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MedSci142 > Lecture 16: Introduction to Reproduction > Flashcards

Lecture 16: Introduction to Reproduction Flashcards

1
Q

What is reproduction?

A

Reproduction is the process by which new individuals of a species are produced and genetic material is passed through generations

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2
Q

What are the 3 main drivers of sex?

A
  1. Want to create new individuals of a species (can occur asexually)
  2. Genetic information can be passed from one generation to another (can occur asexually)
  3. to create new individual who is different form their parents and is able to adapt to the environment
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3
Q

What is reproduction like in males?

A

Constant production of Spermatozoon
300million per day (1500 per second per testicle)
Sperm is the smallest cell in body
Constant fertility from puberty onwards
Gradual decline with age - but fertile most of life

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4
Q

How many spermatozoon are produced per day in a male?

A

300 million per day

1500 per second per testicle

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5
Q

What is reproduction like in females?

A

Cyclical fertility from puberty (14/15 - 40), therefore Limited range of fertility
3-5 days per month
In utero, 7 million follicles, declining near to 0 during Menopause (don’t make any more)
Only about 400 follicles will be ovulated
(in Nz) And only about 2 fetilised
carefull controled
only fertile at limited times per month- regulated through reproductive hormones

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6
Q

What is the difference between the relative cell size of gametes between genders?

A

Sperm = Smallest cell in the body
Egg= Largest cell in the body
17500 sperm weigh as much as 1 female

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7
Q

What is the weight of 1 female Egg equivalent to?

A

17500 sperm

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8
Q

How far do sperm have to swim to reach a woman’s egg?

A

15cm swim to reach woman’s egg

human terms = about 16km

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9
Q

When is gamete quality optimum?

A

Sperm quality = best between 20-45 in men

Egg quality= Narrower range.. About 30 gives rise to More Complications

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10
Q

What is the function of endocrine glands?

A

To control reproductive processes via releasing hormones

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11
Q

What is the role of hormones?

A

Hormones released are Circulating hormones which travel through the blood and bind to specific receptors
If no receptor = No effect

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12
Q

What are the 4 main Endocrine glands?

A

Hypothalamus
Pituitary Gland
Adrenal Gland
Gonads (testes and Ovaries)

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13
Q

What are the two main functions of the Gonads?

A
  1. Produce Gametes: Sperm for males, Eggs for females
  2. Produce reproductive hormones: a. Early development of Genetalia. b. changes in puberty - 2/secondary sexual characteristics. c. adulthood- outgoing maintenance of reproductive function
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14
Q

What are the 2 main types of reproductive hormones?

A

Water soluble Hormones

Lipid Soluble Homrones

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15
Q

What is an exemplar class of a water soluble hormone?

A

Peptides and proteins

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16
Q

What is an exemplar class of a Lipid Soluble Hormone?

A

Steroid Hormones

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17
Q

What are 4 examples of water soluble hormones?

A

(GNRH) Gonadotrophin releasing Hormone
Follicle Stimulating Hormone (FSH)
Lutenising Hormone (LH)
Oxytocin

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18
Q

Which water soluble hormone is secreted by the hypothalamus?

A

GNRH

Gonadotropin releasing hormone

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19
Q

What water soluble hormone is secreted by the Anterior Pituitary?

A 
Follicle Stimulating Hormone (FSH)
Lutenising Hormone (LH)
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20
Q

What water soluble hormone is secreted by the posterior pituitary?

A

Oxytocin

is MADE in the hypothalamus, but is SECRETED from the posterior pituitary

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21
Q

What are some features of Water Soluble Reproductive Hormones?

A

Fast effect
quick changes in activity of different enzymes brings about rapid change in phosphorylation cascade
hormone transported in solution of blood
bind to specific receptor on target tissue
receptors activate G proteins, activate adenylate cyclase, turns ATP –> cAMP
Protein kinase is activated, results in other enzymes being phosphorylated
–> process stops by phosphodiesterase stopping cAMP

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22
Q

What are 3 examples of Reproductive Lipid soluble hormones?

A

Androgens (2 types)
Oestrogens (3 types)
Progestrogens (mainly 1)

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23
Q

What lipid soluble hormones are secreted from the Testes?

A

Androgens (2 types)

-not exclusively

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24
Q

What lipid soluble hormones are secreted form the ovaries?

A

Oestrogen (3 types)
Progesterone (mainly 1)
-not exclusively

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25
Q

What are some features of Lipid Soluble Hormones?

