Neuronal pools

Functional groups of neurons that process and ingrate information.

Sodium-potassium (Na+-K+) pump

A primary active transport system that simultaneously drives Na+ out of the cell against a s steep gradient and pumps K+ back in. Also called Na+-K+ ATPase.

Involuntary nervous system

The autonomic nervous system

Acetylcholinesterase (AChE)

Enzyme present at the neuromuscular junction and synapses that degrades acetylcholine and terminates its action.

Peripheral nervous system (PNS)

Portion of the nervous system consisting of nerves and ganglia that lie outside of the brain and spinal cord.

Nerve growth factor (NGF)

Protein that promotes survival and development of neurons; secreted by their target cells and many other cell types.

Dendrite

Branching neuron process that serves as a receptive, or input, region; transmits an electrical signal toward the cell body.

Synapse

function junction or point of close contact between two neurons or between a neuron and an effector cell.

Nucleus

(1) control center of a cell; contains genetic material; (2) clusters of nerve cell bodies in the CNS.

Conductivity

Ability to transmit an electrical impulse.

Summation

Accumulation of effects those of muscular, sensory, or mental stimuli.

Oligodendrocyte

A type of CNS supporting cell that composes myelin sheaths.

Glial cells

Non-excitable cells of neural tissue that support, protect, and insulate, the neurons. See Neuroglia..

Axon

Neuron process that carries impulses away from the nerve cell body; efferent process; the conducting portion of a nerve cell.

Axon terminals (terminal boutons)

The bulbous distal endings of the terminal branches of an axon.

Microglial cells

A type of CNS supporting cell; can transform into phagocytes in areas of neural damage or inflammation.

Synaptic cleft

fluid filled space at a synapse.

Multiple sclerosis (MS)

Demyelinating disorder of the CNS; causing hardened patches (sclerosis) in the brain and spinal cord.

Afferent (sensory) nerve

Nerve that contains processes of sensory neurons and carries nerve impulses to the central nervous system.

Excitatory postsynaptic potential (EPSP)

Depolarizing graded potential in a postsynaptic neuron.

Reflex

Automatic reaction to stimuli.

Excitability (responsiveness)

Ability to respond to stimuli.

White matter

White substance of the central nervous system; myelinated nerve fibers.

Catecholamines

Epinephrine, norepinephrine, and dopamine; a class of amines that act as chemical transmitters.

Nervous System

Fast-acting control system that triggers muscle contraction or gland secretion.

Inhibitory postsynaptic potential (IPSP)

A graded potential in a postsynaptic neuron that inhibits action potential generation; usually hyperpolarizing.

Myelin sheath

Fatty insulating sheath that surrounds all but the smallest nerve fibers.

Salutatory conduction

Transmission of an action potential along a myelinated fiber in which the nerve impulse appears to leap from gap to gap.

Bipolar neuron

Neuron with axon and dendrite that extend from opposite sides of the cell body.

Action potential

A large transient depolarization event, including polarity reversal, that is conducted along the membrane of a muscle cell or a nerve fiber.

Unipolar neuron

Neuron in which embryological fusion of the two processes leaves only one process extending from the cell body.

Interneuron (association neuron)

Nerve cell located between motor and sensory neurons that shuttles signals through CNS pathways where integration occurs.

Synaptic delay

Time required for an impulse to cross a synapse between two neurons.

Resting membrane potential

Resting membrane potential: the voltage that exists across the plasma membrane during the resting state of an excitable cell; ranges from -90 to -20 millivolts depending on cell type.

Schwann cell

A type of supporting cell in the PNS; forms myelin sheaths and is vital to peripheral nerve fiber regeneration.

Terminal Branches

Branching ends of an axon that allow it to form many axon terminals; telodendria.

Nerve Impulse

A self-propagating wave of depolarization; also called an action potential.

Neuroglia

Non-excitable cells of neural tissue that support, protect, and insulate the neurons; glial cells.

Axolemma

The plasma membrane of an axon

Efferent

Carrying away or away from, especially a nerve fiber that carries impulses away from the central nervous system.

Graded potential

A local change in membrane potential that varies directly with the strength of the stimulus, declines with distance.

Neurotransmitter

Chemical messenger released by neurons that may, upon binding to receptors of neurons or effector cells, stimulate or inhibit those neurons or effector cells.

Neuropeptides

A class of neurotransmitters including beta endorphins and enkephalins (which act as euphorics and reduce perception of pain) and gut-brain peptides.

Nitric oxide (NO)

A gaseous chemical messenger; diverse functions include participation in memory formation in the brain, and causing vasodilation throughout the body.

Innervation

Supply of nerves to a body part.

Afferent

Carrying to or toward a center.

Depolarization

Loss of a state of polarity; loss or reduction of negative membrane potential.

Astrocyte

A type of CNS supporting cell; assists in exchanges between blood capillaries and neurons.

Integration

The process by which the nervous system processes and interprets sensory input and makes decisions about what should be done at each moment.

Central nervous system (CNS)

Brain and spinal cord.

Voluntary nervous system

The somatic nervous system.

Acetylcholine (ACh)

Chemical transmitter substance released by some nerve endings.

Hyperpolarization

An increase in membrane potential in which the membrane becomes more negative than resting membrane potential.

Parasympathetic division

The division of the autonomic nervous system that oversees digestion, elimination, and glandular function; the resting and digesting subdivision.

Psuedounipolar neuron

Another term for unipolar neuron.

Ependymal cell

A type of CNS supporting cell; lines the central cavities of the brain and spinal cord.

Sympathetic division

The division of the autonomic nervous system that prepares the body for activity or to cope with some stressor (danger, excitement, etc..); the fight. fright, and flight subdivision.

Relative refractory period

Follows the absolute refractory period interval when a threshold for action potential stimulation is markedly elevated.

Nerve

A bundle of axons in the peripheral nervous system.

Somatic nervous system

division of the peripheral nervous system that provides the motor innervation of skeletal muscles; also called the voluntary nervous system.

Absolute refractory period

Period following stimulation during which no additional action potential can be evoked.

Synaptic vesicles

Small membranous sacs containing neurotransmitter.

Multipolar neurons

Neurons with three or more processes; most common neuron type in the CNS.

Neuron (nerve cell)

Cell of the nervous system specialized to generate and transmit electrical signals (action potentials and graded potentials).

Nerve Fiber

Axon of a neuron

Electrochemical gradient

To combined difference in concentration and charge; influences the distribution of diffusion of ions

Neuron cell body

The biosynthetic center of a neuron; also called the perikaryon, or soma.