Sexual behaviour Flashcards
What is the enzyme aromatase required for?
- The biosynthesis of oestrogens from testoterone
What changes occur to mammals during the reproductive cycle?
- 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
What happens when a cow has a male and a female twin?
- The female is a freemartin
- Behaves like a bull
- Due to being exposed to testosterone in the uterus
- Ovaries don’t develop properly - sterile
What controls the bulbocavernousus muscle?
Motor neurons which lie in the Onuf’s nucleus in the sacral spinal cord
What is different about male and female brains?
- 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
Describe human sexual arousal processes between the brain and the body.
- Brain feeds into physiologyical effects
- Peripheral arousal system
- Controlled by spinal reflexes and stimulated by thought or touch
- Strong link between brain and body
Why is sexual reproduction confusing?
- Can mistake signals
What are the 3 main sex steroids?
- Progesterone
- Testoterone
- Estodiol
Both males and females have all sex steroids but in different proportions
What is congenital adrenal hyperplasia?
- 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
Why is sexual reproduction expensive?
- 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
What happens if aromatisation of testosterone to estrodiol is blocked?
Causes a build-up of testosterone
What is polyandry?
- 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)
What is the critical point of development in which exposure to different sex hormones can cause an effect on the organism in later life?
Shortly after birth, during development
What happens when treat female rats with testosterone at birth?
- Prevents lordosis (arching of the back downwards prior to mating) in adulthood
What is estrogen?
An estrodiol (female hormone)
What is the structure of the main sex hormones?
Steroids, based on cholesterol
What is the bulbocavernousus muscle?
- Superficial muscle of the perineurium
- In males, it covers the bulb of the penis
- In females, it covers the vestibular bulb
At what point do women perform better in spatial reasoning tests?
When oestrogen is lowest
What is polygyny?
- One male mates with many females
- BUT each female mates with only that male
- Many mammalian species (female invests more into young)
What is testosterone and what can it do?
An androgen (male hormone)
- Linked to agression
- Varies at different times of day
- Can form estrodiol via aromatisation
Why are there more neurons in the Onuf’s nucleus in males?
- The bulbocavernousus is larger in males
What is monogmay?
- 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)
What is the EPOR model?
Model of human sexual response/excitement:
- Excitement
- Plateau
- Orgasm
- Resolution
Why is sexual reproduction complicated?
- Behavioural rituals, signals and sequences
- Leads to predation if incorrect
What do secondary sex characteristics depend upon?
- Sex hormones
- However sometimes effects of sex hormones don’t match genetic sex
Why is sexual reproduction dangerous?
- Can lead to predation
- Risk of pregnancy - infection, illness, death
