Neuroscience Unit 2

UNH Neuroscience 503 with Elizabeth Caldwell

Green porno- praying mantis mating

praying mantis mating behavior is for the male to expect to die when they have penetrated the female, as the female will turn her head around and bite its head off, usually the male does not survive- even less if they try to fight her off.

Green porno- whale mating

whale mating behavior is for the female to turn upside down, waiting for the males to fight over her, whichever male is successful in the fight will be successful in mating with her as she will turn over and allow them near her

Green porno- limpet

limpet mating behavior-sequential hermaphrodites, for a sexless limpet to attach to a rock to protect its flesh, turning into a female, other sexless limpets will attach onto her, multiple at a time even, and turn male as they attach, once a female has been mated, she will die and the next limpet will turn into the female

Green porno- barnacle

barnacle mating behavior- also hermaphrodite and capable of self-fertilization, is for a barnacle to extend its penis to reach inside a far away female barnacle, larvae barnacle climb up the females and drop themselves inside to generate into a mature barnacle- fertilizing as they mature

sexual dimorphism

physical difference between males and females of the same species

Gametogenesis

process by which the body creates gametes (sperm and eggs (ova))

Meiosis

type of cell division that divides the number of chromosomes by half

Male chromosomes

males have an X and Y chromosome- through meiosis they produce two types of sperm; 50% carry an X and 50% carry a Y

Female chromosomes

females have two X chromosomes- through meiosis they can only produce eggs that carry an X chromosome

What is the determining factor of a sexually developed zygote

the sperm

Can both eggs and sperm carry a Y or X chromosome?

No, eggs only carry an X chromosome and sperm can carry either X for Y chromosome, making it the determining factor of a sexually developed zygote

bipotential gonad primordia

the potential for the primordial gonads to become either female or male

internal reproductive tract

early embryos have two tracts inside them- mullerian (uterus and fallopian tubes) and wolffian (vs deferens, seminal vesicles)

what hormone dissolves female ducts to create male ducts

AMH- anti mullerian hormone

female primordial external genitalia

develop into clitoris, labia and outer vagina

what hormone helps the male ducts and external genitalia form

androgen (testosterone)

male primordial external genitalia

develop into penis and scrotum

when does primordial external genitalia differentiate

3rd month of 12 weeks

what are the primary sex characteristics

gonads, internal sex organs, genitalia

What are gonads

testes or ovaries

What are internal sex organs

uterus/ fallopian tubes or vas deferens/ seminal vesicles

what are genitalia

clitoris/vagina or penis/ scrotum

What are parts of the hormonal chain reaction

hypothalamus releases GnRH, GnRH travels to pituitary gland, pituitary gland release gonadotropic hormones (FSH, LH) to reach the gonads, gonads release sex hormone (ovaries- estradiol, testes- testosterone)

What hormone does the hypothalamus release

gonadotropin-releasing hormone

What hormone does the pituitary gland release

gonadotropins

what hormone do the gonads release

ovaires- estradiol, testes- testosterone

What is the end goal of the hormonal chain reaction

sexual maturation

What are secondary sex characteristics

pubic, facial and armpit hair, breast enlargement and hip widening

What is the medial pre optic area

a region at the front of the hypothalamus

what activity is the MPA critical for

elicits male sexual behavior

What activates the MPA

sexual activity

what protein product is increased with MPA activation

Fos

Where is the SDN (sexually dimorphic nucleus) located

the pre optic area

what is the SDN

sexually dimorphic nucleus- a cluster of neurons in the hypothalamus that regulates sexual behavior and gonadotropin release

What one thing is 7x larger in males than in females

sexually dimorphic nucleus

What factor modulates masculinization

maternal care

what were the outcomes in the studies with ewes vs rams

female oriented rams have the largest SDN and more neurons, male oriented rams have half the volume of SDN and neurons as female oriented, and ewes have the smallest volume of SDN and neurons

female sexual behavior circuit

input from genitals, olfactory and vomeronasal into medial amygdala, to ventromedial nucleus of hypothalamus, to PAG of midbrain, to nPGI of medulla,

What primary response and reflex is mediated by the VMH

female sexual behavior, lordosis reflex (pregnancy reflex)

What hormones activate the VMH neurons

estradiol and progesterone

What protein increases when females mate

Fos

Which areas contain estrogen and progesterone receptors

ventromedial nucleus of hypothalamus, medial amygdala, PAG of midbrain

What area when lesioned abolishes sexual behavior in females

ventromedial nucleus of hypothalamus

male sexual behavior circuit

input from central tegmental field, olfactory and vomeronasal into medial amygdala, to medial preoptic area, to PAG and nPGI of medulla

What area when lesioned abolishes sexual behavior in males

medial preoptic area

What area when lesioned disrupts sexual behavior in males

medial amygdala

What's the difference in male and female circuit pathways

Female- hormones turn on circuit to facilitate lordosis, male- MPA turns off inhibitory centers to release sexual reflexes

What are the phases of menstruation

menstruation, proliferative (follicular), ovulation, secretory (luteal)

What happens during menstruation

Low estrogen and progesterone, FSH begins to rise, uterine lining sheds, low hormones signal pituitary to start a new cycle

What happens during proliferative (follicular)

FSH rise stimulates follicle growth, estradiol rises as dominant follicle matures, estradiol rise prepares for ovulation, endometrium rebuilds, estradiol rise triggers LH surge

what happens during ovulation

LH surge, small rise in FSH, estradiol peaks, progesterone prepares to rise, an egg is released, basal temperature rises .5 celsius after ovulation

what happens during secretory (luteal)

progesterone peaks, estradiol prepares to fall, LH and FSH drop, follicle becomes temporary corpus luteum, endometrium thickens and secretes fluid nutrients, temperature stays elevated

What does the corpus luteum do

temporary hormone producing endocrine structure formed from the follicle, produces estradiol and progesterone

what happens after secretory (luteal) if there is no pregnancy

corpus luteum dissolves, progesterone and estradiol drop, lining breaks down, menstruation restarts

Menstruation=

low hormones, lining sheds

Proliferative (follicular)=

FSH and estradiol rise, follicle grows, lining rebuilds

Ovulation =

LH peak, egg (ovum) release, temperature rise

Secretory (luteal)=

progesterone peak, corpus luteum forms from follicle (luteinization), lining thickens and secretes

what happens after secretory (luteal) if there is a pregnancy

Ovum → zygote → blastocyst which implants, corpus luteum continues producing and doesn’t dissolve, uterine lining remains

Which hormone maintains uterine lining

progesterone, estradiol supports

Which brain structure releases FSH and LH

anterior pituitary

What is GnRH and what does it do

gonadotropin releasing hormone, stimulates the pituitary

what is FSH and what does it do

follicle stimulating hormone, stimulates follicle growth and dominant follicle

what is LH and what does it do

luteinizing hormone, causes follicle to rupture and release ovum, turns follicle remnants in corpus luteum