Hormonal Control Of Reproduction Flashcards
What are hormones ?
They are chemical messengers which travel in the bloodstream to their target tissue which has specific receptors. They are produced in endocrine glands
What do hormones play a pivotal role in?
Sexual reproduction in both male and females.
What do hormones control?
The onset of puberty
What is puberty?
The process of physical changes through which a child’s body matures into an adult body capable of sexual reproduction
What is puberty initiated by?
Hormonal signals
What is the pituitary gland stimulated to release?
Follicle-stimulating hormone, luteinising hormone (females) or interstitial cell stimulating hormone (males) by a releaser hormone produced in the hypothalamus
What does FSH do in terms of males?
Promotes sperm production
What does ICSH stimulate in terms of males?
The production of testosterone
What does testosterone also stimulate?
Sperm production (by stimulating meiosis in seminiferous tubules) and activates secretion from the prostate gland and seminal vesicles
Describe negative feedback control?
The body has self-regulating mechanisms, called negative feedback that allows the body to correct changes. When a factor affecting the body’s internal environment deviates from the norm (or set point), the body responds to correct the change
What happens if the concentration of testosterone gets to a high level?
It inhibits the secretion of FSH and ICSH, which decreases the testosterone concentration.
In males what is the LH the same as ?
ICSH
What does the pituitary gland release in females?
FSH and LH
How does FSH affect the ovaries ?
Stimulates the development and maturation of each follicle . It also stimulates follicular tissue to secrete oestrogen
When oestrogen reaches high levels I.e its peak what happens ?
It stimulates a surge in LH by the pituitary gland
What does LH do?
Triggers ovulation.
It also brings about the development of the corpus luteum from the old follicle and stimulates the secretion of progesterone and some oestrogen
What does oestrogen do in terms of hormonal control of the menstrual cycle?
Stimulates the proliferation of the endometrium thereby effecting its repair following menstruation and preparing it for implantation of a blastocyst e.g. thickening
In high levels it stimulates a surge in LH by the pituitary gland
What does progesterone do in terms of the hormonal control of the menstrual cycle?
Promotes further development and vascularisation of the endometrium into a spongy layer rich in blood vessels, making it ready to receive a blastocyst (should fertilisation occur).
In high levels it inhibits the secretion of FSH &à LH
How long does the menstrual cycle usually last?
approx 28 days
What is first day of the cycle?
the first day of a woman’s period (menstruation)
How long does the period usually last?
for 3-7 days
What is the period made up of?
blood and the endometrium
What happens to the period?
it passes out of the body through the vagina
What are the 2 phases the menstrual cycle is divided into?
Follicular phase (1st) Luteal phase (2nd)
What happens as the concentration of oestrogen builds?
it brings about the repair and proliferation of the endometrium following the previous menstruation
What does a high concentration of oestrogen (peak) trigger?
a surge in the production of LH and FSH at anout day 14.
What does a surge in LH cause?
ovulation
What happens when the egg is released and how long can it survive and what does this mean for fertilisation?
it slowly moves along the oviduct & can survive for only 1-2 days. However, sperm can survive for 3-4 days and so fertilisation may occur in 3-4 day window each month.
What is fertility in terms of females?
cyclically fertile
What does high levels of progesterone and oestrogen trigger?
an inhibitory effect on the pituitary gland. Concentrations of FSH and LH drop (and no new follicles develop
What does the lack of LH due to the inhibition by progesterone lead to?
the degeneration of the corpus luteum by about day 22. Hence the levels of oestrogen and progesterone drop
What happens by day 28 in terms of the endometrium?
the levels of oestrogen and progesterone are so low that the endometrium can no longer be maintained and starts to break down (menstruation begins)
