? Where does it occur?

A

Regulated by adrenaline, cortisol, prolactin & GH. T3 & T4 (permissive). Occurs in adipose tissue.

29
Q

What hormones regulate gluconeogenesis? Where does it occur?

A

Regulated by cortisol & glucagon. Occurs in liver.

30
Q

Is gluconeogenesis a catabolic or anabolic process?

A

Anabolic: Gluconeogenesis itself is considered an anabolic process because it involves the synthesis of glucose, which is the construction of a larger molecule from smaller precursors.

31
Q

What are some other effects of Adrenaline and Noradrenaline?

A

– Increase mental alertness
– Increase force of muscle contractions
– Increases heart rate (a little)
– Alters blood flow to tissues - dilates skeletal
muscle blood vessels but constricts most
other blood vessels
– Increases sweat production

32
Q

What is the main glucocorticoid?

A

Cortisol

33
Q

What is the inhibitory effect of glucocorticoids on?

A

The pituitary, decrease production of ACTH

34
Q

Why do cortisol levels remain elevated for some time after exercise

A

Anti-inflammatory

35
Q

ACTH and cortisol levels increase with what type of exercise?

A

– Higher intensity exercise
– Longer duration exercise

36
Q

What are the main metabolic effects of cortisol?

A
  • TAG breakdown (lipolysis)
  • Amino acid breakdown
  • Gluconeogenesis in liver
  • Insulin antagonist
37
Q

What are the main substrate regulatory effects of cortisol?

A
  • decrease glucose uptake into non-exercising muscle
  • decrease amino acid uptake into muscle
38
Q

What is the main stimulator of glucagon?

A

Release humoral
– Stimulated by low blood glucose levels

39
Q

How does exercise modulate the release of glucagon?

A

Release increases during exercise
– Stimulated by intensity & duration of exercise

40
Q

What are the metabolic effects of secretion of glucagon

A
  • Increases glycogenolysis in liver and skeletal muscle
  • Increases lipolysis (breakdown of TGs) in adipose tissue (increase FFAs in blood)
  • Increases gluconeogenesis (from amino acids and glycerol) in liver
41
Q

What is the main stimulator of glucagon?

A

Release humoral
– Stimulated by increased blood glucose

42
Q

What does prolactin do?

A

Initiates and supports milk production from mammary glands

43
Q

How does exercise modulate the release of prolactin?

A

Release increases during high intensity exercise
– Increases more in females exercising without bra support!

44
Q

What is the metabolic effect of secretion of prolactin

A

Increases lipolysis

45
Q

What is the difference in activity and abundance of T3 and T4

A
  • T4 more abundant
  • T3 more active
46
Q

What stimulates the release of T3 and T4

A

Release stimulated by TSH from anterior pituitary (hormonal regulation)

47
Q

How does exercise modulate the release of T4?

A

Exercise increases free T4 by ~35%
– Increased with higher exercise intensity

48
Q

What are the main effects of T3 and T4?

A

– Increase ATP synthesis rate in mitochondria
– Increase metabolic activity of most cells (increase enzyme activity)
– Increase speed of neural reflexes

49
Q

Mostly, what regulates GH?

A

Hormonally regulated (GH-IH, GH-SH)

50
Q

What metabolic effects does GH have? Catabolic, Anabolic and/or Permissive? How?

A

All:

Catabolic:
- Via gluconeogenesis in the liver, and
- stimulates the breakdown of TAGs in adipose tissue (lipolysis)

Anabolic:
- Mainly promotes protein synthesis, and
- promotes cartilage and bone growth

Permissive:
- Stimulates the production of IGF-1 in the liver and other tissue, IGF-1 mediates other anabolic effects, and
- Stimulates the expression of GLUTs, increasing mobility of glucose into the cytoplasm

51
Q

How does exercise modulate the release of GH?

A

– Release proportional to exercise intensity

52
Q

Explain Adr and NA responses to ABSOLUTE WORKLOAD and RELATIVE INTENSITY of exercise

A

ABSOLUTE:
- Exercise training reduces NA and Adrenaline responses to the same absolute workload of exercise,
- After engaging in regular exercise training, individuals may experience a reduction in the release of noradrenaline and adrenaline in response to the same fixed amount or absolute workload of exercise.

RELATIVE:
- Exercise training increases NA and Adrenaline responses to the same relative intensity of exercise,
- Conversely, exercise training may lead to an increase in the release of noradrenaline and adrenaline in response to the same relative intensity of exercise, where intensity is expressed relative to an individual’s maximum capacity.

INTERPRETATION: When individuals engage in exercise training, their bodies become more efficient at handling the stress of exercise, resulting in a reduced catecholamine response to the same absolute workload. However, as fitness levels improve, individuals are capable of exercising at higher relative intensities, leading to increased sympathetic nervous system activation and higher catecholamine release in response to these higher intensity efforts.

53
Q

Explain glucagon responses to ABSOLUTE WORKLOAD of exercise pre- and post-20 weeks of training at 60-80% VO2max

A

ABSOLUTE (<20wks): Glucagon responses to the same absolute workload are reduced after 20 weeks training at 60-80% of VO2max
ABSOLUTE (>20wks): Insulin levels are lower at the same absolute workload after 20 weeks training at 60-80% of VO2max

HUBS2503 (17 decks)

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