Chemical Structures of the Three Main Hormone Types

Examples of Major Classes of Hormones

Two Main Mechanisms of Hormone ActionSurface receptorsEstradiolTestosteronecAMPcGMPSRC-1 CBP

Effect of insulin on glucose uptake and metabolism. Insulin binds to its receptor (1) which in turn starts many protein activation cascades (2). These include: translocation of Glut-4 transporter to the plasma membrane and influx of glucose (3), glycogen synthesis (4), glycolysis (5) and fatty acid synthesis (6)."Insulin glucose metabolism" by User Meiquer English wikipedia. Licensed under CC BY-SA 3.0 via Commons https://commons.wikimedia.org/wiki/File:Insulin_glucose_metabolism.jpg#/media/File:Insulin_glucose_metabolism.jpg

Endocrine Feedback LoopsInsulinEpinephrine?LHTestosteroneT cell lymphocytesGlucose

Hormone Production by the Posterior Pituitary

The Milk Letdown Reflex

Hormone Release by the Anterior Pituitary

Secretions of the Anterior Pituitary

Regulation of Gonadal Steroid HormonesBehaviorBehavior

Integration of circuits at GnRH Neuron

Figure 2: ER in hypothalamic circuits regulates energy metabolism and reproduction.Energy metabolism and fertilitya balance preserved for female health Sara Della Torre, Valeria Benedusi, Roberta Fontana & Adriana Maggi Nature Reviews Endocrinology 10, 1323 (2014)

Hormones Affect Behavior in Many Different WaysHormones play a role in social behavior: (permissive or activational)Oxytocin released duringnursing interactionOrgasmChild birthpromotes pair-bonds in females and males Vasopressinin male prairie voles, facilitates the formation of pair-bonds with femalesTestosteroneinterest in sex in males and femalesIncreased probability of aggressive behavior

Interactive Signals between the Nervous System and the Endocrine System

The Reciprocal Relations between Hormones and BehaviorMore success in getting datesIncreased ConfidenceHigher Testosterone levels

Sex According to Thurber and WhiteMap from Is Sex Necessary? Or, Why You Feel the Way You Do a book of prose by Thurber and White (1929) that spoofs the medical Psychiatric explanations of the everyday reality of marriage, love and romance.

Use of the term SexTo imply Sexual activitybetter to use:sexual intercourse copulation Categories of male or female in reference to reproductionBecause of differences in : Genetics; XX or XYAnatomy such as penis or vaginaBehaviorNursing offspringFighting for territoryCan be problematic when applied to humans Intersex individuals Homosexual behaviorVariable parenting, territorial and foraging behaviorsComplex social organizationShould not be confounded with GenderGender is a combination of phenotypic traitsRecall that Phenotype is Genetics interacting with EnvironmentGender is not easily divided into categories

ReproductionReproductionThe sexual or asexual process by which organisms generate new individuals of the same kind the sexual activity of conceiving and bearing offspring a fundamental feature of all known life Sexual Activity and Reproduction can be separated but often one leads to the other

Stages of Reproductive Behavior

Androgens Permit Male Copulatory Behavior

Neural Circuits for Reproduction in Rodents

Sexual Differentiation in Humans

Sexual Differentiation and Gender Identity (Part 1)

Sexual Differentiation and Gender Identity (Part 2)

Old 12.12

*Chemical structure of hormones:Protein hormone, or peptide hormonea string of amino acidsAmine hormonesmodified amino acids, called monoamine hormonesSteroid hormonesfour rings of carbon atomsHormones exert effects on cells and tissues in the body by:Promoting proliferation, growth, and differentiation of cellsModulating cell activityHormones exert influences in two different ways:1. Protein and amine hormones bind to specific receptors on the surface of a cell and cause release of a second messenger in the cell.2. Steroid hormones pass through the cell membrane and bind to receptors inside the cell.The steroid-receptor complex binds to DNA and acts as a transcription factorcontrolling gene expression.

**Protein and amine hormones act rapidly.When they bind to the extracellular part of a receptor, the receptor changes shape.The intracellular part then activates a second messenger.Cyclic adenosine monophosphate (cyclic AMP or cAMP) is a second messenger that transmits messages of many peptide and amine hormones. Cyclic guanosine monophosphate (cyclic GMP or cGMP) and phosphoinositides are also widespread.Steroid hormones act slowly.When steroid-receptor complexes form they alter protein production, with long-lasting effects.Some steroids act on more than one receptorcalled receptor isoformswith functional differences.Steroid receptor cofactors may be necessary for the cell to respond to the steroid-receptor complexes.Steroid receptor cofactor-1 (SRC-1) and CREB-binding protein (CBP) play a role in sexual dimorphism in the brain.Steroids such as estradiol can also have a nongenomic effecta rapid, brief effect involving neuronal membrane receptors.Testosterone has rapid effects on receptors located in axons and other sites distant from the nucleus.

*Hormones are regulated by feedback systems:Negative feedbackoutput feeds back and inhibits further secretionAn autocrine response involves an endocrine gland releasing hormone and feeding back onto itself.In target cell feedback, the hormone acts on its target cells and has a biological effect.The biological effect is detected by the endocrine gland, and inhibits further release. A more complex endocrine system involves the brain, usually the hypothalamus.The hypothalamus can direct hormone releasethe brain detects the hormones effects and exerts negative feedback onto the hypothalamus.The anterior pituitary gland may also be involved:Tropic hormones are pituitary hormones that affect other endocrine glands.Releasing hormones are used by the hypothalamus to control the pituitary release of tropic hormones.

