(E1, L4) Sex Determination and Differentiation Pt. 2

Question 1

What are the types of sex differences within the rodent brain?

Answer 1

The size of a brain region (# of neurons or volume of brain area)
- The Sexually Dimorphic Nucleus of the Preoptic Area (SDN-POA) (integral for male sexual behavior)
- Anterventral Periventricular Nucleus (AVPV) (larger in females than in males)
Synaptic Connections
- preoptic area: M > F
- Arcuate Nucleus: M < F
- Ventromedial Nucleus of the Hypothalamus: M > F

Question 2

What is the size of the SDN-POA dependent upon?

Answer 2

If T is introduced to either a male or a female within the critical period, the SDN-POA will become larger because of their masculinized brains

Question 3

Can we tell exactly what hormone is present in making the SDN-POA larger? How could we determine which hormones is present?

Answer 3

No, bc T can form into estradiol or DHT bc the enzymes are already there
- try: give estradiol to see if results in larger SDN-POA
- try: block aromatase–> blocks T from becoming other things and would tell us if it is only T actin on SDN-POA

Question 4

Describe Turner’s Syndrome

Answer 4

-XO (single chromosome present)
- A feminine body develops with abnormal ovaries (no steroid production)
- not fertile –> no eggs
- Estrogen treatment induces breast growth and a female-typical puberty
- cardiovascular system affected
- ovaries don’t “turn on”, no periods, need hormonal therapy
- usually shorter in stature

Question 5

Describe Klinefelter’s Syndrome

Answer 5

• XXY (additional chromosome)
• Masculine body develops –> SRY gene = testes
• Testes and penis are abnormally small
• Low T production–> not enough to sustain positive feedback needed to develop internal sex organs
• Infertile due to little to no sperm production
• 1/1,000 births

Question 6

Describe Androgen Insensitivity Syndrome (AIS)

Answer 6

-XY genotype
- Defective androgen receptor on X chromosome, so they don’t respond to androgen
- Develop testes due to the presence of the SRY gene in the Y chromosome
- AMH present: not an androgen so works to repress Mullerian system
- T present but wont work (DHT and E)
- Estradiol is produced and works because it is an estorgen
-DHT does not work
- looks female, but is internally neither male or female

Question 7

Describe Congenital Adrenal Hyperplasia (CAH)

Answer 7

• occurs in both XX and XY genotype but more pronounced in XX
• Lack enzyme that produces cortisol, results in an increased amount of androgens from adrenal gland
• Bodies are partially masculinized because of exposure to increased DHT
• Exogenous cortisol is given to halt excess androgen production at birth
• Affects HPA axis because no negative feedback from cortisol so pituitary gland can’t tell hypothalamus to stop
• Mullerian system, but lots of T means smaller male parts