Ch. 13 The Nervous System: neural tissue
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79 terms
Terms | Definitions |
|---|---|
 nervous and endocrine systems | organ systems that coordinate and direct the activities of other organ systems. |
| nervous system | provides swift, brief responses to stimuli; encompasses all neural tissue in the body |
| anatomical subdivisions of nervous system | central nervous system (CNS) and peripheral nervous system (PNS) |
| central nervous system | brain and spinal cord |
| peripheral nervous system | all of the neural tissue outside the CNS: somatic, autonomic and special visceral sensory receptors |
| afferent division | division of nervous system which transmits sensory information from somatic and visceral receptors and special sense organs to the CNS |
| somatic sensory receptors | monitor skeletal muscles, joints, and the skin |
| visceral sensory receptors | monitor other internal tissues such as smooth muscle, cardiac muscle and glands |
| efferent division | division of nervous system which carries motor commands to muscles and glands |
| somatic nervous system | nervous system included in efferent division; has voluntary control over skeletal muscle contractions |
| autonomic nervous system | nervous system included in efferent division; has automatic, involuntary regulation of smooth muscle, cardiac muscle, and glandular activity |
| neurons | cells in neural tissue, which are responsible for information transfer and processing |
| neuroglia (glial cells) | cells in neural tissue, which are supporting cells in the nervous system |
| parts of neuron | cell body (soma), axon, several dendrites |
| axon | carries information in the form of nerve impulses |
| types of neuroglia | astrocytes, oligodendrocytes, microglia, ependymal cells |
| astrocytes | largest, most numerous glial cells; maintain blood-brain barrier to isolate CNS from general circulation; provide structural support for CNS; regulate ion and nutrient concentrations; perform repairs to stabilize tissue and prevent further injury |
| oligodendrocytes | wrap CNS axons in a myelin sheath |
| nodes of Ranvier | gaps between the myelin wrappings along the axon |
| white matter | regions primarily containing myelinated axons; appear glossy and white |
| microglia | smallest neuroglial cells; phagocytic cells that enculf cellular debris, waste products and pathogens. increase in number as a result of infection or injury |
| ependymal cells | atypical epithelial cells that line chambers and passageways filled with cerebrospinal fluid in the brain and spinal cord. assist in producing, circulating and monitoring CSF |
| cerebrospinal fluid | provides a protective cushion and transports dissolved gases, nutrients, wastes and other materials |
| ganglia | clusters of neuron cell bodies in the PNS |
| peripheral nerves | axons in PNS which are bundled together and wrapped in connective tissue |
| glial cell types | satellite cells and Schwann cells |
| satellite cells | enclose neuron cell bodies in ganglia |
| Schwann cells | aka neurolemmocytes; cover all peripheral axons, whether myelinated or unmyelinated |
| perikaryon | cytoplasm surrounding the nucleus of a neuron |
| perikaryon contents | organelles including neurofilaments, neurotubules, and bundles of neurofilaments (neurofibrils), which extend into the dendrites and axon |
| axon hillock | specialized region of the axon, which connects the inital segment of the axon to the cell body |
| axoplasm | cytoplasm of the axon, contains numerous organelles |
| collaterals | side branches from an axon |
| telodendria | series of fine, terminal extensions branching from the axon tip |
| synaptic terminal | area of the axon where the telodendria end; location where one neuron communicates with another neuron |
| synapse | site of intercellular communication between a neuron and another cell |
| synaptic knob | located where one neuron synapses on another |
| neurotransmitters | specific chemicals which are released during synaptic communication |
| anoxonic neuron | neuron with no distinguishable axon |
| bipolar neuron | neuron with one dendrite and one axon |
| pseudounipolar neuron | neuron with continuous dendrite and axon, with cell body off to one side |
| multipolar | neuron with several dendrites and one axon |
| functional categories of neurons | sensory neurons, motor neurons and interneurons |
| structural categories of neurons | anaxonic, bipolar, pseudounipolar, multipolar |
| sensory neurons | neurons that form the afferent division of the PNS and deliver information from sensory receptors to the CNS |
| motor neurons | neurons that form the efferent pathways that stimulate or modify the activity of a peripheral tissue, organ or organ system |
| interneurons | neurons located between the sensory and motor neurons; they analyze sensory inputs and coordinate motor outputs; can be excitatory or inhibitory |
| exteroceptors | sensory neurons that provide information from the external environment |
| proprioceptors | sensory neurons that monitor position and movement of joints |
| interoceptors | monitor digestive, respiratory, cardiovascular, urinary, and reproductive systems |
| somatic motor neurons | innervate skeletal muscle |
| visceral motor neurons | innervate all peripheral effectors other than skeletal muscles |
| preganglionic fibers | axons extending from the CNS to a ganglion |
| postganglionic fibers | axons connecting the ganglion cells with the periopheral effectors |
| excitability | ability of a cell membrane to conduct electrical impulses |
| action potentials | changes in the flow of sodium and potassium ions, which cause changes in the transmembrane potential |
| nerve impulse | an action potential traveling along an axon |
| neuroeffector junctions | site where synapses permit communication between neurons and other cells |
| chemical synapse | synapse involving a neurotransmitter; communication can occur in only one direction across a synapse- from the presynaptic neuron to the postsynaptic neuron |
| electrical synapse | synapse involving direct physical contact between cells where membranes of presynaptic and postsynaptic cells are tightly bound together and cells function as if they shared a common cell membrane; may be bidirectional |
| neuronal pool | a group of interconnected neurons with specific functions |
| center | a collection of neuron cell bodies with a common function |
| nucleus | a center with a discrete anatomical boundary |
| neural cortex | gray matter that covers portions of the brain |
| tracts | bundles of axons in the white matter of the CNS that share common origins, destinations and functions |
| columns | larger units of tracts in the spinal cord |
| pathways | centers and tracts that link the brain and body |
| sensory (ascending) pathways | carry information from peripheral receptors to the brain |
| motor (descending) pathways | extend from CNS centers concerned with motor control to the associated skeletal muscles |
| divergence | spread of information from one neuron to several neurons or one neuronal pool to several pools. Facilitates the widespread distribution of a specific input. |
| convergence | presence of synapses from several neurons on one postsynaptic neuron. permits variable control of motor neurons. |
| serial processing | pattern of stepwise information processing from one neuron to another or from one neuronal pool to the next. sensory information is relayed between processing centers int he brain |
| parallel processing | a pattern that processes information by several neurons or neuronal pools at one time. many different responses occur at the same time |
| reverberation | neuronal circuits utilizing positive feedback to continue the activity of the circuit. collateral axons establish a circuit to continue to stimulate presynaptic neurons |
| neural tissue | carries information from one part of the body to another in the form of electrical impulses |
| internodes | large areas in myelin |
| initial segment | The axon hillock is a specialized region of an axon. It connects the _______ ________ of the axon to the cell body. |
| parallel processing | a pattern that processes information by several neurons or neuronal pools at one time. Many different responses occur at the same time. |
| endocrine system | adjust metabolic operations and direct long-term changes. |
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