Chapter 4 Flashcards
electrographic seizures
Abnormal rhythmic neuronal discharges; may be recorded by an electroencephalogram.
electrical stimulation
Passage of an electrical current from the uninsulated tip of an electrode through tissue, resulting in changes in the electrical activity of the tissue.
voltmeter
Device that measures the flow and the strength of electrical voltage by recording the difference in electrical potential between two bodies.
electroencephalogram (EEG)
Graph that records electrical activity from the brain and mainly indicates graded potentials of many neurons.
oscilloscope
Device that serves as a sensitive voltmeter by registering changes in voltage over time.
microelectrode
A microscopic insulated wire or a saltwater-filled glass tube whose uninsulated tip is used to stimulate or record from neurons.
diffusion
Movement of ions from an area of higher concentration to an area of lower concentration through random motion.
concentration gradient
Difference in the relative abundance of a substance among regions of a container; allows the substance to diffuse from an area of higher concentration to an area of lower concentration.
voltage gradient
Difference in charge between two regions that allows a flow of current if the two regions are connected.
resting potential
Electrical charge across the insulating cell membrane in the absence of stimulation; a store of potential energy produced by a greater negative charge on the intracellular side relative to the extracellular side.
graded potential
Small voltage fluctuation across the cell membrane.
hyperpolarization
Increase in electrical charge across a membrane, usually due to the inward flow of chloride or sodium ions or the outward flow of potassium ions.
depolarization
Decrease in electrical charge across a membrane, usually due to the inward flow of sodium ions.
action potential
Large, brief reversal in the polarity of an axon membrane
threshold potential
Voltage on a neural membrane at which an action potential is triggered by the opening of sodium and potassium voltage-sensitive channels; about –50 mV relative to extracellular surround. Also called threshold limit.
voltage-sensitive channel
Gated protein channel that opens or closes only at specific membrane voltages.
absolutely refractory
The state of an axon in the repolarizing period, during which a new action potential cannot be elicited (with some exceptions), because gate 2 of sodium channels, which are not voltage sensitive, are closed.
relatively refractory
The state of an axon in the later phase of an action potential during which increased electrical current is required to produce another action potential; a phase during which potassium channels are still open.
nerve impulse
Propagation of an action potential on the membrane of an axon.
node of Ranvier
The part of an axon that is not covered by myelin.
saltatory conduction
Fast propagation of an action potential at successive nodes of Ranvier; saltatory means leaping.
multiple sclerosis (Ms)
Nervous system disorder resulting from the loss of myelin around axons in the CNS.
autoimmune disease
Illness resulting from an abnormal immune response by the body against substances and tissues normally present in the body.
excitatory postsynaptic potential (EPsP)
Brief depolarization of a neuron membrane in response to stimulation, making the neuron more likely to produce an action potential.
inhibitory postsynaptic potential (IPsP)
Brief hyperpolarization of a neuron membrane in response to stimulation, making the neuron less likely to produce an action potential.
initial segment
Area near or overlapping the axon hillock where the action potential begins.
temporal summation
Addition of one graded potential to another that occur close in time.
spatial summation
Addition of one graded potential to another that occur close in space.
back propagation
Reverse movement of an action potential into the soma and dendritic field of a neuron; postulated to play a role in plastic changes that underlie learning.
optogenetics
Transgenic technique that combines genetics and light to excite or inhibit targeted cells in living tissue.
stretch-sensitive channel
Ion channel on a tactile sensory neuron that activates in response to stretching of the membrane, initiating a nerve impulse.
end plate
On a muscle, the receptor–ion complex that is activated by the release of the neurotransmitter acetylcholine from the terminal of a motor neuron.
transmitter-sensitive channel
Receptor complex that has both a receptor site for a chemical and a pore through which ions can flow.
