Chapter 4 Flashcards
(18 cards)
What are the mechanisms through which hormones can influence brain development?
Mechanisms
- Neuronal Survival→ can promote or protect against cell death
- Neural connectivity→ influence dendritic branching, axonal projections and synapse formation
- Receptor distribution→ alter numbers and distributions of receptors
- Neurochemistry→ change neurotransmitters levels and synaptic activity
What are volumetric differences in the brain?
Sizes difference in brain regions, with some larger in males and some in females.
For example, males have a larger medial amygdala, BNST, and SDN-POA, while females have a larger AVPV.
SEE TABLE
What are connective differences in the brain?
Differences in the type or number of synapses or size of neuronal projections that influence communication between brain regions.
Males have more synapses on dendritic shafts, while females have more on dendritic spines.
True or False: The medial preoptic area (MPOA) shows sexual dimorphism.
True.
The MPOA has been observed to have differences in synapse distribution between males and females.
SEE TABLE
What is the significance of the sexually dimorphic nucleus of the preoptic area (SDN-POA)?
It is larger in males due to early testosterone exposure and lesions lead to female-typical sexual behavior.
This suggests a role in inhibiting female sexual behavior in males.
Which brain regions are noted for sexual dimorphism in males?
- Medial Amygdala (20% larger)
- BNST (20)
- SDN-POA
Which brain region is larger in females and why?
AVPV (Anteroventral Periventricular Nucleus) for ovulation
The AVPV plays a role in regulating reproductive functions.
What is the role of testosterone on the SDN-POA and AVPV?
testosterone prevents cell death (apoptosis) in SDN-POA but promotes apoptosis in AVPV
Fill in the blank: The SCN is associated with _______.
[circadian rhythm]
The SCN influences menstrual cycles in females.
What are sex steroid receptors and where are they concentrated?
Receptors for progesterone, estrogen and androgen, highly concentrated in the hypothalamus and limbic system
These receptors play a crucial role in sexual behavior and brain function.
What is the difference in androgen receptor expression between males and females?
Males–> higher androgen receptor binding and mRNA expression in specific brain regions
Females→ higher estrogen and progesterone receptor and mRNA expression
Regions include the medial amygdala, BNST, preoptic periventricular nucleus, ventromedial nucleus of hypothalamus-> males
Preoptic periventricular nucleus, MPON, Ventromedial nucleus-> females
Which neurotransmitter system shows sex differences, particularly in the AVPV?
Dopamine system
Females have more dopamine-containing neurons, and testosterone/estrogen reduces neuron counts in males.
What is the role of kisspeptin in the AVPV?
Regulates GnRH secretion and mediates estrogen-induced LH.
Females have x10 more kisspeptin than males.
What effect does vasopressin have in males compared to females?
Vasopressin inhibits lordosis in female rats.Males have 2-3x more neurons in BNST and medial amygdala, regulating male sexual behavior and aggression and inhibit lordosis in female rats
What does arginine vasotocin (AVT) do in bullfrogs?
- AVT increases vocalization in males
- AVT increases female phototaxis (movement towards call)
—>reproductively relevant behaviours
What is the impact of testosterone on aromatase activity?
Testosterone maintains aromatase activity in specific brain areas and is a prohormone for estradiol or DHT.
High aromatase activity is found in males, particularly in BNST and medial preoptic nucleus.
How does epigenetic regulation influence brain sexual differentiation?
DNA methylation and histone modifications show sex differences, with early-life hormone exposure impacting receptor methylation.
Males exhibit higher ERα promoter methylation than females.
Fill in the blank: Neonatal testosterone exposure _______ methylation patterns.
[masculinizes]
This affects gene expression related to sex-specific behavior.
