Hormonal Communication, Menstrual Cycle and Birth Control (Chapter 15) Flashcards Preview

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Although control by the nervous system is very fast, why is it also very expensive in terms of energy?

1) sodium-potassium pump
2) protein synthesis for pumps
3) maintenance of neurones and Schwann cells


Where are hormones made?

In endocrine glands


What are endocrine glands?

- A group of cells that produces and releases hormones e.g. insulin, ADH, glucagon, adrenaline in a process called secretion
- They contain secretory cells that pass their products directly into the blood ∴ they are ductless glands
- There is no energy cost in maintaining normal levels (unlike nerves with the Na-K pump)


What are hormones?

Cell-signalling molecules that are secreted in tiny quantities and dispersed around the body


Describe how peptide/small proteins hormones work

- They are water soluble ∴ they cannot cross the phospholipid bilayer of the CSM
- They bind to receptors on their target cells which activate second messengers to transfer the signal throughout the cytoplasm


Describe how steroid hormones work

- They are lipid soluble ∴ they can pass through the phospholipid bilayer
- Once they have crossed the CSM, they bind to receptor molecules inside the cytoplasm or nucleus and activate processes e.g. transcription


What happens after puberty in women?

The ovaries and uterus go through the menstrual cycle


What is the menstrual cycle?

A series of changes in the ovaries and uterus that recur approximately every 28 days


What happens in the middle of the menstrual cycle?

1) the female gamete is released in the oviduct
2) if fertilisation occurs while the gametes is in the oviduct, the embryo that develops needs somewhere to embed itself to continue its development


Describe the synchronisation of the uterine and ovarian cycle

The uterine cycle (changes that occur in the uterus) is synchronised with the ovarian cycle to that the endometrium is ready to receive the embryo at the right time to continue its development


What is the menstrual cycle coordinated by?

Glycoprotein hormones released by the anterior pituitary gland and steroid hormones released by the ovaries


What two hormones does the anterior pituitary gland secrete?

1) follicle stimulating hormone (FSH)
2) luteinising hormone (LH)


What do FSH and LH control?

The activity of the ovaries


How is oestrogen secreted?

During the monthly cycle, follicles develop which secrete the steroid hormone oestrogen


How is progesterone secreted?

After the female gamete is released from the ovary at ovulation, the remains of the follicle secretes another steroid hormone progesterone


What kind of hormones are oestrogen and progesterone?

Steroid hormones


How does the menstrual cycle begin?

- With the onset of menstruation, which usually lasts 4-8 days
- During this time, the anterior pituitary gland secretes LH and FSH and their concentrations increase over the next few days


What happens during the first half of the menstrual cycle after LH and FSH have been secreted physically (i.e. in the ovary)?

1) in the ovary, one follicle becomes the 'dominant' one
2) the presence of LH and FSH stimulates the secretion of oestrogen from the cells surrounding the follicle
3) the oestrogen stimulates the endometrium to grow, thicken and develop numerous blood capillaries
4) the surge of LH, due to the high conc of oestrogen, causes the dominant follicle to burst and shed its gamete into the oviduct
5) the follicle collapses to form the corpus luteum (yellow body), which secretes progesterone and some oestrogen - these maintain the lining of the uterus, making it ready to receives the embryo if fertilisation occurs


Describe the hormone cycle during the first half of the menstrual cycle

1) anterior pituitary gland secretes LH and FSH
2) the presence of LH and FSH stimulates the secretion of oestrogen from the cells surrounding the follicle
3) the presence of oestrogen in the blood has a negative feedback effect on the production of LH and FSH ∴ the conc of LH and FSH decrease
4) when the [oestrogen] of the blood has reached a level of 2-4 times its level at the beginning of the cycle, it stimulates a surge in the secretion of LH and, to a lesser extent, FSH
5) progesterone is secreted by the corpus luteum
6) progesterone inhibits the anterior pituitary gland from secreting FSH so that no more follicles develop


What happens during the second half of the menstrual cycle?

1) high levels of oestrogen and progesterone in the second half of the cycle inhibit the secretion of FSH and LH
2) ∴ there is less stimulation of the corpus luteum so it begins to degenerate and secrete less oestrogen and progesterone
3) as the conc of oestrogen and progesterone decreases, the endometrium is not maintained and menstruation begins
4) the decrease also releases the anterior pituitary gland from inhibition ∴ FSH is secreted to begin another cycle


What are the stages leading up to and following ovulation in the ovary?

1) a potential female gamete starts to develop
2) a primary follicle is produced by development of tissues surrounding the developing gamete
3) the primary follicle becomes a secondary follicle
4) the secondary follicle develops into an ovarian/Graafian follicle
5) at ovulation, the gamete is released
6) the remaining tissue forms a corpus luteum
7) the corpus luteum degenerates


Describe what happens in 4 stages in the ovarian and uterine cycle

1) Uterus - most of the endometrium lining is lost during menstruation if fertilisation did not take place in the last cycle
Ovary - follicle develops
2) Uterus - the endometrium develops
Ovary - ovarian follicle produced
3) Uterus - endometrium is most developed and contains many blood vessels
Ovary - ovulation takes place
4) Uterus - endometrium maintained until corpus luteum degenerates
Ovary - a corpus luteum develops and then degenerates


What two things may contraception involve?

1) contraception - preventing fertilisation when sexual intercourse takes place
2) preventing implantation of the embryo


What is the benefit of the birth control pill?

It allows women to have sex without running the risk of becoming pregnant


What is a negative consequence of the birth control pill?

It has contributed to a rise in STI incidence because people have more unprotected sex


What does the pill contain?

Steroid hormones that suppress ovulation


Why are the hormones in the pill normally synthetic and not natural?

Because they are not broken down so rapidly in the body ∴ they last longer


What are combined oral contraceptives (most pills)?

Pills containing both progesterone and oestrogen


How does the birth control pill work to prevent pregnancy?

1) both oestrogen and progesterone suppress the secretion of FSH and LH from the anterior pituitary gland (negative feedback)
2) ∴ they prevent the concentrations of FSH and LH from reaching the levels that would stimulate ovulation (mimics second half of menstrual cycle) ∴ ovulation does not occur


What happens to a woman when she takes the birth control pill?

1) taking the pill daily keeps the concentrations of oestrogen and progesterone high
2) stopping the pill after 21 days allows the concentration of oestrogen and progesterone to fall to the point at which the uterine lining is no longer maintained
3) ∴ menstruation occurs, reassuring the woman that she is not pregnant

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