| A | B |
|---|
| neuron | a nerve cell; the basic building block of the nervous system. |
| dendrite | the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body. |
| axon | the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands. |
| Action potential | a neural impulse; a brief electrical charge that travels down an axon. |
| Synapse | the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this junction is called the synaptic gap or cleft. |
| Neurotransmitters | chemical messengers that traverse the synaptic gaps between neurons. |
| Endorphins | "morphine within” – natural, opiate-like neurotransmitters linked to pain control and to pleasure. |
| Nervous system | the body’s speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous systems |
| Central nervous system | the brain and spinal cord. |
| Nerves | neural “cables” containing many axons. These bundled axons, which are part of the peripheral nervous system, connect the central nervous system with muscles, glands, and sense organs. |
| Sensory neurons | neurons that carry incoming information from the sense receptors to the central nervous system. |
| Motor neurons | neurons that carry outgoing information from the central nervous system to the muscles and glands. |
| Interneurons | central nervous system neurons that internally communicate and intervene between the sensory inputs and motor outputs. |
| Somatic (skeletal) nervous system | the division of the peripheral nervous system that controls the body’s skeletal muscles. Also called the skeletal nervous system. |
| Autonomic nervous system | the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms |
| Sympathetic nervous system | the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations. |
| Reflex | a simple, automatic, inborn response to a sensory stimulus, such as the knee-jerk response. |
| Neural networks | interconnected neural cells. With experience, networks can learn, as feedback strengthens or inhibits connections that produce certain results. Computer simulations of neural networks show analogous learning. |
| Endocrine system | the body’s “slow” chemical communication system; a set of glands that secrete hormones into the bloodstream. |
| Hormones | chemical messengers, mostly those manufactured by the endocrine glands, that are produced in one tissue and affect another. |
| Hypothalamus | a neural structure lying below (hypo) the thalamus; it directs several maintenance activities (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 cerebral hemispheres; the body’s ultimate control and information-processing center. |
| Motor cortex | an area at the rear of the frontal lobes that controls voluntary movements. |
| Sensory cortex | the area at the front of the parietal lobes that registers and processes body touch and movement sensations. |
| Association areas | areas of the cerebral cortex that are not involved in primary motor or sensory functions; rather, they are involved in higher mental functions such as learning, remembering, thinking, and speaking. |
| Plasticity | the brain’s capacity for modification, as evident in brain reorganization following damage (especially in children) and in experiments on the effects of experience on brain development. |
| Corpus callosum | the large band of neural fibers connecting the two brain hemispheres and carrying messages between them. |
| Split brain | a condition in which the two hemispheres of the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them. |
| Hemispheric specialization | each side of the brain specializing in a particular task, also called lateralization. |
