Physiology Lecture Notes: Diffusion, Osmosis, and Control of Autonomic and Fluid Compartments

Vocabulary flashcards covering key terms and definitions from the lecture notes on diffusion, osmosis, and autonomic control in physiology.

Diffusion

Passive movement of molecules from an area of high concentration to an area of low concentration until uniform distribution (equilibrium) is reached.

Passive process

Diffusion is a passive process that requires no energy input; it happens automatically down the concentration gradient.

Concentration gradient

Difference in concentration between two regions; diffusion proceeds from high concentration to low concentration along this gradient.

Equilibrium

A state where concentrations are uniform across space; net diffusion ceases.

Osmosis

Diffusion of water across a semipermeable membrane toward the side with higher solute concentration.

Hydrophilic

Polar solutes that dissolve in water; water-loving.

Hydrophobic

Nonpolar solutes that do not dissolve well in water; lipid-loving.

Polar molecule

A molecule with an uneven distribution of charge, leading to partial positive and negative sides (e.g., water).

Nonpolar molecule

A molecule with an even distribution of charge, not readily soluble in water.

Intracellular fluid (ICF)

Fluid inside cells; makes up about two-thirds of the body's total water.

Extracellular fluid (ECF)

Fluid outside cells; includes interstitial fluid and plasma.

Interstitial fluid

Fluid between cells within tissues; part of the extracellular fluid.

Plasma

Fluid component of blood; the liquid part through which cells and proteins circulate.

Cell membrane

Lipid bilayer that encloses a cell; contains phospholipids and provides a selective barrier between the intracellular and extracellular environments.

Phospholipid

Amphipathic molecule that forms the lipid bilayer of cell membranes.

Viscosity

A fluid’s resistance to flow; higher viscosity slows diffusion.

Temperature

Higher temperature increases molecular motion and speeds up diffusion.

Alveolus

Tiny air sac in the lung where gas exchange with blood occurs.

Capillary

Small blood vessel surrounding alveoli; site of diffusion between air and blood.

Bulk transport

Movement of large amounts of substance via mechanical means (e.g., breathing air in/out, pumping blood by the heart) to overcome diffusion limits.

Anterior

Front (ventral) side of the body.

Posterior

Back (dorsal) side of the body.

Positive feedback

A cycle that amplifies the stimulus; can be pathological if unchecked (e.g., fever); example in labor where the loop eventually stops due to exit of the stimulus.

Negative feedback

A loop that counteracts deviations to maintain homeostasis.

Sympathetic nervous system

Part of the autonomic nervous system that drives the fight-or-flight response; generally increases heart rate and energy mobilization.

Parasympathetic nervous system

Part of the autonomic nervous system responsible for rest-and-digest activities; generally slows the heart rate and conserves energy.

Tonic control

A baseline level of control maintained by one regulatory input (e.g., continuous vascular tone).

Antagonistic control

Two opposing regulatory inputs control a system (e.g., sympathetic vs. parasympathetic inputs to heart rate).