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| Astrocytes | Abundant star-shaped cells that account for nearly half of the neural tissue. |
| Central Nervous System (CNS) | Consists of the brain and spinal cord, which occupy the dorsal body and act as the integrating and command centers of the nervous system. |
| Peripheral Nervous System (PNS) | The part of the nervous system outside the CNS, consists mainly of the nerves that extend from the brain and spinal cord. |
| Microglia | Spiderlike phagocytes that dispose of the debris, including dead brain cells and bacteria. |
| Ependymal Cells. | These glial cells line the central cavities of the brain and the spinal cord. |
| Oligodendrocytes. | Glia that wrap their flat extensions tightly around the nerve fibers, producing fatty insulating coverings called myelin sheaths. |
| Neurons, (nerve cells). | Highly specialized to transmit messages (Nerve Impulses) from one part of the body to another. |
| Cell Body. | The metabolic center of the neuron. |
| Nissl Substance. | Rough ER that are particularly abundant in the cell body. |
| Dendrites. | Neuron processes that covney incoming messages torward the cell body. |
| Axons. | Generate nerve impulses and typically conduct them away from the cell body |
| Axon Terminals. | When axons branch profusely at their terminal end. |
| Neurotransmitters. | The chemicals contained in tiny vescicles, or membraneous sacs, which are located in Axon Terminals. |
| Synaptic Cleft. | A tiny gap that separates each Axon Terminal from the next neuron. |
| Myelin. | A whitsh, fatty material that covers most long nerve fibers. |
| Nodes of Ranvier. | Gaps, or indentations in the Myelin Sheath formed by many individual Schwann Cells. |
| Nuclei. | Cell bodies found in the CNS in clusters. |
| Ganglia. | Small collections of cell bodies found in a few sites ouutside of CNS in the PNS. |
| Tracts. | Bundles of nerve fibers running through the CNS. |
| Nerves. | Bundles of nerve fibers running through the PNS. |
| Sensory, or Afferent, Neurons. | Neurons carrying impulses from the sensory receptors to the CNS. |
| Motor, or Efferent, Neurons. | Neurons carrying impulses from the CNS to the Viscera and/or muscles and glands. |
| Interneurons, or Association Neurons. | Connect the motor and sensory neurons in neural pathways. |
| Multipolar Neuron. | If multiple processes are extending from the cell body. |
| Bipolar Neuron. | A neuron with Two processes- an axon and a dendrite -. |
| Unipolar Neuron. | Have a single process emerging from the cell body. |
| Polarized. | The plasma membrane of a resting, or inactive, neuron.There are fewer positive ions sitting on the inner face of the neurons plasms membrane that there are on its outer face. |
| Depolarization. | An event of an inward rush of sodium ions that change the polarity of the neurons membrane at that site. |
| Action Potential.(nerve impulse) | An electrical event occuring when a stimulus of sufficient intensity is applied to a neuron or muscle cell, allowing sodium ions to move into the cell and reverse the polarity. |
| Repolarization. | Restoration of the membrane potential to the initial resting (polarized) state. |
| Somatic Reflexes. | Include all reflexes that stimulate the skeletal mescles. |
| Autonomic Reflexes. | Regulate the activity of smooth muscles, the heart, and glands. |
| Cerebrum. | A pair of cerebral hemispheres of the brain and are the largest of the brain regions. |
| Gyri. | Elevated ridges of tissue on the surface of the cerebral hemispheres. |
| Sulci. | Shallow grooves that separate the Gyri. |
| Fissures. | Deep grooves which separate the larger regions of the brain. |
| Parietal lobe. | Where the primary somatic sensory area is located, posterior to the central sulcus. |
| Occipital lobe. | The visual area is located in the posterior part of the Occipital lobe. |
| Temporal lobe. | The auditory area here which borders the lateral sulcus; the Olfactory area is found deep inside the Temporal lobe. |
| Frontal lobe. | Includes the Primary Motor Area which is anterior to the Central Sulcus. |
| Broca's Area. | A specialized cortical area that is very involved in our ability to speak; found at the base of the precentral gyrus. |
| Gray Matter. | The gray area of the central nervous system; contains unmyelinated nerve fibers and nerve cell bodies. |
| White Matter. | White substance of the central nervous system, the myelinated nerve fibers. |
| Corpsus Callosum. | A very large fiber tract that connects the cerebral hemispheres. |
| Basal Nuclei. | Gray matter areas deep within the white matter of the cerebral hemispheres; also called basal ganglia. |
| Diencephalon(Interbrain) | Sits atop the brain stem and is enclosed by the cerebral hemispheres. Includes the thlamus, the third ventricle, and the hypothalamus. |
| Thalamus. | A mass of gray matter in the diencephalon area of the brain; relay station for sensory impulses passing upward to the sensory cortex. |
| Hypothalamus. | Makes up floor of the diencephalon; helps regualte body temp, water balance, and metabolism. |
| Limbic System. | This is the emotional system of the body, which the hypothalamus plays a important role in. |
| Pituitary Gland. | the neuroendocrine gland located beneath the brain that serves a variety of functions including regulation of gonads, thyroid, adrenal cortex, water balance, and lactation. |
| Mammillary Bodies. | Reflex centers involved in olfaction, bulge from the floor of the hypothalamus posterior to the pituitary gland. |
| Brain Stem. | The portion of the brain consisting of the medulla, pons, and midbrain. |
| Pons | Any bridgelike structure or part; the brain area connecting the medulla with the midbrain, providing linkage between upper and lower levels of the central nervous system. |
| Medulla Oblongata | Most inferior part of the brain; controls heart rate, blood pressure, breathing, swallowing, and vomiting. |
| Reticular formation. | Involved in the motor control of the visceral organs; plays a role in consciousness and awake/sleep cycles. |
| Cerebellum. | Part of the hind brain; involved in producing smoothly coordinated skeletal muscle activity. |
| Meninges. | The membranes that cover the brain and spinal cord. |
| Dura Mater. | The outermost and toughest of the three membranes covering the brain and spinal cord. |
| Cerebrospinal fluid. | The fluid produced by chloroid plexi; fills the ventricles and surrounds the central nervous system. |
| Blood-brain barrier. | A mechanism that inhibits passage of maerials from the blood into brain tissues. |
