NBB 201 Hormones and Behavior: Sexual Differentiation and Sex Differences

Nature

Biological Inheritance and genetics determine human behavior

Nurture

Society, Culture and social processes determine human behavior

How did Francis Galton view nurture and nature

nature is all that a man brings with himself into world

nurture is every influence from without that affects him after his birth

Why was Francis Galton interested in categorizing types of people?

To prove that human intelligence, talent, and character are traits passed down through heredity.

What was Francis Galton’s goals?

He wanted to increase the birth rate of “good people” and decrease the birth rate of “bad people”

what does eugenics mean

noble in birth

Positive eugenics

increase the birth rate/ population of people who are noble of birth

Negative eugenics

decrease the birth rate/population of people who are unfit

What does eugenics have to do with the nature vs nurture question

Eugenics took one side of the debate to an extreme. Claimed that intelligence, character, criminality are mostly inherited (nature) and those traits were largely shaped environment, education, opportunity, (nurture)

what does eugenics have to do with evolutionary science

Took terms natural selection and survival of the fittest and misapplied it to human societies, Galton wanted to steer human evolution through artificial selection, society believed that unfit people reproduce and weaken the population, so they should intervene through sterilization or encourage the fir to have more children (fitter family fairs)

why is this history relevant to study of science today

eugenics show that science can be shaped by bias, even when it is mainstream and backed by respected institutions, and that scientific claims can have severe real world consequences, from forced sterilization to genocide, new questions arise around gene editing, genetics,

how would these scientists respond to the question of whether a behavior is the result of nature vs nurture

Oyama and West King would argue that behavior is not the result of nature or nurture, it emerges from an ongoing interactions between genes and environment and organism’s own developmental history

Who said organisms inherit developmental systems

oyama

what are the interactants in developmental systems

genome

cell structure

intracellular chemicals

extracellular environment

parental reproductive systems

self-stimulation by organism itself

immediate physical environment

conspecifics and members of other species

climate, food sources, other aspects of the external environment

ontogeny

course of development especially of a single organism

what did eugenics support

conservative and progressive groups were backed by academics and was tied to white supremacist fears

how does the body know to have a 24 hour circadian rhythm

generated by a negative feedback loop

per gene ——→ per mRNA ————→ PER protein ———> PER inhibits its own gene

What are the brain structures in this picture

Key: hypothalamus, pineal glans, optic chiasm, superchiasmatic nucleus

Neurons and hormones integrate with

the physical enviroment

what does negative feedback do

regulates bodily cycles

what are the five chemical communications

intracrine

autocrine

paracrine

endocrine

ectocrine

intracrine

within a cell

autocrine

cell to itself

paracrine

to neighboring cells

endocrine

via bloodstream

ectocrine

between individuals, such as pheromones

neurotransmitter

secreted by: neurons

goes to: other neurons

mode: paracrine

Neurohormone

secreted by: neurons

goes to: bloodstream

mode: endocrine

Hormone

secreted by: endocrine glands

goes to: bloodstream

mode: endocrine

neural signaling is

close and fast

hormonal signaling is

far and slow

There are how many neuron-to-neuron signaling

at least 60

what are dopamine, epinephrine, norepinephrine

neurotransmitters

what is releasing and inhibiting hormones

neurohormones

Describe what is going on in this image

Excitatory

glutamate

Inhibitory

GABA; gamma-Aminobutyric acid

Neuromodulatory (excitatory or inhibitory)

dopamine, serotonin, and norepinephrine

dopamine

a neurotransmitter associated with reward, motor control

serotonin

a neurotransmitter associated with mood, appetite

norepinephrine

a neurotransmitter associated stress response

acetylcholine

attention, muscle contraction

neurotransmitter system

pathway of neurons releasing the same neurotransmitter, systems differ by precursor, main receptor types, and primary function. effects depend on the number and type of receptor

Leung and Farewell summary

the endocrine system is a network of hormones, receptors, carrier molecules, and signaling pathways

hormones act on cells separated from secreting gland, usually via blood, they regulate energy and metabolism, growth, reproduction, and responses to sitmuli

endocrine cell figure

synthesis (golgi) ——→ secretory vesicles———> release across the cell membrane ———> bloodstream—————> hormone receptors on target cells

primary glands

hypothalamus, pineal, pituitary, thyroid/parathyroid, thymus, adrenal, pancreas, ovary, testicle

Secondary endocrine organs

thymus, placenta, heart, stomach, liver, kidney, small intestine, skin, fat cells

hypothalamus

common to all vertebrates and coordinates brain and body via endocrine

hypothalamus regulates

eating and drinking, blood pressure, temperature, sleep wake cycle, emotion, and sexual behavior

hypothalamus is made of

neuronal nuclei that look like normal neurons but act like endocrine glands, since that secrete neurohormones into the blood

hypothalamic neurohormones

CRH, GnRH, TRH, GHRH

Corticotropin-releasing hormone (CRH)

regulates carb, protein, fat metabolism, and water/sodium balance

Gonadotropin - releasing hormone (GnRH)

regulates sexual and reproductive functions, including pregnancy and lactation

Thyrotropin - releasing hormone (TRH)

metabolic cell processes

Growth hormone - releasing hormone (GHRH)

organismal growth

somatostatin

bone and muscle growth (opposite GHRH)

posterior pituitary

contains neurons that produce and secrete peptide hormones

neurons run from hypothalamus to posterior pituitary

what happens at posterior pituitary

neurons release hormones into bloodstream

how does the hypothalamus communicate with the anterior pituitary

through the hypothalamic pituitary portal system, a closed one way blood system

neurons in the hypothalamus make releasing or inhibiting hormones and secrete them into a primary capillary plexus

