230 - Hormones, Sex Determination, Development

Release hormones within the body

Endocrine glands

use ducts to secrete fluids outside the body

Exocrine glands

Example of exocrine glands

tears, sweat

steroids made in brain (testosterone, estrogens)

Neurosteroids

First formal study of endocrineology

Castration, showed that removal of gonads results in behavioral and physiological changes (chickens)

Endocrine communication

hormone released into the bloodstream to act on target tissues

neurons that release hormones into the blood

Neuroendocrine cells

Difference between synaptic and endocrine communication

synaptic much faster and travels along specific laid path, endocrine relatively slow and spread anywhere with blood supply

released chemical diffuses to nearby target cells (i.e synaptic transmission)

Paracrine function

released chemical acts on releasing cell

Autocrine Function

hormones used to communicate between individuals of the same species - released into the environment

Pheromone function

chemicals released by one species to affect the behavior of another species

Allomone Function

Hormones act by changing __ or __ of a behavior

probability, intensity

string of amino acids, large and can’t pass through cell membranes (oxytocin, insulin, leptin)

Peptide hormone

modified amino acids (monoamine hormones)

amine hormones

four rings of carbon atoms (derivatives of cholesterol), pass through cell membrane and bind to receptors inside cell

Steroid hormones

Most common type of hormone in mammals

peptide hormones

Classes of amine hormones

indoleamines(serotonin), catecholamines (epinephrine, dopamine)

genomic action - steroid receptor complex binds to DNA in __ and acts as __ factor, controlling gene expression and __ production, making effects longer lasting

nucleus, transcription, protein

nongenomic action

some steroids like estradiol can have a rapid brief effect involving neuronal membrane receptors

enzyme that converts testosterone into estrogens inside cell

Aromatase

Hormone feedback systems - negative versus positive

negative feedback causes hormones to inhibit further secretion, positive feedback causes an increase in further secretion

autocrine negative feedback loop

involves endocrine cells releasing a hormone whose presence feeds back on the endocrine cell

Target cell feedback

hormone acts on its target cells and has a biological effect, which is then detected by the endocrine gland and further release is inhibited

posterior pituitary secretes which two primary hormones, which are synthesized by neurons where

oxytocin, vasopressin, supraoptic nuclei and paraventricular nuclei of the hypothalamus

Posterior pituitary hormones travel along and into where

pituitary stalk, into the blood supply of posterior pituitary

How does the hypothalamus communicate with the anterior pituitary

hypothalamic neuroendocrine cells synthesize releasing hormones, axons from those cells converge on median eminence (above pituitary stalk), releasing hormones then secreted into blood vessels called hypophyseal portal system and carried to ant. pituitary

What do the releasing hormones stimulate cells in the anterior pituitary to release

tropic hormones

What are hypothalamic neuroendocrine cells that synthesize releasing hormones in the anterior pituitary gland influenced by

circulating messages (other hormones, blood sugar, immune system products) and synaptic inputs from other brain areas

Physiological and behavioral effects of oxytocin

Physiological - oxytocin stimulates uterine contractions and involved in nursing

Behavioral - oxytocin released during nursing and orgasm to facilitate bonding

Sex determination vs differentiation

determination - decision of whether fetus is male or female, chromosome driven

differentiation - process of individuals developing m/f bodies and behaviors, hormone driven

What happens if there is no SRY gene present in the gonads

An ovary forms

What does it mean for gonads to be bipotential

They can become wither testes or ovaries

What two purposes do gonads serve

Production of gametes (sperm, eggs) and production of steroid hormones

What are steroid hormones required for

gamete production, development of secondary sex characteristics, behaviors that bring gametes together

When does testosterone production begin

As soon as testes are formed in utero, helps guide masc development

Male sex determination precursor system

Wolffian ducts

What do the Wolffian ducts develop into, and what shrinks as as a result

Epididymis, vas deferens, and seminal vesicles. Mullerian system shrinks

Female system precursor

Mullerian Ducts

What do the mullerian ducts develop into and what degenerates as a result

oviducts, uterus, vagina, and wolffian system degenerates

If testes are present, what hormone causes regression of the Mullerian system/ defeminizing

Anti- mullerian hormone (AMH)

Role of testosterone in sex differentiation

Masculizes internal organs by promoting development of wolffian system

What hormone is responsible for masculinizing external structures (and lack of feminizes)

Dihydrotestosterone (DHT), converted from testosterone from the enzyme 5a-reductase

In turners syndrome, a person only has one sex chromosome which is?

a single X

Individuals with turners syndrome develop as a __, due to lack of the __ gene, with abnormal ovaries (no __ hormone production or eggs)

female, SRY, steroid

individual has an extra chromosome (XXY), masculine body develops because of Y chromosome but testes and penis are abnormally small, low testosterone production and little-no sperm are produced

Klinefelters syndrome

In Congenital adrenal hyperplasia (CAH), what is missing and what is the result

lack enzyme (21-hydroxylase) that produces cortisol, resulting in increased androgen output from adrenal gland

What happens to external genetalia in females with CAH

partially masculinized because of exposure to increased DHT during development

treatment for CAH

exogenous cortisol given after birth to halt excess and androgen production

Androgen insensitivity syndrome occurs in __ people with defective __ receptors

XY, androgen

In AIS - external systems develop as testes or ovaries and why

testes because of the SRY gene on Y chromosome but will still have female phenotype

What is responsible for masculinizing the brain in early development and why is it converted by

estradiol, converted from testosterone by aromatase

condition in which males and females exhibit marked sex differences in appearance

Sexual dimorphism

what are the key sex differences in the brain

number of neurons, dendritic branching, connectivity

In rats, a nucleus in the sexually dimorphic nucleus of the __ is larger in __

POA, males

How does estradiol permanently alter the brain and when

alters apoptosis/celldeath, change synaptic connectivity, and affects densities during critical period of early development

Deciding factor of what kind of effect hormone will have (orginizational, activational, or both)

timing of its action

Hormone that prevents masculinization of the brain in females

a-fetoprotein, binds to estrogens keeping them from crossing into the brain

steroid hormones have an organizational effect only when?

Only when they are present during the critical period of development

fertilized egg (egg + sperm)

Zygote

three cell layers of human embryo

ectoderm, mesoderm, endoderm

Which cell layer becomes the nervous system

ectoderm

genotype vs phenotype

genotype - sum of genetic info we inherit, determined up fertilization and doesnt change

phenotype - sum of physical characteristics and DOES change

gene expression

cell transcribes gene and starts making protein it encodes , helps guide cellular differentiation

Methylation

modifies DNA and reduces expression of genes

Phenylketonuria (PKU)

recessive genetic disorder where individual doesn’t have enzyme that metabolizes phenalalanine (amino acid present in certain foods), causing brain damage