(PSY 450) Chapter 4: Sexual Dimorphism
Terms in this set (5)
Young found that androgens given early in life.... (1) [increased/decreased] both female experimental groups to display lordosis in adulthood. (2) [Increased/decreased] female mounting behavior. (3) Had [an/no] effect on masculine behavior patterns in males.
Androgens given early in life:
(1) Decreased the ability of both female experimental groups to display lordosis in adulthood.
(2) Enhanced female mounting behavior.
(3) No effect on masculine behavior patterns in males.
Given the findings in Young's study... what three things can be concluded?
There is a clear distinction between organizational effects and adaptation effects
, such that exposure to sex steroid hormones early in development permanently organizes the neural substrate that is needed for subsequent male or female behaviors. The same hormones activate, modulate, or inhibit behavioral functions in adulthood by acting upon these organized neural structures.
Critical periods of prenatal development exist
which an animal is maximally susceptible to the organizing effects of steroids on neural tissue.
(3) Organization of the neural tissues mediating mating behavior is analogous to the differentiation of the genital tracts. That is, the nervous systems of males are normally masculinized and defeminized during development, whereas the nervous systems of females are normally feminized and demasculinzed
Variation is generally more within the sexes than between them. True/False? Why? How does that affect measurements of sexual dimorphism?
True. Because there is considerable overlap between most male and female behaviors. With a large sample size, any small difference in a given behavior can be statistically significant.
Describe any 2 sexually dimorphic regions in the brain. How are they different in the two sexes? Which sexually dimorphic behaviors has each been linked to? What might be the biological basis of these differences?
Medial Preoptic Area (PMOA):
Linked to learning and memory.
- Females had more synapses on spine of dendrite.
- Males had more synapses on shaft of dendrite.
Antroventral Periventricular nucleus
- Larger in females than in males
How do organizational effects of hormones differ from activational effects? Give examples to support how animal models of sexually dimorphic behaviors have shed light on organizational/activational effects and sensitive periods for hormone effects.
Organizational effects differ from activational effects in that organization affects have to do with permanent effects on tissue differentiation of body and brain whereas activational effects are effects that occur later in life.
EX1: One study found that early androgen (testosterone) exposure in female rodents in combination with later androgen exposure developed male typical behaviors. Where as the other experimental groups (EarlyExposure=YES, LaterExposure=NO) did not display male typical behaviors. This study provided supporting evidence for the organizational/activational hypothesis.
EX2: 2d:4d ratio
Operational effects due to early androgen activity (testosterone)
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