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Homeostasis

The body's ability to maintain relatively stable internal conditions.

Positive Feedback Mechanism

A process that amplifies a physiological trend.

Negative Feedback Mechanism

A process that reverses a trend to return to a set-point.

Atom

The smallest unit of an element, made up of protons, neutrons, and electrons.

Proton

A positively charged subatomic particle found in an atom's nucleus.

Neutron

A subatomic particle with no electric charge, found in the nucleus of an atom.

Electron

A negatively charged subatomic particle that orbits the nucleus of an atom.

Isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Covalent Bond

A bond formed when two atoms share electrons.

Hydrophilic

Water-loving; substances that can easily interact with water.

Hydrophobic

Water-fearing; substances that repel water.

Osmosis

The movement of water molecules through a membrane from an area of higher to lower solute concentration.

Suspension

A mixture where solid particles do not dissolve in a liquid.

Colloid

A mixture where particles remain distributed throughout the solution.

Plasma Membrane

A biological membrane that separates and protects the interior of cells from the outside environment.

Glycoprotein

A protein that has carbohydrate molecules attached, often functioning in cell recognition and communication.

Endocytosis

The process of moving substances into a cell by forming vesicles from the cell membrane.

Exocytosis

The process where substances are secreted from a cell via vesicles.

Neuron

A nerve cell that is responsible for transmitting electrical signals throughout the body.

Electrochemical Gradient

A gradient that combines the concentration gradient and the electric potential gradient across a membrane.

pH

A measure of how acidic or basic a solution is.

Buffer

A solution that helps maintain stable pH levels in a system.

Valence Electrons

The electrons in the outermost shell of an atom, crucial for bonding.

Atomic Number

The number of protons in the nucleus of an atom, defining the element.

Mass Number

The total number of protons and neutrons in an atom's nucleus.

Electron Shell

The region around an atom's nucleus where electrons are likely to be found.

Ionic Bond

A chemical bond formed through the transfer of electrons from one atom to another.

Neutral Atom

An atom with an equal number of protons and electrons, resulting in no net charge.

Radioactive Isotope

An isotope that is unstable and emits radiation during its decay.

Electron Configuration

The arrangement of electrons in an atom's electron shells.

Proton and Neutron Mass

Protons and neutrons have approximately equal mass, both much heavier than electrons.

Chemical Symbol

A one or two-letter notation used to represent an element in chemical reactions.

Axon

A long, slender projection of a neuron that conducts electrical impulses away from the neuron's cell body.

Axon Terminal

The endpoint of an axon where neurotransmitters are released into the synapse.

Soma

The cell body of a neuron, containing the nucleus and organelles.

Dendrites

Branch-like structures of a neuron that receive signals from other neurons.

Secretion

The process by which substances are produced and released from cells.

Excretion

The process of removing waste products from the body.

Axoneme

The structural core of a cilium or flagellum, composed of microtubules.

Cilia

Short, hair-like structures that protrude from the surface of some eukaryotic cells, facilitating movement.

Flagella

Long, whip-like structures that enable movement in some bacteria and eukaryotic cells.

Neurotransmitter

Chemical messengers released from axon terminals to transmit signals between neurons.

Ribosome

A cellular structure that synthesizes proteins by translating messenger RNA.

Membrane Organelles

Organelles that are enclosed by membranes, such as the nucleus, mitochondria, and endoplasmic reticulum.

Non-Membrane Organelles

Cellular structures that lack membranes, such as ribosomes and cytoskeleton components.

Cytoskeleton

A network of protein filaments and tubules that provides structural support and facilitates cell movement.

Exocytosis

The process by which substances are expelled from a cell through vesicles that fuse with the plasma membrane.

Inclusion

A stored substance within the cytoplasm of a cell, such as lipid droplets or glycogen granules.

Nucleus

The membrane-bound organelle that contains the cell's genetic material and controls cellular activities.

Rough Endoplasmic Reticulum (RER)

A type of endoplasmic reticulum that is studded with ribosomes and involved in protein synthesis and processing.

Smooth Endoplasmic Reticulum (SER)

A type of endoplasmic reticulum that lacks ribosomes and is involved in lipid synthesis and detoxification processes.

Endocytosis

The process by which cells internalize substances from their external environment by engulfing them with the plasma membrane.