Sexual behaviour Flashcards
a full sexual response cycle
arousal
plateau
orgasm
resolution
neural control of sexual behaviour
cerebral cortex- is where the erotic thoughts occur
and the spinal cord coordinates this brain acitivity with sensory information from the genitals and garnets the critical outputs that mediate the sexual response of the genitals
the best evidence that engorgement can be generated by a simple reflex
is that most men who suffer from a complete transection of the spinal cord at the thoracic or lumbar level can nonetheless have erections when mechanically stimulated
the mechanosensory pathways from the genitals to the somatosensory system
axons from mechanoreceptors in the penis and clitoris collect in the dorsal roots of the sacral spinal cord
they then send branches into the dorsal horns of the cord
and into the dorsal columns through which project towards the brain
engorgement and erection controlled primarily by axons of the
parasympathetic branch of ANS
within the sacral spinal cord the parasymptathic neurones can be excited by either….
mechanosensory activity from the genitals (which directly cause reflexive erection)
or by axons descending from the brain (which account for responses mediated by more cerebral stimuli)
parasympathetic nerve endings release
combo of ACh and vasoactive intestinal polypeptide (VIP) and nitric oxide (NO) directly into erectile tissue
causing a relaxation of smooth muscle in the arteries and the spongy substance of the clitoris and penis
the arteries become filled with blood
viagra
enhancing the effect of NO (nitric oxide)
secretion of lubricating fluids
from the vaginal walls and from man’s bulbourethral gland
what triggers the process of emission
the sympathetic efferent axons
process of emission in male
muscular contraction move sperm from storage sites near testes through two tubes (vas deferens) combine the pserm with fluids from various glands and propel the mixture (semen) into urethra
polygyny
most common among mammals
1 male, many females
but female only mates with that 1 male
‘many women’
harem (type of polygyny)
1 male mates with a set of females
gorillas elaphant seals
polyandry
‘many men’
one female, many males
rare
but in phalarope, a shorebird that breed in cold tundra
polygamy
more than one spouse
vole species and hormones
praire -monogamous
meadow- polygynous
oxytocin and vasopressin
bulbocavernosus
collection of spinal motor neurones at base of penis
and surrounds opening of vagine in women
penile erection
urine ejection
constricts vagina tightly
onuf’s nuleas is the motor neurone pool that controls the BC muscles (located in the sacral spinal cord)
sexual dimorphism of the BC
bigger in men than women
more neurons in Onuf’s nucleus in males because their BC is larger than females
the most distinct sexual dimorphism in mammals is
3rd ventricle within the pre optic area of the anterior hypothalamus
role in reproductive behaviour
lesions in rats leads to disruption of oestrus cycle in females and copulation rate in males
‘sexually dimorphic nucleus’ (of pre optic area of hypothalamus(
5-8x larger in males than females
treating females with testosterone ealrly in development
means they fail to elicit the typical female mating posture: lordosis
when a cow carries twin calves that include both male and female
the female calf is exposed in utero to some testosterone produced by her male twin
as an adult she’s know as a ‘free martin’
will invariably behave like a bull and be infertile
androgen insensitivty (genetic males)
genetic males carrying a defective androgen receptor gene on their X chromosome
they thus have only one copy of it
males with this defective gene cannot respond to androgen
they develop normal testes and produce ample testosterone but they are outwardly female
they have a vagina a clitoris and do not menstruate
and remain infertile
androgen insensitive genentic males look and behave like they are genetically female
congenital adrenal hyperplasia CAH (genetic females)
literally means overgrown adrenal glands present at birth
their adrenal glands over produce androgens
although genetically female, being exposed to abnormally high levels of circulating androgens early intheir development
they have normal ovaries and no testes at birth
but they develop external genitalia that are half way between penis and clitoris
treatment: surgically remove the penis structure
often described as aggressive/boyish