A

Slow effect
actions are longer lasting
hormones are lipid soluble but water insoluble
hormones transported via transport/carrier proteins through capillaries when in blood
released dissolves through lipid bilayer of target cell - diffuses out
enters nucleus and alters gene expression
newly formed mRNA directs synthesis of specific proteins on ribosomes
changes in activity through producing New protein which alters - cell activity and -gene expression
only 2-3% of hormones free at any one times - if too high/too low can be damaging

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26
Q

What is hormone action like?

A

Hormone action is complex
can have more than one effect
often many hormones used

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27
Q

What is the hierarchical arrangement of endocrine glands called?

A

Hypothalamic - Pituitary - Gonadal Axis (HPG)

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28
Q

What does the HPG axis allow for?

A

Signal amplification
go from peaka gram amounts of products produced in hypothalamus
microgram produced in pituitary
milligram amounts produced in gonads

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29
Q

What is GNRH release like?

A

Pulsatile release of GNRH

rather than continuous release

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30
Q

Which hormones act to promote spermatogenesis and oogenesis?

A

LH and FH act to promote spermatogenesis and oogenesis

gonadotropins

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31
Q

Which hormones are regulated by the testes and ovaries and why?

A

FSH and LH are regulated by the testes and ovaries

they act to produce gametes and stimulate sex steroid hormone production

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32
Q

What is the main function of the hypothalamus?

A

homeostatic regulator
for: -reproduction, stress, body temp, hunger and thirst, and sleep
provides major integrating link between nervous and endocrine system
when something changes, brings everything back to normal
a neuroendocrine organ as it process both neural and hormonal information
Aggregation of neurons into areas called NUCLEI (areas of neurons)(not nucleus)

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33
Q

What are the 6 things the hypothalamus acts as a homeostatic regulator of?

A 
reproduction
stress
body temp
hunger and thirst
sleep
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34
Q

What sort of organ is the hypothalamus called?

A

Neuroendocrine organ

as it processes both neural and hormonal information

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35
Q

What is the size and shape of the Pituitary gland?

A

Pear shaped

about 1.5 cm

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36
Q

What are some features of the Pituitary gland?

A

Attaches to the hypothalamus by stalk called the infundibulum
Down growth of the brain
Two anatomically and functionally separate anterior and posterior lobes –> posterior lobe is smaller (1/2 size)
Both required - if one missing, no hormones produced. -if one is overactive(e.g. tumour) there is adverse effects also

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37
Q

Which lobe in the pituitary gland is smaller?

A

Posterior Lobe

is about 1/2 the size

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38
Q

What is another name for the posterior pituitary gland?

A

neurohypophysis

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39
Q

What is the overall function of the neurohypophysis?

A

hormones released and stored

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40
Q

What are some features nuclei connecting the hypothalamus with the neurohypophysis?

A

Neurosecretory neurons are aggregated into uncle - cell bodies
regular neurones can conduct a nerve impulse, releasing NEUROTRANSMITTERS
Usane Bolt: Neurosecretory neurons can conduct a nerve impulse, AND SYNTHESIZE, CARRY + release NEUROSECRETORY PEPTIDE HORMONES
Neurosecretory neurons have long axon tracts which pass into the posterior pituitary

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41
Q

Where are neurosecretory peptide hormones synthesised?

A

in the hypothalamus

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42
Q

Where are neurosecretory peptide hormones travel bound?

A

travel bound to carrier proteins down the axon terminals

43
Q

Where are neurosecretory peptide hormones stored?

A

in secretory vesicles

44
Q

What happens to nerve impulses involving neurosecretory peptide hormones?

A

nerve impulses travel along the axon to trigger exocytosis of the secretory vesicle
releasing the peptide hormones at the posterior pituitary

45
Q

What the two neurosecretory peptide hormones released from the posterior pituitary called?

A 
oxytocin - most exciting
antidiuretic hormones (ADH or vasopressin) - renal function
46
Q

Where are the Where are oxytocin and ADH/vasopressin synthesised?

A

Oxytocin and ADH synthesised int eh hypothalamus

transported to the posterior pituitary, where they are stored and released

47
Q

What is the comparison between Oxytocin and ADH?

A

they have very similar structures but very different specificities of action
-both small peptides
(look similar and only differently two amino acids)
1x controls reproduction and 1x controls renal function

48
Q

What are some key effects of oxytocin?

A

major effects on smooth muscle contraction
secretion stimulated in response to stimulation of nipples
-suppling of milk from child
(lactation) or uterine distention
also a “love” hormone, imported for bonding- love, lust, orgasm
Used to induce labour- uterine stretches and development of contractions and eventual arrival of child

49
Q

What are some key effects of ADH?

A

acts on kidneys to retain water

50
Q

What is another name for the anterior pituitary?

