Problem 5 1.4
Sex issues
Neuroendocrine system
• Endocrine glands secrete hormones into the blood- these hormones travel to organs
and cells where they connect to receptors and transfer the message. The response is
slower than in the nervous system, but the effect is prolonged
• Key glands/ organs- hypothalamus, pituitary gland, adrenal gland, testes/ ovaries
(gonads)
Differences between men and women
• Females have XX chromosomes
• Males have XY chromosomes
• Genitals and brain development depends mainly on the levels of testosterone
• Both men and women start with the same anatomy at the early stages of prenatal
development. Both have Mullerian ducts (female internal structure) and wolffian
ducts (male internal structure). They have undifferentiated gonads that become
either testes or ovaries
• The Y chromosome contains a gene called the SRY gene which produces the SRY
protein (sex-determining region on the Y chromosome)
- This gene causes primitive gonads to develop into testes which are sperm
producing organs. Developing testes produce androgens which increase the
growth in testes causing them to produce more androgens (testosterone)
- Androgens cause primitive wolffian ducts to develop into seminal vesicles (store
semen) and vas deferens (duct from testes to penis)
- Testes produce Mullerian inhibiting hormones (MIH) which cause the Mullerian
ducts to degenerate
• Females don’t have the SRY gene so the gonads develop into ovaries and the
wolffian ducts degenerate
- The ovaries don’t produce MIH so the Mullerian ducts develop into oviducts
Organising vs Activating
• Organising effects- produce long lasting structural effects, the most prominent
effects occur during early development before birth and during puberty
• Activating effects- more temporary, hormone increases activity but only while the
hormone is present, can occur at any time in life
• Hormones can also produce a combination of organizing and activating effects
Brain differences
• Hypothalamus
- Anterior hypothalamus- sexually dimorphic nucleus is larger in males- controls
sexual behaviour
- Parts of the female hypothalamus generate a cyclical pattern of hormone
release- menstrual cycle
Gender anomalies
Sex issues
Neuroendocrine system
• Endocrine glands secrete hormones into the blood- these hormones travel to organs
and cells where they connect to receptors and transfer the message. The response is
slower than in the nervous system, but the effect is prolonged
• Key glands/ organs- hypothalamus, pituitary gland, adrenal gland, testes/ ovaries
(gonads)
Differences between men and women
• Females have XX chromosomes
• Males have XY chromosomes
• Genitals and brain development depends mainly on the levels of testosterone
• Both men and women start with the same anatomy at the early stages of prenatal
development. Both have Mullerian ducts (female internal structure) and wolffian
ducts (male internal structure). They have undifferentiated gonads that become
either testes or ovaries
• The Y chromosome contains a gene called the SRY gene which produces the SRY
protein (sex-determining region on the Y chromosome)
- This gene causes primitive gonads to develop into testes which are sperm
producing organs. Developing testes produce androgens which increase the
growth in testes causing them to produce more androgens (testosterone)
- Androgens cause primitive wolffian ducts to develop into seminal vesicles (store
semen) and vas deferens (duct from testes to penis)
- Testes produce Mullerian inhibiting hormones (MIH) which cause the Mullerian
ducts to degenerate
• Females don’t have the SRY gene so the gonads develop into ovaries and the
wolffian ducts degenerate
- The ovaries don’t produce MIH so the Mullerian ducts develop into oviducts
Organising vs Activating
• Organising effects- produce long lasting structural effects, the most prominent
effects occur during early development before birth and during puberty
• Activating effects- more temporary, hormone increases activity but only while the
hormone is present, can occur at any time in life
• Hormones can also produce a combination of organizing and activating effects
Brain differences
• Hypothalamus
- Anterior hypothalamus- sexually dimorphic nucleus is larger in males- controls
sexual behaviour
- Parts of the female hypothalamus generate a cyclical pattern of hormone
release- menstrual cycle
Gender anomalies
