Behavioral Endocrinology and Hormonal Mechanisms

Vocabulary flashcards covering foundational concepts in behavioral endocrinology, hormone categories, neuroendocrine axes, reproductive cycles, nuclear receptor actions, signal transduction, and neuroscience methodology based on lecture notes.

Behavior

A physical or physiological response to an internal or external stimulus.

Proximate Causation

An approach to studying behavior that addresses the underlying mechanical or physiological mechanisms determining how a behavior works.

Ultimate Causation

An evolutionary approach to studying behavior that investigates why a particular behavior evolved over time.

Immediate Causation

A level of behavioral analysis that examines moment-to-moment physiological mechanisms, such as environmental stimuli and internal hormone levels.

Development (Behavioral Level of Analysis)

A level of analysis focusing on how genes and environmental factors interact across an organism's lifetime to shape mature behavior.

Evolutionary Approach (Behavioral Level of Analysis)

A level of analysis examining how specific behaviors change across generations due to natural selection and shared ancestry.

Adolph Berthold

A Swiss professor of physiology who conducted the first behavioral endocrinology experiment in the mid-1800s using male roosters.

Capons

Castrated male chickens that fail to develop adult male rooster physiological features and behaviors.

Berthold's Castrated Group

An experimental group of cockerels whose testes were removed without replacement, leading to loss of aggression, diminished crowing, and shrunken combs.

Berthold's Reimplanted Group

An experimental group of cockerels whose removed testes were placed back into their own abdominal cavity, resulting in normal rooster development.

Berthold's Transplanted Group

An experimental group of cockerels receiving testes transplanted from a different rooster into their abdominal cavity, resulting in normal male development.

Hormones

Chemical messengers synthesized and released from endocrine glands into the blood to act on specific target organs containing matching receptors.

Exocrine Glands

Glands that secrete chemical substances into specialized ducts leading to the digestive system or outside the body.

Endocrine Glands

Ductless glands that release chemical messengers directly into the body's internal bloodstream.

Neural Communication

A fast ($1\,ms$), specific, all-or-none, and relatively voluntary signaling mechanism that travels along set anatomical pathways.

Hormonal Communication

A slower (hours to days), non-specific, graded, and less voluntary signaling mechanism that travels throughout the body via the circulatory system.

Negative Control (Vehicle)

An experimental control group receiving an inactive substance (such as saline) to establish baseline behavior without altered hormonal effects.

Positive Control (Adrenaline)

A control group injected with a known active agent to guarantee a high-level response and validate the experimental apparatus.

Criteria to Establish Hormone-Behavior Causation

Three rules: 1) Removal of the hormone eliminates the behavior, 2) Restoration of the hormone reinstates the behavior, and 3) Hormone concentrations correlate directly with behavior intensity.

Peptide Hormones

Hormones composed of short amino acid chains ($<50$ amino acids), such as oxytocin and vasopressin.

Protein Hormones

Hormones composed of long polypeptide chains, such as gonadotropins (FSH and LH).

Alternative Splicing

A gene expression process where exons are cut out and introns modified to generate different hormone isoforms, such as GnRH variants in fish.

Endogenous Hormones

Hormones naturally synthesized and secreted inside the body in microscopic quantities.

Exogenous Hormones

Hormones introduced into the body from an outside source, typically administered in higher doses.

Glucocorticoids

Adrenal cortex steroid hormones, such as cortisol, that regulate carbohydrate metabolism and mediate long-term stress responses.

Mineralocorticoids

Adrenal cortex steroid hormones, such as aldosterone, that regulate osmotic balance, water retention, and kidney function.

Monoamine Hormones

Hormones derived from single amino acids, including melatonin, epinephrine, and norepinephrine.

Fatty Acid-Based Hormones

A major chemical class of lipid-derived signaling molecules that includes prostaglandins.

Hypothalamus

An endocrine brain region located at the base of the brain that regulates essential survival behaviors: feeding, fighting, fleeing, and mating.

