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HB4_nervous system
The nervous system
| Term | Definition |
|---|---|
| absolute refractory period | time during an action potential when another action potential cannot be generated because the voltage-gated Na+ channel is inactivated |
| action potential | change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal; unique to neurons and muscle fibers |
| activation gate | part of the voltage-gated Na+ channel that opens when the membrane voltage reaches threshold |
| astrocyte | glial cell type of the CNS that provides support for neurons and maintains the blood-brain barrier |
| autonomic nervous system (ANS) | functional division of the nervous system that is responsible for homeostatic reflexes that coordinate control of cardiac and smooth muscle, as well as glandular tissue |
| axon hillock | portion of the neuron cell body that gives rise to the axon |
| axon segment | single stretch of the axon insulated by myelin and surrounded by nodes of Ranvier at either end (except for the first, which is after the initial segment, and the last, which is followed by the axon terminal) |
| axon terminal | end of the axon, where there are usually several branches extending toward the target cell |
| axon | single process of the neuron that carries an electrical signal (action potential) away from the cell body toward a target cell |
| biogenic amine | class of neurotransmitters that are enzymatically derived from amino acids but no longer contain a carboxyl group |
| bipolar | shape of a neuron with two processes extending from the neuron cell body—the axon and one dendrite |
| blood-brain barrier (BBB) | physiological barrier between the circulatory system and the central nervous system that establishes a privileged blood supply, restricting the flow of substances into the CNS |
| brain | the large organ of the central nervous system composed of white and gray matter, contained within the cranium and continuous with the spinal cord |
| central nervous system (CNS) | anatomical division of the nervous system located within the cranial and vertebral cavities, namely the brain and spinal cord |
| cerebral cortex | outermost layer of gray matter in the brain, where conscious perception takes place |
| cerebrospinal fluid (CSF) | circulatory medium within the CNS that is produced by ependymal cells by filtering the blood |
| chemical synapse | connection between two neurons, or between a neuron and its target, where a neurotransmitter diffuses across a very short distance |
| cholinergic system | neurotransmitter system of acetylcholine, which includes its receptors and the enzyme acetylcholinesterase |
| continuous conduction | slow propagation of an action potential along an unmyelinated axon owing to voltage-gated Na+ channels located along the entire length of the cell membrane |
| dendrite | one of many branchlike processes that extends from the neuron cell body and functions as a contact for incoming signals (synapses) from other neurons or sensory cells |
| depolarization | change in a cell membrane potential from rest toward zero |
| effector protein | enzyme that catalyzes the generation of a new molecule, which acts as the intracellular mediator of the signal that binds to the receptor |
| electrical synapse | connection between two neurons, or any two electrically active cells, where ions flow directly through channels spanning their adjacent cell membranes |
| ependymal cell | glial cell type in the CNS responsible for producing cerebrospinal fluid |
| excitable membrane | cell membrane that regulates the movement of ions so that an electrical signal can be generated |
| excitatory postsynaptic potential (EPSP) | graded potential in the postsynaptic membrane that is the result of depolarization and makes an action potential more likely to occur |
| G protein | guanosine triphosphate (GTP) hydrolase that physically moves from the receptor protein to the effector protein to activate the latter |
| ganglion | localized collection of neuron cell bodies in the peripheral nervous system |
| gated | property of a channel that determines how it opens under specific conditions, such as voltage change or physical deformation |
| glial cell | one of the various types of neural tissue cells responsible for maintenance of the tissue, and largely responsible for supporting neurons |
| graded potential | change in the membrane potential that varies in size, depending on the size of the stimulus that elicits it |
| gray matter | regions of the nervous system containing cell bodies of neurons with few or no myelinated axons; actually may be more pink or tan in color, but called gray in contrast to white matter |
| inactivation gate | part of a voltage-gated Na+ channel that closes when the membrane potential reaches +30 mV |
| inhibitory postsynaptic potential (IPSP) | graded potential in the postsynaptic membrane that is the result of hyperpolarization and makes an action potential less likely to occur |
| initial segment | first part of the axon as it emerges from the axon hillock, where the electrical signals known as action potentials are generated |
| integration | nervous system function that combines sensory perceptions and higher cognitive functions (memories, learning, emotion, etc.) to produce a response |
| ionotropic receptor | neurotransmitter receptor that acts as an ion channel gate, and opens by the binding of the neurotransmitter |
