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action potential  The term used to describe the brief wave of electrical charge that sweeps down the axon during the transmission of a nerve impulse. p. 84
adrenal glands  Important endocrine glands that are instrumental in regulating moods, energy level, and the ability to cope with stress. p. 103
afferent nerves  Sensory nerves that transport information to the brain. p. 80
agonist  A drug that mimics or increases a neurotransmitter's effects. p. 88
all-or-none principle  Once an electrical impulse reaches a certain level of intensity, it fires and moves all the way down the axon without losing any of its intensity. p. 000
antagonist  A drug that blocks a neurotransmitter's effects. p. 88
association cortex  Region of the cerebral cortex in which the highest intellectual functions, including thinking and problem solving, occur (also called association areas). p. 98
autonomic nervous system  Division of the PNS that communicates with the body's internal organs. It consists of the sympathetic and parasympathetic nervous systems. p. 81
axon  The part of the neuron that carries information away from the cell body to other cells; each neuron has only one axon. p. 82
basal ganglia  Located above the thalamus and under the cerebral cortex, these large clusters of neurons work with the cerebellum and the cerebral cortex to control and coordinate voluntary movements p. 94
brain stem  The region of the brain that includes most of the hindbrain (excluding the cerebellum) and the midbrain. p. 92
cell body  Part of the neuron that contains the nucleus, which directs the manufacture of substances that the neuron needs for growth and maintenance. p. 82
central nervous system (CNS)  The brain and spinal cord. p. 81
cerebral cortex  Highest level of the forebrain, where the highest mental functions, such as thinking and planning,take place. p. 78
chromosomes  Threadlike structures that contain genes and DNA. Humans have 23 chromosome pairs in the nucleus of every cell. Each parent contributes one chromosome to each pair. p. 106
corpus callosum  A large bundle of axons that connect the brain's two hemispheres. p. 98
dendrites  Branches of a neuron that receive and orient information toward the cell body; most neurons have numerous dendrites. p. 82
deoxyribonucleic acid (DNA)  A complex molecule that contains genetic information; makes up chromosomes. p. 106
dominant-recessive genes principle  If one gene of a pair governing a given characteristic (such as eye color) is dominant and one is recessive, the dominant gene overrides the recessive gene. A recessive gene exerts its influence only if both genes in a pair are recessive. p. 106
efferent nerves  Motor nerves that carry the brain's output. p. 80
endocrine system  A set of glands that regulate the activities of certain organs by releasing hormones into the bloodstream. p. 102
forebrain  The highest level of the brain. Key structures in the forebrain are the limbic system, thalamus, basal ganglia, hypothalamus, and cerebral cortex. p. 93
frontal lobe  The part of the cerebral cortex just behind the forehead that is involved in the control of voluntary muscles, intelligence, and personality. p. 95
genes  The units of hereditary information. They are short segments of chromosomes, composed of DNA. p. 105
glial cells  Provide support and nutritional benefits in the nervous system. p. 82
hindbrain  The lowest level of the brain, consisting of the medulla, cerebellum, and pons. p. 91
hormones  Chemical messengers manufactured by the endocrine glands. p. 102
hypothalamus  Forebrain structure involved in regulating eating, drinking, and sex; directing the endocrine system through the pituitary gland; and monitoring emotion, stress, and reward. p. 432
Limbic system  Loosely connected network of structures--including the amygdala and hippocampus--that play important roles in memory and emotion. p. 93
midbrain  Located between the hindbrain and forebrain, a region in which many nerve-fiber systems ascend and descend to connect the higher and lower portions of the brain. p. 92
motor cortex  Area of the cerebral cortex that processes information about voluntary movement. p. 97
myelin sheath  A layer of fat cells that encases and insulates most axons. The myelin sheath speeds up the transmission of nerve impulses. p. 82
nervous system  The body's electrochemical communication circuitry, made up of billions of neurons. p. 78
neural networks  Clusters of neurons that are interconnected to process information. p. 80
neuron  Nerve cell that is specialized for processing information. Neurons are the basic units of the nervous system. p. 82
neurotransmitters  Chemicals that carry information across the synaptic gap from one neuron to the next. p. 85
occipital lobe  The part of the cerebral cortex at the back of the head that is involved in vision. p. 95
parasympathetic nervous system  The division of the autonomic nervous system that calms the body. p. 81
parietal lobe  Area of the cerebral cortex at the top of the head that is involved in registering spatial location, attention, and motor control.sensory cortex Area of the cerebral cortex that processes information about body sensations. p. 96
peripheral nervous system (PNS)  The network of nerves that connects the brain and spinal cord to other parts of the body. It is divided into the somatic nervous system and the autonomic nervous system. p. 81
pituitary gland  An important endocrine gland at the base of the skull that controls growth and regulates other glands. p. 102
plasticity  The brain's special capacity for modification and change. p. 79
resting potential  The term given to the stable, negative charge of an inactive neuron. p. 84
reticular formation  A midbrain system that consists of a diffuse collection of neurons involved in stereotypical behaviors such as walking, sleeping, or turning to attend to a sudden noise. p. 579
somatic nervous system  Division of the PNS consisting of sensory nerves, whose function is to convey information to the CNS, and motor nerves, whose function is to transmit information to the muscles. p. 81
synapses  Tiny junctions between two neurons, generally where the axon of one neuron meets the dendrites or cell body of another neuron. p. 85
sympathetic nervous system  The division of the autonomic nervous system that arouses the body. p. 81
temporal lobe  The portion of the cerebral cortex just above the ears that is involved in hearing, language processing, and memory. p. 95
thalamus  Forebrain structure that functions as a relay station to sort input and direct it to different areas of the cerebral cortex. It also has ties to the reticular formation. p. 94







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