Nervous Systems

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Acetylcholine
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A neurotransmitter that carries information across vertebrate neuromuscular junctions and some other synapses. It is then broken down by the enzyme cholinesterase -all nerve-muscle junctions -can be excitatory or inhibitory (heart rate)
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Action Potential
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An impulse in a neuron taking the form of a wave of depolarization or hyperpolarization – impulse transmission -rapid transmission over a longer distance
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Active Transport
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The energy-dependent transport of a substance across a biological membrane against a concentration gradient– that is, from a region of low concentration (of one substance) to one of high concentration
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Afferent
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Carrying to , as in a neuron that carries impulses to the central nervous system , or a blood vessel that carries blood to a structure -input
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All-or-none
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does not vary in strength
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Autonomic
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The portion of the peripheral nervous system that controls such involuntary functions as those of guts and glands. Also called the involuntary nervous system -involuntary functions; heart rate, digestion, excretion, etc.
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Axon
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The part of a neuron that conducts action potentials away from the cell body -rapid passage of action potential
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Axon Hillock
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The junction between an axon and its cell body, where action potentials are generated
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Axon Terminals
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The endings of an axon; they form synapses and release neurotransmitter -multiple contacts with target cell(s)
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Cell Body
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“decision making”; site of graded potential
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Central Nervous System (CNS)
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The portion of the nervous system that is the site of most information processing, storage, and retrieval; in vertebrates, the brain and spinal cord.
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Peripheral Nervous System (PNS)
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The portion of the nervous system that transmits information to and fro the central nervous system, consisting of neurons that extend or reside outside the brain or spinal cord and their supporting cells
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Chemically-gated Channel
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A type of gated channel that opens or closes depending on the presence or absence of a specific molecule, which binds to the channel protein or to a separate receptor in turn alters the 3-D shape of channel protein
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Cholinesterase
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breaks down acetylcholine, removes it from receptors
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Cranial Nerve
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enter brain directly; 12
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Craniosacral
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neurons exits CNS
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Dendrite
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A fiber of a neuron which often cannot carry action potentials. Usually much branches and relatively short compared with the axon, and commonly carries information to the cell body of the neuron. -information input ; initial stimulation
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Depolarization
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A change in the resting potential across a membrane so that the inside of the cell becomes less negative, or even positive, compared with the outside of the cell -causes voltage-gated Na+ channels to open here -voltage-gated Na+ channels open -> Na+ moves in; inside of axon becomes positive
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Diffusion
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Random movement of molecules or other particles, resulting in even distribution of the particles when no barriers are present
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Efferent
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Carrying outward or away from, as in a neuron that carries impulses outward -output
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Equilibrium Potential
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The membrane potential at which an ion is at electrochemical equilibrium, i.e., there is no net flux of the ion across the membrane
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Excitation
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membrane potential moves closer to threshold, increases chance of triggering an action potential
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Excitatory Post-synaptic Potential
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Input from a neuron that causes depolarization of the recipient cell
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Exocytosis
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A process by which a vesicle within a cell fuses with the plasma membrane and releases its contents to the outside -AP opens voltage-gated Ca++ channels; Ca++ ions cause vesicles to release contents at synapse
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Facilitated Diffusion
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Passive movement through a membrane involving a specific carrier protein; does not proceed against a concentration gradient -no ATP needed
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Giant Axon
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increase speed of action potential -in larger invertebrates
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Hyperpolarization
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A change in the resting potential across a membrane so that the inside of a cell becomes more negative compared with the outside of the cell -positive ions out (K+) -more negative; can also occur if negative ions (Cl-) move in
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Inhibition
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membrane potential moves farther from threshold, decreases chance of action potential
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Inhibitory Post-synaptic Potential
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Input from a neuron that causes hyperpolarization of the recipient cell
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Integration
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simultaneous stimulation at many synapses is “evaluated” by cell body
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Interneuron
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A neuron that communicates information between two other neurons -processing connect neuron to neuron in CNS – source of most complexity in nervous system
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Ion Channels
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An integral membrane protein that allows ions to diffuse across the membrane in which it is embedded -Ions diffuse in or out through transmembrane proteins
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Medulla Oblongata
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The portion of the brainstem that connects to the spinal cord
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Membrane Potential
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The difference in electrical charge between the inside and the outside of a cell, caused by a difference in the distribution of ions -electrical charge difference between the inside and outside of a cell
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Midbrain
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One of the three regions of the vertebrate brain. Part of the brainstem, it serves as a relay station for sensory signals sent to the cerebral hemispheres
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Monosynaptic
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A neural reflux that begins in a sensory neuron and makes a single synapse before activating a motor neuron -sensory neuron synapses directly with motor neuron
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Motor Neuron
