Action Potential  -  An action potential is an electrical signal carried through the neuron that, if strong enough, causes the release of neurotransmitters.

Astrocyte  -  Astrocytes are cells that support neurons by keeping the biochemical environment favorable for neuronal functioning.

Axon  -  The axon is part of the neuron that resembles a long arm stretching outward from the soma. It carries the action potential from the soma to the terminal bouton.

Axon Hillock  -  The axon hillock lies where the axon meets the soma. Electrical charge collects at the axon hillock until it is released in an action potential that travels down the axon to the terminal bouton.

Current Clamp  -  Current clamp is a type of single-cell recording in which the neuron's current is held constant and its voltage is recorded.

Dendrite  -  The dendrite resembles many branches stretching out from the soma of the neuron. These branches receive signals from other neurons. The dendrite is covered with many receptors that bind neurotransmitters released from other neurons.

Dendritic Spine  -  Dendrites are covered with dendritic spines that branch out to provide more surface area for neurotransmitters to bind.

Depolarize  -  When the membrane potential of a cell becomes less negative than usual, we say that the cell is depolarized. Depolarization during an action potential is caused by sodium ions flowing into the cell.

Dopamine  -  Dopamine is a neurotransmitter involved in the brain's pleasure system. When we experience pleasure, dopamine levels in the brain increase.

Dopaminergic System  -  The dopaminergic system refers to neurons that make and release the neurotransmitter dopamine. The dopaminergic system is involved in the pleasure response, and deficits in the system may be involved in mental disorders such as schizophrenia.

Electron Microscopy  -  Individual cells, too small to be seen using conventional light microscopy, can be seen using electron microscopy. There are several types of electron microscopes that use very different, complex mechanisms to visualize cells.

Endoplasmic Reticulum (ER)  -  The endoplasmic reticulum is an organelle found in almost all cells in the body, including neurons. It produces proteins necessary for cell survival.

Excitatory Neurotransmitter  -  Neurotransmitters that make the postsynaptic neuron more likely to generate an action potential are called excitatory neurotransmitters.

GABA (Gamma-aminobutryic acid)  -  GABA is an inhibitory neurotransmitter found in many neurons in the brain and spinal cord. It depresses the neurons that receive it, making them less likely to fire an action potential.

Glia  -  Glia are cells that help neurons do their job by performing various support functions. There are three principal types of glia in the central nervous system: astrocytes, oligodendrocytes, and microglia.

Glutamate  -  Glutamate is the most common excitatory neurotransmitter in the central nervous system. Neurons which receive and bind to glutamate become more likely to fire an action potential.

Golgi Apparatus  -  The Golgi apparatus is an organelle found in almost all cells in the body, including neurons. It helps transport newly formed proteins to their proper places in the cell.

Inhibitory Neurotransmitter  -  Inhibitory neurotransmitters are chemicals released by neurons that suppress the activity of other neurons. When a neuron binds to an inhibitory neurotransmitter, it becomes less likely to fire an action potential.

Ion  -  An atom with a positive or negative charge is called an ion. Atoms become charged by having more or fewer electrons than they have in their neutral state. Calcium (Ca2+), sodium (Na+), and potassium (K+) ions play important roles in neurotransmission.

Ion Channel  -  Ion channels lie in the membrane and allow certain ions to flow in and out of the cell. Some ion channels are coupled to neurotransmitter receptors while others depend on the electrochemical gradient in the cell. Ion channels' principal functions are to alter the membrane potential or to let calcium into the cell.

Membrane Potential  -  The membrane potential of a cell can be measured in volts. It is the difference between the electrical charge inside and outside of the cell. The membrane potential is altered dramatically during an action potential.

Microglia  -  Microglia are supporting cells that help repair damaged neurons.

Mitochondria  -  Mitochondria are organelles found in almost every cell in the body, including neurons. They make energy for the cell using sugars and oxygen.

Myelin  -  A thick sheath of myelin covers a neuron's axon to insulate the electrical charge that the axon carries during an action potential. Myelin allows the electrical current to travel farther and faster than it would otherwise. Oligodendrocytes and Schwann cells are responsible for making myelin.

