Homeostasis, the Stress Response, Hierarchy of Life, and Evolution

Comprehensive vocabulary flashcards covering feedback loops, autonomic nervous system divisions, endocrine stress responses, biological levels of organization, and Darwinian natural selection.

Negative Feedback

A regulatory response to a stimulus that counteracts, reverses, or opposes the initial change to maintain homeostasis.

Positive Feedback

A regulatory response that amplifies, reinforces, or accelerates an initial stimulus or reaction.

Sympathetic Nervous System

The branch of the autonomic nervous system that triggers the "fight or flight" response during stress or danger by dilating pupils, halting saliva production, increasing heart rate, and relaxing airways.

Parasympathetic Nervous System

The branch of the autonomic nervous system that promotes "rest and digest," calming the body, conserving energy, and restoring homeostasis after a stressful event.

Cortisol

A stress hormone that maintains the body in a "fight or flight" state; chronic elevation causes health risks including impaired immunity, high heart rate, infertility, heart attacks, and strokes.

Acute Stress

An immediate stress response that is intense in action but short in duration, after which the body quickly returns to parasympathetic homeostasis.

Chronic Stress

A low-intensity, long-duration stress state characterized by continuous cortisol release, worn-down physiological systems, and impaired reaction times to sudden dangers.

Atom

The basic unit of all matter and building block of life that chemically bonds with other atoms to form molecules.

Molecule

The smallest unit of a chemical substance that retains its properties, formed when atoms combine through chemical bonding.

Organelle

A specialized sub-cellular structure ("tiny organ") that performs dedicated life processes inside a cell, such as the mitochondrion.

Cell

The basic structural and functional unit of life and the smallest entity capable of carrying out independent life processes.

Prokaryote

A type of cell that lacks a nucleus and membrane-bound organelles.

Eukaryote

A complex cell possessing a true membrane-bound nucleus and specialized organelles.

Stem Cells

Undifferentiated and non-specialized cells that retain the potential to differentiate into various cell types and execute distinct functions.

Cell Specialization

The developmental process by which undifferentiated cells mature into distinct types with specific roles.

Tissue

A group of differentiated, similar cells organized together to execute a specific function (e.g., muscle or bone).

Organ

A discrete structure composed of different tissues working together to carry out a common physiological task (e.g., heart, lungs, brain).

Organ System

A coordinated group of organs functioning cooperatively to perform major body jobs (e.g., digestive, circulatory, or respiratory systems).

Organism

An individual living entity composed of integrated organ systems functioning together to survive independently.

Population

A group of individuals belonging to the same species that inhabit a specific geographic area.

Community

All the interacting populations of different living species inhabiting a shared environment.

Ecosystem

A dynamic biological community of interacting biotic (living) and abiotic (non-living) factors within a geographical area.

Biome

A broad ecological region defined by the interaction of closely related ecosystems.

Biosphere

The global zone of life on Earth integrating all biotic and abiotic factors across the entire planet.

Epinephrine

A hormone produced in the adrenal medulla during fight-or-flight that increases heart rate and force, dilates airways, raises blood glucose, and selectively adjusts blood vessel diameter.

Norepinephrine

A hormone produced in the adrenal medulla that maintains alertness and blood pressure by moderately increasing heart rate, constricting most blood vessels, and slightly raising blood glucose.

Natural Selection

The evolutionary mechanism wherein individuals with advantageous traits are more fit, survive longer, and reproduce more, passing those traits to future generations.

Variation (Darwinian Theory)

Heritable genetic, behavioral, or physiological differences present among individuals within a species, such as differing stress responsiveness.

Survival of the Fittest

The Darwinian concept where "fitness" refers to being best adapted or suited to survive and reproduce in a specific environmental context.

Baroreceptors

Sensory receptors located in arterial walls that detect elevated blood pressure and signal the brain medulla to lower heart rate and dilate vessels.

Frank-Starling Mechanism

A physiological response in which increased venous return stretches cardiac muscle, stimulating a stronger contraction to increase cardiac output.

Thermoreceptors

Sensory receptors in the skin and hypothalamus that detect body temperature changes, such as increases above $37^\circ\text{C}$, to activate cooling mechanisms like sweating and vasodilation.