 | Term | Definition |
| |
neuron |
a nerve cell |
| |
dendrites |
the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body |
| |
axons |
the extension of a neuron, ending in branching terminal fibers, through which messages pass to other nuerons |
| |
action potential |
a neural impulse; a brief electrical charge that travels down an axon |
| |
myelin sheath |
a layer of fatty tissue segmentally encasing the fibers of many neurons |
| |
threshold |
the level of stimulation required to trigger a neural impulse |
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synapse |
the junction between the axon tip of the sending neuron and the dendrite of the receiving neuron |
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cleft |
synaptic gap |
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neurotransmitters |
chemical messengers that traverse the synaptic gaps between neurons |
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endorphins |
natural, opiatelike neurotransmitters linked to pain control and to pleasure |
| |
nervous system |
the body's speedy, electrochemical communication system, consisting of all the nerve cells of the peripheral and central nervous systems |
| |
central nervous system |
the brain and the spinal cord |
| |
peripheral nervous system |
the sensory and motor neurons that connect the CNS to the rest of the body |
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nerves |
neural cables containing many axons (part of the PNS) that connect the CNS with muscles, glands, and sense organs |
| |
sensory neurons |
neurons that carry incoming information from the sense receptors to the CNS |
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interneurons |
CNS neurons that internally communicate and intervene between the sensory inputs and motor outputs |
| |
motor neurons |
neurons that carry outgoing information from the central nervous system to the muscles and glands |
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somatic nervous system |
the division of the PNS that controls the body's skeletal muscles. |
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autonomic nervous system |
the part of the PNS that controls the glands and the muscles of the internal organs |
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sympathetic nervous system |
the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations |
| |
parasympathetic nervous system |
the division of the nervous system that calms the body, conserving its energy |
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reflex |
a simple, automatic, inborn response to a sensory stimulus |
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brainstem |
the oldest part and central core of the brain, beginning where the spinal cord swells as it enters the skull (automatic survival functions) |
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medulla |
the base of the brainstem (heartbeat and breathing) |
| |
reticular formation |
a nerve network in the brainstem that plays an important role in controlling arousal |
| |
thalamus |
the brain's sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and trasmits replies to the cerebellum and medulla |
| |
cerebellum |
the "little brain" attached to the rear of the brainstem; it helps coordinate voluntary movement and balance |
| |
limbic system |
a doughnut-shaped system of neural structurs at the border of the brainstem and cerebral hemispheres |
| |
amygdala |
two almond-shaped neural clusters that are components of the limbic system and are linked to emotion |
| |
hypothalamus |
a neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion |
| |
cerebral cortex |
the intricate fabric of interconnected neural cells that covers the cerebal hemispheres; the body's ultimate control and information processing center |
| |
frontal lobes |
the portion of the cerebral cortex lying just behind the forehead; involved in speaking and muscle movements and in making plans and decisions |
| |
parietal lobes |
the portion of the celebral cortex lying at the top of the head and toward the rear; includes the sensory cortex |
| |
occipital lobes |
the portion of the back of the head; includes the visual areas, which receive visual information from the opposite visual field |
| |
temporal lobes |
the portion of the cerebral cortex lying roughly above the ears; includes the auditory areas, each of which receives auditory information primarly from the opposite ear |
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motor cortex |
an area at the rear of the frontal lobes that controls voluntary movements |
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sensory cortex |
the area at the front of the parietal lobes that registers and processes body sensations |
| |
association areas |
areas of the cerebral cortex that are not involved primary motor or sensory functions; rather, they are involved in higher mental functions such as learning, remembering, thinking, and speaking |
| |
aphasia |
impairment of language, usually caused by left hemisphere damage |
| |
Broca's area |
controls language expression |
| |
Wernicke's area |
controls language reception |
| |
plasticity |
the brain's capacity for modification, as evident in brain reorganization following damage |
| |
corpus callosum |
the large band of neural fibers connecting the two brain hemispheres |
| |
endocrine system |
the body's slow chemical communication system |
| |
hormones |
chemical messengers that are produced in one tissue and affect another |
| |
adrenal glands |
a pair of endocrine glands just above the kidneys |
| |
pituitary gland |
the endocrine system's most influental gland; regulates growth and controls other endocrine glands |