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A neuron carrying information from the central nervous system to a cell that produces movement -output from CNS to peripheral nervous system (PNS); efferent -stimulate effectors- muscles or glands
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Myelin
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Concentric layers of plasma membrane that form a sheath around some axons; provides the axon with electrical insulation and increases the rate of transmission of action potentials -fat produced by Schwann cells (a type of glial cell)
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Na+/K+ pump
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Anti-porter responsible for primary active transport; it pumps sodium ions out of the cell and potassium ions into the cell , both against their concentration gradients. Also called a sodium-potassium ATPase. -maintains the unequal distribution of Na+ and K+; active transport (uses ATP) -moves Na+ out, K+ in; requires energy returns ions to their original locations after a graded or action potential
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neuroglia
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glial cells – (= “nerve glue”) – support neuron functions; variable in structure
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Neuron
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A nervous system cell that can generate and conduct action potentials along an axon to a synapse with another cell -function is based on changes in electrical charge of the cell -3 categories -a cell -excitable – transmit impulses
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Neurotransmitter
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A substance produced in and released by a neuron (the presynaptic cell) that diffuses across a synapse and excites or inhibits another cell -release at the axon terminal is caused by the action potential -bind to receptors -signaling molecule
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Nodes of Ranvier
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A gap in the myelin sheath covering an axon; the point where the axonal membrane can fire action potentials -Electrically gated ion channels are concentrated at gaps in the myelin sheath
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Norepinephrine
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A neurotransmitter found in the central nervous system and also at the postganglionic nerve endings of teh sympathetic nervous system. Also called noradrenaline -(= noradrenaline): autonomic nervous system, inhibitory or excitatory; a tyrosine derivative
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Parasympathetic
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The division of the autonomic nervous system that works in opposition to the sympathetic nervous system -1 of the 2 autonomic system divisions -Promotes low levels of activity and maintenance functions (digestion, excretion): – “rest and digest”
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Polysynaptic
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-one sensory neuron, one or more interneurons, one motor neuron Examples – postural reflexes, pain reflexes
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Post-synaptic
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The cell that receives information from a neuron at a synapase
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Pre-synaptic
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The neuron that transmits information to another cell at a synapse -reabsorption (reuptake)
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Primary Motor Cortex
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An area of the frontal lobe that controls muscles’ neurons in this area are arranged according to the parts of the body with which they communicate
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Primary Somatorsensory Cortex
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An area of the parietal lobe that receives touch and pressure information from the body; neurons in this area are arranged according to the parts of the body wit which they communicate
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Reflex Arc
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-simplest nerve circuit result in invariable (“hard-wired”) reaction to specific stimulus – can be entirely in the spinal cord -> rapid response – response occurs before the brain processes the info
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Refractory Period
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The time interval after an action potential during which another action potential cannot be elicited from an excitable membrane
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Repolarization
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-return to resting potential -Na+ channels close, inactivate – gated K+ channels open –> K+ moves out – inside of cell returns to negative charge (slightly hyperpolarized
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Resting Potential
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The membrane potential of a living cell at rest. In cells at rest, the interior is negative to the exterior -the membrane potential of a neuron is -60-70 mV (millivolts) – stays constant unless neuron is stimulated -ion locations stable; no change in charge
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Saltatory Conduction
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The rapid conduction of action potentials in myelinated axons’ so called because action potentials appear to “jump” -AP “jumps” from one node to the next between nodes of Ranvier along the axon
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Schwann Cell
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A type of glial cell that myelinates axons in the peripheral nervous system -produces fat (myelin)
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Self-propagating
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-starts at axon hillock, passes undiminished as a “wave” down the axon 1. Na+ ions move in here, cause local depolarization and diffuse down axon 2.depolarization causes voltage-gated Na+ channels to open here
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Spatial Summation
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In the production or inhibition of action potentials in a postsynaptic cell, the interaction of depolarizations and hyperpolarizations produced at different sites on the postsynaptic cell -simultaneous stimulation from two or more nearby synapses; each synapse can be excitatory or inhibitory
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Spinal Nerve
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-connect to spinal cord; 31 in humans
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Sympathetic
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The division of the autonomic nervous system that works in opposition to the parasympathetic nervous system -Promotes high levels of activity – “fight or flight”
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Synapse
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A specialized type of junction where a neuron meets its target cell (which can be another neuron or some other type of cell) and information in the form of neurotransmitter molecules is exchanged across a synaptic cleft -Chemical signaling between neuron and target cell -neurotransmitter release to target cells -junction between axon terminal and target cell (nerve, muscle or gland)
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Synaptic Cleft
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The space between the presynaptic cell and the postsynaptic cell in a chemical synapse -minuteseparation between axon and target cell; 10-20 nanometers
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Synaptic Vesicle
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where neurotransmitters are stored
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Temporal Summation
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In the production or inhibition of action potentials in a postsynaptic cell, the interaction of depolarizations or hyperpolarizations produces by rapidly repeated stimulation of a single point of the postsynaptic cell – multiple stimulation at one synapse in a short period of time – additive (same effect)
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Thoracolumbar
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Threshold
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The level of depolarization that causes an electrically excitable membrane to fire an action potential -critical level
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Voltage-gated Channel
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A type of gated channel that opens or closes when a certain voltage exists across the membrane in which it is inserted
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Voluntary
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done, made, brought about, undertaken, etc., of one’s own accord or by free choice

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