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Nervous System Terms
Neurons that conduct impulses from afferent neurons to or toward motor neurons. They lie in the CNS.
Neurons that transmit nerve impulses away from the brain or spinal cord toward muscles or glands.
Neurons that transmit nerve impulses to the spinal cord or brain.
A neuron that has a single process extending from the cell body. This single process branches to form a central process and a peripheal process. These processes combine to form an axon.
A neuron found in the retina of the eye that has only one axon and one branched dendrite. Least numerous type of neuron.
A neuron that has only one axon but several dendrites. Mostly found in the brain and spinal cord.
They conduct impulses away from the cell body. They vary in length and diameter; a single process that branches.
When synaptic knobs stimulate postsynaptic neurons in rapid succession, their effects can add up to produce an action potential.
Excitable cells that conduct the impulses that make possible all nervous system functions.
Involved in coordinating the body's normal resting activities
Involved in preparing the body to deal with immediate threats to the internal environment.
Part of the nervous system that carries information to the visceral effectors (smooth muscles, cardiac muscle)
Somatic Nervous System
Part of the nervous system that carries information to the skeletal system.
Consists of all of the outgoing motor pathways of the nervous system.
Consists of all of the incoming sensory pathways of the nervous system.
What it is called when voltage gated channels in the axon membrane open because the sum of the local potentials reaches the threshold potential.
A synapse that uses a chemical transmitter to send a signal from the presynaptic cell to the postsynaptic cell.
A temporary hyperpolarization when the inside of the axon membrane is more negative than the resting potential.
A temporary depolarization when both Na channels and K channels open.
The chemicals by which neurons communicate.
Relative Refractory Period
The few milliseconds after the absolute refractory period-when the membrane is repolarizing and restoring the resting potential.
A white, fatty substance.
Found only in the PNS, support nerve fibers by forming a myelin sheath around them.
Cells that have few uses. Some lie clustered around nerve cell bodies. Some are arranged in rows between nerve fibers in the brain and spinal cord.
Glia that form thin sheets that line fluid-filled cavities in the brain and spinal cord. Some produce this fluid.
A delicate layer of fibrous connective tissue surrounding each nerve fiber.
Bundles of peripheal nerve fibers held together by several layers of connective tissues.
The place where nerve information is transmitted from one neuron to another.
A signal conduction route to and from the CNS.
Special Schwann cells that surround the cell body of a neuron.
Nodes of Ranvier
Microscopic gaps in the myelin sheath between adjacent Schwann cells.
The existing nerve tissues that reside in the body besides the CNS.
The brain and the spinal cord.
A limit of local depolarization. If surpassed, it causes Na channels to open.
The membrane potential of an active neuron conducting an impulse.
Absolute Refractory Period
When the Threshold Potential is surpassed, for about half a millisecond, the axon will not respond to any stimulus.
A difference in electrical charge across an axon's plasma membrane.
Cell bodies and unmyelinated fibers.
Bundles of myelinated fibers.
The name for nerves located in the CNS.
A fibrous coat that holds together numerous fascicles to create a nerve.
A connective tissue layer that holds together fascicles.
Bundles of fibers each with its own endonerium.
A structure formed from ribosomes that provide protein molecules needed for the sending of nerve signals from one neuron to another.
Small, stationary cells found in the CNS. They engulf and destroy microorganisms and cellular debris.
Star shaped cells that are the largest and most numerous type of glia. They feed neurons by using glucose and converting it to lactic acid.
Cells that do not conduct information but support the neurons in various ways.
Movement of the membrane potential away form zero.
Movement of the membrane potential toward zero.
A slight shift away from the resting membrane potential in a specific region of the plasma membrane.
Resting Membrane Potential
The membrane's potential maintained by a nonconducting neuron's plasma membrane.
Receptors that receive the stimuli that initiate nerve signals. They receive the stimuli and conduct electrical signals toward the axon of the neuron. They branch from the main body.