cell body
enlarged structure of the neuron containing the nucleus and various organelles.
dendrites
cytoplasmic projections that carry impulses to the cell body.
axons
carry impulses from the cell body.
myelin sheath
white lipoid covering that acts as an electrical insulator that reduces the possibility of an impulse stimulating adjacent nerves. Also accelerates impulse transmission through the axon.
schwann cell
a neuroglial cell that forms the myelin sheath on peripheral nerves.
neurilemma
thin cellular membrane
node of ranvier
space between adjacent Schwann cells. Helps maintain electrical potentials needed for impulse control
synapse
small space between the axon terminal of one neuron and the dendrite of another.
neurotransmitter
Chemical substance that transmits or inhibits nerve impulses at a synapse.
neuroglia
Nerve glue. Support neurons and bind them to other tissues. Play role when nervous system suffers an injury or infection.
astrocytes
Mechanical support for neurons. Form tight sheaths around the capillaries of the brain forming the blood-brain barrier, keeping large molecular substances from entering brain tissue.
oligodendrocytes
help in the development of myelin on neurons of the CNS
microglia
phagocytic properties, and may become very active during times of infection
ependyma
ciliated cells that line fluid-filled cavities of the CNS, especially the ventricles of the brain. Assist in CSF circulation.
neurons
Transmit impulses; identified by the direction the impulse travels.
sensory neurons
Afferent nerves - transmit stimuli to the brain and spinal cord.
motor neurons
Efferent nerves - transmit impulses from the brain or spinal cord to muscles and glands.
brain
center for thought and emotion, interpretation of sensory stimuli, and coordination of body functions
ascending tracts
transmit sensory impulses from different parts of the body to the brain
descending tracts
transmit motor impulses from the brain to muscles and organs.
meninges
three coverings provide limited protection to the brain and spinal cord.
dura mater
outermost covering, tough, fibrous, mostly connective tissue. Beneath is a cavity called subdural space filled with serous fluid.
arachnoid
middle covering, spider-web appearance. Subarachnoid space contains CSF that acts as a shock absorber.
pia mater
innermost covering. Numerous blood vessels and lymphatics that nourish underlying tissues.
peripheral nervous system
All nervous tissue outside the spinal cord and skull.
cranial nerves
12 pairs of nerves that emerge from the base of the skull and may act in a motor or sensory capacity.
spinal nerves
31 pairs of nerves that emerge from the spine and act in motor and sensory capacities.
somatic
transmits sensory impulses to the central nervous system and motor impulses to voluntary (skeletal) muscles.
autonomic
regulates involuntary (visceral) muscles and glands.
sympathetic
division of the autonomic nervous system that prepares the body for "fight or flight
parasympathetic
division of the autonomic nervous system that moderates or reverses the action of the sympathetic nervous system
nervous impulse
physiological change transmitted through certain tissues, especially nerve fibers and muscles, resulting in activity or inhibition
organelle
cytoplasm structure that provides specialized function for the cell
spinal cord
main pathway for transmission of information between the brain and body