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Physiology II > Growth and Development > Flashcards

Growth and Development Flashcards

1
Q

____: activation of adrenal gland production of androgens

A

Adrenarche

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2
Q

In adrenarche, the zona reticularis (adrenal gland) matures, becomes sensitive to ACTH, and leads to the production of what two molecules?

A

1) DHEA (becomes testosterone)
2) DHEA-S (becomes: DHT)

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3
Q

At what age does the adrenal cortex become activates in boys and girls?

A

Age 8

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4
Q

True or False: The presence of testosterone (DHEA) and DHT (DHEA-S) in the peripheral tissues allows for axillary and pubic hair growth

A

True

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5
Q

What are the two causes of Hypothalamus-Pituitary decline during childhood?

A

1) Neural Inhibition of GnRH
2) Absence of adequate excitatory input

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6
Q

Puberty starts at age ___ in girls and at age ___ in boys

A

11 (girls) and 13 (boys)

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7
Q

True or False: Puberty involves the maturation of the HP-gonad Axis

A

True

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8
Q

True or False: From early gestation to until mid puberty, GnRH, LH, and FSH are low, with FSH > LH

A

False - from late infancy to onset of puberty, GnRH, LH, and FSH are low; FSH > LH

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9
Q

GnRH, LH, and FSH are slightly elevated after ___, then decline

A

birth

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10
Q

What FOUR hormones are important for growth in utero?

What SIX hormones are important for growth ex-utero

A

Growth In Utero
1) Fetal IGF-II
2) Fetal Insulin
3) Thyroid Hormone
4) Peptide Hormones

Growth Ex Utero
1) Fetal IGF-I
2) Insulin
3) Sex Steroids
4) Thyroid Hormone
5) Growth Factor
6) Peptide Growth Factor

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11
Q

Which ex-utero growth hormones are permissive for GH?

A

Insulin and Thyroid Hormone

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12
Q

True or False: IGF-II depends on GH

A

False - IGF-I depends on growth hormone

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13
Q

___ ___ are crucial for growth during puberty

A

Sex steroids

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14
Q

Which hormone is important for CNS development?

A

Thyroid Hormone

Note: in 1st trimester, fetus uses the maternal supply of TH. however, in 2nd trimester, fetus makes own supply of TH.

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15
Q

___ is the main growth mode of the fetus

A

Hyperplasia

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16
Q

True or False: Insulin and Fetal Insulin can have anabolic effects

A

True

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17
Q

At puberty, the sensitivity of pulse generator in the hypothalamus to negative feedback factors ____

A

diminishes

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18
Q
A
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19
Q

True or False: Males must reach a certain weight to undergo puberty and have a growth spurt, while Females must reach a certain weight to have first occurrance of menstruation (have menarche)

A

True

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20
Q

Which tissue is responsible for secreting the peptide hormone, leptin?

A

Adipose Tissue

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21
Q

____ reduces inhibitory effects of NPY on Kisspeptin secretion nuclei and may be a PERMISSIVE agent in initiation of puberty

A

Leptin

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22
Q

How can leptin affect GnRH release?

A

By blocking the inhibition by neuropeptide Y (NPY)

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23
Q

What are the four steps of puberty in males?

A

1) Hypothalamic pulse generator becomes LESS sensitive to NEGATIVE feedback = ↑ GnRH

2) ↑LH/FSH due to:
a - sleep elevating GnRH
b - AP becomes more responsive to GnRH

3a) Spermatogenesis

3b) Testosterone syn/sec via: Leydig cells of testes → release of DHT and muscle/skeletal growth (anabolic effect)

4a) DHT →2 sex characteristics and GH

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24
Q

What are the four major steps of puberty in females?

A

1) Sleep activates GnRH=↑LH/FSH
2) Pre-antral follicle (2) → antral follicle
3) estrogen released → growth of endometrium
4) menstruation occurs when estrogen levels DECLINE!

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25
Q

True or False: Rise in Estrogen during the first few cycles after menarche DOES result in LH surge (and, therefore, ovulation)

A

False - rise in estrogen during the first few cycles after menarche does NOT result in LH surge

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26
Q

In females, when do positive feedback loops develop?

A

6-9 months

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27
Q

True or False: The first several menstrual cycles do not produce ovulations

A

True - anovulatory cycle

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28
Q

Menstrual bleeding occurs even in the absence of ovulation because the ___ of the follicular phase is sufficient to promote proliferation of endometrium.

