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nervous system

chief coordinator, acts by chemical changes and electrical impulses

central nervous system

brain and spinal cord

peripheral nervous system

cranial nerves and spinal nerves

cranial nerves

carry impulses to and from the brain

spinal nerves

carry impulses to and from the spinal cord

somatic nervous system

controlled voluntarily, affects skeletal muscle

autonomic nervous system

involuntary, controls smooth muscle, cardiac muscle, and glands, has 2 subdivisions sympathetic and parasympathetic

sympathetic nervous system

prepares body for energy expending stressful or emergency situations

parasympathetic nervous system

maintains homeostasis, conserves body energy, more active under ordinary, restful situations

neuroglia or glial cells

fill spaces, support neurons, and insulate neurons, can reproduce, and act as phagocytes

nerve cell or neuron

functional unit of the nervous system, specialized to react to physical and chemical changes, functions to conduct nerve impulses to other neurons and to cells outside the nervous system


fibers that conduct impulses to the cell body, receive stimuli, receive changes


fibers (one per neuron) that carry impulses away from the cell body

myelin sheath

fatty material that insulates fiber, covers some axons

schwann cells

located in the myelin sheath, produces myelin, wraps around the axon


gaps between the schwann cells, important in speeding the conduction of nerve impulses


outermost membrane of schwann cells, thin coating, helps some peripheral nerves repair themselves after injury

white fibers

myelinated fibers found in the white matter of the brain and spinal cord

gray matter

has no myelin

sensory or afferent neurons

neurons that conduct impulses to the spinal cord and brain

motor or efferent neurons

carry impulses away from the CNS to muscles and glands


inside of neuron is negative, the oustide is positive (when neuron is at rest)

Na+ and K+

needed for nerve impulses, at rest Na are more concentrated on the outside of the membrane and K is more concentrated on the inside

action potential

the inside negative ions rush outside, and the outside positive ions rush inside


as the Na flow into the cell, they raise the charge on the inside of the membrane


K leaves the cell, electrical charge returns to its resting state, and Na and K return to original postitions on either side of the membrane


the junction between 2 neurons, or from a neuron to an effector cell


carry impulses across the gap (synapse) to the next cell

4 neurotransmitters

epinephrine, norepinephrine, dopamine, acetylcholine

neurotransmitters are turned off by?

enzymes, diffusion, recycled

spinal cord

long, thin nerve column, extends from foramen magnum to level of first lumbar vertebrae

how is spinal cord protected?

by vertebral column, meninges, and cerebral spinal fluid

reflex arc

afferent, efferent, RSCNE


receptor, sensory, CNS, motor neuron, effector


rapid, simple, automatic response, specific- a given stimulus always produces the same response

spinal nerves

31 pair, numbered according to the level of spinal cord where they originate, exit through vertebral column, branch out to body parts to connect them with CNS

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