AP Bio Chapter 37: Neurons, Synapses, and Signaling

Neuron

A nerve cell; the fundamental unit of the nervous system, having structure and properties that allow it to conduct signals by taking advantage of the electrical charge across its plasma membrane.

Brain

Organ of the central nervous system where information is processed and integrated.

Ganglion

A cluster (functional group) of nerve cell bodies.

Cell body

The part of a neuron that houses the nucleus and most other organelles.

Dendrite

One of usually numerous, short, highly branched extensions of a neuron that receive signals from other neurons.

Axon

A typically long extension, or process, of a neuron that carries nerve impulses away from the cell body toward target cells.

Synapse

The junction where a neuron communicates with another cell across a narrow gap via a neurotransmitter or an electrical coupling.

Neurotransmitter

A molecule that is released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft, and binds to the postsynaptic cell, triggering a response.

Glia

Cells of the nervous system that support, regulate, and augment the functions of neurons.

Sensory neuron

A nerve cell that receives information from the internal or external environment and transmits signals to the central nervous system.

Interneuron

An association neuron; a nerve cell within the central nervous system that forms synapses with sensory and/or motor neurons and integrates sensory input and motor output.

Motor neuron

A nerve cell that transmits signals from the brain or spinal cord to muscles or glands.

Central nervous system (CNS)

The portion of the nervous system where signal integration occurs; in vertebrate animals, the brain and spinal cord.

Peripheral nervous system (PNS)

The sensory and motor neurons that connect to the central nervous system.

Nerve

A fiber composed primarily of the bundled axons of neurons.

Membrane potential

The difference in electrical charge (voltage) across a cell's plasma membrane due to the differential distribution of ions. This affects the activity of excitable cells and the transmembrane movement of all charged substances.

Resting potential

The membrane potential characteristic of a nonconducting excitable cell, with the inside of the cell more negative that the outside.

Sodium-potassium pump

A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell.

Ion channel

A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.

Equilibrium potential

The magnitude of a cell's membrane voltage at equilibrium, calculated using the Nernst equation.

Gated ion channel

A gated channel for a specific ion. The opening or closing of such channels may alter a cell's membrane potential.

Hyperpolarization

A change in a cell's membrane potential such that the inside of the membrane becomes more negative relative to the outside. This reduces the chance that a neuron will transmit a nerve impulse.

Depolarization

A change in a cell's membrane potential such that the inside of the membrane is made less negative relative to the outside.

Graded potential

In a neuron, a shift in the membrane potential that has an amplitude proportional to signal strength and that decays as it spreads.

Action potential

An electrical signal that propagates (travels) along the embrane of a neuron or other excitable cell as a nongraded (all-or-none) depolarization.

Voltage-gated ion channel

A specialized ion channel that opens or closes in response to changes in membrane potential.

Threshold

The potential that an excitable cell membrane must reach for an action potential to be initiated.

Refractory period

The short time immediately after an action potential in which the neuron cannot respond to another stimulus, owing to the inactivation of voltage-gated sodium channels.

Myelin sheath

Wrapped around the axon of a neuron, an insulating Cora of cell membranes from Schwann cells or oligodendrocytes. It is interrupted by nods of Ranvier, where action potentials are generated.

Oligodendrocyte

A type of glial cell that forms insulating myelin sheaths around the axons of neurons in the central nervous system.

Schwann cell

A type of glial cell that forms insulating myelin sheaths around the axons of neurons in the peripheral nervous system.

Node of Ranvier

Gap in the myelin sheath of certain axons where an action potential may be generated. In Salvatore conduction, an action potential is regenerated at each node, appearing to "jump" along the axon from node to node.

Saltatory conduction

Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.

Ligand-gated ion channel

A transmembrane protein containing a pore that opens or closes as it changes shape in response to a signaling molecule (ligand), allowing or blocking the flow of specific ions; also called an ions tropic receptor.

Excitatory postsynaptic potential (EPSP)

An electrical charge (depolarization) in the membrane of a postsynaptic cell caused by the binding of an excitatory neurotransmitter from a pre synaptic cell to a postsynaptic receptor; makes it more likely for a postsynaptic cell to generate an action potential.

Inhibitory postsynaptic potential (IPSP)

An electrical charge (usually hyperpolarization) in the membrane of a postsynaptic neuron caused by the binding of an inhibitory neurotransmitter from a presynaptic cell to a postsynaptic receptor; makes it more difficult for a postsynaptic neuron to generate an action potential.

Temporal summation

A phenomenon of neural integration in which the membrane potential of the postsynaptic cell in a chemical synapse is determined by the combined effect of EPSPs or IPSPs produced in rapid succession.

Spatial summation

A phenomenon of neural integration in which the membrane potential of the postsynaptic cell is determined by the combined effect of EPSPs or IPSPs produced nearly simultaneously by different synapses.

Acetylcholine

One of the most common neurotransmitter; functions by binding to receptors and altering the permeability of the postsynaptic membrane to specific ions, either depolarizing or hyperpolarizing the membrane.

Glutamate

An amino acid that functions as a neurotransmitter in the central nervous system.

Gamma-aminobutryic acid (GABA)

An amino acid that functions as a neurotransmitter in the central nervous system of vertebrates.

Biogenic amine

A neurotransmitter derived from an amino acid.

Norepinephrine

A catecholamine that is chemically and functionally similar to epinephrine and that acts as a hormone or neurotransmitter; also known as noradrenaline.

Dopamine

A neurotransmitter that is a catecholamine, like epinephrine and norepinephrine.

Seratonin

A neurotransmitter, synthesized from the amino acid tryptophan, that functions in the central nervous system.

Neuropeptide

A relatively short chain of amino acids that survives as a neurotransmitter.

Endorphin

Any of several hormones produced in the brain and anterior pituitary that inhibit pain perception.