Hormones and Behavior

Nature (nature vs. nurture)

The view that biological inheritance and genetics determine human behavior.

Nurture (nature vs. nurture)

The view that society

Galton's definition of nature and nurture (1874)

Nature is all that a person brings with himself into the world; nurture is every influence from without that affects him after birth.

Sir Francis Galton

Cousin of Charles Darwin who framed the "nature and nurture" distinction in 1874; associated with the eugenics movement.

Eugenics

"Noble in birth"; an ideology of preserving and bettering the "national race/stock" through the "scientific management of mating."

Positive eugenics

Increasing the birth rate/population of people considered to be of "noble birth."

Negative eugenics

Decreasing the birth rate/population of people deemed "unfit"; e.g. through forced sterilization and institutionalization.

Forced sterilization and institutionalization (US)

Significant US programs targeting anyone not deemed mentally or physically "fit"; an example of negative eugenics.

Fitter Family Fairs

US county-fair programs where families competed based on physical appearance and dexterity; an example of positive eugenics.

Eugenics in Nazi Germany

Germany copied US programs and expanded them: banned inter-racial/religious/ethnic marriages; encouraged selective breeding for "Aryan" traits; and sent "inferior" people to prison work camps and finally death camps.

Eugenics and the US

Nazi politicians (including Hitler) came to study US eugenics policies; which inspired them.

Popularity of eugenics

Popular in the UK; USA; Europe; and colonies among both conservative and progressive groups; championed by academic and intellectual leaders; tied to white supremacist fears of declining birth rates and loss of political control.

Victims of Nazi eugenic thinking (death camps)

6 million Jewish people; 10-15;000 homosexuals; 240;000 disabled people; and 190;000-250;000 Roma and Sinti people (plus 3.3 million Soviet POWs and 1.8 million non-Jewish Polish people killed on the basis of political opposition).

Miscegenation

A word meaning "racial mixing" invented in 1863.

Anti-miscegenation laws

Laws banning interracial marriage (between "whites and non-whites"); in the US from ~1665 until overturned June 12 1967; in apartheid South Africa from 1949 to 1985.

Eugenics after World War II

Became a taboo term because of its association with the Nazis; many ideas remained but were tempered and described with other terms.

American Eugenics Society (renamed)

Became the "Society for the Study of Social Biology" after WWII.

West and King (1987) quote

"Ask not what's inside the genes you inherited; but what the genes you inherited are inside of."

Oyama (2000) quote on nature and nurture

Nature is the product of the causes we call nurture; at the same time; phenotypic nature is a developmental resource for subsequent interactions.

Dr. Susan Oyama

Developmental systems theorist who argued that organisms inherit developmental systems and not just genes.

Interactants in developmental systems (Oyama)

The genome; cell structure (including organelles); intracellular chemicals; extracellular environment; parental reproductive systems; self-stimulation by the organism; immediate physical environment; conspecifics and members of other species; climate/food sources/and other aspects of the external environment.

Ontogeny

The course of development especially of a single organism.

Conspecific

A member of the same species.

Circadian rhythm feedback loop

A molecular loop: per gene produces per mRNA which is translated into PER protein. The PER protein degrades over a 24 hour period. While it is still in the body it inhibits the production of the PER protein.

Suprachiasmatic nucleus

Brain structure near the optic chiasm (in the hypothalamus) involved in generating circadian rhythms.

Intracrine mediation

Chemical signaling that acts within the cell that produced the signal.

Autocrine mediation

Chemical signaling in which a cell secretes a signal that acts on itself.

Paracrine mediation

Chemical signaling in which a cell secretes a signal that acts on nearby (local) target cells.

Endocrine mediation

Chemical signaling in which a signal travels through the bloodstream to distant target cells.

Ectocrine mediation

Chemical signaling between individual organisms (e.g. airborne chemical signals between animals).

Neurotransmitters

Chemicals secreted by neurons to other neurons (paracrine signaling); e.g. dopamine; epinephrine; norepinephrine.

Neurohormones

Chemicals secreted by neurons into the bloodstream (endocrine signaling); e.g. releasing hormones and inhibiting hormones.

Hormones (as a type of chemical communicator)

Chemicals secreted by endocrine glands into the bloodstream (endocrine signaling).

Hormones (definition)

Chemical messengers that travel through the bloodstream to transmit information from one part of the body to another.

Endocrine system

A network of hormones; hormone receptors; carrier molecules; and signaling pathways that allows communication between cells and organs often over long distances via the circulatory system.

Endocrine cell (hormone release)

Cell that packages hormone in secretory vesicles (via the Golgi apparatus) and releases it into the bloodstream to reach target cells with hormone receptors.

Target cell

A cell with receptors for a particular hormone allowing it to respond to that hormone.

Neural vs. hormonal communication

Neural communication is close in space and quick in time; hormonal communication is far in space and slow in time.

Number of neurotransmitters in the brain

At least 60.

Excitatory neurotransmitter (example)

Glutamate.

Inhibitory neurotransmitter (example)

GABA (gamma-aminobutyric acid).

Neuromodulatory neurotransmitters

Neurotransmitters that can be excitatory or inhibitory depending on context; e.g. dopamine; serotonin; norepinephrine.

Dopamine (function)

A neurotransmitter associated with reward (also motor control).

Serotonin (function)

A neurotransmitter associated with mood (also appetite and sleep).

Norepinephrine (function)

A neurotransmitter associated with the stress response.

Neurotransmitter system

A pathway made of neurons that release the same neurotransmitter (e.g. a dopamine pathway).

