Lecture 24- Sex and sexuality

Question 1

How is sex genetically determined?

Answer 1

• XX= females -XY= male

Question 2

What gene on the Y chromosome determines male development?

Answer 2

-there are few genes on the Y chromosome -SRY gene determines this -SRY leads to development of testosterone secreting cells in early development

Question 3

What does absence of SRY result in?

Answer 3

-female phenotype (this is the default phenotype)

Question 4

What are the sex hormones (3)?

Answer 4

1. Testosterone= (androgen) male sex hormone 2. Estradiol (estrogen)=female sex hormone 3. Progesterone (other main female sex hormone)

Question 5

What is the pathway by which sex hormones are made?

Answer 5

-

Question 6

What is really important for sex hormone production?

Answer 6

-presence of cholesterol

Question 7

What does aromatose do?

Answer 7

-converts testosterone to estradiol (estrogen)

Question 8

What is 5-alpha dihydrotestosterone?

Answer 8

-converted by 5-alpha reductase from testosterone -stronger type of the androgen

Question 9

When do sex steroids appear in males?

Answer 9

-In males, circulating testosterone seen early in foetal development – Falls to very low levels after birth – Rises again at puberty

Question 10

When do sex steroids appear in females?

Answer 10

-In females, circulating estrogen and progesterone appear at or around puberty – Fall to very low levels at menopause – Testosterone synthesized in adrenal cortex- present throughout life

Question 11

What does testosterone do in females after menopause?

Answer 11

as the other hormones in females disappear from 45-55 -then testpsterone takes up the function of the steroid hormones tp keep the whole system functioning

Question 12

What is the difference between males and females in presence/absence of sex steroids in utero?

Answer 12

males have testosterone and some and progesterone circulating

Question 13

When is testosterone the highest in males?

Answer 13

-higheset at 20 and falls to a third by 75

Question 14

What are the sites of estrogen action in a rat brain?

Answer 14

–At synapses, membrane action –In cell bodies, DNA transcription, estrogen receptors (ER)

Question 15

What are the effects estrogen in the brain?

Answer 15

-alter neurotransmitter synthesis, releaser and re-uptake -alter membrane permeability -promotes or inhibits transcription (protein synthesis)

Question 16

How is PMS mood explained?

Answer 16

-estrogen and progesterone and testosterone can act on cell membrane directly= this is likely to account for the mood of PMS!!!! -alter the action of GABA receptors

Question 17

What are the brain areas with estrogen receptors?

Answer 17

-Most regions with ER involved in sexual behaviour or regulation of steroid production

Question 18

Are the androgen and progesterone receptors found in overlapping but distinct regions?

Answer 18

-yes -similar subcellular sites of action

Question 19

How does hypothalamus come into sex steroids?

Answer 19

-sets their levels by feedback •Hypothalamus acts to cause release of hormones (FSH, LH) from the pituitary that regulate production of estrogen or testosterone •Hormone secretion depends on environment and levels of the relevant sex steroid -at this level the hormones have neural effect as it has feedback!

Question 20

Can sex steroids get through the blood brain barrier?

Answer 20

-yes as they are steroids= lipid soluble

Question 21

What are the gender dimorphisms in humans? (4)

Answer 21

1. Sexual behaviour 2. Pain 3. Cognitive function 4. Maternal behaviour

Question 22

What are the differences in sexual behaviour between the genders?

Answer 22

• – Mating,courtship,bonding,rhythms
• rats=females get into position for sex if injected with testosterone then try to mount instead= must be hormone mediated

Question 23

What is stress-mediated analgesia?

Answer 23

if you stress an animal they feel pain less= males and females have different versions and are different pharmacologically

Question 24

How do females and males differ in cognitive function?

Answer 24

1.Males score better than females on spatial rotation tasks 2.Males score higher, and lower, than females on tests of higher mathematical skills (at low end of mathematical skills= more males than females -females have a tighter grouping around the mean) 3. Females perform better in learning during period after puberty

Question 25

What is the sexually dimorphic nucleus of preoptic area (SDN-POA)?

Answer 25

-differs in male and female rats -larger in males -subthalamic nuclei -function in sexual behaviour and response to mating -humans have a similar thing but at least 4 nuclei

Question 26

If you inject a female rat with testosterone shortly after birth how is the SDN-POA affected?

Answer 26

• converted to male structure by testosterone treatment around birth
• see it is larger in a male but similar if female with testosterone= these females will try to mount
• part of the brain driving the mountaing
• can masculinize the brain by progesterone too as it is then converted by the nucleus to testosterone

Question 27

What is the firing of SDN-POA of a female rat at different stages of mating?

Answer 27

*insertion of penis, ejaculation arrows

Question 28

What is the firing of neurons of SDN-POA in a male monkey when exposed to a receptive female?

Answer 28

-reacts on seeing the female already

Question 29

Does stress reduce reaction to painful stimuli?

Answer 29

-yes

Question 30

How does male and female mediated analgesia differ?

Answer 30

1: Swim in warm water analgesia depends on endogenous opioids -Males more sensitive to antagonists than females 2:• Swim in cold water analgesia depends on NMDA receptors in males, but not in females - Difference disappears if estrogen is removed

Question 31

What are the organizational effects of steroids?

Answer 31

-Occur during development and determine structure -will not change, like the preoptic nuclei thing -happens at a time when no estrogen circulating in females so all detrmined by testosterone or its absence

Question 32

What is androgen insensitivity?

Answer 32

-lack of testosterone receptors or not working – Androgen-insensitivity syndrome leads to genotypic males being phenotypic females

Question 33

What do the individuals with androgen insensitivity look and behave like?

Answer 33

• More feminine than women in several ways –more female behaviour than females as they do not have any testosterone and none of the responses to it even females have -tall, fair hair -some breasts, usually quite attractive -do not get periods usually -organiational effect

Question 34

Are there many effects in brain due to conversion of testosterone to estradiol via aromatase within neurons?

Answer 34

-yes -local conversion as it is in a neuron, within it -organisational effect

Question 35

What are the activational effects of steroids?

Answer 35

• Responses to levels of circulating hormones once development is complete

Question 36

What are examples of activational effects of steroids? (5)

Answer 36

1 .Estradiol increases number of dendritic spines in hippocampus (means more potential synapses in hippocampus at certain times of the month=following menopause women are more vulnerable to dementia due to this (and that they live longer) 2. Premenstrual syndrome 3. Stress mediated analgesia 4. Aggression due to use of anabolic steroids (androgens) 5. Regulation of steroid hormone production

Question 37

What is the social life of prairie and montane voles?

Answer 37

•Prairie voles pair bond, although not strictly monogamous, first mating leads to strong changes in behaviour •Montane voles are polygamous – No pair bonds,love them and leave them

Question 38

How does the social bonding or lack of happen in the voles?

Answer 38

•Difference is in expression of oxytocin receptors in females and in form of vasopressin synthesised in males

–Markedly different between two types of vole

–Oxytocin receptors more dense in reward system of females

–Vasopressin molecule longer in males

• Mating releases vasopressin in males and oxytocin in females
• Blocking vasopressin prevents pairing in prairie vole males
• Giving long vasopressin to an unmated male induces pairing with novel female even when mating does not take place
• Blocking oxytocin prevents pairing in females