Hormones and behaviour test 1

What is endocrinology?

The study of how chemical messengers called hormones coordinate physiological functions and behaviors across the body

How do hormones differ from neurotransmitters in their primary mode of communication?

Neurons communicate via localized neurotransmitter release across synaptic clefts at axon terminals, whereas hormones are secreted into circulation to act on distant target cells throughout the body

What does "typecasting" a hormone mean?

Oversimplifying a hormone by assigning it a single, limited function (like sex or stress), despite it having widespread, multi-system physiological and metabolic roles

What major metabolic function does estrogen serve outside of female reproduction?

Estrogen acts as a potent metabolic hormone regulating body weight and fat distribution in both females and males

What physiological functions does cortisol perform beyond responding to stress?

Cortisol regulates cardiovascular function, immune responses, and osmotic fluid balance

What is the single gut peptide hormone known to stimulate hunger?

Ghrelin is the primary gastrointestinal peptide that stimulates appetite

What is GLP-1 and what is its physiological role?

GLP-1 is a gut-derived peptide hormone that suppresses appetite and serves as the molecular basis for GLP-1 receptor agonist medications like Ozempic

What is autocrine signaling?

A signaling mechanism where a secreted hormone binds to receptors on the exact same cell that produced and released it

What is paracrine signaling?

Local chemical communication where a secreted hormone diffuses through adjacent tissue to act on nearby target cells

What is endocrine signaling?

Classical hormone signaling where a chemical messenger is released into the bloodstream to act on distant target tissues

What is exocrine or ectocrine signaling?

The secretion of chemical signals, such as pheromones, outside the body into the environment to alter the physiology or behavior of another organism

What was Arnold Berthold's landmark 1849 experiment?

Berthold castrated male roosters before puberty and observed that re-implanting or subcutaneously transplanting the testes back into the body fully restored normal adult male physical traits and aggressive behaviors

What core principle did Arnold Berthold’s rooster experiment prove?

Testes release a blood-borne chemical messenger into circulation that directs male physiological and behavioral development independently of direct nerve connections

Who coined the term "hormone" and what is its biological meaning?

Ernest Starling coined the term from the Greek word ormao, meaning "to stir up" or "excite"

How was insulin historically isolated by Frederick Banting?

Banting isolated insulin by extracting active pancreatic tissue from pigs, requiring hundreds of animal pancreases to treat a single diabetic patient

What is an organizational effect of a hormone?

An irreversible structural or anatomical modification induced by hormones during a specific, critical developmental window

What is an activational effect of a hormone?

A reversible physiological or behavioral response triggered by circulating hormones in adult organisms that wanes upon hormone removal and can be rescued by re-administration

How does male brain sexual differentiation occur in rodent development?

Testicular testosterone enters the male brain during early critical developmental periods and is converted into estrogen by the enzyme aromatase, masculinizing brain circuits

What happens if estrogen synthesis or signaling is blocked in a developing male brain during the critical period?

The brain fails to masculinize, permanently preventing the expression of adult male-typical sexual and aggressive behaviors

Can an adult female rodent be converted to exhibit full male sexual behavior simply by injecting testosterone in adulthood?

No, because the critical developmental window for organizational masculinization of brain circuits has closed

Why is the hypothalamus considered the master gland of the endocrine system?

The hypothalamus contains discrete neural nuclei that produce releasing and inhibiting factors that directly control all anterior pituitary hormone secretions

What are hypothalamic nuclei?

Anatomically distinct clusters of neuronal cell bodies within the hypothalamus that synthesize specific peptides and neurotransmitters

What is the median eminence?

A specialized capillary-rich region between the hypothalamus and pituitary gland where hypothalamic axons secrete releasing factors into the portal blood system

How does the hypothalamus communicate with the anterior pituitary lobe?

Hypothalamic releasing factors travel through the hypophyseal portal blood vessels to bind surface receptors on anterior pituitary endocrine cells

How does the hypothalamus communicate with the posterior pituitary lobe?

Hypothalamic neurons send direct axonal projections into the posterior pituitary to release non-releasing peptide hormones directly into general circulation

Which two major peptide hormones are released directly by the posterior pituitary?

Oxytocin and vasopressin (antidiuretic hormone / ADH)

What is tonic hormone release?

The pattern of hormone secretion that occurs in discrete, synchronized pulses rather than as a constant continuous stream

What is negative feedback in an endocrine system?

