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Nervous System
Sections 1-4, 7-11
43
Anatomy
11th Grade
02/18/2009

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Term
neuron
Definition
structural and functional units of the nervous system that are specialized to react to physical and chemical changes in their surroundings; nerve cells
Term
nerve impulse
Definition
electrochemical changes that transmit information
Term
nerve impulse
Definition
electrochemical changes that transmit information
Term
cell body
Definition
portion of the nerve cell that inculeds a cytoplasmic mass and a nucleus, and from which nerve fibers extend
Term
dendrites
Definition
process of a neuron that recieves input from other neurons
Term
axons
Definition
a nerve fiber; conducts a nerve impulse away from the neuron cell body
Term
Nerves
Definition
bundles of axons in the peripheral nervous system
Term
neuroglial cells
Definition
specialized cells of the nervous system that produce myelin, communicate between cells, and maintain the ionic environment
Term
central nervous system (CNS)
Definition
the brain and spinal cord
Term
peripheral nervous system (PNS)
Definition
portions of the nervous system outside the central nervous system
Term
sensory receptors
Definition
specialized structure associated with the peripheral end of a sensory neuron specifc to detecting a particular sensation and triggering a nerve impulse in response, which is transmitted to the central nervous system
Term
effectors
Definition
muclses that are outside the nervous systme that contract and glands that secrete when stimulated by nerve impulses
Term
somatic nervous system
Definition
motor pathways of the peripheral nervous system that lead to the skin and skeletal muscles - under concious control
Term
autonomic nervous system
Definition
portion of nervous system that controls the viscera (organs) - unconcious control
Term
myelin
Definition
fatty material that forms a sheathlike covering around some axons
Term
microglial cells
Definition
neuroglial cell that supports neurons and phagocytizes
Term
oligodendrocytes
Definition
type of neuroglial cell that forms myelin (only in the CNS)
Term
astrocytes
Definition
type of neuroglial cell that connects neurons to blood vessels
Term
ependymal cells
Definition
a membrane composed of neuroglial cells that line the ventricles of the brain
Term
Schwann cells
Definition
type of neuroglial cell that surrounds an axon of a peripheral neuron, forming the neurilemma sheath and myelin
Term
neurofibrils
Definition
a fine, cytoplasmic threads that extends from the cell body into the process of a neuron
Term
neurilemma
Definition
sheath formed from Schwann cells on the outside of some axons
Term
nodes of Ranvier
Definition
narrow gaps between Schwann cells
Term
trigger zone
Definition
a sensitive part of an axon where a nerve impulse originates
Term
ganglia (singular - ganglion)
Definition
a mass of neuron cell bodies, usually outside the central nervous system
Term
sensory neurons
Definition
a neuron that transmits an impluse from a receptor to the central nervous system
Term
interneurons
Definition
a neuron between a sensory neuron and a motor neuron that lie entirely in the CNS
Term
motor neuron
Definition
a neuron that transmits impulses from the central nervous system to an effector
Term
synapse
Definition
the functional connection between the axon of a neuron and the dedrite or cell body of another neuron or the mebrane of another cell type
Term
neurotransmitter
Definition
chemical that an axon end secretes on an effector (muslce or gland) or another neuron
Term
excitatory neurotransmitter
Definition
increases postynaptic membrane permeability, which may trigger a nerve impulse
Term
inhibitory neurotransmitter
Definition
decreases the permeability of the postsynaptic membrane, lessening the chance that a nerve impulse will occur
Term
neuronal pools
Definition
groups of neurons that make hundreds of synaptic connections with each other an dwork together to perform a common function
Term
facilitation
Definition
subthreshold stimulation of a neuron that increases responsiveness to further stimulation
Term
divergence
Definition
impulses from one neuron can stimulate two or more neurons - can amplify an impulse spreading it to more neurons in the pool
Term
convergence
Definition
any single neuron in a neuronal pool receives impluses from two or more incoming axons - have a summative effects
Term
afferent fibers
Definition
also called sensory fibers; neuron processes that bring sensory information to the CNS
Term
efferent fibers
Definition
also called motor fibers - carry impulses from the CNS to effectors
Term
sensory nerves
Definition
a nerve that consists of sensory neuron axons
Term
motor nerves
Definition
a nerve that consists of motor neuron axons
Term
mixed nerves
Definition
nerve that includes both sensory and motor neuron fibers
Term
reflex arc
Definition
a nerve pathway, consisting of a sensory neuron, interneuron, and motor neuron, that forms the structural and functional bases for a reflex
Term
reflex
Definition
a rapid, automatic response to a stimulus
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