**The pituitary gland (or hypophysis) releases important hormoneshas two main parts:Anterior pituitary (adenohypophysis)Posterior pituitary (neurohypophysis)The two parts of the pituitary gland are separate in function.The pituitary stalk, or infundibulum, connects the pituitary to the hypothalamus.The stalk contains blood vessels and many axons, which only extend to the posterior pituitary.The posterior pituitary secretes two principal hormones:Oxytocininvolved in reproductive and parenting behavioralso in uterine contraction and the milk letdown reflexArginine vasopressin (AVP) or vasopressin, or antidiuretic hormone (ADH)increases blood pressure and inhibits urine formationVasopressin and oxytocin can also serve as neurotransmitters in the hypothalamus.

*****Hormones play a role in social behavior: (permissive or activational)Oxytocin released duringnursing interactionOrgasmChild birthpromotes pair-bonds in females and males Vasopressin in male prairie voles, facilitates the formation of pair-bonds with femalesTestosteroneinterest in sex in males and femalesIncreased probability of aggressive behavior

*BP6e-Fig-05-23-0.jpg *biopsych4e-fig-12-01-0.jpg *Four stages of reproductive behavior:Sexual attractionAppetitive behaviorCopulationPostcopulatory behaviorSexual attraction brings males and females togethermay be synchronized with:Physiological readiness to reproduce, indicated by odors reflecting estrogen levels in femalesLearned associations, such as appearancesAppetitive behaviors establish, maintain, or promote sexual interaction.A proceptive female may approach males or perform ear-wiggling.Male behaviors include staying near the female, sniffing, singing, and nest-building.Copulation involves one or more intromissions in which the male penis is inserted into the female vagina.Following stimulation the male ejaculates sperm-bearing semen into the female.After first copulation, a refractory phase followslength varies with species.The Coolidge effect refers to the faster resumption of mating behavior, with a different partner.If a female is willing to copulate, she is sexually receptive, or in estrus.Postcopulatory behavior varies across species.In a copulatory lock, occurring in dogs and some mice, the penis swells temporarily and cannot be withdrawn from the female.Postcopulatory behavior may include parental behaviors to nurture offspring.

*Hormones are important in mating behaviors.A castrated male loses interest in mating because testosterone is no longer produced.Behavior is restored with testosterone treatmentthe activational effect; hormones briefly activate behavior.

*In female rats, the ventromedial hypothalamus (VMH) is crucial to the lordosis response through steroid actions.Estrogen increases dendritic trees of neurons in the VMH.Estrogen also stimulates progesterone receptors, which in turn contribute to lordosis through protein production.The VMH sends axons to the periaqueductal gray in the midbrain, which projects to the medullary reticular formation.This in turn projects to the spinal cord via the reticulospinal tract.As the male mounts, sensory information via the spinal cord evokes lordosis.In male rats, the medial preoptic area (mPOA) coordinates male copulatory behavior.The mPOA sends axons to the ventral midbrain, then to the basal ganglia to coordinate mounting.Axons also project through brainstem nuclei to the spinal cord.One nucleus, the paragigantocellular nucleus (PGN) has fibers that normally inhibit the erection responsemPOA signals counteract the inhibition.The vomeronasal organ (VMO) detects chemicals called pheromones, which activate male arousal.VMO information is sent to the medial amygdala, and in turn to the mPOA.

*Sexual differentiation is the process by which individuals develop bodies and behaviors that are either male or female. Sex determination is the early developmental event that decides if a fetus will be male or female.If the sperm that enters the egg has an Y chromosome, the offspring is maleif an X chromosome, the offspring is female.The early indifferent gonads begin to change into ovaries or testes in the first month.SRY genesex-determining region on the Y chromosomeis responsible for the development of testesWithout an SRY gene, an ovary forms.Hormones secreted by gonads, mainly from the testes, direct sexual differentiation.Embryos have early tissues for both male and female structures.The wolffian ducts and the mllerian ducts connect the gonads to the body wall.In females, the mllerian ducts develop into the fallopian tubes, the uterus, and vaginaonly part of the wolffian ducts remains.In males, the wolffian ducts develop into the epididymis, vas deferens, and seminal vesicles, and the mllerian ducts shrink.Two hormones from the testes make the system masculine:Testosterone promotes the development of the wolffian system.Anti-mllerian hormone (AMH) induces the regression of the mllerian system.Testosterone also masculinizes other structures:Other tissues form the prostate gland, scrotum, and penis. 5-reductase is an enzyme that converts testosterone into the more powerful dihydrotestosterone (DHT), necessary to form genitalia.

*Two hormones from the testes make the system masculine:Testosterone promotes the development of the wolffian system.Anti-mllerian hormone (AMH) induces the regression of the mllerian system.Testosterone also masculinizes other structures:Other tissues form the prostate gland, scrotum, and penis. 5-reductase is an enzyme that converts testosterone into the more powerful dihydrotestosterone (DHT), necessary to form genitalia.In Turners syndrome, a person only has one sex chromosomea single X.The individual develops as a femalewithout the SRY gene, and no masculinizing effects take place.

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