A regulatory loop where the end-product hormone inhibits further secretion from the upstream glands or hypothalamus to keep levels within a homeostatic range

What is positive feedback in an endocrine system?

A regulatory loop where a hormone stimulates further release of itself or associated hormones, such as oxytocin surges during labor contractions or estrogen triggering the ovulatory LH surge

What is the pathway of the Hypothalamic-Pituitary-Adrenal (HPA) axis?

The hypothalamus releases CRH, which triggers the anterior pituitary to release ACTH, which stimulates the adrenal cortex to release cortisol/corticosterone

What is the pathway of the Hypothalamic-Pituitary-Gonadal (HPG) axis?

The hypothalamus releases GnRH, which triggers the anterior pituitary to release LH and FSH, which stimulate the gonads to release sex steroids (testosterone, estrogen, progesterone)

What is the pathway of the Somatotrophic Axis?

The hypothalamus releases GHRH (stimulated) or somatostatin (inhibited), controlling anterior pituitary growth hormone (GH) release, which acts on the liver to release IGF-1

What are the four primary chemical classifications of hormones?

1. Steroid hormones,

2. peptide hormones,

3. monoamine hormones

4. lipid-based hormones

What is the universal biochemical precursor for all steroid hormones?

Cholesterol is the precursor molecule from which all adrenal and gonadal steroid hormones are synthesized

What enzyme converts testosterone into estradiol?

Aromatase (P450 aromatase)

What enzyme converts testosterone into dihydrotestosterone (DHT)?

5α-reductase

How are peptide hormones synthesized in endocrine cells?

Genes are transcribed into mRNA, translated on the rough endoplasmic reticulum as large pre-pro-peptides, and cleaved by enzymes in Golgi vesicles into biologically active peptides

What is pro-opiomelanocortin (POMC)?

A large precursor pro-hormone protein that is enzymatically chopped by prohormone convertases (PC1 and PC2) into multiple active peptides, including ACTH, β-endorphin, and MSH

What precursor amino acid yields the catecholamines dopamine, norepinephrine, and epinephrine?

Tyrosine

What precursor amino acid yields serotonin and melatonin?

Tryptophan

What are eicosanoids?

Lipid-based hormones derived from phospholipids and arachidonic acid, including prostaglandins, prostacyclins, and leukotrienes

Why do lipophilic steroid hormones bind intracellular nuclear receptors?

Steroid hormones easily cross hydrophobic cell membrane lipid bilayers to bind receptors inside the cytoplasm or nucleus, where the hormone-receptor complex acts as a transcription factor

What structural feature allows steroid receptors to bind directly to target DNA sequences?

Two zinc finger domains located within the highly conserved DNA-binding domain (C domain) of the receptor

What is a G-Protein Coupled Receptor (GPCR)?

A 7-transmembrane domain cell-surface receptor that, upon hormone binding, activates intracellular G-proteins and second-messenger cascades (like cAMP or IP3/DAG)

What is a Receptor Tyrosine Kinase (RTK) mechanism?

A transmembrane cell-surface receptor (e.g., for insulin or leptin) where ligand binding induces receptor dimerization and autophosphorylation of intracellular tyrosine residues

What is the difference between homologous and heterologous receptor regulation?

Homologous regulation occurs when a hormone regulates its own receptor population, whereas heterologous regulation occurs when one hormone regulates the receptor numbers for a different hormone

What is an ultimate level of analysis in behavioral neuroendocrinology?

An evolutionary explanation that addresses why a behavior evolved, framed around natural selection, sexual selection, or reproductive success.

What is a proximate level of analysis in behavioral neuroendocrinology?

A mechanistic explanation that focuses on how a behavior occurs at the immediate physiological, cellular, neural, or hormonal level.

What are the primary systems and cellular levels used to analyze proximate mechanisms?

Examining neural circuits, endocrine glands, lesion effects, neurotransmitter alterations, cell membrane properties, and gene/protein expression.

What was Jean-Baptiste Lamarck's proposed mechanism of evolution?

Inheritance of acquired characteristics, which claimed that physical changes an organism develops through use or disuse during its lifetime (e.g., a giraffe stretching its neck) are passed to offspring.

How did Charles Darwin's theory of natural selection differ from Lamarck's view?

Darwin proposed that ancestral populations possessed pre-existing trait variations, and environmental pressures selectively favored individuals whose pre-existing traits better adapted them to survive and reproduce.

What key observation did Darwin make regarding Galápagos finches?

Finches across different islands possessed distinct beak shapes (such as long thin beaks for extracting insects between rocks vs. short thick beaks for cracking seeds) specifically adapted to local food sources.

