Unit 2.2 Hormonal Control of Reproduction Flashcards
What are hormones
Chemical messengers produced by endocrine glands that take information around the body
What do target tissues have so only that tissue is affected by the hormone
Target tissues have : cells with complementary receptor proteins - for specific hormones, so only that tissue is affected
How do hormones travel
By the bloodstream
What do hormones control in reproduction
- the onset of puberty
- sperm production
- the menstrual cycle
What does the hypothalamus do at puberty
Secretes a releaser hormone whose target is the pituitary gland
How does the pituitary gland respond to the releaser hormone
By producing 2 hormones ( FSH + ICSH in males // FSH + LH in females)
What is FSH
A follicle stimulating hormone
What is ICSH
An interstitial cell-stimulating hormone
What is LH
A luteinising hormone
What do the release of hormones by the pituitary gland trigger
The onset of sperm production (males) and the menstrual cycle (females)
What does FSH do (males)
Promotes sperm production in the seminiferous tubules
What does ICSH do
Stimulates the interstitial cells to produce testosterone
What does testosterone do
- stimulates sperm production
- activates the seminal vesicles & prostate gland to produce secretions (fluids)
What is negative feedback control
The body had self-regulating mechanisms called negative feedback, allowing the body to correct changes. When a factor affecting the body’s internal environment deviates from its norm (set point) the body responds to correct the change)
Example of negative feedback control
As testosterone concentration builds up in bloodstream it reaches a level that inhibits FSH & ICSH secretion.
This leads to a decrease in testosterone concentration.
So, the pituitary gland releases FSH & ICSH again.
What does FSH (females)
- Stimulates the development & maturation of each follicle.
- Stimulates the ovary to secrete oestrogen by the follicle in the follicular phase
What does LH do
-Triggers ovulation
-Brings about development of the corpus luteum from the follicle, the corpus luteum then secretes progesterone
What are the ovarian hormones
Oestrogen & Progesterone
What does oestrogen stimulate
The proliferation (cell division) of the endometrium (inner layer of the uterus). This prepares the uterus for implantation of an embryo
What do high levels of oestrogen stimulate
The cells lining the cervix to secrete a watery mucus making it more easily penetrated by sperm
What do peak levels of oestrogen stimulate
-A surge in the secretion of LH which triggers ovulation.
-The production of LH by the pituitary.
What does the follicle do in the luteal phase
Develops into a corpus luteum & secretes progesterone
What does progesterone promote
The further development & vascularisation of the endometrium, preparing it for implantation if fertilisation occurs
Vascularisation meaning
Formation of blood vessels
Proliferation meaning
Cell division
Endometrium meaning
The inner layer of the uterus
What prevents further follicles from developing
The negative feedback effect of the ovarian hormones on the pituitary gland & the secretion of FSH & LH
What does a lack of LH lead to
Degeneration of the corpus luteum with a subsequent drop in progesterone levels, leading to menstruation
What happens to the corpus luteum & progesterone if fertilisation occurs
The corpus luteum does not degenerate & progesterone levels remain high
What 2 hormones does progesterone inhibit
FSH & LH by the pituitary gland
What happens once a month for menstruation
An egg is released from the ovary and passes down the oviduct. During this time the lining of the uterus has to repair and enrich in the event the egg is fertilised
What happens to the uterus if no sperm encounter the egg
The uterus lining breaks down & passes out of the body
How long is the menstrual cycle
28 days (first day of menstruation is day 1)
What does the ovary secrete in the menstrual cycle
Oestrogen
What does the corpus luteum secrete in the menstrual cycle
Progesterone
What is the first phase of the menstrual cycle called
The follicular phase