| leakage channel | ion channel that it is opens and is not gated to a specific event, also known as a non-gated channel |
| ligand-gated channels | another name for an ionotropic receptor for which a neurotransmitter is the ligand |
| mechanically gated channel | ion channel that opens when a physical event directly affects the structure of the protein |
| membrane potential | distribution of charge across the cell membrane, based on the charges of ions |
| metabotropic receptor | neurotransmitter receptor that involves a complex of proteins that cause metabolic changes in a cell |
| microglia | glial cell type in the CNS that serves as the resident component of the immune system |
| multipolar | shape of a neuron that has multiple processes—the axon and two or more dendrites |
| muscarinic receptor | type of acetylcholine receptor protein that is characterized by also binding to muscarine and is a metabotropic receptor |
| myelin sheath | lipid-rich layer of insulation that surrounds an axon, formed by oligodendrocytes in the CNS and Schwann cells in the PNS; facilitates the transmission of electrical signals |
| myelin | lipid-rich insulating substance surrounding the axons of many neurons, allowing for faster transmission of electrical signals |
| nerve | cord-like bundle of axons located in the peripheral nervous system that transmits sensory input and response output to and from the central nervous system |
| neuron | neural tissue cell that is primarily responsible for generating and propagating electrical signals into, within, and out of the nervous system |
| neuropeptide | neurotransmitter type that includes protein molecules and shorter chains of amino acids |
| neurotransmitter | chemical signal that is released from the synaptic end bulb of a neuron to cause a change in the target cell |
| nicotinic receptor | type of acetylcholine receptor protein that is characterized by also binding to nicotine and is an ionotropic receptor |
| node of Ranvier | gap between two myelinated regions of an axon, allowing for strengthening of the electrical signal as it propagates down the axon |
| nonspecific channel | channel that is not specific to one ion over another, such as a nonspecific cation channel that allows any positively charged ion across the membrane |
| nucleus | in the central nervous system, a localized collection of neuron cell bodies that are functionally related; a “center” of neural function |
| oligodendrocyte | glial cell type in the CNS that provides the myelin insulation for axons in tracts |
| peripheral nervous system (PNS) | anatomical division of the nervous system that is largely outside the cranial and vertebral cavities, namely all parts except the brain and spinal cord |
| postsynaptic potential (PSP) | graded potential in the postsynaptic membrane caused by the binding of neurotransmitter to protein receptors |
| process | in cells, an extension of a cell body; in the case of neurons, this includes the axon and dendrites |
| propagation | movement of an action potential along the length of an axon |
| refractory period | time after the initiation of an action potential when another action potential cannot be generated |
| relative refractory period | time during the refractory period when a new action potential can only be initiated by a stronger stimulus than the current action potential because voltage-gated K+ channels are not closed |
| repolarization | return of the membrane potential to its normally negative voltage at the end of the action potential |
| response | nervous system function that causes a target tissue (muscle or gland) to produce an event as a consequence to stimuli |
| resting membrane potential | the difference in voltage measured across a cell membrane under steady-state conditions, typically -70 mV |
| Schwann cell | glial cell type in the PNS that provides the myelin insulation for axons in nerves |
| saltatory conduction | quick propagation of the action potential along a myelinated axon owing to voltage-gated Na+ channels being present only at the nodes of Ranvier |
| sensation | nervous system function that receives information from the environment and translates it into the electrical signals of nervous tissue |
| soma | in neurons, that portion of the cell that contains the nucleus; the cell body, as opposed to the cell processes (axons and dendrites) |
| somatic nervous system (SNS) | functional division of the nervous system that is concerned with conscious perception, voluntary movement, and skeletal muscle reflexes |
| spatial summation | combination of graded potentials across the neuronal cell membrane caused by signals from separate presynaptic elements that add up to initiate an action potential |
| spinal cord | organ of the central nervous system found within the vertebral cavity and connected with the periphery through spinal nerves; mediates reflex behaviors |
| stimulus | an event in the external or internal environment that registers as activity in a sensory neuron |
| summate | to add together, as in the cumulative change in postsynaptic potentials toward reaching threshold in the membrane, either across a span of the membrane or over a certain amount of time |
| synapse | narrow junction across which a chemical signal passes from neuron to the next, initiating a new electrical signal in the target cell |
| synaptic cleft | small gap between cells in a chemical synapse where neurotransmitter diffuses from the presynaptic element to the postsynaptic element |