Who co-developed the theory of natural selection alongside Charles Darwin?

Alfred Russel Wallace, a naturalist who independently formulated the theory through his own field observations.

What did Darwin mean by the phrase "survival of the fittest"?

The survival and persistence of individuals possessing adaptive physical or behavioral traits that best fit their specific environmental niche.

What is a major historical misconception associated with "survival of the fittest"?

It was falsely translated as "survival of the strongest" and used historically to justify British imperial domination, social hierarchies, and racial superiority.

What key anatomical adaptation distinguishes human evolution from most other mammals?

An exceptionally high brain-to-body mass ratio, which correlates with advanced cognitive function, social bonding, empathy, and complex communication.

What is Richard Dawkins' "Selfish Gene" hypothesis?

The theory that the gene is the fundamental unit of natural selection, and organisms act as survival vehicles driven by genes to maximize their own replication.

What is inclusive fitness?

An organism's overall evolutionary success, calculated by its own reproductive output plus the support it provides to the survival and reproduction of genetically related kin.

How does the Selfish Gene theory explain altruism toward kin?

Individuals are more likely to perform self-sacrificing or helpful acts for genetic relatives because doing so promotes the survival and propagation of shared genes.

How can environmental experiences cause rapid phenotypic changes without altering DNA sequence?

Through epigenetic mechanisms, such as DNA methylation, which alter how genes are expressed in response to environmental triggers or trauma.

What do metabolic differences between U.S. and Mexican Pima Indians demonstrate about epigenetics?

U.S. Pima Indians living on reservations with processed diets have high rates of obesity and type 2 diabetes due to altered gene methylation, whereas genetically similar Mexican Pima Indians living traditional mountain lifestyles remain lean and healthy.

What is sexual selection?

A form of natural selection favoring traits that enhance an individual's ability to compete over mates and reproduce, even if those traits increase mortality risk.

What is anisogamy and how does it drive sex differences?

Anisogamy is the fusion of two dimorphic gametes—females produce few, large, nutrient-rich eggs (macrogametes), while males produce vast numbers of small, mobile sperm (microgametes).

Why do seemingly maladaptive physical traits (such as a peacock's tail or a cardinal's bright red feathers) persist in nature?

They serve as honest signals of health, high testosterone, and low parasite load to attract females, enabling males to mate before dying.

Why did Darwin shift his theoretical emphasis from "survival of the fittest" to "survival to reproduce"?

Because surviving to a long age is evolutionary irrelevant if an organism fails to mate and pass its genes on to the next generation.

What are the four primary mechanisms of premating competition over mates?

1. Scrambles (rapid location)

2. endurance rivalry (reproductive persistence)

3. contests (fighting/weapons)

4. mate choice (attracting/stimulating partners).

What is sperm competition?

Post-copulatory competition between the sperm of different males to fertilize a female's eggs, selecting for traits like mate guarding, copulatory plugs, or high sperm volume.

What extreme mating adaptation is observed in the praying mantis?

Sexual cannibalism, where the female eats the male's head during copulation, which removes brain inhibition and increases sperm transfer to fertilize her eggs.

How do largemouth and smallmouth bass exhibit a role reversal in parental care?

Polyandrous females lay eggs in multiple nests and leave, while males construct nests, fertilize eggs, fast for up to a month, and aggressively protect the eggs and hatched fry.

What is the predominant reproductive strategy among mammalian species?

Polygyny, where a small proportion of dominant males mate with multiple females, characteristic of roughly 85% of mammalian species.

How does reproductive success differ between male and female sea lions?

Females display uniform, low-variance reproductive success (most produce 25–50 pups over a lifetime), whereas male success is highly skewed, with alpha males siring over 150 offspring and low-ranking males siring zero.

Where do male sea lions direct most of their reproductive energy compared to females?

Males expend energy on fierce male-to-male physical competition for territory and female harems, whereas females allocate energy toward gestation and maternal care.

What is male dispersal in animal colonies?

The movement of young or low-ranking males to neighboring colonies to challenge rivals and increase rank, which prevents inbreeding with female relatives.

How did Robert Trivers define parental investment?

Any investment by a parent in an individual offspring that increases that offspring's chance of surviving and reproducing at the cost of the parent's capacity to invest in future offspring.

According to Trivers, when is an individual's ultimate reproductive success truly achieved?

When their offspring successfully grow up and reproduce themselves (i.e., when the parent becomes a grandparent).

