Chapter 4

Question 1

Electrographic seizures

Answer 1

Abnormal rhythmic neuronal discharges; may be recorded by an electroencephalogram

Question 2

Electrical stimulation

Answer 2

Passage of an electrical current from the uninsulated tip of an electrode through tissue, resulting in changes in the electrical activity if the tissue

Question 3

Electroencephalogram (EEG)

Answer 3

Graph of electrical activity from the brain, which is mainly composed of graded potentials from many neurons

Question 4

Voltmeter

Answer 4

Device that measures the strength of electrical voltage by recording the difference in electrical potential between two points

Question 5

Oscilloscope

Answer 5

A specialized device that serves as a sensitive voltmeter, registering changes in voltage over time

Question 6

Microelectrode

Answer 6

A microscopic insulated wire or a saltwater-filled glass tube whose uninsulated tip is used to stimulate or record from neurons

Question 7

Diffusion

Answer 7

Movements of ions from an area of higher concentration to an area of lower concentration through random motion

Question 8

Concentration gradient

Answer 8

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

Question 9

Voltage gradient

Answer 9

Difference in electric potential between two regions that allows a flow of current if the two regions are connected

Question 10

Resting potential

Answer 10

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

Question 11

Equilibrium (reversal) potential

Answer 11

The membrane potential for an individual ion, at which there is no net (overall) flow of that particular ion from one side of the membrane to the other

Question 12

Nernst equation

Answer 12

Calculates the equilibrium potential (also referred to as the Nernst potential) for an ion based on the charge on the ion (i.e., its valence) and its concentration gradient across the membrane

Question 13

Graded potential

Answer 13

A small voltage fluctuation across the cell membrane

Question 14

Hyperpolarization

Answer 14

Increase in electrical charge across a membrane, usually due to the inward flow of chloride ions or the outward flow of potassium ions

Question 15

Depolarization

Answer 15

Decrease in electrical charge across a membrane, usually due to the inward flow of sodium ions

Question 16

Excitatory postsynaptic potential (EPSP)

Answer 16

Brief depolarization of a neuron membrane in response to stimulation, making the neuron more likely to produce an action potential

Question 17

Inhibitory postsynaptic potential (IPSP)

Answer 17

Brief hyperpolarization of a neuron membrane in response to stimulation, making the neuron less likely to produce an action potential

Question 18

Initial segment

Answer 18

Area near where the axon meets the cell body, which is rich in voltage-gated channels; these channels generate the action potential

Question 19

temporal summation

Answer 19

Addition of graded potentials to each other, when the potentials occur close in time

Question 20

Spatial summation

Answer 20

Addition of graded potentials to each other, when the potential occurs close in space

Question 21

Action potential

Answer 21

Large, brief reversal in the polarity of an axon membrane

Question 22

Threshold potential

Answer 22

Voltage of a neural membrane at which an action potential is triggered by the opening of sodium and potassium voltage-activated channels; about -50 mV relative to the extracellular surroundings. Also called threshold limit

Question 23

Voltage-activated channel

Answer 23

Gated protein channel that opens or closes only at specific membrane voltages

Question 24

Back propagation

Answer 24

Reverse movement of an action potential into the soma and dendritic field of a neuron; postulated to play a role in the plastic changes that underlie learning

Question 26

Absolutely refractory

Answer 26

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 the sodium channels, which are not voltage activated, is closed

Question 27

Relatively refractory

Answer 27

The state of an axon in the later phase of an action potential, during which higher-intensity electrical current is required to produce another action potential; a phase during which potassium channels are still open

Question 28

Nerve impulse

Answer 28

Propagation of an action potential on the membrane of an axon

Question 29

Node of Ranvier

Answer 29

The part on an axon that is not covered by myelin

Question 30

Saltatory conduction

Answer 30

Fast propagation of an action potential at successive nodes of Ranvier; saltatory means "leaping"

Question 31

Multiple sclerosis (MS)

Answer 31

Nervous system disorder resulting from the loss of the myelin sheath around axons in the CNS

Question 32

Autoimmune disease

Answer 32

Illness resulting from an abnormal immune response by the body against substances and tissues normally present in the body

Question 33

Stretch-activated channel

Answer 33

Ion channel on a tactile sensory neuron that becomes activated in response to stretching of the membrane, initiating a nerve impulse

Question 34

End plate

Answer 34

On a muscle, the receptor-ion complex that is activated by the release of the neurotransmitter acetylcholine from the terminal of a motor neuron

Question 35

Transmitter-activated channel

Answer 35

Receptor complex that has both a receptor site for a chemical and a pore through which ions can flow