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62 Cards in this Set

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  • Back
A nerve cell. (Extra Note: A nerve is a bundle of axons held together as a unit by connective tissue)
The cell body of a neuron; in general, the body.
Long extension from neuron cell body
Fine processes of a neuron that typically provide the main receptive area for synaptic inputs from other neurons
The elongated cylindrical process of a neuron along which action potentials are conducted; a nerve fiber.
Axon terminals
The end of an axon; typically, the site where signals are passed to another cell.
Action potential (AP)
Transient all-or-none reversal of a membrane potential produced by regenerative inward current in excitable membranes
Passive electrical properties
The physical properties of cells that control the movement of an electrical signal through a nerve in the same way that electrons move along a wire or ions move through an aqueous solution in a beaker.
Active electrical properties
The cellular properties of neurons and muscle fibers that allow them to generate and transmit action potentials.
Transporting or conducting toward a central region; centripetal
A connection between a neuron and a target cell at which activity in the presynaptic (transmitting)cell influences the activity of the postsynaptic (receiving) cell
Transporting or conducting from a central region toward the periphery.
Neuronal circuit
A set of interconnected neurons.
Located on the sending side of a synaptic connection
Located on the receiving side of a synaptic connection
Graded signals (graded response)
A response that increases as a function of the energy of the stimulus; a membrane response that is not all-or-none.
Sensory neurons
Transmit information collected from external stimuli (e.g., sound, light, pressure, or chemical signals) or which respond to stimuli inside the body (e.g., blood oxygen level, the position of a joint, or the orientation of the head).
Link other neurons within the central nervous system
Motor neurons (motoneurons)
Carry signals to effector organs, causing contraction of muscles or secretion by gland cells.
Central nervous systen (CNS)
The collection of neurons and parts of neurons that are contained within the brain and spinal cord of vertebrates or within the brain, main nerve cord, and major ganglia of invertebrates.
The major neuronal center within the body; typically located at the anterior of the body.
An anatomically distinct collection of neuronal somata.
Spinal cord
The portion of the vertebrate central nervous system that is encased in the vertebral columns, extending from the caudal end of the medulla; consists of a core of gray matter and an outer layer of white matter.
Glial cells (neuroglia)
Nonexcitable supportive cells associated with neurons in nervous tissue.
A class of glial cells with few processes that wrap axons in the central nervous system, forming myelin sheaths.
Schwann cells
A glial cell that wraps around peripheral axons to produce an insulating myelin sheath
(E or V) The electromotive force, or electric potential, expressed in volts, When the work required to move 1 coulomb (C) of charge from one point to a point of higher potential is 1 joule (J), or ¨ù.184 calories (cal), the potential difference between these points is said to be 1 volt (V).
Membrane potential
The electric potential measured from within a cell relative to the potential of the extracellular fluid, which is by convention considered to be zero; the potential difference across a membrane.
Resting potential, Vrest
The normal membrane potential of a cell at rest.
An increase in the potential difference across a membrane, making the cell interior more negative than it is at rest.
Threshold potential
The potential at which a response (e.g., an action potential or a muscle twitch) is produced.
Ion selectivity
Most membrane channels allow only one or a few ionic species to cross the membrane; that is, they exhibit ion selectivity.
Voltage-gated channels
A channel whose conductance depends upon the transmembrane electric potential difference.
Leak channels
The passive change in membrane potential in response to hyperpolarizing current takes place independently of gated ion channels. Instead, the ionic current that produces passive electrical responses flows across the membrane primarily through K+ - selective channels that are always open. These K+ channels, called leak channels, are largely responsible for maintaining the resting potential across the plasma membrane.
Input resistance
The total resistance encountered by electric current flowing into or out of a cell.
Capacitative current
Current entering and leaving a capacitor
Dielectric constant
A measure of the degree to which a substance is able to store electric charge under an applied voltage.
Time constant
(¥ó) A measure of the rate of accumulation or decay in an exponential process; the time required for an exponential process to reach 63% completion. In electricity, it is proportional to the product of resistance and capacitance and determines how rapidly a membrane charges or discharges.
Electrochemical potential
The electric potential developed across a membrane by a chemical concentration gradient of an ion that can diffuse across the membrane.
Steady state
(dynamic equilibrium) a condition in which the value of a variable does not change, but continuous expenditure of energy is required to maintain the constancy.
Dynamic steady state
In biological systems, in which exchanges of matter and energy occur continuously across the boundaries of the system, the stability of the system is referred to as a dynamic steady state.
Goldman equation
The equation describing the steady-state potential for a system in which two or more species of diffusible ions are separated by a semipermeable membrane; if only one species can diffuse across the membrane, the equation reduces to the Nernst equation.
Threshold current
The threshold current is the intensity of stimulating current that is just sufficient to bring the membrane to the threshold potential and elicit an AP.
The reversal of membrane potential during an action potential; the period of time during which the cell becomes inside-positive.
After-hyperpolarization, (undershoot)
The transient period at the end of an action potential when Vm is more negative than Vrest; also called undershoot
Absolute refractory period
The period during or after an action potential when a second stimulus produces no action potential.
Relative refractory period
The period following an action potential during which another action potential, possibly partial, may be triggered, but only if the stimulus is more intense than usual.
Phasic response
The response of a neuron that, when stimulated continuously by a current of constant intensity, accommodates rapidly and generates action potentials only during the beginning of the stimulus period.
Tonic response
The response pattern of neurons that, when stimulated continuously by a current of constant intensity, accommodate slowly and fire repetitively with gradually decreasing frequency.
Evolution through natural selection leading to an organism whose physiology, anatomy, and behavior are matched to the demands of its environment.
Voltage clamping
An experimental method of imposing a selected membrane potential across a membrane by means of feedback control.
Patch clamping
A recording technique in which a microelectrode is sealed tightly against a cell membrane and the transmembrane potential is held constant; can be used to measure ionic currents through single ion channels or across the membrane of an entire cell.
Tetrodotoxin (TTX)
The puffer fish poison, which selectively blocks voltage-gated sodium channels in the membranes of excitable cells.
Selectivity filter
The current hypotheses explaining how a channel selects among ions are based partly on ionic size and partly on other properties of the permeant species, such as net charge and, importantly, ease of dehydration. The region of the channel that determines its selectivity is called the selectivity filter.
Spike-initiating zone
The region of an axon where an action potential is initiated; in many, but not all, neurons, located at the axon hillock.
Nernst equation
An equation for calculating electrochemical equilibrium conditions; defines the electric potential difference across a membrane that will just balance the concentration gradient of a single permeant ionic species
The reduction or reversal of the potential difference that exists across a membrane compared with Vm at rest.
All-or-none signals
A condition in which the magnitude of a cells response is independent of the strength of a stimulus above some threshold value. If an input signal brings the cell to its threshold, the amplitude of the response is maximal; if the stimulus fails to bring the cell to threshold, there is no response.
Ligand-gated channels
A channel that opens when a specific molecule or molecules bind to the extracellular domain of the channel protein.
electrochemical equilibrium
the state in which the concentration gradient of an ion across a membrane is precisely balanced by the electric potential across the membrane
electrochemical gradient
the sum of the combined forces of the concentration gradients and electric gradients acting on an ion
Electrically excitable
Although a stable voltage (or electric potential difference) exists across the plasma membrane of all animal cells, only the membranes of electrically excitable cells (e.g., neurons and muscle fibers) can respond to changes in their transmembrane potential difference by generating APs.