Under abundant environmental conditions, which sex of offspring do mother deer preferentially invest in?

Male offspring, because a healthy, high-quality male can potentially sire a massive number of offspring, yielding a higher evolutionary payout.

Under harsh environmental conditions or high predation, which sex of offspring do mothers preferentially invest in?

Female offspring, because females represent a lower-risk, guaranteed route to pass on genetic material.

How do female hamsters respond to severe food restriction during lactation?

They engage in selective infanticide (cannibalizing male pups) to preserve resources and raise their remaining female pups.

What is Parent-Offspring Conflict?

An evolutionary conflict over resource allocation that occurs when the cost of continued parental care to the parent's future reproduction outweighs the benefit to the offspring's inclusive fitness.

7. Animal Emotions, Cognition & Social Adaptations

What was Charles Darwin's proposal in "The Expression of the Emotions in Man and Animals"?

That humans and non-human animals share an evolutionary lineage and possess homologous neural systems that experience similar emotional states such as fear, attachment, and pain.

Which shared subcortical brain structures mediate emotional processing in both rodents and humans?

Structures such as the amygdala (for fear and threat processing) and the hypothalamus (for neuroendocrine regulation and basic drives).

What is Theory of Mind in evolutionary cognitive psychology?

The advanced cognitive ability to recognize and understand that other individuals possess distinct mental states, perceptions, and beliefs different from one's own.

Who developed the concept of milieu intérieur in 1865?

French physiologist Claude Bernard proposed milieu intérieur, stating that the constancy of the internal bodily environment is the essential condition for a free and independent life

Who coined the term "homeostasis" and in what year?

Harvard physiologist Walter Bradford Cannon coined the term "homeostasis" in 1926 and expanded it in his 1932 book The Wisdom of the Body

What Greek roots form the word "homeostasis"?

It derives from the Ancient Greek words hómos (meaning "similar") and stasis (meaning "standing still" or "condition")

What is Cannon's four-part definition of homeostasis in open biological systems?

1. Homeostasis requires active maintaining mechanisms

2. resists tendencies toward change through opposing factors

3. relies on synchronized cooperating pathways

4. results from organized self-government

Why is homeostasis described as a dynamic flux rather than a static state?

Organisms undergo continuous internal and external fluctuations, oscillating between high and low normal limits rather than remaining fixed at a static point

What is a physiological comfort zone?

A biological tolerance range bounded by upper and lower limits within which an organism functions normally without triggering corrective stress responses

What are the core components of a homeostatic negative feedback loop?

A stimulus acts on a sensor/receptor, which sends afferent input to a control center, which sends efferent output to an effector that reverses the initial imbalance

How does a negative feedback loop maintain homeostatic balance?

The effector produces a physiological or behavioral response that opposes and neutralizes the direction of the original disturbing stimulus

Which physiological parameters operate within a relatively wide homeostatic range?

Ambient temperature and thermoregulation, where minor deviations are comfortably managed before emergency responses are needed

Which physiological parameters operate within a very narrow homeostatic range?

Blood oxygen levels, blood pH, and extracellular ion/electrolyte concentrations (such as sodium, calcium, and chloride)

Why must blood oxygen and glucose levels be tightly regulated?

Oxygen is required for cellular respiration, and glucose is the primary, easily accessible fuel for brain and cellular energy metabolism

Why does the brain closely monitor circulating electrolyte ions like calcium, sodium, and chloride?

Precise ionic charges and concentration gradients across cell membranes are essential for generating electrical action potentials in neurons

What is the definition of allostasis?

The dynamic physiological process of achieving stability through change, where the body alters set points in anticipation of future demands

Who introduced the concept of allostasis and allostatic load?

Sterling and Eyer (1988) and Bruce McEwen (1998) introduced allostasis to describe the energetic cost and set-point shifts driven by chronic adaptation

What is the immediate biochemical response to an initial drop in food or glucose intake?

Circulating glucocorticoids trigger glycogenolysis, breaking down stored glycogen in the liver and skeletal muscles into free glucose

What metabolic shift occurs if food deprivation continues past several hours?

The body shifts to lipolysis, breaking down adipose fat tissue into usable energy, which yields abundant energy but requires higher metabolic effort to burn

What extreme metabolic emergency measures occur during prolonged starvation after fat stores are depleted?

The body metabolizes structural muscle protein, drastically reduces basal metabolic rate, and shuts down non-essential processes like gastrointestinal mucosal cell renewal