topic 2 - neural and hormonal control of sexual behaviour

Question 1

two components of sexual behaviour

Answer 1

appetitive behaviour - behaviour aimed at finding and obtaining a sexual partner
consummatory behaviour - behaviour of the actual sexual act

Question 2

role of pheromones

Answer 2

• putative role
• external stimuli for sexual interest
• definition = species-typical molecules that trigger a specific response in another animal of the same species
• in mammals = detected by vomeronasal organ
• debated whether humans’ is functional
• olfactory epithelium can detect some pheromones in humans
• Women’s t-shirts smell sexier during fertile phase of menstrual cycle
  -Androstadienone (in male sweat) triggers alertness, good mood and sexual arousal in women (but poor mood in men)
  -Estratetraene activates male, but not female hypothalamic areas

Question 3

role of sex hormones

Answer 3

• internal motivation for sexual interest
• in males = suppression of testosterone reduces sexual interest, anticipations of sexual encounter increases testosterone, no correlation for individual diffs
• in females = sexual interest fluctuates with cycling ovarian hormones, androgens increase effect of oestradiol x3, increase in testosterone as well in females with anticipation

Question 4

how is testosterone involved in females anticipation of sexual activity?

Answer 4

• study measured testosterone in saliva leading up to long distance partner visiting - anticipation of sex
• large spike day before visiting partners
• lowered after visiting

Question 5

what are the four stages of arousal?

Answer 5

excitement, plateau, orgasm, resolution

Question 6

how is the parasympathetic nervous system involved in excitement?

Answer 6

the parasympathetic nervous system stimulates relaxation of smooth muscle in blood vessels. This allows more blood to enter the genitals causing penile/clitoral erection (tumescence), engorgement of the labia and vaginal lubrication. smooth muscle relaxation involves signally by Nitric Oxide which increases the levels of cyclic GMP. Viagra inhibits the breakdown of cGMP by phosphodiesterase 5 meaning the smooth muscle remains relaxed

Question 7

the sympathetic nervous system and orgasms

Answer 7

• when the sympathetic nervous system is stimulated along with pulsatile release of oxytocin = series of smooth muscle contraction in pelvic floor
• requires disinhibition of central nervous system
• nucleus paragigantocellularis (nPGi) in medulla inhibits orgasm circuitry in lumbar spinal cord - through serotonin
• during intercourse, the hypothalamus inhibits the peri-aqueductal gray (PAG) which is what normally stimulates the nPGi

Question 8

resolution

Answer 8

• active inhibition of sexual motivation
• during orgasm = blood oxytocin levels peak, prolactin is released
• oxytocin involved in pair bonding
• high prolactin levels suppress sexual motivation