Gonadotropin-Releasing Hormone (GnRH)

A hypothalamic neurohormone that serves as the primary master regulator of reproductive hormone cycles.

Anterior Pituitary Gland

The vascular portion of the pituitary originating from roof-of-mouth epithelial tissue that synthesizes and releases TSH, ACTH, Prolactin, FSH, LH, and GH.

Acromegaly

A clinical condition resulting from the excessive secretion of growth hormone (GH) by the anterior pituitary gland.

Posterior Pituitary Gland

A neural extension of the base of the brain that stores and directly releases hypothalamic hormones (oxytocin and vasopressin) into the bloodstream.

Oxytocin

A posterior pituitary peptide hormone that stimulates uterine contractions during birth, milk ejection, and social bonding.

Vasopressin (ADH)

A posterior pituitary peptide hormone that regulates osmotic balance, fluid retention, and blood pressure in animals.

Thyroid Hormones

Hormones such as thyroxine secreted by the thyroid gland that control metabolic rate, somatic growth, brain development, and thermoregulation.

Hyperthyroidism

A pathological state caused by excessive thyroid hormone secretion, leading to elevated blood pressure and chronic anxiety.

Hypothyroidism

A pathological state caused by insufficient thyroid hormone secretion, leading to sleep dysregulation and extreme temperature sensitivity.

Pancreatic $\beta$ Cells

Endocrine cells within the Islets of Langerhans that synthesize and release insulin when blood glucose levels rise.

Glycogenesis

The insulin-stimulated liver process of converting excess blood glucose into stored glycogen to restore baseline blood sugar levels.

Pancreatic $\alpha$ Cells

Endocrine cells within the Islets of Langerhans that synthesize and release glucagon when blood glucose levels fall.

Glycogenolysis

The glucagon-stimulated liver process of breaking down stored glycogen into free glucose molecules to raise blood sugar levels.

Type I Diabetes

A juvenile-onset metabolic disorder caused by an autoimmune deficiency of pancreatic $\beta$ cells, requiring daily external insulin injections.

Type II Diabetes

An adult-onset metabolic disorder where peripheral body tissues develop insulin resistance, resulting in initial insulin overproduction followed by $\beta$ cell exhaustion.

Adrenal Medulla

The inner core of the adrenal gland that secretes monoamine hormones epinephrine and norepinephrine during acute stress.

Pineal Gland

A central brain gland, historically called the 'seat of the soul,' that secretes melatonin during dark hours based on input from the suprachiasmatic nucleus.

Human Chorionic Gonadotropin (hCG)

A placental hormone released upon embryonic implantation that maintains the corpus luteum and serves as the primary marker for pregnancy tests.

HPG Axis

The Hypothalamic-Pituitary-Gonadal neuroendocrine feedback loop that governs gamete production and reproductive steroid synthesis.

Neurovascular Hypothesis

The model stating that anterior pituitary function is controlled by hypothalamic neurohormones secreted into a specialized portal blood vessel supply rather than direct neural connections.

Estrous Cycle

A short reproductive cycle found in many non-primate mammals (such as $4\text{--}5$ days in rats) where ovulation is tightly coupled with receptive sexual behavior.

Menstrual Cycle

A reproductive cycle occurring in primates ($\approx 28$ days in humans) characterized by monthly shedding of the uterine lining, where ovulation is not strictly tied to sexual behavior.

Follicle Stimulating Hormone (FSH)

An anterior pituitary gonadotropin that targets the ovaries to stimulate follicle cell development and estradiol secretion.

Luteinizing Hormone (LH)

An anterior pituitary gonadotropin that triggers follicle rupture during ovulation and promotes luteinization into the corpus luteum.

Corpus Luteum

A temporary endocrine structure formed from a ruptured ovarian follicle that secretes high levels of progesterone and estradiol to maintain the uterine lining.

