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

Question 1

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

Answer 1

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

Question 2

Where are hormones made?

Answer 2

In endocrine glands

Question 3

What are endocrine glands?

Answer 3

• 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)

Question 4

What are hormones?

Answer 4

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

Question 5

Describe how peptide/small proteins hormones work

Answer 5

• 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

Question 6

Describe how steroid hormones work

Answer 6

• 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

Question 7

What happens after puberty in women?

Answer 7

The ovaries and uterus go through the menstrual cycle

Question 8

What is the menstrual cycle?

Answer 8

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

Question 9

What happens in the middle of the menstrual cycle?

Answer 9

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

Question 10

Describe the synchronisation of the uterine and ovarian cycle

Answer 10

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

Question 11

What is the menstrual cycle coordinated by?

Answer 11

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

Question 12

What two hormones does the anterior pituitary gland secrete?

Answer 12

1) follicle stimulating hormone (FSH)

2) luteinising hormone (LH)

Question 13

What do FSH and LH control?

Answer 13

The activity of the ovaries

Question 14

How is oestrogen secreted?

Answer 14

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

Question 15

How is progesterone secreted?

Answer 15

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

Question 16

What kind of hormones are oestrogen and progesterone?

Answer 16

Steroid hormones

Question 17

How does the menstrual cycle begin?

Answer 17

• 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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What happens during the second half of the menstrual cycle?

Answer 20

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

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

What two things may contraception involve?

Answer 23

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

Question 24

What is the benefit of the birth control pill?

Answer 24

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

Question 25

What is a negative consequence of the birth control pill?

Answer 25

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

Question 26

What does the pill contain?

Answer 26

Steroid hormones that suppress ovulation

Question 27

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

Answer 27

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

Question 28

What are combined oral contraceptives (most pills)?

Answer 28

Pills containing both progesterone and oestrogen

Question 29

How does the birth control pill work to prevent pregnancy?

Answer 29

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

Question 30

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

Answer 30

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

Question 31

Although the combined pill is very effective at preventing conception, why can’t even one pill be missed?

Answer 31

This might allow ovulation to take place and fertilisation to occur if the woman has unprotected sex at this time

Question 32

How else can hormones be given to prevent pregnancy?

Answer 32

1) though a skin patch (hormones absorbed through skin)
2) implant under skin
3) injection that is effective for several months
With these methods, no menstruation takes place

Question 33

If they may allow ovulation to occur, how do progesterone only pills work to prevent pregnancy?

Answer 33

1) they reduce the ability of sperm to fertilise the egg

2) they make the mucus secreted by the cervix more viscous ∴ less easily penetrated by sperm

Question 34

When is the morning-after pill taken?

Answer 34

After unprotected sexual intercourse

Question 35

How long does the morning-after pill work for?

Answer 35

Up to 72 hours after intercourse

Question 36

How does the morning-after pill work?

Answer 36

• It contains a synthetic progesterone-like hormone and if taken early enough, reduces the chances of sperm reaching and fertilising an egg
• However, in most cases, it probably prevents pregnancy by stopping the embryo implanting in the uterus

Question 37

What are some examples of protein hormones?

Answer 37

Insulin, ADH and glucagon

Question 38

What are some examples of steroid hormones?

Answer 38

The sex hormones

Question 39

What is menstruation?

Answer 39

The shedding of the endometrium (lining of the uterus) at the start of the menstrual cycle