When dominant antral follicle becomes atretic without releasing the egg, the consequent drop in estrogen trigger sloughing off of the endometrium

A

Estrogen

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29
Q

If there is no E2 positive feedback → no ____ → follicle becomes ____→ decline in ____

A

No E2 positive feedback → no ovulation → follicle becomes atretic → estrogen decreases

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30
Q

What conditions can delay menarche?
(hint: MI SIC)

A
  • malnutrition
  • imbalance of thyroid
  • caloric insufficiency
  • stress
  • intense, consistent exercise
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31
Q

What two hormones leads to the following effects in both males and females?

  • release of growth hormone - bone deposition
  • pubertal growth spurt
  • closure of epiphyseal plates
A

Testosterone and Estrogen

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32
Q

____ leads to protein synthesis for muscle growth (anabolic effect) in males only

A

Testosterone

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33
Q

What are the two periods in one’s life when growth is VERY pronounced?

A

1) First two years of life
2) Puberty (growth spurt)

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34
Q

Testosterone and estrogen DIRECTLY increases ____ and INDIRECTLY increase ____ via increase in ___

A

body growth; GH (growth hormone)

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35
Q

___ favors release of GnRH

A

IGF-1

36
Q

Both __ and ___ can stimulate gonadal function

A

IGF-1 and GH

37
Q

True or False: Testosterone is the only hormone that plays a critical role in pubertal growth spurt

A

False - testosterone and estrogen

38
Q

True or False: Both GnRH and Growth Hormone are secreted in a pulsatile fashion

A

True

39
Q

True or False: Pulsatile secretions of growth hormone produce a greater increase in body weight and longitudinal bone growth (when compared to continuous secretion of GH)

A

True

40
Q

The sexually differentiated pattern of GH secretion only becomes manifest at ___

A

puberty

41
Q

Describe frequency and magnitude of GH release in females vs. males?

A

Males:
- regular, high magnitude secretory bursts

Females
- irregular, lower magnitude secretion pattern

42
Q

True or False: During childhood there is a steady decline in plasma GH

A

False - there is a steady rise

Especially in first two years of life + at puberty

43
Q

Why is pubertal release of GH particularly elevated?

A

Stimulation by testosterone and estrogen

44
Q

True or False: As one ages, there is a decline in sex hormones and GH secretion

A

True
- May contribute to muscle wasting, decrease in skeletal muscle mass, and decrease metabolic rate

45
Q

What time of the day do the strongest secretion of GH occur?

A

At night (during stage 3 and 4 of sleep)

46
Q

What stimulates GH Secretion
(hint: HELGAS EGS)

A

H - hypoglycemia
E - elevated AA
L - low free FA
G - GHRH
A - acute moderate stress
S - sleep

E - exercise
G - ghrelin
S - sex steroids

47
Q

Inhibitors of GH release?

(hint: SO EH -E^2 H^4)

A

S - somatostatin
O - obesity

E - elevated IGF-1
E - elevated GH

H - hyperglycemia
H - high free FA
H - hypothyroid
H - high chronic cortisol

48
Q

Where structure is growth hormone released from?

A

Anterior pituitary

49
Q

Which two hypothalmic hormones regulate release of GH from anterior pituitary?

A

1) Growth hormone releasing hormone (GHRH)

2) Somatostatin (growth hormone inhibitory hormone)

50
Q

True or False: Somatostatin stimulates secretion of GH while GHRH inhibits GH secretion

A

False -
Growth Hormone Releasing Hormone (GHRH) stimulates secretion of GH

Somatostatin inhibits GH secretion

51
Q

What are the two roles of Somatostatin (GHIH) in the anterior pituitary?

A

1) Inhibits release of GH
2) Inhibits TSH release

52
Q

How are negative feedback loops utilized to inhibit GH secretion?

A

Elevation of plasma GH/IGF-1 inhibits GH secretion

53
Q

___ operates with a short feedback loop to decrease release of GHRH

___ operates with a:
short feedback loop that decreases ____ secretion

AND

long feedback loop that decreases ___ release and increases ___ release

A
54
Q

A large drop in which two energy substrates will elevate plasma growth hormone?

A

Glucose or free fatty acids

note: elevation of plasma glucose or free fatty acids can REDUCE plasma growth hormone

55
Q

___ is a counter regulatory hormone to insulin

A

Growth hormone

56
Q

How does an increase in plasma levels of free amino acids affect growth hormone secretion?

