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        | branch of psychology concerned with the links between biology and behavior |  
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        | neurons that carry incoming information from the sensory receptors to the brain and spinal cord |  
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        | neurons that carry outgoing information from the brain and spinal cord to the muscles and glands |  
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        | neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs |  
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        | the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body |  
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        | the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands |  
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        | a layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next |  
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        | a neural impulse; a brief electrical charge that travels down an axon |  
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        | the level of stimulation required to trigger a neural impulse |  
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        | the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. |  
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        | chemical messages that cross the synaptic gaps between neurons |  
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        | a neurotransmitter's reabsorption by the sending neuron |  
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        | "morphine within" - natural, opiatelike neurotransmitters linked to pain control and to pleasure |  
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        | neurotransmitter that enables muscle action, learning, and memory |  
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        | neurotransmitter that influences movement, learning, attention, and emotion |  
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        | neurotransmitter that affects mood, hunger, sleep, and arousal |  
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        | neurotransmitter that helps control alertness and arousal |  
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        | GABA (gamma-aminobutyric acid) |  
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        | a major inhibitory neurotransmitter |  
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        | a major excitatory neurotransmitter that is involved in memory |  
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        | the body's speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous system |  
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        | the brain and spinal cord |  
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        | peripheral nervous system |  
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        | sensory and motor neurons that connect the CNS to the rest of the body |  
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        | bundled axons that form neural cables connecting the CNS with muscles, glands, and sense organs |  
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        | division of the PNS that controls the body's skeletal muscles |  
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        | part of the PNS that controls the glands and muscles of the internal organs |  
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        | sympathetic nervous system |  
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        | division of the ANS that arouses the body, mobilizing its energy in stressful situations |  
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        | parasympathetic nervous system |  
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        | division of the ANS that calms the body, conserving its energy |  
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        | a simple, automatic response to a sensory stimulus |  
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        | body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream |  
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        | chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream and affect other tissues |  
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        | a pair of endocrine glands that sit just above the kidneys and secrete hormones (epinephrine and norepinephrine) that help arouse the body in times of stress |  
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        | the endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls the endocrine gland |  
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