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ANSC3104 Reproduction > Control of reproduction > Flashcards

Control of reproduction Flashcards

1
Q

Neural control

A
  • Nerves release neurotransmitters directly onto the target tissue
  • Usually operates via the spinal cord
  • Quick response
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2
Q

Neuroendocrine control

A
  • Combined efforts of nerves and hormones
  • Usually operates via spinal cord
  • Relies on transport of hormone through circulatory blood
  • Faster than just endocrine response
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3
Q

Endocrine control

A
  • Hormones operating independent of the nerves

* Relies on transport of hormones through circulatory blood

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4
Q

Example of neural response

A

Ejaculation:

  • Sensory stimulation of glans penis (temperature & pressure)
  • Afferent neuron to spinal cord
  • Motor neuron to target tissue
  • Sudden & powerful contraction of urethralis, bulbospongiousus and ischiocavernousus muscles
  • Expulsion of semen
  • Very quick response
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5
Q

Neuroendocrine reflex

A

Message sent to brain

Triggers release of hormones

Hormones affect target tissue

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6
Q

Example of neuroendocrine control

A

Milk Ejection:

Suckling stimulates udder

Neural response goes up to brain

Causes release of oxytocin from the posterior lobe of the pituitary

Oxytocin travels through circulation down to mammary gland

Causes contractions of the muscle basket around mammary alveoli

Squeezes the milk out through ducts

Initially fast response - slows down a bit when hormone has to travel through circulation (takes roughly 30 sec for milk ejection)

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7
Q

Endocrine control

A

Stimulation of hormone release into circulation

Travels to target tissue

Binds to appropriate receptors

Start to initiate response in cells

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8
Q

Example of endocrine control

A

Spontaneous ovulation:

Follicles on ovary produce oestrogen

As follicles get bigger they produce more oestrogen

Oestrogen concentration in bloodstream increases

Feeds back to the surge centre of the hypothalamus (positive feedback)

Hypothalamus releases GnRH

GnRH travels to anterior pituitary

Causes the release of LH into circulation

Travels back down to ovary

Causes follicle to burst open and release its egg = ovulation

Slow process - can take hours to a couple of days depending on species

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9
Q

Where is GnRH produced?

A

Hypothalamus

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10
Q

GnRH function

A

Controls release of gonadotropins from anterior pituitary:

  • Follicle stimulating hormone (FSH)
  • Luteinising hormone (LH)
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11
Q

Tonic release of GnRH

A

Occurs in males & females

Small pulsatile GnRH release throughout reproductive life

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12
Q

Surge release of GnRH

A

Occurs in females only

High amplitude, high frequency pulses of GnRH when stimulated by high oestrogen levels

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13
Q

FSH function

A

Follicle stimulating hormone

Stimulates follicular growth in females - hence increases production of oestrogen

Stimulates Sertoli cells in males - hence initiates spermatogenesis

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14
Q

Lh functions

A

Lutenizing hormone

Induces ovulation of mature follicles - hence formation of the corpus luteum & production of progesterone

Stimulates testosterone production in males

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15
Q

Where are gonadotropins released?

A

Anterior pituitary

GnRH is released in hypothalamus - travels to anterior pituitary - causes release of gonadotropins

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16
Q

List the steroid hormones

A

Testosterone
Progesterone
Oestrogen

17
Q

Where is testosterone released in males?

A

In the testes

18
Q

What cells produce testosterone in males?

A

Interstitial cells/ Leydig cells in the seminiferous tubule

19
Q

Production of sex steroids are under the control of what?

A

The hypothalamohypophyseal tract

Via positive & negative feedback or GnRH

20
Q

Hypothalamo-hypophyseal tract

A
  • A capillary system connecting the hypothalamus with the anterior pituitary
  • Allows small amounts of GnRH to have an immediate effect on the pituitary before being diluted into the blood
  • One of the ways the body has adapted to speed up the endocrine response allows GnRH to travel very quickly from hypothalamus to anterior pituitary to trigger the release of another hormone
21
Q

Negative feedback

A

Suppression of release, therefore maintained concentration of target hormone, this is used in homeostasis

  • Product later in pathway suppresses release of hormones earlier in pathway
  • Negative feedback drives control of testosterone in males
22
Q

Positive feedback

A

Stimulation of release therefore increase in concentration of targeted hormone

Positive feedback = high levels of hormone release

• E.g. Release of oestrogen in high levels from late stage follicles causing huge release of LH

23
Q

Testosterone function

A

Male behaviour & aggression

Spermatogenesis

Growth of secondary sex glands and muscle

Development of typical male characteristics, e.g. antlers

24
Q

Oestrogen functions

A

Increases blood flow in the uterus

Growth of uterine endometrial glands

Secretory activity of oviduct

Smooth muscle motility

Sexual receptivity

Closure of epiphyseal growth plate in bones

Mammary duct growth

25
Q

Progesterone functions

A

Uterine endometrial gland growth - getting ready for implantation

Secretory activity of oviduct and endometrial glands

Mammary lobular growth

Quiescence of uterus

Progesterone = pregnancy hormone

26
Q

Is the hypothalamus the same in males and females?

A

No it is structurally different

female has surge area

27
Q

How do primary follicles differ from primordial follicles?

A
  • Primary follicles differ to primordial follicles as they are bigger and can be receptive to gonadotropins (primordial follicles lack LH & FSH receptors)
28
Q

Inhibin

A

Key role in the control of follicular growth

Inhibits the releases of FSH

Switches the release of gonadotropins from being preferential for FSH to preferential to LH – inducing ovulation

29
Q

How does an egg remove excess chromosomes?

A

By exuding a polar body

It does this twice

30
Q

Microscopically how do you know if an egg is ready to be fertilised?

A

if you see an egg with a polar body you know that egg is ready to be fertilized

ANSC3104 Reproduction (6 decks)

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