Hormonal control of reproduction U2

Chemical messengers produced by endocrine glands and secreted directly into the bloodstream.

At puberty, the hypothalamus in the brain secretes a releaser hormone that targets the pituitary gland.

Secretes 2 hormones: FSH LH (in females) ICSH (in males)

The pituitary gland releases FSH promoting sperm production in the seminiferous tubules. ICSH stimulates the production of testosterone from the interstitial cells. Testosterone also stimulates the production of sperm and activates both the prostate gland and seminal vesicles to secrete fluids.

Target Tissue - Seminiferous Tubules Effect - Promotes sperm production

Target Tissue - Interstitial cells Effect - Stimulates testosterone production

Further stimulates sperm production, also activates the prostate gland and seminal vesicles to produce secretions.

A type of regulation in biological systems in which the end products of a process reduces the stimulus of that same process.

Lasts around 28 days, first day of menstruation regarded as day 1. Follicular phase (approx day 1-14) Luteal phase (approx day 15-28)

FSH stimulates the development of a follicle, in the ovary, and the production of oestrogen by the follicle. Oestrogen stimulates repair and proliferation of the endometrium, preparing it for implantation, and affects the consistency of cervical mucus by making it more easily penetrated by sperm. Peak levels of oestrogen act on the pituitary gland and stimulate a surge in secretion of LH. The surge in LH triggers ovulation. The highest concentration of oestrogen is just before ovulation (increased chance of fertilisation). Ovulation is the release of an egg from a follicle in the ovary, it usually occurs around the midpoint of the menstrual cycle.

in the luteal phase the cells of the follicle develop into a corpus luteum and start to secrete progesterone. Progesterone promotes further development and vascularisation of the endometrium, preparing it further for implantation if fertilisation occurs. Progesterone also causes thickening of the cervical mucus. Progesterone inhibits the secretion of FSH and LH by the pituitary, which prevents further follicles from developing, this is also an example of negative feedback.

Overproduction of testosterone is prevented by negative feedback mechanisms. High testosterone levels inhibit the secretion of FSH & ICSH from the pituitary gland, resulting in a decrease in the production of testosterone by interstitial cells.

High levels of oestrogen and progesterone inhibit the secretion of FSH & LH by the pituitary gland, which prevents further follicles from developing.

Corpus luteum degenerates and the progesterone and oestrogen levels decrease. Low levels of these hormones result in the onset of menstruation.

Corpus luteum does not regenerate and the progesterone levels stay high, this maintains the endometrium and prevents a miscarriage. The zygote then begins to proliferate into a ball of cells called a blastocyst. The placenta then takes over the production of progesterone. High progesterone inhibits the pituitary gland from secreting FSH & LH meaning no more follicles will develop, this is why when women are pregnant, they no longer menstruate.