Unit 4 Flashcards
What is genetic sex?
- x/y chromosome complement
- x chromosome inactivation and escape
- sry gene
- epigenetics
Which partner determines sex?
fathers in humans
How many genes does the x chromosome have?
500
How many genes does the y chromosome have?
50 genes
What are the female chromosomes ?
XX
What are the male chromosomes ?
XY
What is gonadal sex?
- internal reproductive systems (testes and ovary formation)
- consequences of testicular testosterone surge and aromatization in early life, puberty and adult hormone cycles
What is gonadal sex directed by?
- early hormone exposure
What is the SRY?
- sex determining region
- encodes testes determination factor (TDF) on y-chromosome
What does the SRY do?
- causes embryonic undifferential tissue to develop into testes instead of ovary
What do embryonic testes secrete?
- testosterone and MIH
What can testosterone do?
- can bind to endocrine receptors or can be metabolized into estrogen
What is MIH?
- mullerian-inhibiting hormone
- causes regression of mullerian ducts
Are humans female by default?
- no, instead of SRY females have other inhibitory hormones maintaining the ovary
- there is active repression of transdifferentiating genes
Can gonadal sex and genetic sex be disassociated?
yes
What is phenotypic sex?
- external genitals
- secondary sex characteristics,
- behavior and neuron properties
What is gender identity?
individuals perception of their sex
What mediates the effects of biological sex?
- neural and gonads
- these influences can permanently sexually differentiate neurons or induce temporary, sex-specific changes
- environment can also change
Where do sex steroid hormones come from?
- synthesized from cholesterol
- can be produced by gonads under the direction of HPG- axis or locally synthesized neurosteroids in brain
- fatty structure allows for action at nuclear receptors or membrane receptors
- concentrations may vary based on brain region
What hormone is the most abundent in males?
testosterone
When do the testes release androgens?
- early development and adulthood
Are testosterone levels constant?
vary over the course of a day
How is T converted into estradiol?
- conversion happens in the brain by aromatase
When do ovaries release estrogen?
starting at puberty
What hormones are most prominent in females?
- estradiol and progesterone
Are estradiol and progesterone levels constant?
- no, vary based on cycle
- menstrual cycle is around 25 days
- estral cycle (rodents) is around 4 days
What can estradiol do?
- can act on multiple extranuclear receptor types to change neuron function
- effect depends on what receptor and where
- localization of receptors allows for a localized effect of steroid hormones
Is the neruoendocrine environment the same for all people?
no dynamic and varies by sex
What are the direct/ acute effects of sex steroid hormones?
- alter membrane excitability, sensitivity to NT, NT Release, especially in the presynaptic terminal
- modulate functions of enzymes, channels, NT receptors
What are the indirect/ long term effects of sex steroid hormones
- promote or inhibit gene transcription through action of cytoplasm
What is organizational hormone action?
- permanent, irreversible
- happens in specific developmental pyramids like early in life
- hormone binds, causes change, leaves, change stays
Where does organizational hormone action occur?
- brain and reproductive organ development
What is activational hormone action?
- temporary
- usually associated with adulthood, but can occur in any developmental pyramid
- hormone leave and change goes away
Where does activational hormone action occur?
- estrous and other mammalian sexual cycles
What happens if estradiol is metabolized?
it can be masculinized
What is the organizational / activational hypothesis posits?
- early hormone exposure organizes neural substrates subserving behaviors and later exposure activates the sexually differentiated the neural substances
Where is testosterone converted into estradiol by aromatase
cytoplasm
Do female gonads produce estrogen durin the early stages of deveopment?
no
What triggers the masculinization of the nervous system?
estradiol binding to estrogen
What can testosterone do?
- bind to androgen receptors to masculinize
- be converted to estradiol by aromatase
How can masculinization occur?
- through androgen receptors alone
- through estrogen receptors alone
- both
- which one is highly specified
- animal study: newborn female rats are treated with estrogen develop masculine behaviors and brain morpholgy as adults
What is neural sex differentiation dependant on?
