Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

hormones > Lyons and Lourdon > Flashcards

Lyons and Lourdon Flashcards

1
Q

Polygamy

A

Male has more than 1 female mate
95% of mammalian species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why is polygamy the major mating system

A

evolution of pregnancy and lactation means reproductive costs largely on female

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the gonadorophin axis?

A

Brain (decapeptide) –> LH and FSH in pituitary gland –> Gonads –> behaviour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the principles of the neuroendocrine system (BRAIN)?

A
  • produces low mol. weight peptides which act in anterior pituitary to release larger glycoprotein hormomes
  • hormones of posterior pituitary secreted from nerve terminals in hypoT.
  • many of these hormones also act via other pathways in the brain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the principles of the neuroendocrine system (Gonads)?

A

Produces sex steroids:
- act locally to regulate gonadal function
- act on body to differentiate development and physiology
- act on brain to regulate behaviour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How do peptides function in neuroendocrine system?

A
  • peptides from the brain act on peripheral physiology via pituitary gland
  • they also act directly on brain behaviour
  • peptides involved in specific physiological function also act on sexual behavioural pathways in the CNS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do we know that the brain is sexually dimorphic?

A
  • GnRH causes release of LH and FSH
  • sex steroids and gonadal peptides feedback to regulate pituitary activity
  • GnRH also acts directly on brain and facilitates lordosis behaviour in females when injected
    THEREFORE - peptide controls both pituitary gonadotrophins & sexual behaviour
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is lordosis

A

characteristic sexually receptive behaviour in female rodents
- occurs in certain stage of oestrous cycle
- cannot exhibit without ovaries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is the brain masculinesed?

A
  • the brain is female by default
  • oestrogen causes masculinisation of male brain and sexual dimorphism, but not in women
  • BECAUSE, there is a short window of opportunity
  • ovaries produce 100x less test than testis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the Aromatisation hypothesis?

A
  • Aromatised oestrogen metabolites of testosterone masculinses the brain in the hypothalamus
  • AFP system ‘swamped’ by oestrogen injection led to doubts over its validity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does testosterone do?

A

Effects the brain, libido, deepens voice, increases lean muscle mass, male sex organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does testosterone secretion effect hormomes?

A

Developing testis secrete test, stimulates Wolffian Duct Formation & Mullerian Inhibiting Hormone, which causes Mullerian duct to generate leading to the absence of a uterus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the Jost hypothesis?

A

secretion of androgens & MIH by foetal testis during critical stages of development accounts for full range of sexually dimorphic urogenital traits observed at birth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

MIH

A

Mullerian Inhibiting Hormone (MIH/AMH) is large molecularly, TGH-ß super family

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is gender determined in mammals?

A
  • small region on tip of Y, location of SRY gene which is sex determining part
  • SRY switches on sertoli cells in gonad, differentiating them
  • they can support germ cells, and they stimulate development of Leydig cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What do Leydig cells do

A

make testosterone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What do Sertoli cells do

A
  • secrete substance initiating meiosis
  • secrete testicular fluid
  • conc. test locally
  • release MIH
  • protext spermatids from immune system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Castrate

A

XY:
- lack of androgen effect on long bone growth
- small penis, no body hair
- pubic hair originates from adrenal glands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Kinefelters

A

XXY:
- Small testis, low testosterone, limited breast development
- no spermatozoa produced (XXY cells don’t survive outside testis)
- scant body hair

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

XY digenesis

A

XY:
- X-linked supressor of SRY
- Male karyotype, undevelopeed female appearance
- no testi development, ovaries develop then degenerate
- normal vagina
- no ovaries = no sex steroids, no pubes/breasts
- tall
- ‘little boy with vagina’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Testicular feminisation

A

XY:
- no androgen receptor
- testicular oestrogen drives breast development
- voluptous breasts, no testosterone signal opposing oestrogen
- MIH prevents uterus formation
- intra-abdominal testes as body can’t read test. signal
- short, blind-ending vagina
- raised as girls

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Turner’s syndrome

A

XO:
- X missing
- ovaries or steak gonads
- Mullerian ducts present (no testis, no MIH)
- Wolffian duct absent (no test)
- Lack of germ cells = lack of sex steroid production
- no breasts, thick neck, socially awkward

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Guevedoces

A
  • raised girls
  • puberty –> test rises to sufficient levels to virilise body
  • testis descent, penis develops and grows
  • cannot synthesis 5a-DHT because of mutation
24
Q

5a-DHT

A

essential substrate of testosterone, far more potent

25
Q

why is hyena mating difficult?

