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MVST1B HR > Puberty > Flashcards

Puberty Flashcards

1
Q

D: puberty

A

The transition phase that takes a person from being a sexually immature child to a sexually mature, reproductively fertile adult.

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2
Q

first signs of puberty?

do they show fertility?

A
  • In females, menarche (first menstruation) is the most definitive sign.
  • In males, first ejaculation (often nocturnal) is a sign of similar degree of maturity.

• These do NOT signify fertility, more a sign that the gonads have awakened and are beginning to assume adult levels of activity

  • First menstrual cycles - anovulatory
  • First ejaculate - small quantities of seminal plasma and no sperm
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3
Q

do boys have their growth spurt 2 years later than girls?

A

yes - hence taller

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4
Q

T or F

Lean body mass and body fat are virtually identical in prepubescent boys and girls

A

T

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5
Q

tanner stages female

A
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6
Q

tanner stages male

A
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7
Q

describe Cryptorchid testes

A

• Testicular descent occurs during fetal development

  • 3-4% of males
  • Impaired spermatogenesis
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8
Q

Puberty involves _____ activation of the reproductive axis

A

Puberty involves central activation of the reproductive axis

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9
Q

T or F

Puberty in primates involves re-awakening of the HPG axis

A

T

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10
Q

Puberty in primates involves re-awakening of the HPG axis

elaborate.

A

High gonadotrophic hormone levels in Rhesus monkeys during first 20 weeks of life.

HPG axis suppressed by GABAergic inhibition of GnRH release

At puberty, GABA inhibition removed and stimulatory inputs onto GnRH neurons.

This pattern observed in gonadectomized monkeys so not dependent on sex steroids

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11
Q

Puberty in primates involves re-awakening of the HPG axis

is it dependantn on hte sex steriods?

A

no

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12
Q
A
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13
Q

GnRH pulsatility ______ at puberty

A

GnRH pulsatility increases at puberty

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14
Q

Amplitude and frequency of GnRH pulses regulates LH and FSH levels

How?

A
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15
Q

does GnRH fluctuate more in adults?

A

no - mcuh less fluctuations

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16
Q

LH, FSH and oestradiol levels rise

Early cycles not associated with

……

A

LH, FSH and oestradiol levels rise

Early cycles not associated with

ovulation

17
Q

Rise in ……..causes onset of spermatogenesis and rise in testosterone from testes.

A

Rise in FSH and LH causes onset of spermatogenesis and rise in testosterone from testes.

18
Q

in males what causes growth of accessory sex glands and secondary sex characteristics

A

Androgens cause growth of accessory sex glands and secondary sex characteristics

19
Q

Describe Growth hormone

A
  • • Secreted from anterior pituitary in greater amounts near to puberty
  • • Responsible (along with androgens) for growth of long bones and tissues
  • • Major effect on protein synthesis and glucose homeostasis
  • • GH deficiency => short stature, delayed sexual maturation
20
Q

describe thyroid hormones near puberty

A
  • Increase in secretion from thyroid gland, secondary to increased thyroid stimulating hormone (TSH) from anterior pituitary
  • May account for rise in metabolic rate in both sexes
  • Also essential for body growth
21
Q

4 factors which can affect the onset of puberty

A
  • Genetic
  • Metabolic
  • Social
  • Environmental
22
Q

how can GWAS be used to identigy genes associated with puberty ?

how else can we identify genes involved in puberty?

A

Genes affecting puberty can be identified by genetic association studies looking for regions of the genome that segregate with reproductive phenotype (eg precocious puberty in girls) – eg MKRN3.

Genes can also be identified by studying individuals that do not go through puberty and identifying the causative mutation eg. Kisspeptin, Neurokinin B pathways.

23
Q

what do yo uknwo about MKRN3

A

normally Delays puberty:

• MKRN3 mutations cause early puberty.

Protein – big

Binds Zinc

Involved in protein degredation thorugh ubiquitin pathway

Cannot degrade GnRN = more GnRH released

24
Q

how are Kisspeptins involved in puberty?

A
  • kisspeptins encoded by the Kiss1 gene
  • signal through Kiss1 receptors (G protein) Expressed by GnRH neurons
  • Kisspeptin binding causes GnRH depolarisation and GnRH release
    *
25
Q

how can mutations in Kiss1 or the Kiss1R gene affect puberty?

A
  • Hypogonadotrophic + hypogonadism
  • lack of puberty / developement
  • smal testicle size
  • Absence of secondary sexual development (for example, pubic, facial, and underarm hair)
26
Q

how do mutations in the neurokinin B gene / receptor gene affect puberty?

A

family in turkey - didnt go through puberty.

Severe congenital hypogonadotrophic hypogonadism

Neurokinin B, a member of the substance P–related tachykinin family, is highly expressed in arcuate KISS1 hypothalamic neurons.

mutation = no puberty

27
Q

why is the age at which puberty is onset decereasing?

A

Body weight is a critical determinant of the age of puberty

Puberty begins around 47 kg for girls and 55 kg for boys

people get bigger faster - diet

28
Q

Puberty begins around ___ kg for girls and __ kg for boys

A

Puberty begins around 47 kg for girls and 55 kg for boys

29
Q

Overweight childerne enter puberty ______ than skinny ones

A

Overweight childerne enter puberty earlier than skinny ones

30
Q

Some human genetic disorders in Leptin pathway result in ______ of puberty

A

Some human genetic disorders in Leptin pathway result in failure of puberty

31
Q

injecting leptin to ob/ob mouse can ______ fertility

A

injecting leptin to ob/ob mouse can restore fertility

32
Q

In animals, _____ can delay sexual maturity.

A

In animals, stress can delay sexual maturity.

33
Q

info:

controversial

A

Controversial, but some stressors (emotional or physical) can delay puberty in humans.

Opposite also proposed – stress during infancy and childhood can accelerate puberty (e.g. family stress)

Evidence? Girls who grow up in the absence of biological father, especially with stepfather present, tend to enter puberty earlier

34
Q

environment al factors affecting puberty

A

Pollutants

  • Some chemicals in industrial synthesis of plastics act as weak oestrogens,
  • Controversial, but exposure to some of these “xenoestrogens” may accelerate puberty.
  • Phytoestrogens in various plants – high in soya.
  • Some pollutants (dioxins, polychlorinated biphenyls) may delay male puberty.

Altitude

  • For every 100m increase in altitude, puberty delayed by 3 months.
35
Q

fat

A

mamba

36
Q
A

MVST1B HR (13 decks)

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