- genetics
- epigenetics (environment)
- hormone exposure
- hard to generalize between neuron types
What are activational effects of basic hormone action?
- naturally occurring fluctuation in dendritic spine density on adult hippocampal pyramidal neurons
Where is the site of excitatory synapse formation on dendrites that have spines?
the dendritic spines
What happens in adult female rats with changes is estradiol and progesterone levels over the estrous cycle?
- the number of dendritic spines fluctuates
- increase in the hippocampal spine number coincides with female rat peak fertility
What are sex dimorphisms?
-clearly defined unconditional physical or behavioral differences between male and female individuals of the same species
What is an example of a sex dimorphism?
- lion’s mane or spinal nucleus of the bulbocaernosus (SNB)
What is the SNB?
- a neural sex dimorphism in rats
- SNB neurons innervate bulbovacernosus (BC) muscles at the base of the penis
- during early life more SNB neurons die in femaes than males
What is onuf’s nucleus?
- neural sex dimorphism in humans that is analogous to the SNB in rats
- located in sacral spinal cord
- innervate BC mucles surrounding the vagina and the base of the penis
- male is bigger because males have more motor neurons there
What are latent sex dimorphism mechanisms of E2-induced synaptic potentiation in the hippocampus?
- in females the presynaptic releases beta and post releases alpha
- in males the postsynaptic releases beta and the pre releases alpha
What is a latent sex dimorphism?
- one aspect of a trait is the same for females and males, but the mechanisms underlying the trait are different
- just the effect is the same
What is a sex difference?
- physical or behavioral difference between male and female individuals of the same species that vary along a continuum, data overlaps
What are examples of sex differences?
- height, differences in cognition
- ESPC frequency rat nucleus acumens core
- connectome
- dendritic spine density in hippocampal neuron
- a lot of unknown because not widely studied
- drug abuse
What are the sex differences in the connectome?
- males have greater ipsilateral connectivity and females have greater contralateral connectivity
- males and females differ in brain connectivity as a whole
- 100% of documented differences in neuroanatomy
What are some sex differences in drug abuse?
- higher rates of drug abuse in men, but sex differences in experiences and progression of addiction
- female rats acquire self- administration ore rapidly than males (willing to do a task for the drug more)
- discrete trial
- progressive ratio schedule
What is the discrete trial procedure for sex differences in drug abuse?
- rats have access to drug at certain periods of the day
- female rats exhibit extended binging and increased drug intake
What is the progressive ratio schedule for sex differences in drug abuse?
- progressive increase in responses required for drug infusion
- intact female rats reach higher final ratios than males
Where do sex differences occur?
- gentic, molecular, anatomical/physiological level
- occur in every organ measured so far
What two organs differ the most in terms of gene-expression between males and females?
- liver and brain
What is the problem with sex differences in trials?
- sex is widely undrported, we need more trials to record sex
- we need more trials to include both males and females (trials are going back to strictly male
What can sex differences at the neural level do?
- increase or decrease sex differences in observed behavior
What does the hypothalamus do?
-regulates all basic physiological needs
- maintains homeostasos
How does the hypothalalmus maintain homeostasis?
- gets info from internal sensors and nucleus of solitary tract (autonomic)
- compares info with set biological points
- integrates somatic behavioral info with autonomic visceral and endocrine responses
-makes adjustments where needed
How does the hypothalamus make adjustments to maintain homeostasis?
- behavior responses (somatic)
- ANS responses (visceral)
- endocrine responses (hormonal)
What are the parts of the hypothalamus?
- dorsal striatum
-NA - hypothalamic nucleus
- many more
What does the dorsal striatum control?
motor control
What does the NA control?
- reward and motivation
What does the hypothalamus control neuroendocrinally?
-feeding and reproduction
What is the hypothalamic nuclei?
- can be sexually dimorphic
-ex. SDN preoptic area controls male copopulatory info
How is the pituitary gland divided?
- anterior and posteriorly
What origin does the anterior pituitary have?
- non-neural origin
What origin does the posterior pituitary have?
neural origin
What are the two groups of neurosecretory neurons?
- magnocellular
- parvocellular