Key Area 2- Hormonal Control of Reproduction Flashcards
What is a hormone?
A chemical that is produced at one site, and has an effect on another site.
What are hormones produced by?
Endocrine glands. (They are secreted directly into the blood stream)
What happens when a hormone reaches its target tissue?
It brings about a specific effect.
What do hormones produced in the hypothalamus and the pituitary gland control?
The onset of puberty, sperm production and the menstrual cycle.
What does the hypothalamus secrete at puberty?
A releaser hormone whose target is the pituitary gland.
What hormones is the pituitary gland stimulated to release?
FSH (follicle-stimulating hormone, in males and females), and ICSH (interstitial cell-stimulating hormone, in males) or LH (luteinising hormone, in females0
What does the release of these hormones trigger?
The onset of puberty, for example sperm producion and the menstrual cycle.
What happens when FSH arrives in the bloodstream at the testes? (EFFECT)
It promotes sperm production in the seminiferous tubules.
What happens when ICSH arrives in the bloodstream at the testes? (EFFECT)
It stimulates the interstitial cells to produce the male sex hormone testosterone.
What does testosterone stimulate and activate?
It stimulates sperm production in the seminiferous tubules, and activates the prostate gland and seminal vesicles to produce their secretions
Describe the negative feedback control of testosterone production by FSH and ICSH.
- As the concentration of testosterone builds up in the bloodstream, it reaches a level where it inhibits the secretion of FSH and ICSH by the pituitary gland
- This leads to a decrease in testosterone concentration, which then triggers the pituitary gland to again make FSH and ICSH
- And so on…
Where is FSH and ICSH released from?
The pituitary gland
Where is testosterone released from?
Interstitial cells
What is the target of FSH?
Seminiferous tubules
What is the target of ICSH?
Interstitial cells
What is the targets of Testosterone?
Seminiferous tubules, prostate gland & seminal vesicles and the pituitary gland
What are the effects of Testosterone?
Sperm production, produce secretions and negative feedback of FSH and ICSH
What are the Two stages of the menstrual cycle?
The Follicular phase and the Luteal phase
What does FSH (secreted from pituitary gland) stimulate when it reaches the ovary?
- The development and maturation of a follicle
- The production of oestrogen by the follicle
What happens when the ovary wall secretes oestrogen?
- It stimulates proliferation (cell division) of the endometrium (inner layer of the uterus) following menstruation, preparing it for implantation
- Affects the consistency of cervical mucus making it more easily penetrates by sperm
What do high concentrations of oestrogen trigger?
The production of LH and FAH by the pituitary gland at approximately ‘day 14’
What does the surge of LH cause?
.It directly causes ovulation by causing the follicle to rupture and release the ovum
.The ovum then moves along the oviduct, and over this very short period of 2-3 days, fertilisation may occur if the ovum meets a sperm
What is ovulation?
.It is the release of an egg (ovum) from a follicle in the ovary. It usually occurs around the mid-point of the menstrual cycle
What happens during the luteal phase?
.LH stimulates the follicle to develop into the corpus luteum
.The corpus luteum secretes progesterone
.The rise in progesterone concentration stimulates further development and vascularisation of the endometrium so it becomes thick, spongy and has an increase in vascular blood vessels, preparing it for implantation if fertilisation occurs
.High levels of oestrogen and progesterone trigger an inhibitory effect on the pituitary gland, so concentrations of FSH and LH drop as a result preventing further follicles from developing at this time. This is an example of negative feedback control
What happens if fertilisation doesn’t occur?
.The lack of LH leads to the degeneration of the corpus luteum with a subsequent drop in progesterone levels leading to menstruation
.Menstruation involves the loss of the inner layer of the endometrium accompanied by a small volume of blood for a few days
What happens if fertilisation does occur?
.The corpus luteum does not degenerate and progesterone levels remain high preventing menstruation from taking place
