Lecture 2

Question 1

Menstrual Cycle

Answer 1

2 purposes:

• suitable environment for implantation should the oocyte be fertilised
• transport gametes to site of fertilisation

Ends in endometrial shedding – menses (lining is lost) – if implantation fails

Only occurs in humans, other primates, some bats & shrews

Question 2

Oestrous Cycle

Answer 2

Behavioural strategy to ensure mating at time of ovulation

Question 3

Attractiveness

Answer 3

males prefer ‘smell’ of females in middle rather than end of cycle

Question 4

Receptiveness

Answer 4

more willing to accept male advances

Question 5

Proceptivity

Answer 5

evidence for enhanced sexual motivation

a study which looked at 50 hetero couples, females were more likely to mate during the luteal phase

Question 6

Cycle - from hypothalamus to sex steroids

Answer 6

sex steroids in males negatively feeds back to GnRH

sex steroids in females positively and negatively feeds back to GnRH

Question 7

sex steroids acts on

Answer 7

the uterine tubes

endometrium lining

Question 8

Puberty

Answer 8

immature individual acquires the physical and

behavioural attributes which will allow him or her to reproduce

Question 9

What controls the timing of puberty?

Answer 9

Genetics and external factors

Question 10

Genetics

Answer 10

twin studies (identical and non) show that genetic influences are the single 
largest factor accounting for variation in pubertal development

Question 11

External factors

Answer 11

may modulate the timing and tempo of puberty preset by genetic regulation

	- stressful events
	- intra-family relationships
	- endocrine disrupting chemicals
	- adiposity (key one)

Question 12

Age of Menarche

Answer 12

Decreased by 2-3 months / decade between 1840 & 1970

In developed countries – decrease has ceased over last 40 years

Question 13

Role of nutrition in initiation of puberty

Answer 13

puberty is later in countries with “sub-optimal” socioeconomic status

Question 14

Delayed puberty

Answer 14

malnutrition (e.g. anorexia nervosa)
elite athletes (e.g. gymnasts & ballerinas)

Question 15

Advanced puberty

Answer 15

obesity

Question 16

Leptin

Answer 16

hormone produce by white adipose tissue

levels increase at start of puberty

k/o mice have low Gn levels & underdeveloped gonads

similar phenotype in humans with mutations in leptin or receptor abnormalities reversed by leptin therapy

Question 17

Role of kisspeptin in initiation of puberty

Answer 17

Produced by hypothalamus
- Arcuate nucleus - GnRH pulse generation

• APN - sexually dimorphic (more in ♀), allows for a positive feedback in the hypothalamus important for GnRH / LH surge & ovulation

Question 18

disruption of Kiss1 gene

Answer 18

failure of sexual maturation / infertility

treatment of juvenile rats with kisspeptin advances timing of puberty

Question 19

GPR54

Answer 19

expressed by GnRH neurones

kisspeptin activation of GPR 54 stimulates GnRH release

7 transmembrane

Question 20

G (guanine) Proteins

Answer 20

heterotrimeric: consist of - a- and b-subunits

GPCR induce a conformational change in -subunit

exchange of GDP for GTP & dissociation of -subunit

Question 21

G protein subunits

Answer 21

- 4 families of -subunit: 
		Gaq - activates  phospholipase C
		Gas – activates  adenylate cyclase
		Gai – inhibits adenylate cyclase
		Ga12 – Rho family of GTPases

Question 22

Cascade

Answer 22

Hormone 
Receptor 
Gaq - ABY
PLC/ DAG
IP3
PIP2
CA2+ - ER
PKC - MAPK - GnRH gene expression