A

Adenhypophysis

-lobe isn’t produced in the brain

51
Q

What is the overall function of the anterior pituitary?

A

upgrowth from top of mouth early in development

-lobe not produced in the brain

52
Q

What are some key features of the anterior pituitary?

A

Lobe not produced in the brain
Connected to the hypothalamus via a HUMORAL or VASCULAR connection (portal)(rather than neural)
Neurosecretory neurons are short and don’t have hypothalamus
release connects into portal blood vessels
Nuclei present (cell bodies of neurosecretory neurons) and short tons
Portal system- a vascular arrangement - therefore hormones aren’t diluted in blood system -
-AVOIDS DILUTION
vascular arrangement in which blood flows from one capillary bed to another without going through the heart

53
Q

What happens with hormones in the anterior pituitary gland?

A

releasing (+ve) and inhibiting (-ve) hromones (9 types) act on specific secretory cells arranges in clumps at the (stored as vesicles in termini) termini of the Hypophyseal Portal Blood Vessels

54
Q

What do gonadotrophs produce?

A

2x gonadotropins:

FSH and LH

55
Q

What is the summary of neurosecretory action in the anterior pituitary gland?

A

Neurosecretory neurons synthesize releasing and inhibiting hormones in their cell body into vesicles, which travel to the axonal terminus
In response to nerve impulses, these neurosecretory peptide hormones are secreted into linking hypophyseal portal vessels
fast acting –> rapid effects

56
Q

What is involved in the regulation of the pituitary secretory cells?

A

homeostatic mechanisms involving negative and positive feedback loops regulate hormone levels
releasing and inhibiting hormones have either a positive of negative effect on anterior pituitary
which determines if it produces inhibiting or releasing hormones
when a hormone acts on a target tissue it seeds out either 1. inhibiting signal (stop hormone production) 2. releasing signal (more of hormone)

57
Q

What does the regulation of Gonadotropin secretion involve?

A

Comes above via negative feedback system to ensure relatively constant (homeostasis) supply of FSH/LH
Just before ovulation- –> + feedback
endocrine relationships are complex systems of amplification, controlled by a series of feedback loop

58
Q

What sort of feedback do sex hormones show?

A

-ve negative feedback

on the -pituitary and hypothalamus

59
Q

What are elements of pulsatile release?

A

hypothalamus secretions are released in discrete burst 9once every 1-2 hours)
seen as pulsatile release of pituitary hormones (FSH/LH)
This prevents receptor desensitisation and down regulation

60
Q

What is the rate of secretions from the hypothalamus?

A

once every 1-2 hours

release plus long period of time, to ensure maximum effect

61
Q

What are the two hormones which regulate gonadal activity?

A

FSH

LH

62
Q

What to FSH and LH do?

A

contact from pituitary –> gonads
bind to receptors in ovary/testes
promote synthesis of sex steroid hormones and gametogenesis
same hormones in boys and girls, but have different target tissues

63
Q

What is the role of FSH in females?

A

growth of ovarian follicles

64
Q

What is the role of LH in females?

A 
Secretion of female sex hormones
Stimulates ovulation (LH SURGE) v. important
65
Q

What is the role of FSH in males?

A

growth of spermatozoon(oa)

66
Q

What is the role of LH in males?

A

stimulates production of testosterone

67
Q

What are sex steroids?

A

after puberty, regular production of sex hormones

68
Q

What are some features of sex steroids?

A

made from body through cholesterol
-diet
-made endogenously from body
cholesterol converted to different forms of hormones inside cells based on structure
produced by gonads, effect on target tissues
structure is similar to cholesterol - different groups around 4 rings
but very different functions, actions and specificities –> also acts on target tissue

69
Q

What are some features of Androgens?

A

mostly associated with male
but females produce androgens, although little compared to males (10-100x more)
Testosterone and 5 alpha Dihydrotestosterone (more potent and more important effect on target tissue)
Testosterone is the main secretory product of the testes
mainly associated with the development and maintenance of male characteristics (external and internal) and fertility, from puberty –> adulthood

70
Q

What are key properties of Androgens?

A

male sex development –> early + puberty
external and internal genetalia
spermatogenesis
sexual behaviour
muscle development
-abuse anabolic steroids-precursors in body building
females - for libido/sexual behaviour/interest in sexual activity

71
Q

What are some key properties of Oestrogens?

A 
female sex development
growth of endometrium
regulation of menstrual cycle
bone growth (men + women)
male spermatogenesis
72
Q

What are some features of Oestrogens?

