Active Transport
*A protein- mediated process that expends energy to enable a molecule to cross a cell membrane
Afferent Axon
*Axon that brings information into a structure
Astrocytes
*Star-shaped glia that synchronize the activity of axons
Axon
*Thin fiber extending from the neuron cell body that sends signals to other neurons
Absolute refractory period
*A time when the membrane is unable to produce an action potential
Action potential
*Messages sent by axons
All-or-none law
*Principle that the amplitude and velocity of an action potential are independent of the stimulus that initiated it
Axon hillock
*A swelling where the axon emerges from the cell body
Blood-brain Barrier
*Mechanism that excludes most chemicals from entering the brain
Cell Body
*Structure containing the nucleus, ribosomes, and mitochondria
Concentration gradient
*Difference in distribution of ions across the neuron’s membrane
Dendrites
*Branching fibers of a neuron that receive information from other neurons
Dendritic Spines
*Short outgrowths that increase the surface area available for synapses
Depolarize
*To reduce polarization towards zero across a membrane
Efferent Axon
*Axon that carries information away from a structure
Electrical gradient
*Difference in electrical charges between the inside and outside of the cell
Graded potentials
*A membrane potential that varies in magnitude in proportion to the intensity of the stimulus
Glia
*Type of cell in the nervous system that, in contrast to neurons, does not conduct impulses over long distances
Glucose
*A simple sugar
Hyperpolarization
*Increased polarization across a membrane
Interneuron
*A neuron whose axons and dendrites are all confined within a given structure. Also called an intrinsic neuron
Local anesthetic
*Drug that attach to the sodium channels of the membrane, stopping action potentials
Local neurons
*Neurons without an axon
Microglia
*Glial cells that remove waste material and other microorganisms from the nervous system
Motor Neuron
*Neuron that receives excitation from other neurons and conducts impulses to a muscle
Myelin Sheath
*Insulating material that covers vertebrate axons
Myelin
*An insulating material composed of fats and proteins
Myelinated axons
*Insulating material that covers vertebrate axons
Neurons
*Cells in the nervous system that receive information and transmit it to other cells
Nodes of Ranvier
*Interruptions in the myelin sheath of vertebrate neurons
Oligodendrocytes
*Glial cells that form myelin sheaths (CNS)
Presynaptic Terminal
*End bulb of axon that releases neurotransmitters
Polarization
*Same as an electrical gradient
Propagation of the action potential
*Transmission of an action potential down an axon
Radial Glia
*Cells that guide the migration of neurons and the growth of axons and dendrites during embryological development
Refractory period
*Time when the cell resists the production of further action potentials
Relative refractory period
*Time after the absolute refractory period that requires a stronger stimulus to initiate an action potential
Resting potential
*The potential across the membrane at rest
Salutatory conduction
*The jumping of action potentials from node to node
Selective permeability
*Ability of some chemicals to pass more freely than others through a membrane
Schwann Cells
*Glial cells that form the myelin sheath in the PNS
Sensory Neuron
*Neuron that is highly sensitive to a specific type of energy (light, sound, etc)
Sodium-potassium pump
*Mechanism that actively transports sodium ions out of the cell while drawing in two potassium ions
Threshold
*Minimum amount of membrane depolarization necessary to trigger an action potential
Voltage-gated channels
*Membrane channel whose permeability to sodium (or some other ion) depends on the voltage difference across the membrane
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