Homeostasis, Hormones, and Sexual Development: Key Concepts for Biology

What is homeostasis?

The process by which the body's substances and characteristics are maintained at their optimal level.

What is a system variable?

A variable controlled by a regulatory mechanism.

Define set point.

The optimal value of the system variable in a regulatory mechanism.

What is a detector in a regulatory mechanism?

A mechanism that signals when the system variable deviates from the set point.

What is a correctional mechanism?

A mechanism that is capable of changing the value of the system variable.

What is negative feedback?

A process whereby the effect produced by an action serves to diminish or terminate that action.

What are intracellular fluids?

Fluids contained within cells.

What are extracellular fluids?

All body fluids outside cells.

What is osmoreceptor?

A neuron that detects changes in the solute concentration of the interstitial fluid.

What triggers osmometric thirst?

An increase in the osmotic pressure of the interstitial fluid relative to the intracellular fluid.

What is vasopressin?

A hormone released by the posterior pituitary that raises blood pressure and enables kidneys to reabsorb water.

What causes volumetric thirst?

Hypovolemia, or a reduction in the volume of intravascular fluid.

What is angiotensin II?

A peptide hormone that constricts blood vessels, retains sodium and water, and produces thirst.

What is the role of the median pre-optic nucleus?

It integrates signals from OVLT, SFO, and the nucleus of the solitary tract to drive drinking behavior.

What is ghrelin?

A hormone that stimulates hunger, with levels increasing before a meal.

What is glucoprivation?

A dramatic fall in the level of glucose available to cells.

What is lipoprivation?

A dramatic fall in the level of fatty acids available to cells.

What is leptin?

A hormone secreted by adipose tissue that may be involved in long-term satiety.

What happens when insulin levels are high?

They generally decrease appetite.

What is the function of CCK (cholecystokinin)?

It reduces gastric emptying and promotes satiety.

What is the feast or famine hypothesis?

The need for building blocks and fuel, balancing food availability, metabolism, body weight, and nutrition.

What is the role of the lateral hypothalamus?

It regulates hunger.

What are NPY neurons?

Neurons that, when excited, signal hunger.

What is the relationship between NPY and CART neurons?

When NPY neurons are inhibited and CART neurons are excited, it signals satiety.

What is the significance of circumventricular organs?

They are specialized brain regions that detect changes in blood composition and influence thirst.

What is adipsia?

A lack of drinking, often caused by damage to circumventricular organs.

What is the difference between sex and gender?

Sex refers to genetic and physiological attributes, while gender refers to identity and behaviors.

What are the two types of hormone effects in sexual development?

Organizational effects (development of sex organs and brain) and activational effects (activation of processes later in life).

What determines the genetic sex of an offspring?

The genetic sex is determined by whether the sperm carries an X or Y chromosome.

What are the three categories of sex organs?

Gonads (testes and ovaries), internal sex organs, and external sex organs.

What is the role of the SRY gene?

The SRY gene on the Y chromosome determines whether testes or ovaries develop.

What happens if the SRY protein is absent?

If SRY protein is absent, ovaries develop.

What is the default sex organ development?

The default is female, requiring no hormones for development.

What is Anti-Mullerian Hormone?

A peptide secreted by fetal testes that inhibits the Mullerian system, acting as a defeminizing hormone.

What are androgens?

Masculinizing hormones that promote the development of the Wolffian system, including testosterone and dihydrotestosterone.

What is Androgen Insensitivity Syndrome?

A condition where an XY male has testes but develops female external characteristics and cannot become pregnant.

What is Persistent Mullerian Duct Syndrome?

An XY male with both male and female internal sex organs due to lack of defeminization.

What is Turner's syndrome?

A condition with only one sex chromosome (usually XO) resulting in female sex organs but no gonads.

What initiates sexual maturation?

Sexual maturation begins around puberty, including the development of secondary sex characteristics.

What are Gonadotropin-Releasing Hormones (GnRH)?

Hormones released from the hypothalamus that stimulate the production of gonadotropic hormones.

What are the two gonadotropic hormones produced by the anterior pituitary gland?

Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH).

What is the menstrual cycle?

A monthly cycle in female primates where the uterine lining is shed and mating can occur at any time.

What is the estrous cycle?

A reproductive cycle in non-primate mammals where the endometrium is reabsorbed without pregnancy.

What role does estradiol play in the menstrual cycle?

Estradiol promotes the growth of the uterine lining and triggers LH release.

What is the function of prolactin?

A hormone important for milk production and maternal behavior.

What is the medial preoptic area responsible for?

It plays a role in maternal behavior and is stimulated by prolactin.

What is the pup avoidance response?

A behavior that must be removed for maternal behavior to occur.

What is the role of dopamine circuitry in maternal behavior?

Dopamine circuitry is involved in the motivation and rewards for maternal behavior.

What is the relationship between VMH activity and aggression in males?

VMH activity in males is correlated with aggression and must be inhibited for mating behavior.

What is the significance of the 'see-saw' control in mating and aggression?

It describes how the same neural circuits can activate different behaviors (mating vs. aggression) in males and females.

What are the effects of testosterone loss on sexual behavior?

It can influence willingness and ability to engage in sexual behavior, often linked to social status.

What is the role of pheromones in sexual behavior?

Pheromones interact with the vomeronasal organ and amygdala to influence sexual behavior.