A

most females but also males (though females 10-100x more0
main roles is the development and maintenance of female characteristics and fertility
DOESNT play a major role in early sexual development
The main site of oestrogen production is in the granolas cells of the growing follicle
Oestradiol, oestrone, oestriol

73
Q

What are some important features of Oestradiol?

A

produced by growing follicle (granolas cell)
main oestrogen
puberty –> menopause vast amount produces
regulates menstrual cycle

74
Q

What are some important features of oestrone?

A

weaker
important for male/post-menopause women
-only oestrogen secreted, also produced pre
in adipose (fat)

75
Q

What is the role of progestagens?

A

Progesterone are major steroidal hormone of the corpus lutetium and placenta
after ovulation
only act in males

76
Q

What are prodestagens associated with?

A

Progestagens are the DRUG OF PREGNANCY

associated with PREPARATIONS of pregnancy and its MAINTENANCE of foetus

77
Q

What is the main type of hormone?

A

Water soluble hormones which travel in the blood

78
Q

How can you stop all reproductive function?

A

by castrating someone
cutting off one element of the HPG axis
-tiny organs but completely control reproduction

79
Q

Where does the hypothalamus sit?

A

in the CNS

80
Q

what pathway does the hypothalamus take to communicate with the posterior lobe?

A

Neural direct pathway

81
Q

What pathway doe the hypothalamus take to communicate with the anterior lobe?

A

Humoral indirect pathway
Vascular
Portal system

82
Q

What is the nuclei in the hypothalamus?

A

A grouping of cell bodies in the hypothalamus

83
Q

What is the purpose of the portal system, in particular the hypophyseal portal system?

A

It avoid dilution (of special hormones(bits of perfume- a little drop))
hormones go directly to the secretory hormones, WITHOUT being diluted in the blood system

84
Q

How many types of secretory cells are present in the anterior pituitary?

A

5

85
Q

What are secretory cells like?

A

Taxis
pick up messages from hormones, through portal system, and secreotry cells will go of an do what they want to do
completely different functions
will produce their own hormones

86
Q

What is the role of secretory cells?

A

arranges at the bottom of the portal system
arranged in clumps
go off and perform their own functions (produce their own distinctive pituitary hormones which will have an affect on their target tissue)
then will regulate pituitary and hypothalamus via BOTH NEG and POS feedback by things produced in the target tissue

87
Q

When is their positive regulation in the HPG axis?

A

only time of positive feedback

once every month

88
Q

Why is their homeostasis in the gonads?

A

constant homeostatic reproductive activity to bring about production of the sex hormones

89
Q

What is the pathway of regulation of the pituitary secretory cells?

A

Hypothalamus -+/- -> anterior pituitary –> Pituitary hormone –> Target tissue –(mainly - but once monthly +)–> anterior p and hypothalamus

90
Q

What is the pathway of regulation of gonadotrophin secretion?

A

Hypothalamus –GnRHin portal-blood –> Anterior pituitary: Gonadotrophs —> FSH and LH in systemic-blood –> Gonads —Sex hormones NEGve always –> Hypothalamus and anterior p

91
Q

What is the feedback of sex hormones like?

A

always negative
back to regulate hypothalamus and anterior pituitary
to regulate ant. pituitary’s gonadotrophin secretion

92
Q

What are the two types of androgens?

A

Testosterone

5 alpha dihydrotestosterone (more portent and important - esp in its effect on target tissue)

93
Q

Which hormone is important for libido?

A

Androgens

94
Q

What is libido?

A

Interest in sexual activity

sex drive

95
Q

Which oestrogen is most potent?

A

Oestradiol

therefore will only produce from puberty–> menopause

96
Q

Why is oestradiol only produced from puberty –> menopause?

A

as it is the only time there is growing follicles (follicle growth)
will decline dramatically after menopause

97
Q

What form oestrogen is in males/post menopausal woman?

A

Oestrone
is weaker than previously oestradiol
IMPORTANT in MALES

98
Q

When is oestriol important and where is it produced?

A

Important in the: softening of the cervix during labour (pregnancy hormones)
Produced: by the placenta

99
Q

Which is the most dimorphic hormone?

A

Progestagens

only produced in femalse

100
Q

Which sex hormone is exclusive to women?

A

Progestagens

101
Q

What is the need for the pulsatile release of both FSH and LH?

A

regulate spermatogenisis and oogeneisis

pulsatile, so don’t get sick of hormone, but instead has max effect

102
Q

What are the testes and ovaries regulated by?

A

the 2 gonadotropins

FSH and LH

103
Q

Why are the testes and ovaries regulated?

A

so they can produce gametes, also stimulate Sex STEROID hormone production

MedSci142 (20 decks)

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