Ingestion, Thirst, and Feeding — Key Terms (Video Notes)

Vocabulary flashcards covering key terms related to ingestion, thirst regulation, and feeding control as presented in the lecture notes.

Homeostasis

Process by which the body maintains substances and characteristics at their optimal level.

System variable

A variable controlled by a regulatory mechanism.

Set point

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

Detector

Mechanism that signals when the system variable deviates from the set point.

Correctional mechanism

Mechanism capable of changing the value of the system variable.

Negative feedback

Process where the effect of an action reduces or terminates that action.

Satiety mechanism

Process that signals fullness and inhibits further intake (e.g., drinking).

Inhibition

Suppression of a response, such as stopping drinking when satiated.

Intracellular fluid

Fluid contained within cells.

Extracellular fluid

All body fluids outside cells.

Intravascular fluid

Fluid found within blood vessels.

Interstitial fluid

Fluid that bathes cells and fills spaces between them.

Isotonic

Having equal osmotic pressure to the contents of a cell.

Osmometric (osmotic) thirst

Thirst produced by increased osmotic pressure in interstitial fluid relative to intracellular fluid.

Osmoreceptor

Neuron that detects changes in solute concentration of interstitial fluid.

Circumventricular organs (CVOs)

Brain regions with rich blood supply along the ventricular system, lacking a typical blood–brain barrier.

OVLT (organum vasculosum of the lamina terminalis)

CVO lacking a blood–brain barrier; major site of osmoreceptors near the third ventricle.

SFO (subfornical organ)

CVO near the third ventricle with osmoreceptors involved in thirst.

Median preoptic nucleus

Hypothalamic nucleus whose output drives drinking behavior; integrates osmoreceptor signals.

Vasopressin (antidiuretic hormone, ADH)

Hormone from the posterior pituitary that promotes water reabsorption and can raise blood pressure; inhibits urine production; alcohol inhibits it.

Angiotensin II

Peptide hormone that constricts vessels, promotes water and sodium retention, and stimulates thirst and salt appetite.

Renin

Kidney enzyme that converts angiotensinogen to angiotensin II.

Hypovolemia

Reduction in the volume of intravascular fluid (blood loss, dehydration).

Volumetric thirst

Thirst produced by hypovolemia; involves kidney–brain interactions.

Ghrelin

Hunger-stimulating hormone released from the stomach; rises before meals.

Cholecystokinin (CCK)

Digestive hormone that promotes satiety by slowing gastric emptying and signaling fullness.

Distension

Stretch of the stomach sensed by receptors; signals via the vagus nerve to promote satiety.

Vagus nerve

Cranial nerve transmitting visceral signals (e.g., stomach distension) to the brain.

NPY neurons

Neuropeptide Y neurons in the arcuate nucleus; promote hunger when activated.

CART

Cocaine- and amphetamine-regulated transcript; promotes satiety and inhibits feeding.

Leptin

Hormone from adipose tissue signaling long-term energy stores; promotes satiety.

Lateral hypothalamus (LH)

Brain region associated with hunger/prompting feeding.

Arcuate nucleus

Hypothalamic nucleus that coordinates feeding by influencing LH and VMH; contains NPY and CART neurons.

Ventromedial hypothalamus (VMH)

Brain region associated with satiety and inhibition of feeding.

Orexin

Hypothalamic peptide that stimulates feeding and arousal.

MCH (melanin-concentrating hormone)

Hypothalamic peptide involved in promoting feeding and energy balance.

Adipsia

Lack of drinking due to damage to circumventricular organs or related pathways.

Glucose

Primary brain fuel; blood sugar level influences feeding via hormones like insulin and glucagon.

Insulin

Hormone that rises before and after meals; generally decreases appetite by signaling energy abundance.

Glucagon

Hormone that raises blood glucose when levels are low.

Glycogen

Stored glucose in liver and muscles; converted from glucose when energy is abundant.

Lipoprivation

Dramatic fall in fatty acids available to cells, contributing to meal initiation signals.

Glucoprivation

Dramatic fall in glucose available to cells; triggers feeding signals.

Prader-Willi syndrome

Genetic condition characterized by insatiable hunger and obesity, linked to dysregulated hunger signals.