| synaptic end bulb | swelling at the end of an axon where neurotransmitter molecules are released onto a target cell across a synapse |
| temporal summation | combination of several graded potentials at the same location on a neuron resulting in a strong signal from one input |
| thalamus | region of the central nervous system that acts as a relay for sensory pathways |
| thermoreceptor | type of sensory receptor capable of transducing temperature stimuli into neural action potentials |
| threshold | membrane voltage at which an action potential is initiated |
| tract | bundle of axons in the central nervous system having the same function and point of origin |
| unipolar | shape of a neuron which has only one process that includes both the axon and dendrite |
| voltage-gated channel | ion channel that opens because of a change in the charge distributed across the membrane where it is located |
| white matter | regions of the nervous system containing mostly myelinated axons, making the tissue appear white because of the high lipid content of myelin |
| anterior column | white matter between the anterior horns of the spinal cord composed of many different groups of axons of both ascending and descending tracts |
| anterior horn | gray matter of the spinal cord containing multipolar motor neurons, sometimes referred to as the ventral horn |
| arachnoid mater | middle layer of the meninges named for the spider-web–like trabeculae that extend between it and the pia mater |
| ascending tract | central nervous system fibers carrying sensory information from the spinal cord or periphery to the brain |
| Broca’s area | region of the frontal lobe associated with the motor commands necessary for speech production and located only in the cerebral hemisphere responsible for language production, which is the left side in approximately 95 % of the population |
| brain stem | region of the adult brain that includes the midbrain, pons, and medulla oblongata |
| cauda equina | bundle of spinal nerve roots that descend from the lower spinal cord below the first lumbar vertebra and lie within the vertebral cavity; has the appearance of a horse's tail |
| cerebellum | region of the adult brain connected primarily to the pons and is largely responsible for comparing information from the cerebrum with sensory feedback from the periphery through the spinal cord |
| cerebral cortex | outer gray matter covering the brain, marked by wrinkles and folds known as gyri and sulci |
| cerebral hemisphere | one half of the bilaterally symmetrical cerebrum |
| cerebrum | region of the adult brain responsible for higher neurological functions such as memory, emotion, and consciousness |
| corpus callosum | large white matter structure that connects the right and left cerebral hemispheres |
| cranial nerve | one of twelve nerves connected to the brain that are responsible for sensory or motor functions of the head and neck |
| descending tract | central nervous system fibers carrying motor commands from the brain to the spinal cord or periphery |
| diencephalon | region of the adult brain that includes the thalamus and hypothalamus |
| dorsal (posterior) nerve root | axons entering the posterior horn of the spinal cord |
| dorsal (posterior) root ganglion | sensory ganglion attached to the posterior nerve root of a spinal nerve |
| dura mater | tough, fibrous, outer layer of the meninges that is attached to the inner surface of the cranium and vertebral |
| endoneurium | innermost layer of connective tissue that surrounds individual axons within a nerve |
| epineurium | outermost layer of connective tissue that surrounds an entire nerve |
| fascicle | small bundles of axons or muscle fibers enclosed by connective tissue |
| frontal lobe | region of the cerebral cortex directly beneath the frontal bone of the cranium |
| hypothalamus | major region of the diencephalon that is responsible for coordinating autonomic and endocrine control of homeostasis |
| kinesthesia | general sensory perception of movement of the body |
| lateral column | white matter of the spinal cord between the posterior horn on one side and the axons from the anterior horn on the same side |
| lateral horn | region of the spinal cord gray matter in the thoracic, upper lumbar, and sacral regions that is the central component of the sympathetic division of the autonomic nervous system |
| longitudinal fissure | large separation along the midline between the two cerebral hemispheres |
| meninges | protective outer coverings of the CNS composed of connective tissue |
| occipital lobe | region of the cerebral cortex directly beneath the occipital bone of the cranium |
| olfaction | special sense responsible for smell, which has a unique, direct connection to the cerebrum |
| olfactory nerve | first cranial nerve; responsible for the sense of smell |
| optic nerve | second cranial nerve; responsible for visual sensation |
| paravertebral ganglia | autonomic ganglia superior to the sympathetic chain ganglia |
| parietal lobe | region of the cerebral cortex directly beneath the parietal bone of the cranium |
| perineurium | layer of connective tissue surrounding fascicles within a nerve |
| pia mater | thin, innermost membrane of the meninges that directly covers the surface of the CNS |
| posterior columns | white matter of the spinal cord that lies between the posterior horns of the gray matter, sometimes referred to as the dorsal column; composed of axons of ascending tracts that carry sensory information up to the brain |