The hypophyseal portal veins carry them directly to the anterior pituitary, where they stimulate or inhibit the release of the anterior pituitary’s own hormones

Those hormones are secreted into a secondary plexus and then travel into general circulation

what comes from the posterior pituitary

nothing is made there, does not produce any hormones, it is the site where hypothalamic neurohormones are released into the bloodstream (vasopressin AVP, also called anti diuretic hormone (ADH) and oxytocin

How is posterior pituitary different from anterior pituitary

the hypothalamus controls the anterior pituitary through blood (portal system) and tells it what to release, while the posterior pituitary is an extension of the hypothalamus, where hypothalamic neurons release their own hormones directly into the blood.

what are the two hormones posterior pituitary release

vasopressin (AVP) (anti-diuretic ADH)

Oxytocin

Anterior pituitary

neurons in hypothalamus produce releasing or inhibiting hormones

what exclusive bloodstream does hypothalamus to send hormones to anterior pituitary

hypothalamic- pituitary portal system

neurons synapse on primary plexus

closed “one-way” blood system

stimulate or inhibit release of anterior pituitary’s own hormones

secreted into secondary plexus

travel general circulation

what anterior pituitary hormones act on other glands

Andrenocorticotropic hormone (ACTH)

Gonadotropins (LH, FSH)

Thyroid- stimulating hormone (TSH)

Act on target tissues

growth hormone (GH)

prolactin

Hormones levels

secretion, bioactive vs inactive (bound to binding proteins) degradation by enzymes

hormone receptors

affinity, density, location

sensitivity to hormones

dose-dependence and receptor density,

dose dependence

trait value rises linearly with hormone concentration, other relationships include step function, inverted U, Independent

receptor density

more receptors means a stronger response and faster feedback loop, up regulation- more receptors down regulation = fewer

sensitivity example

high DHT sensitivity of androgen receptors means a higher propensity for hair loss

Finasteride

blocks the enzyme that converts testosterone to DHT. The slide asks whether this a variation in levels, receptors, or sensitivity. It changes hormone levels, because it reduces DHT

steroid

small, cholesterol based, not soluble; needs carrier proteins, not stored (signal to make = signal to release) slow half life- long

mechanism for steroid

crosses membrane'; hormone receptor complex acts as a transcription factor (DNA——> mRNA———> protein) changing gene expression

peptide

large, made of amino acids soluble, no carrier needed, stored in endocrine cells, fast, half life is short

mechanism of peptide

Can’t cross membrane; binds membrane receptor → signal transduction (amplification) → second messengers → cellular response

hormone regulation

regulated by cell by products and by the hormone itself

negative feedback

the product inhibits the gland,

positive feedback

the product stimulates more hormone

example of negative feedback

parathyroid hormone and blood calcium; the CRH ——> ACTH ——> cortisol loop (short and long loop inhibition)

example of positive feedback

mid cycle estrogen stimulating LH, and oxytocin during birth, which the instructor says to know

1. contractions push the baby’s head against the cervix

2. signals go from cervix to the brain

3. the brain stimulates the pituitary to secrete oxytocin

4. oxytocin travels to the uterus via the bloodstream

5. oxytocin amplifies contractions, and the cycle repeats

endocrinology

study of hormones, their production, targets, and effects

behavioral endocrinology

the interaction between hormones and behavior

hormones affect behavior

by acting on sensory systems, the CNS, and effectors

behavior affects hormone

it is a two way loop

finch example

removing the testes stops singing, testosterone injections

challenge (wingfield)

male - male challenges over mates or territory raise testosterone, but predator challenges don’t

sex

based in biological, sexed traits

Gender

emerges from social constructions and is associated with personal identity

how do biologists talk about sex in non-human animals

biological sex (makes ovum or sperm; sex typed biology, and sex types behavior. Goymann talking about non-human gender adds nothing meaningful

binary vs bimodal

height is not binary, it is bimodal with overlapping values, Sex-related traits are often bimodal rather than strictly binary

How does the 2025 U.S government (White House) definition define female and male

defined at conception by gamete: female = sex that produces large reproductive cell, male =sex that produces the small reproductive cell

anisogamy

two dramatically different gamete sizes (sex and 2 sexes) evolved independently from isogamy several times in eukaryotes, all animals are anisogamous

isogamy

similar sized gametes (sex but no sexes)

what is actually present at conception

the sex chromosome X and Y, one pair of the 23 in humans, Y is largely responsible for downstream development of male sexed traits

sex chromosome variation and mosaicism

variation exits in sex chromosomes, Mosaicism: chromosomes are not uniform throughout the body

name the kind of sex you can measure

chromosomes, genital development, gonadal development, gametogenesis, secondary sexual characteristics, makes a single definition hard

why isn’t sex more binary

sex determination is increasingly seen not as linear cascade with binary switch, but as flexible, multiply determined system with environmental sensitivity and rapid evolutionary change, sex related phenotypes are not made by one conserved developmental program