Sexual behaviour

Question 1

What is the enzyme aromatase required for?

Answer 1

• The biosynthesis of oestrogens from testoterone

Question 2

What changes occur to mammals during the reproductive cycle?

Answer 2

• Inititation of sexual encounters increases prior to ovulation
• Areas of flesh exposed by women change throughout cycle
• Some species, sexual attractiveness changes
• Synaptic denstiy in the hippocampus changed in relation to levels of oestrogen
• Synapses more sensitive to excitatory synaptic inout for the labatory

Question 3

What happens when a cow has a male and a female twin?

Answer 3

• The female is a freemartin
• Behaves like a bull
• Due to being exposed to testosterone in the uterus
• Ovaries don’t develop properly - sterile

Question 4

What controls the bulbocavernousus muscle?

Answer 4

Motor neurons which lie in the Onuf’s nucleus in the sacral spinal cord

Question 5

What is different about male and female brains?

Answer 5

• Show sexual dimorphism (structural differences)
• Male brains are larger
• The sexually dimorphic nucleus (SDN) in the pre-optic area of the hypothalamus is larger in males
• Differences in testosterone receptors and aromatase activvity

Question 6

Describe human sexual arousal processes between the brain and the body.

Answer 6

• Brain feeds into physiologyical effects
• Peripheral arousal system
• Controlled by spinal reflexes and stimulated by thought or touch
• Strong link between brain and body

Question 7

Why is sexual reproduction confusing?

Answer 7

• Can mistake signals

Question 8

What are the 3 main sex steroids?

Answer 8

• Progesterone
• Testoterone
• Estodiol

Both males and females have all sex steroids but in different proportions

Question 9

What is congenital adrenal hyperplasia?

Answer 9

• In females
• Adrenal gland secretes high levels of an androgen in early life
• Ovaries present but external genitalia are indistinct (intermediate between clitoris and penis)
• CAH women often agressive and ‘male-like’
• Possible due to masculinisation of the brain that would normally occur in boys

Question 10

Why is sexual reproduction expensive?

Answer 10

• High metabolic cost of pregnancy
• Need to raise young so they can look after themselves
• Even unsuccessful reproductive cycles use up huge amounts of energy and effort

Question 11

What happens if aromatisation of testosterone to estrodiol is blocked?

Answer 11

Causes a build-up of testosterone

Question 12

What is polyandry?

Answer 12

• One female mate with many males
• BUT, each male mates with just that female
• Rare in mammals
• Occurs in finches (determine quality of sperm and reject lesser)

Question 13

What is the critical point of development in which exposure to different sex hormones can cause an effect on the organism in later life?

Answer 13

Shortly after birth, during development

Question 14

What happens when treat female rats with testosterone at birth?

Answer 14

• Prevents lordosis (arching of the back downwards prior to mating) in adulthood

Question 15

What is estrogen?

Answer 15

An estrodiol (female hormone)

Question 16

What is the structure of the main sex hormones?

Answer 16

Steroids, based on cholesterol

Question 17

What is the bulbocavernousus muscle?

Answer 17

• Superficial muscle of the perineurium
• In males, it covers the bulb of the penis
• In females, it covers the vestibular bulb

Question 18

At what point do women perform better in spatial reasoning tests?

Answer 18

When oestrogen is lowest

Question 19

What is polygyny?

Answer 19

• One male mates with many females
• BUT each female mates with only that male
• Many mammalian species (female invests more into young)

Question 20

What is testosterone and what can it do?

Answer 20

An androgen (male hormone)

• Linked to agression
• Varies at different times of day
• Can form estrodiol via aromatisation

Question 21

Why are there more neurons in the Onuf’s nucleus in males?

Answer 21

• The bulbocavernousus is larger in males

Question 22

What is monogmay?

Answer 22

• One male and female form an EXCLUSIVE relationship

- Eg. swans mate for life (they must see dead body of mate to mate with a different swan)

Question 23

What is the EPOR model?

Answer 23

Model of human sexual response/excitement:

• Excitement
• Plateau
• Orgasm
• Resolution

Question 24

Why is sexual reproduction complicated?

Answer 24

• Behavioural rituals, signals and sequences

- Leads to predation if incorrect

Question 25

What do secondary sex characteristics depend upon?

Answer 25

- Sex hormones | - However sometimes effects of sex hormones don't match genetic sex

Question 26

Why is sexual reproduction dangerous?

Answer 26

- Can lead to predation | - Risk of pregnancy - infection, illness, death