| posterior horn | gray matter region of the spinal cord in which sensory input arrives, sometimes referred to as the dorsal horn |
| prefrontal lobe | specific region of the frontal lobe anterior to the more specific motor function areas, which can be related to the early planning of movements and intentions to the point of being personality-type functions |
| proprioception | general sensory perceptions providing information about location and movement of body parts; the “sense of the self” |
| somatosensation | general senses related to the body, usually thought of as the senses of touch, which would include pain, temperature, and proprioception |
| spinal nerve | one of 31 nerves connected to the spinal cord |
| subarachnoid space | space between the arachnoid mater and pia mater that contains CSF and the fibrous connections of the arachnoid trabeculae |
| subcortical nucleus | all the nuclei beneath the cerebral cortex, including the basal nuclei and the basal forebrain |
| sympathetic chain ganglia | autonomic ganglia in a chain along the anterolateral aspect of the vertebral column that are responsible for contributing to homeostatic mechanisms of the autonomic nervous system |
| temporal lobe | autonomic ganglia in a chain along the anterolateral aspect of the vertebral column that are responsible for contributing to homeostatic mechanisms of the autonomic nervous system |
| terminal ganglion | autonomic ganglia that are near or within the walls of organs that are responsible for contributing to homeostatic mechanisms of the autonomic nervous system |
| thalamus | major region of the diencephalon that is responsible for relaying information between the cerebrum and the hindbrain, spinal cord, and periphery |
| vagus nerve | tenth cranial nerve; responsible for the autonomic control of organs in the thoracic and upper abdominal cavities |
| ventral (anterior) nerve root | axons emerging from the anterior or lateral horns of the spinal cord |
| ventricles | spaces for cerebrospinal fluid to circulate through the brain |
| acetylcholine (ACh) | neurotransmitter that binds at a motor end-plate to trigger depolarization |
| adrenal medulla | interior portion of the adrenal (or suprarenal) gland that releases epinephrine and norepinephrine into the bloodstream as hormones |
| adrenergic | synapse where norepinephrine is released, which binds to α- or β-adrenergic receptors |
| cholinergic | synapse at which acetylcholine is released and binds to the nicotinic or muscarinic receptor |
| collateral ganglia | ganglia outside of the sympathetic chain that are targets of sympathetic preganglionic fibers, which are the celiac, inferior mesenteric, and superior mesenteric ganglia |
| craniosacral system | alternate name for the parasympathetic division of the autonomic nervous system that is based on the anatomical location of central neurons in brain-stem nuclei and the lateral horn of the sacral spinal cord; also referred to as craniosacral outflow |
| epinephrine | signaling molecule released from the adrenal medulla into the bloodstream as part of the sympathetic response |
| fight-or-flight response | set of responses induced by sympathetic activity that lead to either fleeing a threat or standing up to it, which in the modern world is often associated with anxious feelings |
| G protein–coupled receptor | membrane protein complex that consists of a receptor protein that binds a G protein—that is activated by that binding and in turn activates an effector protein (enzyme) that creates a second-messenger molecule in the cytoplasm of the target cell |
| ganglionic neuron | specifically refers to the cell body of a neuron in the autonomic system that is located in a ganglion |
| muscarinic receptor | type of acetylcholine receptor protein that is characterized by also binding to muscarine and is a metabotropic receptor |
| nicotinic receptor | type of acetylcholine receptor protein that is characterized by also binding to nicotine and is an ionotropic receptor |
| norepinephrine | signaling molecule released as a neurotransmitter by most postganglionic sympathetic fibers as part of the sympathetic response, or as a hormone into the bloodstream from the adrenal medulla |
| parasympathetic division | division of the autonomic nervous system responsible for restful and digestive functions |
| postganglionic fiber | axon from a ganglionic neuron in the autonomic nervous system that projects to and synapses with the target effector; sometimes referred to as a postganglionic neuron |
| preganglionic fiber | axon from a central neuron in the autonomic nervous system that projects to and synapses with a ganglionic neuron; sometimes referred to as a preganglionic neuron |
| rest and digest | set of functions associated with the parasympathetic system that lead to restful actions and digestion |
| sympathetic chain ganglia | series of ganglia adjacent to the vertebral column that receive input from central sympathetic neurons |
| sympathetic division | division of the autonomic nervous system associated with the fight-or-flight response |
| terminal ganglia | ganglia of the parasympathetic division of the autonomic system, which are located near or within the target effector, the latter also known as intramural ganglia |
| thoracolumbar system | alternate name for the sympathetic division of the autonomic nervous system that is based on the anatomical location of central neurons in the lateral horn of the thoracic and upper lumbar spinal cord |
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