A

Increase in plasma levels of free amino acids leads to INCREASE in growth hormone secretion

57
Q

Growth hormone requires normal levels of ___ and ____

A

Thyroid hormone and cortisol

58
Q

Thyroid hormone enhances the sensitivity of the growth hormone-synthesizing cells in the pituitary to ___ and enhances sensitivity of target cells to growth hormone itself

A

GHRH

59
Q

How does thyroid hormone deficiency affect GH release and its effects?

A

Hypothyroidisim leads to decreased GH release

60
Q

While moderate levels of ____ stimulates GH release. However, with prolonged exposure to high levels, there is a direct inhibition of ___ release

A

cortisol; growth hormone

61
Q

___ is a peptide hormone released by the stomach in response to fasting and hypoglycemia. It promotes appetite!

A

Ghrelin

62
Q

What are the three DIRECT effects of GH?

A

1) Provides metabolic substrates for growth (spares glucose for brain during starvation)

2) Stimulates synthesis of IGF-1 (somatomedin)

3) Regulates gonadal function - participating in maturation of gametes + production of sex steroids + regulation of lactation/pregnancy

63
Q

Indirect effect of GH?

A

Through action of IGF-1, growth hormone stimulates growth in different tissues (albeit: a limited amount)

64
Q

What are two mechanisms by which GH spares glucose for the brain?

A

1) Enhances protein synthesis
2) Shifts metabolism of non-CNS tissues

65
Q

Which molecule stimulates uptake of amino acids in skeletal muscle, as well as increases the number of ribosomes in those muscles?

A

Growth Hormone

66
Q

What type of amino acids favor release of GH

A

Dietary amino acids

67
Q

What are three mechanisms by which GH increases plasma fatty acids?

A

1) Stimulates lipolysis in adipose tissues

2) Increase plasma free fatty acids that become available to cells for energy production

68
Q

How do high free fatty acids affect GH release?

A

High free fatty acids suppress release of GH

69
Q

What is a reliable way to estimate growth hormone?

A

Measure IGF-1 (longer hald life)

70
Q

What is the predominant IGF found in kids and adults, whose production strictly depends on GH stimulation?

A

IGF-1

71
Q

Which IGF is the characteristics form seen in the fetus and does NOT depend on GH stimulation?

A

IGF-2

72
Q

GH acts on the ___ to stimulate production of IGF-1, which then acts in classical endocrine fashion

A

liver

73
Q

True or False: Growth hormone can stimulate production of IGF-1 at target tissue level in the bones. This locally IGF acts in endocrine fashion

A

False - while GH can stimulates IGF-1 production in target tissues in bones - this locally made IGF acts in AUTOCRINE/PARACRINE fashion

74
Q

True or False: All activators and inhibitors of GH release indirectly affect secretion of IGF-2

A

False
All activators and inhibitors of GH release indirectly affect secretion of IGF-1!

75
Q

What type of receptor does IGF-1 bind to?

A

Tyrosine kinase

76
Q

In bone, ____ increases production of epiphyseal cartilage and stimulation of linear growth.

A

IGF-1

77
Q

True or False: Once long bones have matured and epiphyses have sealed, IGF-1 continues to stimulate linear growth

A

False - IGF-1 can NO LONGER stimulate linear growth (instead: it will increase width of bones)

78
Q

In bones, there is ____ growth before puberty and ___ growth after puberty

A

linear growth before puberty
radial growth after puberty

79
Q

Malnutrition, hypothyroidism, and low insulin inhibits:
A. IGF made by liver
B. IGF made by bone

A

A. IGF made by liver

80
Q

IGF-1 is transported in the plasma via ____

A

IGF binding protein

81
Q

Why do abused and emotionally deprived kids fail to grow to their full potential stature?

A

High stress levels reduce GHRH release from hypothalamus and GH from pituitary

82
Q

What causes Laron’s dwarfism?

A

Mutation in GH receptor (insensitive to GH)

83
Q

What are the following descriptions features of:
- No IGF-1 release
- Linear growth is compromised, as is metabolic activity of GH
- commonly have low glucose, high cholesterol, and obesity

A

Laron’s dwarfism

84
Q

A pituitary tumor that develops before puberty can cause ____ because epiphyseal plates have not yet sealed, giving way to LONGITUDINAL growth

A

Gigantism

85
Q

Individuals with ____ develop pituitary tumors AFTER puberty, which gives way to RADIAL GROWTH

A

Acromegaly

86
Q

Which ex utero hormone will increase amino acid uptake and protein synthesis?

A

Insulin

Physiology II (23 decks)

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