A
  • female has peniform clitoris
  • clitoris has to rupture female retractor muscles
  • high neonatal and perinatal mortality
  • distance of vagina to cervix huge
  • pup can lodge in peniform clitoris
26
Q

Reason for sexual mimicry?

A
  • Social dominance
  • Sperm fitness and selection
  • Competition aggression hypothesis
27
Q

sexual dominance

A
  • genital sniffing part of social greeting - behaviour
  • male infanticide? female aggression?
  • problem = does this compensate for high reproductive cost of masculinised external genetalia?
28
Q

sperm fitness and selection

A
  • females highly promiscuous and polyandrous
  • advantage = complex sex promotes sperm selection
  • problem = hyenas testes small and oestrous cycle suggests not
29
Q

Competition aggression hypothesis

A
  • intense competition for food
  • polyandrous means bigger females
  • females also more aggressive, in charge of everything
  • could masculinised genetalia be a by product of this?
30
Q

Advantages of hyenas sexual mimicry

A
  • females size masculinsed behaviour promotes mother’s enhanced status
  • essential to support energetic demands - lactation and parental care
31
Q

Disadvantages of hyeneas sexual mimicry

A
  • pseudopenis starts development before foetus is exposed to androgens
  • therefore pseudopenios can be bi-product of enhanced androgen exposure
32
Q

What does the Hyena’s placenta do?

A

Converts ovarian androstenedione to testosterone via high levels of hydroxysteroid dehydrogenase

33
Q

How is mammals sex determined?

A

X inactivation

34
Q

how is bird sex determined?

A
  • females are heterogametic, mechanism for sex determination unknown
  • DMRT1 is candidate switch gene
35
Q

What does DMRT1 do

A

Candidate switch gene in birds
- 2 doses for males
- 1 for females

36
Q

how does showy plumage come about?

A
  • not result of masculinisation by test
  • develops as a consequence of chromosomal sex
  • ZZ male, ZW female
  • OESTROGEN CRUCIAL
37
Q

Why do male birds sing and females chatter?

A
  • due to oestrogen promoting axonal growth of RA region, masculinises song circuitry
38
Q

what does castration in birds prove?

A

castration does not block sexually dimorphic development, therefore birds must get oestrogen from elsewhere (Brain)

39
Q

gyandromorph

A
  • rare, two embryos fuse = lateralised dimorphism
  • not just plumage
  • not in mammals
  • ## female one side, male the other
40
Q

Platypus?

A

mammal physiology, reptilian/bird sex determination

41
Q

evidence for marsupial sex determination

A
  • embryonic diapause
  • males have scrotum and testis, females pouches and mammary glands
42
Q

Embryonic diapause?

A

marsupials have it –> lactation induced negative feedback. wont be fertile until after breastfeeding stops

43
Q

How does chromosomes effect sex in marsupials

A

X = no pouch but a scrotum
XX = no scrotum, but a pouch & mammary gland

44
Q

TSD

A

temperature-dependant sex determination
alligators, turtles, tuataras

45
Q

features of TSD

A
  • all have same karyotype
  • in alligators, 100% male at high temperature and window (21-28 days)
  • known as thermos-temporal regulation
  • elegant way of matching population to available resources
  • no sex chromosomes
46
Q

mechanism of TSD

A
  • oestrogen
  • aromatisation of testosterone to oestrogen is crucial
  • oestrogen activates female pattern development
  • blockade of oestrogen leads to male
  • OESTROGEN CORE COMPONENTA
47
Q

primary sexual characteristics

A

uterus, vagina, penis

48
Q

secondary sexual characteristics

A

during or after puberty
pubic hair, voice deepens

49
Q

Sperm competition

A

female mates with many males (promiscuous) in one cycle
Results in huge testis and abundance of sperm

50
Q

gorilla mating

A
  • Harem (3/4 females)
  • small testis
  • small window to copulate
51
Q

chimp mating

A
  • promiscuous
  • big testis
52
Q

Colour in primates

A
  • most colourful mammals
  • vision is key, at expense of olfaction
  • colour is badge
  • mandrills increase colour with rank increase (and testosterone)
53
Q

How do females advertise fertility

A

oestrous swelling

54
Q

Primates spermatozoa

A
  • size of mid piece is related to social mating structure in primates
  • Midpiece comprises densely packed mitochondria and energy in the absnece of glycolytic support
  • mitochondrial loading associated with motility and flagellum motility
55
Q
A

hormones (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions