W2 - Endocrine System & the Impact of Exercise

Question 1

List the factors regulating growth + maturation

Answer 1

Genotype

Endocrine System

Environment

Question 2

What are the 2 types of hormones that have the ability to act on a target cell?

Answer 2

Circulating hormones

Local hormones

Question 3

Circulating hormones

Answer 3

Use bloodstream

Receptors can be up or down regulated depending on the conc of the hormone

Question 4

Local hormones

Answer 4

Act on neighbouring cells in absence of the bloodstream.

Question 5

What are the types of local hormone?

Answer 5

Paracrine (Near or besides)

Autocrine (self)

Question 6

Which are quick to activate or inactivate, circulating or local hormones?

Answer 6

Local hormones are quicker due to not requiring the bloodstream as transport.

Question 7

What type of hormone is the GH?

Answer 7

Anabolic

Question 8

Functions of the GH

Answer 8

Bind to cell receptor to stimulate cell division

Production of IGF-1

Question 9

Release of GH

Answer 9

Intermittent + pulsatile

Over 24hrs.

Increased amount of ‘bursts’ with age into adolescence.

No apparent sex differences

Question 10

What influences increase GH secretion

Answer 10

Sleep

Fasting/under nourished

Sex steroid hormones

Question 11

What influences decreased GH secretion

Answer 11

Body fatness

Stress causing increase in cortisol

Hyperglycaemia

Inflammatory markers

Question 12

What are the responses to those that have a GH deficiency?

Answer 12

Reduced stature, muscle + bone mass

Augmented adiposity

Question 13

First process occurring in the H-P-G axis

Answer 13

CNS stimulates the hypothalamus to synthesise GHRH + GHIH

Stimulus from the hypothalamus can cause an up regulation in the gonadotropins via the GnRH.

Question 14

GHRH

a.k.a somatocrinin

Answer 14

Stimulates anterior pituitary to secrete GH

Question 15

GHIH

a.k.a somatostatin

Answer 15

Inhibits anterior pituitary from secreting GH.

Question 16

GnRH

Answer 16

Plays a key role in modulating FSH + LH.

• Both important in maturation

Question 17

What happens when FSH + LH have been released into the bloodstream to target the gonads?

Answer 17

At the gonads…

Responsible for the release of oestrogen or testosterone.

These enter bloodstream to act on other tissues w/ matched receptors i.e bone or muscle to facilitate w/ development

Question 18

What is the INDIRECT anabolic action of the GH

Answer 18

Occurs via IGF-1 (predominantly occurring in the liver).

Question 19

IGF-1 can be free in the blood but most is bound to what?

Answer 19

IGFBP-3 - Anabolic, accounts for 80% IGF binding

IGFBP-2 - Catabolic

Question 20

How can IGFs operate?

Answer 20

Endocrine

Autocrine

or

paracrine hormones

Question 21

What are IGFs responsible for

Answer 21

The indirect anabolic activity of the GH

Question 22

What does IGF-1 do?

Answer 22

Promotes cell growth + inhibits cell death.

Question 23

Laron Syndrome

Answer 23

High levels of GH

Can’t generate IGF-1

GH insensitivity

Question 24

IGF-1 secretion

Answer 24

Mirrors that of GH in childhood + adolescence.

Lack of sex difference before puberty.

Sex differences manifest at pubertal timing.

Question 25

What is a key determinant of growth during infancy, rather than the role of the endocrine system ?

Answer 25

Adequacy of nutrition

Question 26

The combined effect of what levels in boys results in greater linear growth of bone and what does this account for?

Answer 26

Combined effect of the augmented GH, IGF-1 + testosterone levels in boys results in greater linear growth of bone which account for these particular sex differences.

Question 27

By which axis is the prepubertal growth regulated by?

Answer 27

GH-IGF-1 Axis

Question 28

What axis shows minimal sex differences during childhood + adolescence?

Answer 28

GH-IGF-1 axis

Question 29

By which axis is pubertal growth regulated by?

Answer 29

H-P-G axis. Results in a rapid linear growth + sexual development characteristics

Question 30

What does the GH response to exercise depend on?

Answer 30

Duration + intensity of exercise bout Fitness level Timing of blood sampling Refractoriness of pituitary GH secretion Environmental factors affecting GH response

Question 31

GH + IGF-1 response to acute exercise

Answer 31

Acute exercise is a potent stimuli for altering GH + IGF-1. In response to exercise, the freely circulating IGF-1 are mobilised + redistributed towards the muscle

Question 32

How can GH response to acute exercise be blunted?

Answer 32

If a pre-exercise spike in GH exists. - Refractory period (~3 hrs).

Question 33

Define pituitary refractoriness

Answer 33

Time in which the normal pituitary gland will not respond sufficiently to exercise stimulation for GH release.

Question 34

What happens to the change in IGF-1 + GH as intensity of exercise changes

Answer 34

The higher the intensity, the greater change in IGF-1 + GH.

Question 35

Is the response of IGF-1 + GH to exercise dependent or independent of exercise duration?>

Answer 35

Independent

Question 36

Does prolonging the exercise bout change where the peak in the hormone occurs?

Answer 36

NO

Question 37

What is the GH response to acute exercise related to?

Answer 37

Descriptive characteristics... - Age - Maturity - Weight Status

Question 38

To which exercise are higher levels of GH response associated with?

Answer 38

Aerobic exercise - Compared to anaerobic

Question 39

Relate maturity to GH levels

Answer 39

The more mature an ind is the greater the peak in post-exercise GH levels -- Tells us that the ability of exercise to augment the GH is dependent on age + level of maturation.

Question 40

What should GH blood sampling be timed to?

Answer 40

Exercise-induced GH peak

Question 41

What is positively related to anabolic growth markers?

Answer 41

Fitness + muscle size

Question 42

What has been shown that short term exercise training (<5 weeks) results in?

Answer 42

Initial catabolic phase which is correlated with change in fitness + muscle size.

Question 43

What has been shown that long term exercise training (>5 weeks) result in?

Answer 43

Anabolic rebound occurs. Seems to occur close to the tapering period. Associated with performance gains.

Question 44

How long should aerobic exercise last for the stimulation of GH secretion?

Answer 44

At least 10 mins

Question 45

What blunts the GH response to aerobic exercise?

Answer 45

Obesity +/or increased weight status

Question 46

Who has higher GH response after aerobic exercise compared to who....

Answer 46

Those in more advances stages of puberty have a higher GH response after aerobic exercise compared to early puberty.

Question 47

What is GH response to 15 mins of aerobic exercise dependent on?

Answer 47

Maturity status Relevant for boys + girls.

Question 48

What did Stokes et al find surrounding anaerobic exercise?

Answer 48

That the increase in GH levels was sig greater when resistance was 7% of body mass than 9%.

Question 49

What does intense exercise do to anabolic mediators and inflammatory cytokines?

Answer 49

Leads to reductions in anabolic mediators Profound increases in inflammatory cytokines = This may explain the development of a paradoxical catabolic state in the initial phases of training programs.

Question 50

Potential negative to acute exercise

Answer 50

Might cause markers of GH + IGF-1 to be suppressed alongside markers of inflammatory cytokines i.e IL-6. Could be detrimental due to elevated levels of these inflammatory markers over a long period of time being associated with detrimental changes in adaptations to tissue + the system.