GnRH Pulse Generator

The rhythmic, episodic release pattern of hypothalamic GnRH necessary to prevent desensitization and shutdown of anterior pituitary gonadotropin receptors.

RU486

A progesterone receptor antagonist used in combination with prostaglandins to induce medical abortions by blocking progesterone activity and causing uterine contractions.

Follicular Phase

The first phase of the menstrual cycle (Days $1\text{--}14$) during which rising estrogen levels promote ovarian follicle growth prior to ovulation.

Luteal Phase

The second phase of the menstrual cycle (Days $15\text{--}28$) dominated by corpus luteum secretion of progesterone to prepare the endometrium for potential pregnancy.

Estradiol Positive Feedback Switch

The physiological event around Day 13 where sustained high estradiol concentrations switch from negative feedback to positive feedback, triggering the pre-ovulatory LH surge.

Ligand

Any endogenous or exogenous chemical molecule that binds specifically to a target receptor site.

Agonist

A ligand or pharmacological agent that binds to and activates a receptor, mimicking endogenous biological activity.

Antagonist

A pharmacological agent that binds to a receptor site and blocks endogenous ligands from activating it.

Kinase

An enzyme that transfers a phosphate group onto a target protein, altering its physical shape and activating its function.

Dephosphorylation

The enzymatic removal of a phosphate tag from a protein to terminate intracellular signal transduction.

cAMP

An intracellular second messenger produced by adenylate cyclase that mediates hormone signal amplification for LH, FSH, oxytocin, and vasopressin.

Phospholipase C (PLC)

A membrane-bound effector enzyme activated by G-proteins that cleaves phosphoinositol into second messengers DAG and $IP_3$.

Inositol Triphosphate ($IP_3$)

A soluble second messenger that binds to receptors on the endoplasmic reticulum to trigger the intracellular release of $Ca^{2+}$.

Diacylglycerol (DAG)

A membrane-bound second messenger generated by PLC that acts alongside released $Ca^{2+}$ to activate Protein Kinase C (PKC).

Central Dogma of Molecular Biology

The fundamental framework describing the flow of genetic information: DNA is transcribed into mRNA, which is translated into protein.

TATA Box

A DNA promoter sequence that binds TATA-binding protein (TBP) and TFIID to recruit RNA Polymerase II for eukaryotic transcription.

DNA-Binding Domain (DBD)

A specialized structural region on nuclear receptors that binds specific hormone response elements (HREs) on genomic DNA.

Ligand-Binding Domain (LBD)

A structural domain on nuclear receptors where specific lipophilic steroid hormones bind to induce receptor dimerization and activation.

Activation Function 1 (AF1)

An N-terminal domain of steroid receptors that promotes gene transcription independently of ligand binding.

Activation Function 2 (AF2)

A C-terminal activation domain located within the LBD of nuclear receptors that requires ligand binding to interact with transcriptional coactivators.

Progestin Receptor Isoforms (PR-A and PR-B)

Two distinct protein forms transcribed from the same gene: full-length PR-B ($933$ amino acids) acts as a transcript activator, whereas shorter PR-A acts as a functional inhibitor.

Estrogen Receptor Subtypes (ER$\alpha$ and ER$\beta$)

Two receptor subtypes transcribed from different genes that share $96\%$ DBD similarity but only $53\%$ LBD similarity, permitting subtype-selective drug development.

Orphan Nuclear Receptors

Receptors sharing structural homology with classic nuclear receptors whose specific natural endogenous ligands remain unknown.

Selective Estrogen Receptor Modulators (SERMs)

Synthetic compounds (such as Tamoxifen) that exhibit tissue-specific agonist or antagonist activities at estrogen receptors.

In Situ Hybridization

A quantitative histological technique using radioactively labeled nucleic acid probes to visualize specific mRNA sequences within individual cells.

Western Blot

A quantitative molecular assay using gel electrophoresis and antibody probes to detect and measure specific protein levels in tissue homogenates.