Glossary

enzyme that converts testosterone into DHT

A procedure that removes a structure and/or its function

occurs during the rising and falling phase of the action potential. Another action potential cannot be fired under any circumstance during this time.

enzyme that breaks down acetylcholine

Alpha (α) rays are high energy rays emitted by radioactive particles. α-rays are comprised of alpha (α) particles, each of which carries two positive charges. Based on its mass, it was apparent that each α-particle is equivalent to a Helium (He) nucleus, with two protons and two neutrons.

The long process that extends from the cell body; transmits the action potential from the cell body to the axon terminal.

Beta (β) rays are emitted by radioactive materials. β-rays were found to be made up of high energy electrons; so each β-particle is an electron, moving at a high speed because breakdown of radioactive atoms results in emission of electrons which are accelerated to a high speed..

Cell division in the early embryo, following fertilization. Initial cell divisions are synchronized, since expression is controlled by translation of maternally contributed mRNA and enzymes. After a few cycles of cell division, embryonic transcription starts, at which point each cell starts to develop differently.

Current flow is essentially any movement of ions; conversely, ion flow is assessed as current

Processes that branch out in a tree-like fashion from the neuronal cell body and are the main target for incoming signals received from other neurons.

More electronegative elements have atoms that easily attract or accept electrons. Oxygen is an important biologically relevant electronegative element; in fact, oxygen is the most electronegative biologically relevant element.

Stage in development where all the precursor (stem) cells are arranged in a single layer, ready for gastrulation.

Stage in development where the zygote transforms into a 3-layered structure, with defined ectoderm, mesoderm and endoderm. In most animals, this involves folding in which one group of cells passes under or below other cells to create multiple layers.

Vary in magnitude, depending on input. Graded potentials thus differ from action potentials, which are all or none (binary).

An atom or molecule that carries a net positive or negative charge (See Fig E3, chapter Bioelectricity). Net charge is changed by the loss or gain of electrons.

Charged particles are generally hydrophilic, since they can assimilate within the fluid structure of polarized water molecules.

Malleability is the property of a metal that allows it to be beaten (hammered) into extremely thin sheets. Gold can be made into sheets that are only a couple of atoms thick! These sheets are so thin, that some are used as decoration in very expensive sweets in South Asia, especially during weddings and festivals.

The basic cellular unit of the brain that is electrically excitable and can transmit information to other cells through synapses.

Mesodermal cylinder formed during gastrulation. It serves as a signaling center, and specifies ventral cells of the neural tube as motor neurons, while dorsal cells develop into sensory interneurons under the influence of epidermal signaling.

The model of an atom where all subatomic particles are distributed evenly within the atom, like plums, raisins, and nuts in a pudding. Note that by this time, scientists already knew that atoms were made up of subatomic particles, named neutrons, protons and electrons.

The cell body, which houses the nucleus and other organelles necessary for cellular functioning.