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.