Neuron  -  Neurons are cells that carry and transmit electrical signals in the central and peripheral nervous systems.

Neurotransmitter  -  Neurotransmitters are chemicals secreted by neurons as a result of an action potential. Neurotransmitters bind to receptors on other neurons and impact those cells, usually by making them either more or less likely to fire an action potential.

Node of Ranvier  -  Nodes of Ravier are periodic openings in the myelin sheath coating the axon. These holes help propagate the action potential by allowing ions to flow in and out of the cell at those points.

Nucleus  -  The nucleus is an organelle present in every cell in the body, including neurons. The nucleus contains all of the cell's DNA.

Oligodendrocyte  -  Oligodendrocytes are supporting cells that aid neurons by manufacturing the myelin sheath that insulates the axon.

Organelle  -  An organelle is a small, membrane-bound enclosure within a cell that performs some function necessary for the cell's survival.

Postsynaptic Neuron  -  At a synapse, where two neurons connect, the neuron whose dendritic or somatic receptors bind neurotransmitters is called the postsynaptic neuron.

Postsynaptic Receptor  -  Postsynaptic receptors lie in the membrane of the postsynaptic neuron, usually on the dendrite. These receptors bind to the neurotransmitters released from the presynaptic neuron and subsequently cause some change to the postsynaptic cell, often making it either more or less likely to fire an action potential.

Presynaptic Neuron  -  At a synapse, where two neurons connect, the neuron whose axon releases neurotransmitters is called the presynaptic neuron.

Repolarize  -  When the membrane potential of a cell becomes less positive during an action potential, returning the neuron's voltage to its usual levels, we say that the cell is repolarized. Repolarization during an action potential is caused primarily by potassium ions flowing out of the cell.

Resting Membrane Potential  -  The resting membrane potential of a cell is the electrical gradient, in volts, across the cell's membrane when no action potential is being fired. The resting membrane potential of a neuron varies with the type of neuron being studied, but it is usually between -40 and -90 millivolts.

Ribosome  -  A ribosome is a specialized vesicle used to transport newly formed proteins across the cell.

Schwann Cell  -  Schwann cells are supporting cells which form the myelin sheath on neurons in the peripheral nervous system.

Selective Serotonin Reuptake Inhibitor (SSRI)  -  Depression seems to be linked to a deficit in the neurotransmitter serotonin. SSRIs are a class of drugs that alleviate depression by increasing the length of time that serotonin stays in the synapse after it is released, making it more likely to bind to postsynaptic receptors. Prozac is one well-known SSRI.

Serotonin (5-HT)  -  Serotonin is a neurotransmitter released by many of the brain's neurons. It has been linked to psychological disorders such as depression and obsessive- compulsive disorder. A deficit in levels of serotonin can be corrected with a recently developed class of drugs called SSRIs.

Single-Cell Recording  -  Single-cell recording is a method used in research to observe voltage or current changes in a cell. An electrode is inserted into one neuron and measures electrical charges in that neuron.

Soma  -  The soma is the main body of a neuron and contains all of the organelles. The dendrites and axon of a neuron radiate outward from the soma.

Synapse  -  A synapse is a point of communication between two neurons (one sending a signal and the other receiving it).

Synaptic Cleft  -  The space between two neurons is called the synaptic cleft. Neurotransmitters are released from the axon of the presynaptic neuron into the synaptic cleft, where they float around until they are picked up by receptors on the postsynaptic neuron.

Terminal Bouton  -  The terminal bouton is a bubble-like structure that lies at the end of the axon. Vesicles filled with neurotransmitters sit in the terminal bouton, waiting for a strong action potential to signal their release.

Vesicle  -  A vesicle is a membrane-bound bubble that can hold supplies for the cell. When a strong action potential reaches the terminal bouton, vesicles containing neurotransmitters fuse with the neuron's membrane and release their contents into the synapse, sending a signal to the next neuron.

Voltage Clamp  -  Voltage clamp is a type of single-cell recording in which the neuron's voltage is held constant and its current is measured.