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AB120 - Ch. 48
Neurons, Synapses, and Signaling
62
Biology
Undergraduate 1
02/21/2010

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Term
sensory neurons
Definition
sensory receptors (CNS); external stimuli (light, sound, touch, heat, smell, and taste); internal stimuli (blood pressure, blood CO2, muscle tension, etc...)
Term
interneurons
Definition
neurons--> neurons (integrate sensory input)
Term
motor neurons
Definition
CNS-->effector cells (muscle or endocrine cells)
Term
central nervous system (CNS)
Definition
brain and spinal cord; integrates information
Term
peripheral nervous system (PNS)
Definition
nerves that connect CNS to rest of animal's body
Term
neurons
Definition
functional unit of nervous system that transmits information throughout body
Term
cell body
Definition
contains nucleus ans cellular organelles of the neuron
Term
dendrites
Definition
fiberlike processes specialized to receive input from other neurons
Term
axons
Definition
fiberlike processes specialized to conduct infomation toward synapse
Term
axon hillock
Definition
conical region of axon that joins the cell body
Term
myelin sheath
Definition
insulating layer surrounding the axons of some neurons
Term
synaptic terminals
Definition
site at the end of axons where neurotransmitters are released
Term
synapse
Definition
narrow gap between syanptic terminal and effector cell
Term
presynaptic cell
Definition
transmitting cell at a synapse
Term
postsynaptic cell
Definition
the target cell of a synapse
Term
neurotransmitters
Definition
chemical messengers of the nervous system
Term
glia
Definition
supporting cells that assist, structurally support, protect, and insulate neurons
Term
astrocytes
Definition
provide structural and metabolic support
Term
blood-brain barrier
Definition
naturally occurring barrier created by the modification of brain capillaries (as by reduction in fenestration and formation of tight cell-to-cell contacts) that prevents many substances from leaving the blood and crossing the capillary walls into the brain tissues
Term
radial glia
Definition
form tracks along which neurons migrate (developing embryo)
Term
oligodendrycytes
Definition
form myelin sheath (CNS)
Term
Schwann cells
Definition
form myelin sheath (PNS)
Term
membrane potential
Definition
voltage difference accrose the plasma membrane of a cell
Term
resting potential
Definition
membrane potential of inactive neuron
Term
equilibrium potential
Definition
resulting membrane potential that would arise if membrane were permeable to one ion alone (represents point at which electrical gradient exactly balances concentration gradient)
Term
ungated ion channels
Definition
always open (responsible for resting potential)
Term
gated ion channels
Definition
open or close in response to one of three stimuli
Term
stretch-gated ion channels
Definition
respong to mechanical deformation of membrane
Term
ligand-gated ion channels
Definition
respond to specific chemcicals (e.g. neurotransmitter)
Term
voltage-gated ion channels
Definition
respond to changes in membrane potential
Term
excitable cells
Definition
capable of generating large changes in their membrane potentials (due to opening and closing of gated ion channels)
Term
depolarization
Definition
membrane voltage becomes less negative (e.g. opening of Na+ channels)
Term
hyperpolarization
Definition
membrane voltage becomes more negative (e.g. opening of K+ channels)
Term
graded potentials
Definition
magnitude of hyperpolarization of depolarization varies with strength of stimulus
Term
action potential
Definition
an all-or-none electrical event that propagates down axons
Term
refractory period
Definition
short interval following an action potential during which axon cannot be stimulated to fire another action potential
Term
saltatory conduction
Definition
rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of the Ranvier to another, skipping the myelin-sheathed regions of the membrane
Term
synaptic cleft
Definition
separates presynaptic and postsynaptic cell
Term
synapse
Definition
junction where one neuron communicates with another ell across a narrow gap; neurotransmitter molecules released by the neuron diffuse across the synapse, relaying messages to the other cell
Term
synaptic vesicles
Definition
membranous sac containing neurotransmitter molecules at the tip of an axon
Term
neurotransmitter
Definition
moleculte that is released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft and binds to the postsynaptic cell, triggering a response
Term
direct synaptic transmission
Definition
chemical synapse in which neurotransmitter opens ligand-gated ion channels in postsynaptic cell that changes this cell's membrane voltage directly
Term
excitatory postsynaptic ptotential (EPSP)
Definition
causes postsynaptic cell to depolarize (drives membrane potential towards threshold)
Term
threshold
Definition
potential that an excitable cell membrane must reach for an action potential to be initiated
Term
ihibitory postsynaptic potential (IPSP)
Definition
causes postsynaptic cell to hyperpolarize (drives membrane potential away from threshold)
Term
summation
Definition
ADDITIVE effect of EPSPs and IPSPs
Term
temporal summation
Definition
additive of effects of PSPs from single synapse (repetition adding, single note)
Term
spatial summation
Definition
additive effects of PSPs from multiple synapses (multiple adding, chord)
Term
indirect synaptic transmission
Definition
neurotransmitter binds to a receptor other than an ion channel
Term
acetylcholine (ACh)
Definition
released at neuromuscular juctions (skeletal muscles); neurotransmitter
Term
norepinephrine
Definition
neurotransmitter
Term
epinephrine
Definition
neurotransmitter
Term
dopamine
Definition
affects sleep, mood, attention, and motor skills; neurotransmitter
Term
serotonin
Definition
affects sleep and mood; neurotransmitter
Term
GABA
Definition
inhibitory neurotransmitter
Term
glycine
Definition
inhibitory neurotransmitter
Term
glutamate
Definition
excitatory neurotransmitter
Term
aspartate
Definition
excitatory neurotransmitter
Term
substance P
Definition
mediates pain perception; neurotransmitter
Term
endorphins
Definition
natural analgesics; neurotransmitter
Term
nitric oxide (NO)
Definition
neurotransmitter
Term
carbon dioxide
Definition
neurotransmitter
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