Precursor/Neurotransmitter synthesis

Neurotransmitters are synthesized and released by neurons.

Main receptor types

Effect of a neurotransmitter on a target is dependent on the number and type of receptors.

Primary function

These systems/pathways can be broadly categorized but have significant interactions

Dopamine pathways

mesolimbocortical pathway, mesostrial pathway, and nigrostriated pathway

Hypothalamus (overview)

Brain structure common to all vertebrates that coordinates between brain and body via the endocrine system; essential for homeostasis and behavior.

Functions regulated by the hypothalamus

Eating and drinking; blood pressure and heart rate; body temperature; sleep-wake cycle; emotional states; sexual functions and behaviors.

Hypothalamic nuclei

Clusters of neuronal cell bodies in the hypothalamus; they act like endocrine glands but are morphologically conventional neurons.

Corticotropin-releasing hormone (CRH)

Hypothalamic neurohormone that regulates carbohydrate; protein; and fat metabolism and water/sodium balance.

Gonadotropin-releasing hormone (GnRH)

Hypothalamic neurohormone that regulates sexual and reproductive functions including pregnancy and lactation.

Thyrotropin-releasing hormone (TRH)

Hypothalamic neurohormone involved in metabolic cell processes.

Growth hormone-releasing hormone (GHRH)

Hypothalamic neurohormone involved in organismal growth.

Somatostatin

Hypothalamic neurohormone involved in bone and muscle growth but with the opposite effect of GHRH.

Dopamine (as a hypothalamic hormone)

Primarily a neurotransmitter but has some hormonal function.

Posterior pituitary

Contains axon terminals of neurons that run from the hypothalamus; it does not produce hormones but is the site where hypothalamic neurohormones are released into the bloodstream.

Hormones released at the posterior pituitary

Vasopressin (AVP; same hormone as anti-diuretic hormone or ADH) and oxytocin (OT).

Vasopressin (AVP) vs. anti-diuretic hormone (ADH)

They are the same hormone.

Anterior pituitary (control by hypothalamus)

Hypothalamic neurons produce releasing or inhibiting hormones that stimulate or inhibit release of the anterior pituitary's own hormones.

Hypothalamic-pituitary portal system

A closed "one-way" blood system in which hypothalamic neurons synapse on a primary capillary plexus and send hormones to the anterior pituitary where they act on a secondary plexus.

Anterior pituitary hormones

ACTH; gonadotropins (LH and FSH); TSH; growth hormone (GH); and prolactin; secreted into the secondary plexus and then the general circulation.

Anterior pituitary hormones that act on other glands

ACTH; gonadotropins (LH and FSH); and TSH.

Anterior pituitary hormones that act on other target tissues

Growth hormone (GH) and prolactin.

Adrenocorticotropic hormone (ACTH)

Anterior pituitary hormone that acts on the adrenal cortex.

Thyroid-stimulating hormone (TSH)

Anterior pituitary hormone that acts on the thyroid.

Secondary endocrine organs

Organs with other main functions that also secrete hormones: thymus (mainly immune function); placenta (pregnant female mammals only); heart; stomach; liver; kidney; small intestine; skin; and fat cells.

Endocrinology

The study of hormones; their production; their target cells; and their effects.

Behavioral endocrinology

A subset of endocrinology studying the interactions between hormones and behavior.

Sources of variation in hormone levels

Variation in secretion; bioactive vs. inactive levels (binding proteins); degradation by enzymes.

Sources of variation in hormone receptors

Affinity; density; and location.

Dose-dependent function

A simple relationship in which trait expression increases in proportion to hormone concentration; many hormones do not follow this pattern.

Relationships between hormone concentration and trait expression

Many are possible including dose-dependent; step function (single or multiple); inverted U function; independent; and steep graded function (Hau & Goymann 2015).

Receptor density

The number of receptors on a target cell; higher density produces a stronger response and faster feedback loops.

Up-regulation

An increase in the number of receptors on a target cell.

Down-regulation

A decrease in the number of receptors on a target cell.

Prairie vole vs. montane vole receptors

Prairie voles (monogamous) have more oxytocin receptors (OTR) in the nucleus accumbens; montane voles (polygynous) have more vasopressin receptors (AVPR) in the lateral septum.

Hormone sensitivity

Differences in receptor affinity for the same hormone between receptor types or between individuals.

DHT sensitivity example

Where androgen receptors have high DHT sensitivity there is a higher propensity for hair loss.

Finasteride

A drug that blocks the enzyme that converts testosterone to DHT.

Three types of vertebrate hormones

Steroid hormones; peptide hormones; and amine hormones.

Steroid hormones (structure and solubility)

Small hormones comprised of a cholesterol subunit; not soluble in blood so they must bind to water-soluble carrier proteins for transport.

Steroid hormones (storage)

Not stored; the signal to produce is the signal to release.

Steroid hormones (speed and half-life)

Slow acting (hours to days) with a long biological half-life (degrade after hours or days).

Examples of steroid hormones

Glucocorticoids (e.g. cortisol); androgens; estrogens; and progestagens (e.g. progesterone).

Steroid hormone action

The hormone-receptor complex acts as a transcription factor that transcribes DNA to mRNA; mRNA is translated into proteins; changing gene expression over hours or days.

Transcription factor

A protein (here the steroid hormone-receptor complex) that binds DNA and drives transcription of DNA into mRNA.

Peptide hormones

Large hormones made of a few amino acids (peptide) or many amino acids (polypeptide).